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PBS Kids Super Why Time Travel Adventure Finger Family Song!

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Is time travel really possible? Here’s what physics says

The ability to jump forward and backwards in time has long fascinated science fiction writers and physicists alike. So is it really possible to travel into the past and the future?

Doctor Who is arguably one of the most famous stories about time travel. Alongside The Time Machine and Back to the Future, it has explored the temptations and paradoxes of visiting the past and voyaging into the future .

In the TV show, the Doctor travels through time in the Tardis: an advanced craft that can go anywhere in time and space. Famously, the Tardis defies our understanding of physical space: it's bigger on the inside than it appears on the outside .

Time: The Ultimate Guide

To mark the  60th anniversary of Doctor Who , we're exploring the big questions about time, including the science of time travel, how clocks have shaped humanity, and even the mind-bending temporal consequences of flying into a black hole.  Read and watch more from   Time: The Ultimate Guide .

While time travel is fundamental to Doctor Who, the show never tries to ground the Tardis' abilities in anything resembling real-world physics. It would be odd to complain about this: Doctor Who has a fairy-tale quality and doesn't aspire to be realistic science fiction.

But what about in the real world? Could we ever build a time machine and travel into the distant past, or forward to see our great-great-great-grandchildren? Answering this question requires understanding how time actually works – something physicists are far from certain about. So far, what we can say with confidence is that travelling into the future is achievable, but travelling into the past is either wildly difficult or absolutely impossible.

Let's start with Albert Einstein's theories of relativity, which set out a description of space, time, mass and gravity. A key outcome of relativity is that the flow of time isn't constant . Time can speed up or slow down, depending on the circumstances.

"This is where time travel can come in and it is scientifically accurate and there are real-world repercussions from that," says Emma Osborne, an  astrophysicist at the University of York, in the UK.

For example, time passes more slowly if you travel at speed, though you need to start approaching the speed of light for the effect to be significant. This gives rise to the twin paradox, in which one of two identical twins becomes an astronaut and whizzes around in space at close to the speed of light, while the other stays on Earth. The astronaut will age more slowly than their Earthbound twin. "If you travel and come back, you are really younger than the twin brother," says Vlatko Vedral, a quantum physicist at the University of Oxford, in the UK. Twins Scott and Mark Kelly did this for real when Scott spent months in space , albeit not at speeds close to that of light.

Similarly, time passes more slowly for you if you are in an intense gravitational field, such as a black hole. "Your head is ageing quicker than your feet, because Earth's gravity is stronger at your feet," says Osborne.

Doctor Who used this as the setup for season 10 finale World Enough and Time, in which the Twelfth Doctor and his friends are trapped on a spaceship close to a black hole. At the front of the craft, closer to the black hole, time passes more slowly than at the rear. This means the small group of Cybermen at the rear of the craft are able to develop into a huge army in, from the Doctor's point of view, a matter of minutes. This effect of gravity on time also features in the plot of the film Interstellar.

In our everyday lives, these relativistic effects are too tiny to be noticed. But they do affect the satellites that we use for global positioning system (GPS) . "The clocks above click faster than the clocks on Earth", and must be constantly readjusted, says Osborne. "If we didn't, Google Maps would be wrong about 10km (six miles) a day ."

Relativity means it is possible to travel into the future. We don't even need a time machine, exactly. We need to either travel at speeds close to the speed of light, or spend time in an intense gravitational field. In relativity, these two acts are essentially equivalent. Either way, you will experience a relatively short amount of subjective time, while decades or centuries pass in the rest of the Universe. If you want to see what happens hundreds of years from now, this is how to do it.

In contrast, going backwards in time looks far, far harder.

"It may or may not be possible," says Barak Shoshany, a theoretical physicist at Brock University in St Catharines, Canada. "What we have right now is just insufficient knowledge, possibly insufficient theories."

Relativity offers some options for backwards time travel, but this time they are much more theoretical. "People tie themselves up in knots trying to find ways to rearrange space-time in order to make time travel to the past possible," says Katie Mack, a theoretical cosmologist at the Perimeter Institute for Theoretical Physics in Waterloo, Canada.

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• The people who think in nanoseconds
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One way is to create a closed time-like curve: a path through space and time that loops back on itself. A person who followed the path would eventually find themselves at the same time and place where they started. A mathematical description of such a path was published by logician Kurt Gödel in a 1949 study , and many others have followed.

However, this doesn't look like a promising approach for several reasons.

"We don't know whether this exists anywhere in the Universe," says Vedral. "This is really purely theoretical, there's no evidence."

It's also not at all obvious how we could make such a thing. "Even if we had much greater technological powers than we currently do, it seems unlikely that we would be able to create closed time-like curves on purpose," says Emily Adlam, a philosopher at Chapman University in California, US.

Even if we could, says Vedral, we wouldn't want to. "You would literally be repeating exactly the same thing over and over again," he says.

Doctor Who used a similar setup in the classic episode Heaven Sent, in which the Doctor lives the same few hours over and over again for billions of years. However, this didn't involve a closed time-like curve, but rather repeated use of a teleporter.

In a similar vein, in a 1991 study physicist Richard Gott set out a mathematical description of a wild scenario in which two " cosmic strings " moved past each other in opposite directions. According to his calculations, this would create closed time-like curves looping around the strings.

That sounds handy, but where might we find a pair of cosmic strings? They are hypothetical phenomena that may have formed in the very early Universe, according to some theories. None have ever been detected. "We don't have any reason to believe cosmic strings exist," says Mack. Even if they do exist, it would be an incredible stroke of luck to find two moving neatly in parallel. "We don't have any reason to believe that would happen."

Why is the Tardis a police box?

The Tardis allows Doctor Who to travel through time. It also has an iconic appearance. Owing to a faulty camouflage system, it has got stuck in the form of an old British police box. Within the show, the camouflage function is called the chameleon circuit, which is a distressing mistake because chameleons mostly change colour to signal to each other, not to disguise themselves.

There is another phenomenon that is seemingly allowed by relativity:  wormholes . In theory, it is possible for space-time to be folded like a piece of paper, allowing  a tunnel to be punched through  to create a shortcut between two widely-separated points. "Wormholes are theoretically possible in general relativity," says Vedral.

However, again, the problems quickly mount up. First, we have no evidence that wormholes actually exist. "It's been shown mathematically that they can exist, but whether they exist physically is something else," says Osborne.

What's more, if wormholes do exist, they will be incredibly short-lived. "Often wormholes are described as two black holes that have joined to each other," says Osborne. This means a wormhole would have an incredibly intense gravitational field. "It would collapse under its own gravity."

Real wormholes would also be microscopically tiny . You couldn't fit a person, or even a bacterium, through one.

In theory, both these problems can be solved – but this requires an enormous amount of something called "negative energy". This is something that may occur on the absolute tiniest scale, within spaces smaller than atoms. An energy field must have an overall positive energy, but there can be tiny pockets of negative energy within it, says Osborne. "What you'd want is these tiny pockets of locally negative energy expanded," she says. "I don't think that's possible in any way."

Vedral sums it up: "It doesn't sound like a very realistic proposal."

So much for time travel based on relativity. What about the other great theory of the Universe: quantum mechanics?

Whereas relativity describes the behaviour of large objects like humans and galaxies, quantum mechanics describes the very small – in particular, particles smaller than atoms, such as electrons and photons. On these subatomic scales, physics operates in ways that confound our intuitions.

One of the peculiar observations that has emerged from the study of the quantum realm is non-locality. A change in a particle's state in one location can instantaneously influence another "entangled" particle somewhere else – something Einstein referred to as "spooky action at a distance". This has been " shown experimentally many times" in Nobel Prize winning research, says Adlam.

"A lot of physicists are very unhappy with the possibility of non-locality," says Adlam. That's because, for the effect to be instantaneous, the information must be conveyed from place to place at faster than the speed of light. This is supposed to be impossible.

In response, some physicists have proposed alternative ways to interpret the experiments . These interpretations get rid of the non-locality – but in doing so they mess with our understanding of time.

"Instead of having an instantaneous non-local effect, you would just send your effect into the future, and then at some point it would turn around and go back into the past," says Adlam. "It would look instantaneous." But in reality, the effect would have gone on a journey into the future and back again.

This interpretation appears to introduce "retrocausality": that is, events in the future having an effect on the past. This goes against our intuition: we imagine events occurring in a straight line, from the past to the present to the future . In these peculiar quantum setups, information may be travelling into the future and then back into the past.

The first thing to note is that this interpretation of the experiments is far from universally accepted . Plenty of quantum physicists argue that introducing retrocausality is just as unsettling as introducing non-locality, or even worse.

Even if retrocausality is real, it probably won't help us become Time Lords. "Retrocausality's not quite the same thing as time travel," says Adlam.

For one thing, our observations of non-locality have all involved tiny numbers of particles. Scaling up to a human, or even something smaller like a piece of paper, would be an enormous challenge.

It isn't even possible to send a message into the past, says Adlam. "The retrocausality is very specifically hidden by the way it's implemented."

This is best understood by thinking through an experiment. Suppose Adam conducts a measurement in the lab. However, the result he gets is dependent on a measurement that Beth does later. In other words, Beth's experiment in the future controls the outcome of Adam's experiment in the past. However, this only works if Beth's experiment destroys all the records of what Adam did and saw.

"You sort of in some sense would be sending a signal to the past, but only by destroying all the records of everything that happened," says Adlam. "You wouldn't be able to make practical use of that, because you necessarily had to destroy the records of succeeding and sending that signal."

So there we have it. On our current understanding of the Universe, we could potentially travel into the future, but travelling into the past may well be a total no-no.

The only remaining loophole is that the theories this is based on are incomplete. Relativity and quantum mechanics work very well for certain aspects of the Universe, but they also aren't compatible. This suggests we need a deeper theory that unifies the two, but despite decades of effort we don't have one. "Until we have that theory, we cannot be sure," says Shoshany.

Of course, there is another way of looking at it: in the time it has taken you to read this article, you've already travelled seven minutes or so into the future. You're welcome.

If you liked this story,  sign up for The Essential List newsletter  – a handpicked selection of features, videos and can't-miss news delivered to your inbox every Friday.

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Time travel is possible, but it’s a one-way ticket

Chenoa van den Boogaard , Physics and Astronomy editor

The ability to travel through time, whether it is to fix a mistake in the past or gain insight into the future, has long been embraced by science fiction and debated by theoretical physicists. While the debate continues over whether travelling into the past is possible, physicists have determined that travelling to the future most certainly is. And you don’t need a wormhole or a DeLorean to do it.

Real-life time travel occurs through time dilation, a property of Einstein’s special relativity . Einstein was the first to realize that time is not constant, as previously believed, but instead slows down as you move faster through space.

As part of his theory, Einstein re-envisioned space itself. He coined the phrase “spacetime,” fusing the three dimensions of space and one dimension of time into a single term. Instead of treating space as a flat and rigid place that holds all the objects in the universe, Einstein thought of it as curved and malleable, able to form gravitational dips around masses that pull other objects in, just as a bowling ball placed in the centre of a trampoline would cause any smaller object placed on the trampoline to slide towards the centre.

A computer-generated representation of Einstein’s curved spacetime. The Earth creates a gravitational dip in the fabric of spacetime which is deepest at its core. Courtesy and © of NASA

The closer an object gets to the centre of the dip, the faster it accelerates. The centre of the Earth’s gravitational dip is located at the Earth’s core, where gravitational acceleration is strongest. According to Einstein’s theory, because time moves more slowly as you move faster through space, the closer an object is to the centre of the Earth, the slower time moves for that object.

This effect can be seen in GPS satellites, which orbit 20,200 kilometres above the Earth’s surface. These satellites have highly precise clocks onboard that gain an average of 38 microseconds per day due to time dilation. While this time gain seems insignificant, GPS satellites rely on their onboard clocks to maintain precise global positioning. Running 38 microseconds fast would result in a positioning error of nearly 10 kilometres, an error that would increase daily if the time difference were not constantly corrected.

A more dramatic example of time dilation can be seen in the movie Interstellar when Matthew McConaughey and his crew land on a planet with an extreme gravitational field caused by a nearby black hole. Because of the black hole’s intense gravitational influence, time slows dramatically for the crew on the planet, making one hour on the surface equal to seven years on Earth. This is why, when the crew returns to Earth, Matthew McConaughey’s daughter is an old woman while he appears to be the same age as when he left.

So why hasn’t humanity succeeded in making such drastic leaps forward in time? The answer to this question comes down to velocity. In order for humanity to send a traveller years into the future, we would either have to take advantage of the intense gravitational acceleration caused by black holes or send the traveller rocketing into space at close to the speed of light (about 1 billion km/h). With our current technology , jumping a few microseconds into the future is all humans can manage.

But if technology one day allows us to send a human into the future by travelling close to the speed of light, would there be any way for the traveller to use time dilation to return to the past and report her findings? “Interstellar travel reaching close to the speed of light might be possible,” says Dr. Jaymie Matthews , professor of astrophysics at the University of British Columbia, “[but] this voyage is one way into the future, not back to the past.”

If we can’t use time dilation to return to the past, does this mean that the past is forever inaccessible? Perhaps not. Einstein proposed that time travel into the past could be achieved through an Einstein-Rosen bridge, a type of wormhole. Wormholes are theoretical areas of spacetime that are warped in a way that connects two distant points in space.

A visualization of a wormhole: The fabric of spacetime curves back upon itself, forming a bridge between two distant locations. Image by Panzi , CC-BY 3.0

Einstein’s equations suggested that this bridge in space could hypothetically connect two points in time instead if it were stable enough. “At the moment, even an Einstein-Rosen bridge cannot [be used to] go back in the past because it doesn’t live long enough – it is not stable,” Matthews explains.

“Even if it was stable, it [requires] other physics, which we don’t have. Hypothetical particles and states of matter that have “exotic” physical properties that would violate known laws of physics, such as a particle having a negative mass. That is why “wormholes” are only science fiction.”

While it would be fascinating to travel back in time to see the dinosaurs or to meet Albert Einstein and show him the reality of time travel, perhaps it is best if the past remains untouched. Travelling to the past invites the possibility of making an alteration that could destroy the future. For example, in Back to the Future , Marty McFly travels to the past and inadvertently prevents his parents from meeting each other, nearly preventing his own existence. But if he had undone his own existence, how could he have travelled back in time in the first place?

Marty’s adventures are a variation of the grandfather paradox: what happens if you go back in time and kill your grandfather before your father is conceived? If you are successful, how is it possible that you’re alive to kill your grandfather in the first place?

A recent study at the University of Queensland may have the answer to this baffling paradox. In this study, the researchers prove mathematically that paradox-free time travel is possible, showing that the universe will self-correct to avoid inconsistencies. If this is true, then even if we could travel back in time, we would never be able to alter events to create a different future.

While these new findings are enlightening, there appears to be more evidence that, although time dilation can allow us to glimpse the future, we will never be able to visit the past. As the late Stephen Hawking said in his book Black Holes and Baby Universes , “The best evidence we have that time travel [into the past] is not possible, and never will be, is that we have not been invaded by hordes of tourists from the future.”

Banner image by Alex Lehner, CC BY 2.0

240 thoughts on “ Time travel is possible, but it’s a one-way ticket ”

How do I go about time travel? what do I need how do I get those required things?

Very large ring magnets and some mathematics and will to see it in reality.

How about a sphere magnet ship…

hoe about 3d time and hemi synch or portals augmented reality,power of suggestion..drugs pcp binural tones frequency amplitude .virtual computing ie.

I’m a time traveling tourist, Stephen Hawking was wrong.

Time is simply a measurement of space under the amount given its mass and the amount of light and dark in which governs its mass in a 4dimensional reality step outside of the force in which permenates its flow one would reside there would be no past present or future there be a fixed permance of a constant here and now and so ok then what is to come.

Very well explained article !!

But I think if physics says time travel can be possible then it’s definitely possible. Considering not to go back to your childhood and fix things but rather can go to the past but as invisible person to them. So that,

No actions by you would impact your future.

Regards, Kirankumar DR

Tell me more

Yes.. I wish I can do this too 🙂

We will understand it better, by and by…

I have a theory for warp speed, but nasa would have to put it to the test…check my Facebook

I am reading for this drive , i am ready , without think my life safe or not

@Ravi chandila English translation please?

Please someone help me I just want to send a message to myself in my past.,to get the love of my life, he never revealed to me his feelings now my life is ruined by the decision of my elders Please help me, it’s question of my life and death. Nazneen

Is time travel machine is their, if the time travel machine is true can it move to the past . To bring back my lost life

That’s the problem you know.. it is not there that’s why we aren’t able to travel time..and yes it it will be built then you will be able to do so…..

damn my life is also lost and broken but still no one can give a time machine for free

DO NOT change the future. That’s why people like you couldn’t go. One wrong person to ruin it for the rest of us

On the point of time reversal, it is evidently impossible. The Uncertainty Principle prohibits spacetime reversal. The Universe is unable to remember its past (as a consequence of the Uncertainty Principle), therefore the Universe cannot reorganise itself.

Can I have to go on my past with another time travel it is a possible when just tell me about one thing that can I have to go in my past one year

we dont need magnets.we need a strong gravitational force to warp spacetime allowing us to travel through with speed of sound or speed of light or faster.we need to learn how to control such force carefully or it could be lethal.gravity slows down time.but it can theoratically work both ways.if we can reverse the gravity’s natural reaction we could speed up a spacecraft faster than light(its all relative(and theoratical))

I WAS ACTUALLY JUST THINKING THE SAME THINFG BEFORE READING YOUR PIECE. VERY WELL EXPLAINED, AND IT DOES MAKE ALOT OF SENSE. WELL DONE.

oh and I forgot to add it can be the key to look into the universe and also travelling time(theoratical).speed and gravity are the key to the universe(theory not proved)

All you really need is a crystal diode with 16 sides, a large pain of glass, and a frequency transmitter near a bathtub full of ice cold water….if you reach the right frequency you can travel through time forward and reverse…

Magnetized metal(VCR Reading Head), to read time out of the Magnetosphere all around earth. The Magnetosphere kills 2 birds with one stone- it protects earth and it records human time:

Mystery solved and I will explain, I was in a coma 3 months and I experienced things, I traveled time forward and backward, it is not a one way ticket. Movies and songs are recorded on magnetic tape in a VCR tape Cartridge or Cassette tape,   Magnetic tape recording works by converting electrical signals into magnetic energy, which imprints a record of the signal onto a moving tape covered in magnetic particles.   3D life on earth(a movie), and the Magnetosphere all around earth coming from the core of earth(MAGNETIC ACTIVITY) without Atom Made Tape, is like a movie on magnetic Atom made tape in a VCR tape cartridge. Revolution and Rotation is the motor(VCR).

This is why people have those freaky Deji’vu feelings like they have lived this before, BECAUSE YOU HAVE, and how people can be psychic, and how there is Prophecy in the Bible. When a person dies, their Spirit- MIND(Thoughts, Feelings, Urges(Physical and mental personality)) breaks out of human body- a stopped heart is what releases the spirit from the human body. Then the Soul(Life) with the memory of your existence in it breaks out of spirit and goes back to your birthday with a erased memory, meanwhile your spirit goes back in time to when you were a teenager starting the mental puberty, maturity from that adult spirit you died with in last life.In that old movie Star Wars or maybe it was the Empire Strikes Back, there is a scene where Princess Laya plays like a 3D movie, that is EXACTLY how its of life on earth.

Mr Snow, I believe you as I have seen it too. As humans we have deep knowledge of things we cannot rationally explain but you have done a great job here.

I thought that Analogy would be a better and easier way to explain, or in a picture of the earth from far out in space with the atmosphere around it looks like a DVD disk and the earth being the center sticker but is in 3D.

Actually you are on to several things here. I have also had the infusion of knowledge that also had to do with comparing life to recorded movies and music. I know you were using it to explain your theory, but I do think there is something there, I always have. When you watch a movie you are seeing the past. Why can’t you somehow use a recording as a base to go back into? I agree with everything you said here, and it’s worth looking into.

Jeffrey, very interesting idea!! Could be something to that. As far as your coma experiences, I think there are things we just do not understand and are nearly impossible to explain. Perhaps time IS like a video tape, or a DVD? Magnetism is one of the forces of nature. I too have had some odd experiences that suggest that we are able to perceive things beyond our five known senses.

I think if you have had a near death experience, such as being in a coma, then you have experienced the powerful hallucinations provided by the chemical substance DMT which your body creates naturally in times of extreme trauma, but also found in most plants and used recreationally by some who are brave enough and into that kind of thing. Your theory is interesting, but completely unproven and as far as I know untested. If things were so simple, I’m sure many scientists would have already thought of such an idea and tested it.

How do I travel through time

Be alive and live life to the fullest is the best way to travel through time ! OR Befriend grey aliens../ They may hold the key to the sum of all knowledge in the universe..

Sounds good will it work

Really log vaps mil sakte hau h kya

Can you plz explain I didn’t get it

You dont first all you are not experienced in the field of the space time continum and you could you upset the already fragile and multitude of alternate realitys that have looping due irresponsible ones who somehow gotten the technology causing another altered time frame there are a disarray multiple reality which are looping in earths 4dimensonal time frame time traveling is not for a vacation or just to get a joy ride its a serious and complex reality not be joked about it is a real thing and certain individual have are upset the balance of earths original time zone note now the gaurdians of this region of milky way the galatic order of the light keepers Angelic gaurdians of the (names with held)are working over time ooh nice pun (over TIME) ha wow to restore Earth back to a original time continum

Who said I want a joy ride, my life is devastated even my kids are suffering, I want to commit suicide but can’t leave my kids back, Being captive for most of my life, if my life is changed nothing will be disturbed, only thing happens is 3 life’s will be saved. And more so over I don’t want to travel I just want to send a message to myself in my past plz on the date of 30th May 1996. My life is ruined plz help me, it was my dad,brother, sister who pushed me into the dungeon and my husband and his family took over the charge of torturing me. Nazneen

I want to go back in time and tell my 5 year old self to burn the creepy dolls that my mom bought cause there is demons in it at the same time I will kidnap and torture my dad right now go back in time and show the younger version of my dad show him what will happen to his future self if he don’t get rid of those possessed objects and keeps letting my mom buy those antiques I’m 18 now I’m single no girlfriend no friend alone nothing very depressed too and I try to remember the positive things that happened in my life which there aren’t many tho but the demons keep squeezing my memory brain and my mom keeps on making so much loud noise including her damn mouth I have attempted to burn the demonic dolls but I only burned them for a minute or two with gas cause I was worried I might accidentally set my whole neighborhood on fire but then my mom threw it all in the recycle instead of the trash so the demons just keep bothering me its driving me nuts he he.

Access to a Quantum Computer Network on the web would be a good start. A series of ChatBots and webhook sites strategically placed in not only space, but in time. A series of algorithms and I think information can be transferred backwards to ones self…

How do we know that there are no horde of tourists among ourselves?

How do we know we’re all not tourists?

We’re all time travelers. We all travel into the future daily. 1 second at a time. Lol…

Agreed! I had the same thought!

Excellent question

If is possible, I would like to go back to: January the 1st 1975 & relive the 70’s as I prefer that decade to the awful one I am facing now, Back then We had more police our streets & left our front doors open, Those days were far much more better .

https://3netra.co.in/61-2/

Please do comment on my blog post regarding time travel

how about you ask the flash to help you

I need the time travel so I’m fails so many times i love time travel i have to go fast and future so i have no idea im travel is a my dream so my dream solution plz say me i have time travel so please help me someone please…..

I think you are over reacting

When we look at the stars now it is what they looked like years ago so what if we go to the stars and look down?

You cant go to the stars. It will just take billions and billions of years to go even to the next nearest star than our Sun- proxima centuri. Sorry to say, but do you think that you will be alive all those years??

You can do that without going to the stars… our planet reflects light as well thus making it visible from other parts of the universe…. has the word “reflection” crossed your mind ? 😉

Contact me on my hangout I will help you [email protected]

bro just time travel its not that hard

Please help me to time travel, can I see myself when I go back in time like Harmaini sees herself in Harry potter?? Or can I send messages to myself I know the particular date when to send. It’s not the mistake I had done in my past but it was done by my father and brother who are safe, happy enjoying their lives,my life is totally ruined Please help me. Nazneen

I want to go back in time to save my wife .it was a bad mastake she died .that could be changed i need to go back and save her. Please help me.yours gordon sutcliffe

Would love to hear more how it’s possible, as I am really so desperate to go back in time. I lost my wife 6mons back because of COVID and I will do the impossible things to make it happen.

DMT Experience

what is that?

Dmt experience. Time travel, out of body and sometimes superhuman capabilities.

Jump into a black hole

We have to lose something(the past) to gain something(the future) in time travel.Time cannot be played with.Am I correct.

you need to have d e t e r m i n a t i o n

Time machine is possible

speeder than light LOL

speeder than light cuz if the light break it limits it will move backward in time

Don’t Just don’t disturb the past

I want to go back in time and see my dad. I miss him.

mee too raina I lost my father the day before you posted the comment 18th may, crap it hurts me so much. I would rather die to bring those moments back….

Everything is connected . Time isn’t real .

It is universe we travel to and not a time line in one universe

Ask trump….Mandela effect…. dmt 5th dimension

u need an X-WING starfighter and a lightsaber to fight the knights at past and a R2-B2 to track

The fact that no one has time travelled to the past is the proof that time travelling will NEVER exist.

Others have. Portals open most of the time. Example: Miami Fl. Magnetic Material gets bombarded by the sun. Which fractures and formed portals within that area. Ley lines can lead to the portals of travel within miami for just to start. One can laugh or wonder if. In my experience jumping for the better the word of it (Movie Jumper) can be done. You can either Teleport or Time Travel. Our sun open these portals everyday. The best time when Sun spots start to emerge. All that electrons traveling at light speed is enough to rupture our magnetic fields on Earth. You will return of course. Like water on a lake or an ocean time will corrects itself. Your inner clock is your ticket back home. With a little math,fourth dimensional thinking,a magnetic meter, the right location,history research and luck. You may get to expirence it. First clue….cold spots…it may not be a ghost.

Plz can you help me please help me you can save my life

I wish I could help you, I can sense your sufferings.

You need a bag of hyperlink modules to start, then nuclear beepbeep gatangas, when you have that come back here and I will tell you what you need next.

You need high voltage beepbeep gatangas and a large broonasic magnet of about 450 Gauss, come back here when you have these and I will tell you the rest.

you need an old fashioned police box

If you rotate the center of the earth in the opposite direction, then the whole earth can be moved back in time, on the other hand, if you move the center of the earth and change its position by separating it from the part of the earth, then you will be able to time correctly. Let’s reach the other side.

How I could time travel any time travel machines inverted

give audition in the flash series..

I think that to go back in time you’d to travel faster than the speed of light since time stops at the speed of light but if you wanted to go back to say mlk’s assassination you would need to go at least 10 times the speed of light

You don’t want to, the moment you wrote that message is a historical point in time.

When time travel is possible, you should d̵͔̮͉̣̯̳͌i̩͒̍̆͟ͅs͎̲̖͙̺ͬ̽̊͆͢r̖̹͆͂̚͘ê̛̫̪̱͇̘̩ͬg̖͉̤͚ͭͣ̊̌͜a̯̗͚̬͍̱̦͑͂͒͡ṟ̝ͦ͗͘d͋҉̪̖̥͔̟̟͚̻ ͎̬ͧ̔́i̧͚̫̻̇ͮͫ̆t̩̻͉̩̘̰̠̫̓̂̕ ̦̻̳̦̉͆̊̇̀i̴̗͍̞͙͇ͣ̈́mͦ̑ͦ̚͏͚̜̬̹̘̟̭m̱͕̻͇̮̠̰̼ͫ̌͆͡e̢͈̜̱ͩd̵̦͙͔̭̹̃̿̈̚ͅi̛̖̬͓͚̩̝̗ͯa̦͎̭̣̭̘͔͙̅̏́ṯ̴̟ͥ̀͗e̵͎̭͓̟͗ͨ̂͒l̼͕͕ͦͦ͜y̸͙̯̺̘͉ͣ,͈̻͙̭̺̘̞̑ͫ͜ ͔̗̣͒͜d̶͇͚͉̦̞̗͛̍o̞̮̻̲̜̠̒ͩ̈́̀ͅ ̲̙̦̮̺̉́͂̏̀ṋ̞͖̌͠o̬͕̯̩͓̮̫̝͛ͩ̐͛͜t̼̙̿͊͆̕ ̲͚̲̬̦̗̐̀m̢̹̜̭̠̬͗̆ͣą̲̺̻͈̹͎̈́̇̉͛ǩ̜̪̱̀e̜̳͔͉̣͓̓͗͘ ̉҉̲̞̘͈ͅc̴̦̣̝͇͈̙̋ͥ́o̫͇͇̘̻̠̹͎ͯ̀n̺̹̣̦̔̇̾͢t͚̹͚̙̞̪̗̺̄͂͜a̞̗̖̻̩͉̋͛̆͘c͙̙̎͘t̻̠̣͉̹̠̣̲̐ͧͩ̈́̕ ̶͕̗̬̿w͓̞͍̹̰͖͉ͦ͐͡i͎̞̾ͦ̃̈́̕t̜̺̖̭̍ͦ͞h͙̰̬̖͎̰͛̇ͮͫ͡ ͣͯ͏͕̻͚̹̺ā̱̙̝̦̤̼̥͡n̶͔̜ͥ͆̌̋y̷͓̻̺̺͉͇̻ͨọ̱͙̜̈́̉ͣ̔͟ņ̦̟͔̜̫̗̒ͬe̡͕̮̓͂̚ ̡͓̘͚̭̹͔̉͐͋̽t̖͍͚̝̬͈̝͌͋͘ͅẖ̗̖͚̼͔͕͆̓̾͜a͈̣͍͕͍̋ͦͩͭ͢t̖̪̤̳͎̱̏͡ ̛̻̠̼̬̓ͫl̶̞̤̣͔̗͔̂ͅö̹̞̦̖͚̫̜̱́ͯ͠o̧̯̱̪̓ͮ̋k͉͎̝̻̓ͧ̕s̤͈̪̍͟ ̤̞̳͔̝̪̟̹̔̂ͨ͜h̛̝̲̰̻͗̅̏̃u̜̙͐̇̈͝m̧̞̮̟̦̳̟̊a̸͓̺̲̼̜͊͛̐n̶̳̮̒.͇̻͚͓̳̺̜̱͋ͬ͗ͩ͢

It’s Close I can feel it

Yes it becomes a history but my life also in the past changes and the present also with it. The way I’m suffering from the pain and want to end my life I’m 100% sure at least sure no one around me is or was as hopeless and horrible as my hubby I’m devastated I really want to send a message to my past it may not start but it will definitely change. I was forced, not given any option, my father and brother gave me wrong information and had no concerns for me. It was just survival for me. I repent for not killing myself when I had time, but now if I have a chance why not. Now when I’m out of my marriage I come to know a guy then had feelings for me, was madly in love and wanted to ask for my hand, now I want to inform my self and change everything plz help me.

I too would like to go back in time. I just wish he lived a happy eternal life. I would just like to repeat to come back in 2020.

I heard from a guy in Idaho that time travel is possible. You’ll need to go online and purchase a pogo stick looking device and make sure not to forget the crystals.

I think u need a black-hole-proof spaceship, go to the centre, escape the black hole and viola! You are now in the past. If you can’t escape, then you’d travel to a time where that black hole didn’t exist.

Believe me you time travel! If not physically then you do mentally,like you through dreams.

Though they sale it online, it would not take the chance. It is as simple as beating the speed of light and having some system to send you to the time you want. Time however is not real, and were just traving universes. It will all be in the open in 2028 according to other travelers.

All you need base on how to travel to time is very simple but had to find firstly find a way to get to space through a space rocket secondly find a very perfect consifigration for traveling to tiTme then find a very fast rocket that could create a form of force reaction in space in order yo enable fast speed in space for the break through of non gravity in space and make sure that while doing all you activities is not far away from planet and not also to close to planet earth and make sure that you are with wristwatchs whose time is set disame then you can to the future

Man you can get all you need for too build a time machine in your local store man, man I sure wished I’d kept mine but it frightened the heck off me man, sometimes when I fart I find a grape in my pants

time travel is a fake, baseless and delusional idea. If you believe in that crap then tell us if we are living in the future or in the past. To travel backward the entire system has to return all along with nature and events, it won’t be for you alone except time travel only happens in the mind.

you would need to get about 1,000,000 pounds of silicon and then somehow conduct enough energy to make 500 cars run without an engine and then go to a nuqular power plant and somehow make a portal. but the whole world could go out of orbit if you do that so I wouldent sugest it.

Time machine is good and bad because,with the time machine you will know about your future which is not good.

Is time travel actually a real thing because if it is then I need it because I am trying to go back in time to fix all of my mistakes

So what if time travel is the reason that we now believe there are other realities in our own world.this could be that a Time traveler we could only go back and couldn’t come back, and on doing so if you do something to change the past in stead make a new reality.making other things are deferent and ours realty stays the same . sometimes reality gets mixed up make the mandela effect that we see today

Time in the future it is faster then now. The past is slower so you can travel . It is up to you. One way is to meditate. You can travel and see any body you want right now. You can fly faster then light. That is one way. You go to the future. To go to the past you sleep for a long time. Some time you go to the future or the past. Your heart well stop and your body gets cold. Sometimes you can control it sometimes you can’t.

but how do we know that is really true ? i mean i want to figure this out, i want to time travel, but how is it that simple ? so many people have been trying to figure this out for many years and its that simple ?

Yeah what if you get stuck in there what do you do than

You cant go there in the first place. Dont worry. With current technology, we will only end up messing some few microseconds. Highly doubtful, if we can end up getting the news of travelling hundreds of years in our lifetime.

wait what would happen if someone saw you while you where in past/future i’m curious

Time is an illusion based on perceived reality and is only relative to our limitations. Time isn’t what it seems and all things can’t be figured out

Im on a school computer looking this up and i found this article and scrolling trough it and ive not heard one statement here as good as yours bro

This is blowing my mind people, then I see the school boy on the post. Great stuff, whoever reads this is already capable of travelling through time. Think about all people who have posted on this thread, now think about who will read mine. Now think of those €opposite trolls $ who never ever bother posting on you tube thread etc. But ONE comment from one of the time travellers who wrote on this thread. So that opposite troll is me,I don’t normally post.however because of previous comments I’m posting here. And I love the DMT shit I loved that and lived that one out in real life,,,,another day.

So my point is ifOne or two threads have made me write this….then what will my post make others write , think…..then I could travel back and not write this…. then what. Love the conception of time how can u travel something that doesn’t YOU perceive to be time, like a train can only run on its train tracks, a car can only drive on a road etc It’s posibble I know it is. Sometimes when u have fun times moves swift but locked in jail it goes snail pace. U c me. I write letters to myself from past from future. Remember everything that happens in present becomes part the past. But the future is what you hold in your hands. Question is, now you know….what the f are u gonna do about it?.. 01/04 ==== 21

Hahahah only realised school boy is named BIG dick pissing myself laughing I gotta go pee. Respect certified

so not halal mode

True so were not traveling in time. It is just different universe (on what we call) different time, day, tears, etc.

You would be scared for life

you will desepear

Maybe it has happened before and we just don’t know that they’re from the future. If people in the future time traveled, the would know that it’s dangerous to mess with the past and would pretend to be part of the past.

I believe time travel is already possible, however we cannot fix past mistakes without altering future predicaments. Say we stop JFK’s assasination, that would completely change the future from that point forward to one none of us can know/guess or conclude the effects? Other time travel purposes go to the future I think that from now our world will die off before 2096 basdd on overpopulation, global warming & polution as such creating islands of plastic waste in our oceans. The best thing my opinion go back to the garden of Eden, kill that Serpent Satan before he tricks Eve into the forbidden fruit. Then let God raise, enlighten & teach us how to be humanly sustainable on his planet & I guarantee technology & smart phones? Ain’t no part of it!!

Time travel possible but one n only theory of Stephen hawking

How it is possible to jump in time …??

Many ways. The most used is creating a black hole which can be done in a few ways. 1) traveling forwards or backwords faster than the speed of light 2) been known during heavy lightning strikes. Each way is a fast movement that opens the black hole. It has been done by the Government since the 1980s though they claimed they never beet the speed of light until 2002. However, Time is a illusion and their for we are actually traveling different universe that are differnt than ours even if the difference is by 1 thing. Each universe may have (what we call) different time, days and years. And each time we change that time line we created a new one. It is belief as CERN has said they destroy 5 universe, that they can travel to them. Since 2012 it has seem we been shifting and is now belief they have possibly came together. The event is known as The Mandela Effect.

No one has the right theory in my thinking. Only a few things are wrong. It is universes with (what we call) different time, days and years we are traveling to and not time itself as it is a illusion. Their is no stop to how much we can do, or where we can go. No limit as such say.

There is no God. No magical serpent or Garden of Eden ever existed. Basing a scientific theory on archaic stories does no one any good.

You choose a hopeless eternity. I choose hope through the promise of salvation through Christ for those who believe. You see, I have child in heaven. Thankfully, have a hopeful reality that I can embrace. There is a God. Our known universe is only 14 or so billion years old… is it mathematically possible that random molecules out of the Big Bang mixed in just the right way from to form a complex cellular organism… with DNA… and result in humans and such diversity of life forms? It’s naive to accept this as a result of chance. Think about it. How is that remotely possible without a creator?

Hahaha. You make it seem as tho the big bang happened, and we just popped into existence? Naw it’s called evolution baby, we started out as microscopic organisms, seriously, when did you drop out of school? But that’s like saying a some guy writes a book to explain away natural phenomenons that they were to stupid (un-evolved) to grasp and the concept good and bad and the eternal damnation, And thus, the Bible, and boom, everyone now was made by God, hahaha. When you can prove he/she exists, and that the Bible was a autobiography, and not just some twisted piece of Fiction, that has no real basis in reality, and cannot be proved to be more that a work of Fiction. Rather than being used as the16th Century control tact, ‘be good or you’ll go to hell’. But I guess that’s what they mean when they say ignorance is bliss, (maybe if I was as ignorant as y’all believers I’d believe to). But I can’t see how a ‘GOD’ would ever ask one of its creations to kill another.. Genocide, Crusades, all the ethnic cleansing.. All In the name of God Almighty! Hahahahahhaaa. Aliens are more believable than this shit, and theirs no proof they exist either. Hahahahaha. Fug’n Bible thumpers. ‘Step out side your faith and see the world for what it really is, a complex organism, mad of gravity and dust, quite a unique specimen! And we, yes Bible bangers, this includes you, are destroying it like the bubonic plague.’. ‘The end is coming and it’s our fault’

Have you taken the time to read The Old Testament and the prophecies therein that came to be ?.

How do you explain that ?.

My last post should read GS not G

You have not had an encounter yet with God. Don’t be so certain on yuour theory of evolution. He came and shook my reality to it’s core. Made thing possibly that no one could ever explain.

What are you talking about? Ur so wrong and funny in every way.

BlissfullyInformed just told me his comment was all an April fools prank. He believes in Jesus and was just fooling.

Time travel is very much possible just as you decided to come existence in this century meaning one can decide to be in another time zone . life is all about numbers, you just have to work on numbers

I’m pretty sure ppl don’t decide to come into existence. If that were true I wouldn’t be replying to your comment.

Un like your other reply, I understand what you mean. Each timeline (or universe as some see it) can easily be traveled to at will. No different than traveling threw your time you want to visit.

Science has proven a few things from the Bible is true. God does exist. Christians are confused with time and what it says. For a example. God created the world, as science even belives it was God who created the big bang, yet the bang has happen itself creating the moon, planets and stars. Christians also fail to understand chapter 1 and 2 of gen. spoke of two different creations which can be why we see dinosaurs before humans as chapter 1 spoke of animals first and humans 2nd. Their also was different time than, as without the moon a full day is 6 hours. It would take 4 days back than to equal are 1 day. Time is lost and Christians are just confuse on that time. That does not proof their is no God. As they have already found the robes of Jesus and remains of Noah’s ark, it proves much did happen. The bible only has less than 50% of what was written.

Changing the past is impossible, because if we went back into the past, that means we were already there during the time you experienced it.

We all know how to get into time travel but how do we get out……..

You don’t need time travel – all you need is life. And what is life? Life is the evolution of the impossible into the inevitable over an infinite amount of time.

if it is shown that if something, such as a solution to a particular class of equations, were possible, then two mutually contradictory things would be true, such as a number being both even and odd. The contradiction implies that the original premise is impossible.

This is called proof by impossibility. Thus if some traveled back in time far enough to kill his grandfather, we have the contradiction and therefore it is impossible.

You could argue that he would be able to time travel, but not kill his grandfather. However almost anything a person does going back in time would cause the same contradiction, thererfore it is the traveling back in time that is impossible.

Actually, it probably is possible to travel back in time, however to do so, you would also have to travel so far in space that you cannot see anything that happened before your current time due to the speed of light, because this to could affect the future.

The reason I am here is that, i really want to go back the day when our matriculation exam was just finished. Everything around me is peaceful and happy. Currently, I am living in dire situation. People are dying outside on the streets. Smokes everywhere. Everything is in doom. Ah, yeah. I really miss my past. If you are reading this, you can judge me in anyways. I just want to live peacefully and happily.

You must live in Portland

I entirely know what you say and how you feel, Robin. I am totally convinced that future is no promise to offer a better place to live. World is becoming unnecessarily more complex and more horrible and more insecure. Therefore, travelling back in time to a point where things were still far away from such ordeals is what I aspire. But I think if it is possible to travel back in time without the possibility of carrying our lived experiences with us, it will be useless as we will be repeating the same mistakes over and over again. Now, this begs the questions “in what type of physique could we imagine ourselves back there if such time travel becomes possible? That is, becoming younger again in a physical regression (as I said this would be a torture without having learned from all these later years)? Or appearing at our desired times in our present physique and age? I believe the most ideal one would be if we appeared at our desired point in time at the same age that we were at that point of time with a good feeling of our later lived experiences.

Mam all u need to do is just run faster as much as u can or visit the black hole because in both condition time just slow it down ….

Time travel is simple. If you do happen to travel to the past you create a new time line not affecting the time line you left. In essence you going to the past is now your future. Even if you were able to return you may never know if you remained in your time-line or created a new one. So even if you changed something in your travels it would happen in the future not the past.

Sorry time traveling is not possible, there is no way you can go into the past or the future ‍♂️. You can only be in the time you are already in.

Incorrect. General relativity allows time travel into the future. You need a space ship that can travel extremely fast though, approaching the speed of light, or you need to get close to a supermassive black hole.

It is travel into the past that there is no known practical way to do, and is probably impossible.

So what happens when we Die? Where do we go? I want to go back in time so I can meet my childhood friends…

Simple question from a simple mind:

At what point, when a person says they are from the future, do we stop throwing them in the funny farm and actually start listening??

When they show actual proof. Not just some random prediction of the future.

I don’t believe that “glimpses into the future” could be possible. If it were so, we could glimpse blueprints of the future that we could bring back to the present and build before they were invented. My personal.beleif is in any time frame there is only one active time which is the present. The past no longer exists and the future hasn’t occurred yet, so there is no such thing as ‘time travel’ except for the frame we are in now.

First off time is not real we make time if you travel anywhere all you are doing is beating the Earth speed try this for a mathematical equation the Earth travels a thousand miles per hour you’re not beating human time that is your own equation the Earth travels a thousand miles per hour a space shuttle travel 17,000 mph you can beat time that you made so time is not real you are only beating the Earth speed if you go in a space shuttle and go around the earth 17,000 miles per hour the Earth only travels a thousand miles per hour plus it has all types of gravitational pull from the Moon Earth’s access on the til t you figure out the mathematical equation I cannot time travel is real if you can beat the Earth speed and we can it has nothing to do with its 12:00 it’s 1:00 that’s not real time is made up as a mathematical equation you can beat the Earth speed you can go back into the Earth’s time in a space shuttle but you’re not beating anything except the Earth’s speed think about that one time is not real at all all it is is a mathematical equation think about that one real long

What I’m trying to say is this a space shuttle travel 17,000 mph the Earth travels a thousand you beat it 16 times faster that’s all you did you’re not beating any time you’re not beating 1:00 you’re not beating 3:00 all you’re doing is beating the Earth’s time you can go in reverse around the Earth 17,000 mph okay you can go forward with the Earth’s centrifugal force 17,000 miles per hour you’re not beating anything you’re beating a mathematically equation that we we created astronauts been traveling time for instance for years and haven’t told us because of the space shuttle that does travel 17,000 mph it beats the Earth speed 16 times a boggles my mind you have the Earth access the moon gravitational pull but you can get in a space shuttle and travel 17,000 miles per hour and beat the Earth’s speed 17 times think about it

If any scientist or anybody can actually answer this question how do you set up this equation with the Earth spinning a thousand miles per hour you have the moon pulling gravity the Earth’s access on until I want to know tell me then wondering for a while this equation popped into my head about 2 years ago I’m not a math whiz or anything I just thought about it weird how the mind works I’m not into space or any space stuff at all I’m Samanthas boy friend John antos wrote this

I liked your post and the knowledge you given. I also written a post on Time Travel.

how would any of that stuff be true because e’*34+Em would stop all the forss of vissecs and how would we do it if you now what i mean??? also thanks for the scuff for my project

I would love it if I had a real life time machine here with me now which could take me to anytime I want, the past, present or future. If I had a time machine here with me now, I would go to the past in September 2004 when I was born and give myself to another family that is actually rich and not this horrible family that I have now.

that not nice

Close but not quite right scientists of the idiotic variety, yes, you don’t want people to travel back in time to mess with their own pasts, of course, but you say it’s impossible, but it’s not, and I’m always ignored with my crazed crackpot theories, so what’s the harm in telling the truth as I see it, while it could be possible to travel to the past, here in lies the problem with rewriting the future, while some believe it’s possible to travel back in time, but it’s very expensive and definitely a one-way trip to the future or to the past. Basically Doc Brown got the mechanism for time travel almost right but the energy out put needs to be quadrupled instead, allowing for the ‘physical item, being or vehicle’ to transport through time without killing the time traveler in question. Wormholes are unpredictable, until warp speed for spaceships are a thing, it is not possible for the space ships to achieve time travel, unless they want to enter a black hole, which I would not recommend. as you need warp speed to survive the emptiness of the black hole, without being ripped to shreds. Say for example, Back to the future 1, the timeline doesn’t erase it continues on without the ‘said time traveler’ in existence basically the Marty from Wimpy George’s timeline did time travel to the past and messed with his parent’s meeting so to speak, but never return to the same timeline therefore Marty A went known as a Missing Child in timeline A, while it continues on without him, however Marty A became Marty B/C, in the Successful George Timeline. So that is what I’m talking about. the timeline changes only for the time traveler themselves the ones who are left behind don’t experience a thing of timeline rewritten-ism, as it would never happen in the first place. The other thing is if you want to mess with your own childhood, to make a better life for the past self, the key thing to remember it’s not really you. It’s an alternative version of you, that you interfered with. creating a parallel timeline to it’s original, yet slightly different. Yes it would be awkward to raise yourself. but as long as you are staying in the past, nothing should happen until the age you traveled back in time, unless of course you touched your past self and suddenly de-aged and merged with your past self, is an option 1, option 2 the future self explodes spreading guts all over the place and therefore the past self, of you became a murderer of your future self, I am more inclined to believe option 1 as option 2 seems a little too out there. Basically you would have two memories one of the former timeline and one of the current different timeline. Still traveling through time is truly a one way trip and if you want to travel through time, you would need some time travel mechanism, the way you scientist talk is basically a dream version, or an OBE version (OUT-OF-BODY-EXPERIENCE) which is basically a vivid/lucid dream which is not true time travel, the true time travel is based on the BTTF Trilogy not the idiotic versions you preach about. I believe I’ve said enough.

Mystery solved and I will explain, I was in a coma 3 months and I experienced things, I traveled time forward and backward, it is not a one way ticket. Movies and songs are recorded on magnetic tape in a VCR tape Cartridge or Cassette tape, Magnetic tape recording works by converting electrical signals into magnetic energy, which imprints a record of the signal onto a moving tape covered in magnetic particles. 3D life on earth(a movie), and the Magnetosphere all around earth coming from the core of earth(MAGNETIC ACTIVITY) without Atom Made Tape, is like a movie on magnetic Atom made tape in a VCR tape cartridge. Revolution and Rotation is the motor(VCR).

This is why people have those freaky Deji’vu feelings like they have lived this before, BECAUSE YOU HAVE, and how people can be psychic, and how there is Prophecy in the Bible. When a person dies, their Spirit- MIND(Thoughts, Feelings, Urges(Physical and mental personality)) breaks out of human body- a stopped heart is what releases the spirit from the human body. Then the Soul(Life) with the memory of your existence in it breaks out of spirit and goes back to your birthday with a erased memory, meanwhile your spirit goes back in time to when you were a teenager starting the mental puberty, maturity from that adult spirit you died with in last life.In that old movie Star Wars or maybe it was the Empire Strikes Back, there is a scene where Princess Laya plays like a 3D movie, that is EXACTLY how its of life on earth.

If only wish I could undo everything what I’ve done wrong in the past, I’d be more happier

And that my friend is absolutely what you do not or would not know. Everyone focuses on what they don’t or haven’t had rather than what positives they do have around them. To change the ingredients of a past life only changes the flavour you have in this life, it does not make you happier.

No, travel to the future is not possible. Like, future is unpredictable and always have been so give up on that field

Already has been, and has been proven.

Time travel is not so possible for every one , but there are already time travelers on earth #@*

Who are these time travelers?

Depends if it is the Governments (they done it since the 80s), or if it was a Accidental travel, or a simple us creating our own machine. Either way, one can easily find storys, and other evidence with a good research. I have a website that shows the effects of change cause by time travel.

They are out their (done by the government since the 80s) but the future is open with time travel (told its open since 2028) so they travel back much.

Time travel 101-

Create a closed loop circuit around a full metal structure, hermetically seal it and bring O2, Use two tesla coils to create north and south poles. (Artificial Magneto sphere.) Make sure to pain the outside in lead to prevent any cosmic rays from penetrating the materials on the inside. (Radiation = bad). Connect a ball made of w/e with wires that alternate the current from the coils to w/e panel on the outside of the structure to make it move via inductive magnetic / electric Lorentzo (Lorentzo = ExMfield = Velocity. = Antigravity) Create Antigravity by using forces from the inside reactor. (Pressurized Mercury, and Tesla Turbine.) Then Move 10-100x faster than light depending on the charged field, Friction will be added to the electric field instead of the craft allowing the G-forces not to crush you inside. The field will take the pressures of outer space, The temperature of space will allow for super conductivity of the structure.

Eventually you will arrive in the future, if you stay in one place. but account for the movement of earth in your travel log. To see outside you will need a monitor / camera system, as any leaks through a viewing area will cause death by radiation from the cosmic rays from the field you have created.

The O2 can be used as a backup generator, through air pressure and the tesla turbine.

There are many different ways to make wormholes, but the curvature of space is really hard to calculate to send a machine far out to the end and create a link with the machine that wants to travel there. And leaving one behind to get back.

If you can imagine it, it can be done. You just need the knowledge of not dying to complete it.

U.S.S. Tourist, You’re a time traveler or just insanely smart.

You don’t need to go the speed of light. Human Time is recorded in the magnetospere as a movie is record, ed on magnet VCR Tape or a song on a record. A VCR or record does not have to go light speed to retrieve the recorded info. All of life is recorded in 3D by our Magnetosphere. My Analogy is imagine a VCR tape cartridge being the earth, imagine life on earth being the movie but in 3D with out adom made tape, imagine Rotation and Revolution of Earth being the VCR putting all in to motion- playing. That is how its done, the magnetosphere kills two birds with one stone, it protects earth and records time, human time is in a magnetic bubble that is why the Bible refers our time is different from gods time and this is how God the maker(PLANET OF UNITED SUPREME BEINGS) can flip through our time to know everything. By the way long before life on earth, he built the original 7 wonders of world(Pyramids) to Pump the Seven gasses into the atmosphere of this planet found in the goldilocks zone, so Life can live on it, and that life of all types is his technological cyborgs that grow and multiply on earth also he seeded it with plant, trees, sea creature and things that fly,. Anyway that above is how time is recorded.

Until recently, I thought my neighbor was a crackpot until he actually invented a time machine. He utilized an ordinary closet, and showed me the sophisticated (to me) instrumentation he had installed. I was very skeptical at first, until he offered a small demonstration and entered the time coordinates and energized his invention. To my amazement, when I opened the door, the clock on the wall was 30 minutes later than when we stepped into the machine. OMG!!! Destroy this thing before it destroys us!!!.

So happy to have my husband back after 6 months of separation. get any kind of relationship/marriage help you want from….Robinsonbuckler11 @gmail com………………………

I find it odd that people say time travel isn’t possible yet… If time travel is possible, it has always existed. Meaning, there is not past present it future, only our perception of time. What we know as past present and future have always been occurring simultaneously, so travel was invited the moment the universe wss formed. Dinosaurs are roaming the earth right now, and forever. A version of me is typing this and has always been typing this, within this perceived moment of “time” and time travel has always happened, whether or not we exist in that reality at the right “time” to observe time travel is the only question.

I find it odd that people say time travel isn’t possible yet… If time travel is possible, it has always existed. Meaning, there is no past present or future, only our perception of time. What we know as past present and future have always been occurring simultaneously, so travel was invited the moment the universe was formed. Dinosaurs are roaming the earth right now, and forever. A version of me is typing this has always been typing this, within this perceived moment of “time” and time travel has always happened, whether or not we exist in that reality at the right “time” to observe time travel is the only question.

Their had to be one point however, when it was created and started, and for that, there was nothing but the current time. Once it was created, than we had a pass, present and future to which we can go back to millions of years to see Adam and Eve with the dinosaurs or go millions of years in the future. However, given the events that changes, each time a new time line has been created. We also have destroyed the planet and repopulated many times in the last million years. Each event changed, or something we do different (without traveling) enters a new universe where some things may be different or the same. Today are universe are shifting a lot.

To be fair, even if it is a one way trip into the past, that doesn’t stop machines going back. We could send a machine back and order it to do anything we want and then tell it to meet us at a certain time in the future. We send it back, then go straight to the meeting point we agreed and then we’ll be able to prove if it worked or not.

I’m a girl who has read a book about seeing future through a box. So is it actually possible?

Time travel has been done on purpose by the Government since the late 1980s. From research, the mostly use kids, or future Presidents. Their are some cases where people have been struck by lightning or came across some tragically event that cause them to leave their timeline either forward or behind in time. The Mandela Effect is the current cause of how things go wrong when time travel is not done right. Click on my name to see the website.

Even as traveling to a location as a future or pass date is possible as what people here mean. However, as you said, it is numbers. Time is a illusion and we do not travel threw time, just universe that are different than ours. What we call time dates and months is what changes each universe. We are all from different universes today as they came together. The mandela effect is a fine example.

thx to eleon wont we soon be able to digitize our conscious being, then accelerate that data pass the speed of light some how then download it into some android or something…..i dunno…..just a thought

I want to go to my elementary school again. Someone help me out, I know its Idiotic but stil.. I am not good at science. As far I understood, 1) we can trace through time if we travel fast than speed of light.. I think memory os the only thing that is faster than light, Yeah I can go to Paris within 1 sec in my memory but yeah its illustion, i want in real 2) Through Blackhole – I think its Bermuda triangle

if you travel back in time you will still be your age now. That is how it worked with others. No one gets younger otherwise traveling to far back would kill you. No school would let you return to school as a adult so not possible.

Plz help me I just want to send a message to myself in my past and save my self from a beast plz help Nazneen

Would love to experience many moments in life again for the first time again!

I think that time traveling should be left alone, for the sake of humanity. There are some things we’re not ready for yet.

Well stephen hawking may be wrong. I mean, the study proved that the universe self corrects itself to prevent inaccuracies. So maybe tourists from past do visit us but we don’t remember them as the universe alters our memory. If you guys have read about Butterfly Effect, a simple mistake today may grow through years to become a giant disaster in future so if you think of it, oncoming tourists from future may cause giant inaccuracies. Imagine this, You have travelled to past. You brought two cakes for yourself, so you pay the shopkeeper 20$. The shopkeeper invests the 20$ in stocks, strikes gold there and becomes a rich businessman.His daughter goes to Cambridge and marries someone else than the person she was supposed to marry according to time. Can you imagine the magnitude of inaccuracy after 100 years? Therefore, whatever the tourists from future do, is corrected by the universe and we don’t remember it. Creepy, but food for thought.It also adds a special meaning to the word ‘Fate’.

How much wacky terbacky (i.e. weed) you be smokin’ JOE JOE?

Hmmmm…. As brilliant of a mind as Stephen Hawkins was, how is he so sure that he would even recognize hordes of tourists from the future? Almost everyone is aware of the warning of the Butterfly Effect. So I’m sure any future visitors Intelligent enough for Past-Time travel would be amply attuned to this.

Most future people coming to the pass (our time) seems careless and not intelligent. Most are taking FBI lie detector test and telling us what is happening in the future. That is a bad idea, because if you tell us (example) who is the next President, and the Government does not like the person they than can change that event to let someone else in (as seen in 2020) One should never acknowledge who he or she is or why they are their. Most traveling is to get knowing of the pass or to pick up certain things. Since are pass is changing, events are changing and are timelines are messed up, someone made a mistake. The Mandela Effect is a fine example.

Wow that’s great plz help me go to my past plz,I can’t do it by my own at least help me send a msg to myself in my past Nazneen

I think it is possible, but time traveling is really just changing universe created by different time lines. Our whole solar system is in a whole different place now and Earth is much smaller in this universe from the one I grew up end. Someone has already changed the timeline.

Roads? Where we’re going, you don’t need roads!

Youre wrong about your measurement of speed for traveling, in order for time to slow down, with inside an object compared to outside. Scientists proved that time with inside an object at an excelorated speed actually appeared to have slown down during the duration of time for the test. The speed was far less then the terminal speed of a rocket for NASA at 256,000 kms p/h.

In to the volicity of space. Generating a vacuum of space, could be no different the the actual transport of matter over frequency where in fact matter can be carried by sound. It is believed that an alien civilization harnessed this energy in the form of bolisks that where believed to carry the same properities and in consideration of harmonic resinance, the simularities could be used in order to carry large weight. In accordance with a documentry on theoretical science.

However the properties, present the fact that a working property controdicts your counter intuative theory of gravitational deceloration of matter to colide within itself to absorb all things into non existance as to the transfer of matter into energy, rather then your idiolisms of transfer between dimentional space to another destination that is not linked or the transfer between time that isnt, either.

However to reproduce the fabric of time within space in a practical measurement as I have mentioned, would put an end to all the lunacy of an unmeasureable field, which people fail to identify. Like running into a glass window. Only to not know what forcefield is present.

Time travel into the past can be achieved simply going faster than the speed of light.

The closer you get to the speed of light the slower time goes

If you reach the speed of light time stops

If you go faster than the speed of light it starts to reverse

Why does no one seem to know this?

Christopher Reeves did this in Superman 3 brah.

Any time travel, pass and future, is by going faster than the speed of light. It is said by reversing that that you can go back in time. However, I assume since the Government has done this since the 80s they have better ways (maybe tying in a date) and not having to go to a unknown date.

I want to send a message to myself in the past on a particular date plz can you help me, this means a lot lot lot to me,plz help me Nazneen

Why don’t we drop the declaratory statements that it “is or isn’t possible!” Until someone actually does so. Just say “maybe”.

People have and their are records both to the pass and future. The Government has done it since the 80s as part of the “star wars project” and are much better at it today. This explains the black holes in the sky of 2019, and the CERN destroying 5 parallel universes in 2013. We also see changes because of time travel events changing time. The Mandela Effect is a find example.

I want to send a msg to myself and my family in the past ,is it possible plz help me my life will be saved one who helps me saves me and my kids from a pack of beasts,

The worst idea ever. We all want to do this and where does it stop. A lottery win does not sound bad if you knew the actual location, time and place. After a while though, would you not want to write that hit song, become the author of the Harry Potter books, stop 9/11? The idea of giving your pass self (a time time travel was not proven) information of the future could change things in a major way. This would cause one small thing to change creating many others to change. This has already happen in simple ways of the The Berenstein Bears changing to The Berenstain Bears. This is a small event but this event “The Mandela Effect” now has over 3,000 changes.

What if you decided to give your pass self information about a lottery ticket that would be a winner, bought late at night and he was hit by a car on the way to get it. Changes the whole future. However, If detailed right, done right, with no large changes, it may not effect much, but to know your being given info from yourself in a future time (when that was not known much or provrn back than) You would either assume it is a joke or you gone crazy.

I don’t want to win a lottery, my decision about my career and studying was right but my family and their cruelty has put me into this worst condition I just want to go back complete my studies and live a life like a human not like a animal or slave,help me plz Nazneen

Can someone take me to 2013? i can pay later to all of you in bitcoins so its a win win and you dont need to do anything, just wait

LOL but still complicating on my side

You travel in your dreams where time and space colloids ..That’s y sometimes the dream which you dreamt might be a 10 mins reel time but you felt dreaming whole time like 6 to 8hrs .. Probably even traveling to parallel universe

I agree. Dreams as we know it is not a simple sleep. The part of the brain we do not use while awake, we use at night. This is the phenomenon part of the brain that can do thing we feel a human can not do. We of course use less than 30% of our brain. By the use of 100% of the brain we would use both sides and be able to do common things such as read thoughts, move things without touching them etc. The idea of using this side of the brain, would be the theory we can leave our bodies and visit different universe, see what could of happen shall we done something different, and even see future events. This may be why we notice different memories to some things as we could of held some from another reality.

It would be very weird, however, if we were trapped in that universe, or another body and fail to return to ours. Is that how people die in their sleep?

i just fell like going to late 70’s, where i can see majority of family.. i am willing to trade life for it…..

Time travel to the pass is just as common as the future. However, as both has been done it is NOT travel threw time. Time is a illusion we created. We are actually traveling threw different universe with (what we call) different time, dates, years, etc. The Mandela Effect is a find example how traveling threw different reality’s change the time lines.

As a add on to the above, Time travel is not a theory, has been proven, and has been done by the Government since the 1980s. Their is many residue in our history to even show some time travel storys to be real.

Where can one get a reverse watch, is it really possible to go back in past with its help, is it sooo easy ,plz help me ??????? Nazneen

US20060073976A1- search this patent number,this describes the process for time travelling,I really don’t think magnetic energy will work,maybe heat focused on a specific point could expand the fabric of space and make a hole in it.even then I will the hole take you to another time.it would be one thing to time travel but selecting a point in time would be impossible.you could only travel to the time you device was built?

Is there a watch which back travels in time or reverse time watch? Is it true? How to get one? But with that how can I send a message to myself in my past, plz help Nazneen

I don’t believe such a watch exist and their are plenty of smart minds with huge funds trying to travel.right now there are only theories.

Thank you very much for your response. I just want to send a message to myself in my past. Nothing much will be changed but 3 literally dying devastating lives will be saved. We are suffering for the mistakes and egoistic arrogance of others so if possible plz help me

Traveling back in time isn’t just a when problem, it’s a *where* problem. Where was the place you’re standing right now a thousand years ago, or a thousandth of a second ago? There is no useful answer to those questions, so there’s nowhere to travel back in time to.

Traveling forward in time? You’re doing it now.

when you step through a door is time lost when you come back through? lets say you return days Later how much time did you loose. what exactly is Time,.? is dialation a safe way to return ,. a Blackhole will assist you in in travel, the question is will you arrive safe,.

Traveling back in time is impossible. 2 reasons why that are never taken into account.

A) The stuff you are made of ( subatomic material) is being used by something else. It I not like you are a facsimile of the already existing material. What you are made of is exactly the same existing material. The problem is exact stuff can not exist in 2 different places in the same point in time. You will either : Decompile or fall out of phase with the universe. Both bad outcomes for the time traveler.

B) Lets look at it from logical commonsense. You have a bar of gold . You intend to send the bar back 1 second in time. Now you have 2 bars of gold . You send those 2 bars back one second . You have 4 bars …… do that 50 times . You have over 900 trillion bars of gold. All made of the exact subatomic particles. The more the bars back the more the existing mass of the universe increase. What are the consequences of changing the mass of the universe . Hence the paradox . Information can not be destroyed., It also can not be created.

At least this is the way my brain perceives going back in time.

Time is a function of change. None of the 4 forces The strong force , The weak force , Electromagnetism and Gravity can not work without time.

I will figure out time travel one day but only for the past.

I wish I could travel back to 18th of June to save my mom.

Is time travel really a one way ticket? Theoretically, if you can go one way, you should be able to go back.

Time is not one way. It’s consequences are however irreparable given certain circumstances and is not something that should be taken lightly or thought of in a manner of disregard. I’ve only very recently decided to take to your social platforms regarding space and time.

You can try finding me on Instagram. I’m not familiar with these platforms to better direct you there. My Instagram name is johnrvh

On Twitter it seems to be @_JohnRvH

If I go forward I will have to pay extra bills and taxes. I don’t think I can afford it.

You’re the first person I’ve come across in this timeline that has a sense of humor. Thankfully, going forward is not possible if that future hasn’t been created yet.

timetraval is no joke if its created the whole universe could go out of orbit.

Cauchy problem converging to non minimal terraces as t → +∞

Stephen Hawking may he rest in peace a genius but not all knowing. As far as he knows we haven’t been flocked by tourists, in the same maybe these UFO sightings are actually time travelers from the future coming to the past to view how we really lived why things really happened the way they did, etc. To limit the imagination of possible and impossible is wrong then you create fantasy. And we have learned from history that there is truth in fantasy. I.e. the different mythos of the different ancient cultures from around the world including those of the Norse. Improbable and probable should be more appropriate. It’s possible because it can be imagined improbable die to the right math or this or that not existing or matching up. I also believe that if time travel to the past were possible that the changing of something in the past would create a new timeline running current with your timeline at which will inevitably collide and will cause the collapse of the universe at which point a new universe will be born.

so i think the speed of light is only relative to deciding a point of destination -initially- as specific gravity of destination needs to be ascertained to calculate the frequency needed to run an alcubierre-white engine to bend space correctly to cross space ‘quickly’, the point of reference may well be jupiter in our solar system for the fact of the moons that orbit it, i surmise that by using a ‘dead end ‘ equation that usually puts notable mathematicians into the outer regions by trying to solve it may actually be the key as calculations end in a loop of 4-2-1 ie 3N+1; this process of calculation creates a sine wave over time/distance relative to specific gravity of chosen destination – as time is determined by gravity therefore if the speed of light to a destination can be used to ascertain the specific gravity of a ‘body’ to visit ie a star or sun due to receivable resonant frequencies emitted by the body, then the constrictions of the speed of light do not exist other than to give a constant, by using the 3N+1 method of calculation ,once the speed of light and returning resonant frequencies of a destination are determined the calculation can be extrapolated to match the distance giving the end point -in doing this the sine wave required can be ascertained and be condensed to create a wormhole and allow the alcubierre-white engine to ‘bend or distort space enough so that the bubble you are in matches the required specific gravity of the destination – the frequency of the body nearest to the destination point should be used and resonated inside the bubble to create synchronicity of frequency and cause attraction i also believe that travelling through space require the ability to see things from different perspectives and it requires the ability to navigate through a series of what may be described as “Aims Windows” where your point of view needs to change inherently with a given position at a given point in the galaxy

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Is Time Travel Possible?

We all travel in time! We travel one year in time between birthdays, for example. And we are all traveling in time at approximately the same speed: 1 second per second.

We typically experience time at one second per second. Credit: NASA/JPL-Caltech

NASA's space telescopes also give us a way to look back in time. Telescopes help us see stars and galaxies that are very far away . It takes a long time for the light from faraway galaxies to reach us. So, when we look into the sky with a telescope, we are seeing what those stars and galaxies looked like a very long time ago.

However, when we think of the phrase "time travel," we are usually thinking of traveling faster than 1 second per second. That kind of time travel sounds like something you'd only see in movies or science fiction books. Could it be real? Science says yes!

This image from the Hubble Space Telescope shows galaxies that are very far away as they existed a very long time ago. Credit: NASA, ESA and R. Thompson (Univ. Arizona)

How do we know that time travel is possible?

More than 100 years ago, a famous scientist named Albert Einstein came up with an idea about how time works. He called it relativity. This theory says that time and space are linked together. Einstein also said our universe has a speed limit: nothing can travel faster than the speed of light (186,000 miles per second).

Einstein's theory of relativity says that space and time are linked together. Credit: NASA/JPL-Caltech

What does this mean for time travel? Well, according to this theory, the faster you travel, the slower you experience time. Scientists have done some experiments to show that this is true.

For example, there was an experiment that used two clocks set to the exact same time. One clock stayed on Earth, while the other flew in an airplane (going in the same direction Earth rotates).

After the airplane flew around the world, scientists compared the two clocks. The clock on the fast-moving airplane was slightly behind the clock on the ground. So, the clock on the airplane was traveling slightly slower in time than 1 second per second.

Credit: NASA/JPL-Caltech

Can we use time travel in everyday life?

We can't use a time machine to travel hundreds of years into the past or future. That kind of time travel only happens in books and movies. But the math of time travel does affect the things we use every day.

For example, we use GPS satellites to help us figure out how to get to new places. (Check out our video about how GPS satellites work .) NASA scientists also use a high-accuracy version of GPS to keep track of where satellites are in space. But did you know that GPS relies on time-travel calculations to help you get around town?

GPS satellites orbit around Earth very quickly at about 8,700 miles (14,000 kilometers) per hour. This slows down GPS satellite clocks by a small fraction of a second (similar to the airplane example above).

GPS satellites orbit around Earth at about 8,700 miles (14,000 kilometers) per hour. Credit: GPS.gov

However, the satellites are also orbiting Earth about 12,550 miles (20,200 km) above the surface. This actually speeds up GPS satellite clocks by a slighter larger fraction of a second.

Here's how: Einstein's theory also says that gravity curves space and time, causing the passage of time to slow down. High up where the satellites orbit, Earth's gravity is much weaker. This causes the clocks on GPS satellites to run faster than clocks on the ground.

The combined result is that the clocks on GPS satellites experience time at a rate slightly faster than 1 second per second. Luckily, scientists can use math to correct these differences in time.

If scientists didn't correct the GPS clocks, there would be big problems. GPS satellites wouldn't be able to correctly calculate their position or yours. The errors would add up to a few miles each day, which is a big deal. GPS maps might think your home is nowhere near where it actually is!

In Summary:

Yes, time travel is indeed a real thing. But it's not quite what you've probably seen in the movies. Under certain conditions, it is possible to experience time passing at a different rate than 1 second per second. And there are important reasons why we need to understand this real-world form of time travel.

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What we think we know about time travel

Credit: Universal Pictures

It's strange living in a post- Back to the Future world. Not only have we surpassed the date of the future portrayed in Back to the Future Part II , we're also 30 years removed from the release of the third and final film , which premiered in theaters on May 25, 1990.

Over the course of three movies, we saw Marty McFly and Doc Brown travel throughout recent human history and the near future, going as far back as the Wild West and as far forward as the unimaginably distant 2015. The Back to the Future films are fanciful science fiction comedies, not meant to be taken seriously. The science is accurate only insofar as it serves to tell a good story.

Still, is it possible to go forward and see our mistakes before they happen? Is it possible to go back and fix things that are already in our past? Here's what we know — or think we know — about time travel.

WHAT IS TIME?

Time: the great equalizer. Time doesn't care about you at all. You can't gain more of it, and you can't give it away. Irrespective of any other thing about you, each of us lives through the same 24 hours every day. Right?

Not exactly.

Time is mushy. It's variable. Some have called it wibbly-wobbly. And it turns out, you can manipulate it if you try hard enough, thanks to Einstein.

We evolved in a sort of medium environment. Human beings are medium-sized objects, somewhere between the very small (quarks, electrons, atoms, and the like) and the very large (planets, stars, and supermassive black holes). And we operate at medium speeds, faster than the slow movements of tectonic plates, but slower than the speed of light.

Physics operates in pretty predictable ways in the world we inhabit. Gravity impacts objects in ways we can accurately measure; comets orbit and return at regular intervals. We know when solar eclipses will happen because the cosmic dance of the sun and moon follows along a known path. Time ticks onward in one direction and at a consistent rate. All is as it should be, all is according to plan.

Outside of our medium-sized world, however, things can get weird.

Physics breaks down when you get too small, or too massive. Gravity does things we can't quite work out, quantum effects find their way in. Things cease to play by the rules as we know them. Likewise, the faster we accelerate beyond our medium speed, the weirder time gets.

Special relativity concluded that the speed of light is consistent for all observers. Photons moving through a vacuum travel at a staggering 186,282 miles per second.

That speed is impressive all on its own. It's fast enough that the time delay between when light hits an object, bounces off, and enters our eyes is so short as to not be noticed. Which is good, especially for our ancient ancestors. It would have been difficult to evade predators if we were already half-swallowed by the time we noticed them.

The speed of light, though, becomes even more impressive and bizarre, because of the way it remains constant no matter the position or speed of the observer. Let's break down what that means. The actual speed of any given object is a combination of its personal speed, combined with the speed of any other objects acting upon it.

For instance, let's suppose you're reading this while sitting down. Your personal speed is zero. You aren't moving at all, relative to any objects you're in contact with. Easy enough. But maybe you're on a train on your way to work, and that train is traveling at 75 miles per hour.

Your speed then becomes the combined speed of you and the speed of the train. Let's go further. The train is traveling at 75 miles per hour relative to the Earth, but the Earth is traveling at 67,000 miles per hour around the Sun. Furthermore, the Sun is traveling at 514,000 miles per hour around the center of our galaxy.

Assuming the train, the Earth, and the Sun are all traveling in the same direction, your total speed is actually 581,075 miles per hour.

That doesn't even take into account the speed of the galaxy through space, but you get the point. To someone sitting on the train with you, our speed is zero. Your speed is different to an observer standing on the ground outside the train, it's different to someone observing from the Sun, or from the center of the galaxy. The position of the observer matters, it changes the outcome.

Speeds compound, that's the way things work in the Medium world. Not so with light.

Replace the train traveler with light and everything we expect about compounding speeds goes out the window. The apparent speed of light remains the same, 186,282 miles per second, regardless of the position or relative speed of the observer. Light gets no faster and no slower.

Special Relativity suggests an elegant, if counterintuitive, solution to this problem. As objects increase in speed, time moves more slowly. Changing the length of each tick of the clock allows the speed of light to remain consistent no matter how fast you're traveling in respect to it.

When Special Relativity was published, these ideas were just numbers on a page, but they've been confirmed by observation and experimentation. In fact, engineers have to account for time dilation when designing satellites.

Because they are orbiting at speeds much faster than we're accustomed to on the ground, a satellite's internal clocks will run more slowly. The difference is very small, but can stack up over time. Since satellites often need to have accurate timekeeping, this time dilation has to be accounted and corrected for.

It gets even more complicated because of gravity.

Gravity bends spacetime and, since GPS satellites orbit so far away from the surface of the Earth, they feel the effects of gravity less than we do, which has the opposite effect of causing the clocks to tick more quickly. All told, GPS satellites in orbit would drift 38 microseconds into the future every day if we didn't account for relativity.

It's a small amount, it would take about 72 years for their clocks to drift ahead of ours by one second, but it's enough to wreak havoc with GPS services, pretty quickly.

Besides, the synchronicity of our clocks isn't the important bit. What's important is the reality that those satellites are actually time-traveling at a rate of one second every 72 years. The effect is slow, but that's only because the fraction of the speed of light at which their traveling is small.

Time isn't static. It's personal. We aren't all experiencing the passage of time in the same way or at the same rate. Every time you get in a car, a train, or a plane, every time you go for a jog or even stagger to the bathroom in the middle of the night, you're altering the way you travel through time.

GRAVITY AND SPEED

Now that we know we can alter our relationship to time, by altering our speed or by manipulating gravity, how can we use that to our advantage and travel to distant temporal locales?

Speed is probably our best bet right now.

Considering the timescale of human existence, we've made incredible strides in increasing our maximum speed over the last several decades. It was once believed we would never break the sound barrier; that was accomplished by Chuck Yeager in 1947, a little more than 70 years ago.

That was the first time a human being traveled faster than 343 meters per second. That's about ten-thousandth of a percent of the speed of light. Pretty fast by human standards — very slow on the cosmic scale.

A little more than a decade later, Neil Armstrong, Buzz Aldrin, and Michael Collins blasted off in a rocket, headed for the Moon. Their top speed was 25,000 miles per hour, more than 32 times faster than Yeager. Still, the crew of Apollo 11 was traveling at only 6.94 miles per second, roughly 0.0037 percent of the speed of light.

Getting closer, some of those zeroes are falling off. Still, it's a long way away.

That's about where we top off, for now. At least for crewed vehicles. We have created faster spacecraft.

The Parker Solar Probe, launched in 2018, was sent on a mission to study the Sun's corona. It approached to within 18.7 million kilometers, granting it the honor of closest approach of any artificial object.

At its fastest, it was traveling 430,000 miles per hour, or, 119.4 miles per second. That gets us to 0.064 of the speed of light.

We'd have to get moving more than 15 times faster than the fastest craft we've ever built to hit one percent the speed of light.

Even at those speeds, we'd notice a difference in relative time of about 26 minutes over the course of a year.

If you really want to time-travel in a significant way, you have to get much faster.

At 90 percent of the speed of light (167,653.8 miles per second), a craft traveling for 10 years according to their own clock would arrive back on Earth to discover that nearly 23 years had passed.

At 99.99 percent of the speed of light, a craft traveling for one year would come back to a world that had aged more than 70 years in their absence.

At 99.99999 percent of the speed of light, for a year, more than 2000 years would pass on Earth.

The point is, the closer you get to the speed of light, the more time dilation is experienced.

Achieving those speeds, however, is incredibly unlikely and probably impossible. Physics conspires against us in this regard. Any object with mass increases in mass as it approaches the speed of light . In effect, it gets heavier, which requires more fuel to continue to accelerate. Eventually, you reach an infinite mass and infinite energy requirement. It's like pushing a stone up a continuously inclining hill. It gets harder the closer you get to the top.

Which is too bad, because nearing the speed of light would allow us to travel forward in time, with minimal investment of personal time. And, if we could break the light speed barrier, all bets are off. The math suggests that it might allow us to violate causality and travel back.

If speed isn't the answer, then what about gravity?

Since we know space and time are intimately tied together, and that gravity impacts both (see GPS satellites, above) sufficiently warping space-time would create closed time loops. At least according to research by theoretical physicist Amos Ori at the Technion-Israel Institute of Technology in Haifa.

Ori suggests using focused gravitational fields to bend spacetime into a donut-shaped vacuum.

There is one speed bump: A traveler would only be able to go to time-destinations that occurred after the creation of the donut. No going back to see the dinosaurs or save your mom from marrying the wrong person. No preventing things that have already happened before the creation of the machine. Additionally, the gravitational fields required are on the order of those created by black holes, far beyond what we're capable of creating or controlling.

For now, time travel is outside of our capability, at least as it's portrayed in movies. If you really want to evade the ticking of the clock, your best bet is to run as fast as you can.

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Can we time travel? A theoretical physicist provides some answers

Emeritus professor, Physics, Carleton University

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Peter Watson received funding from NSERC. He is affiliated with Carleton University and a member of the Canadian Association of Physicists.

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Time travel makes regular appearances in popular culture, with innumerable time travel storylines in movies, television and literature. But it is a surprisingly old idea: one can argue that the Greek tragedy Oedipus Rex , written by Sophocles over 2,500 years ago, is the first time travel story .

But is time travel in fact possible? Given the popularity of the concept, this is a legitimate question. As a theoretical physicist, I find that there are several possible answers to this question, not all of which are contradictory.

The simplest answer is that time travel cannot be possible because if it was, we would already be doing it. One can argue that it is forbidden by the laws of physics, like the second law of thermodynamics or relativity . There are also technical challenges: it might be possible but would involve vast amounts of energy.

There is also the matter of time-travel paradoxes; we can — hypothetically — resolve these if free will is an illusion, if many worlds exist or if the past can only be witnessed but not experienced. Perhaps time travel is impossible simply because time must flow in a linear manner and we have no control over it, or perhaps time is an illusion and time travel is irrelevant.

Laws of physics

Since Albert Einstein’s theory of relativity — which describes the nature of time, space and gravity — is our most profound theory of time, we would like to think that time travel is forbidden by relativity. Unfortunately, one of his colleagues from the Institute for Advanced Study, Kurt Gödel, invented a universe in which time travel was not just possible, but the past and future were inextricably tangled.

We can actually design time machines , but most of these (in principle) successful proposals require negative energy , or negative mass, which does not seem to exist in our universe. If you drop a tennis ball of negative mass, it will fall upwards. This argument is rather unsatisfactory, since it explains why we cannot time travel in practice only by involving another idea — that of negative energy or mass — that we do not really understand.

Mathematical physicist Frank Tipler conceptualized a time machine that does not involve negative mass, but requires more energy than exists in the universe .

Time travel also violates the second law of thermodynamics , which states that entropy or randomness must always increase. Time can only move in one direction — in other words, you cannot unscramble an egg. More specifically, by travelling into the past we are going from now (a high entropy state) into the past, which must have lower entropy.

This argument originated with the English cosmologist Arthur Eddington , and is at best incomplete. Perhaps it stops you travelling into the past, but it says nothing about time travel into the future. In practice, it is just as hard for me to travel to next Thursday as it is to travel to last Thursday.

Resolving paradoxes

There is no doubt that if we could time travel freely, we run into the paradoxes. The best known is the “ grandfather paradox ”: one could hypothetically use a time machine to travel to the past and murder their grandfather before their father’s conception, thereby eliminating the possibility of their own birth. Logically, you cannot both exist and not exist.

Read more: Time travel could be possible, but only with parallel timelines

Kurt Vonnegut’s anti-war novel Slaughterhouse-Five , published in 1969, describes how to evade the grandfather paradox. If free will simply does not exist, it is not possible to kill one’s grandfather in the past, since he was not killed in the past. The novel’s protagonist, Billy Pilgrim, can only travel to other points on his world line (the timeline he exists in), but not to any other point in space-time, so he could not even contemplate killing his grandfather.

The universe in Slaughterhouse-Five is consistent with everything we know. The second law of thermodynamics works perfectly well within it and there is no conflict with relativity. But it is inconsistent with some things we believe in, like free will — you can observe the past, like watching a movie, but you cannot interfere with the actions of people in it.

Could we allow for actual modifications of the past, so that we could go back and murder our grandfather — or Hitler ? There are several multiverse theories that suppose that there are many timelines for different universes. This is also an old idea: in Charles Dickens’ A Christmas Carol , Ebeneezer Scrooge experiences two alternative timelines, one of which leads to a shameful death and the other to happiness.

Time is a river

Roman emperor Marcus Aurelius wrote that:

“ Time is like a river made up of the events which happen , and a violent stream; for as soon as a thing has been seen, it is carried away, and another comes in its place, and this will be carried away too.”

We can imagine that time does flow past every point in the universe, like a river around a rock. But it is difficult to make the idea precise. A flow is a rate of change — the flow of a river is the amount of water that passes a specific length in a given time. Hence if time is a flow, it is at the rate of one second per second, which is not a very useful insight.

Theoretical physicist Stephen Hawking suggested that a “ chronology protection conjecture ” must exist, an as-yet-unknown physical principle that forbids time travel. Hawking’s concept originates from the idea that we cannot know what goes on inside a black hole, because we cannot get information out of it. But this argument is redundant: we cannot time travel because we cannot time travel!

Researchers are investigating a more fundamental theory, where time and space “emerge” from something else. This is referred to as quantum gravity , but unfortunately it does not exist yet.

So is time travel possible? Probably not, but we don’t know for sure!

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Time Travel

There is an extensive literature on time travel in both philosophy and physics. Part of the great interest of the topic stems from the fact that reasons have been given both for thinking that time travel is physically possible—and for thinking that it is logically impossible! This entry deals primarily with philosophical issues; issues related to the physics of time travel are covered in the separate entries on time travel and modern physics and time machines . We begin with the definitional question: what is time travel? We then turn to the major objection to the possibility of backwards time travel: the Grandfather paradox. Next, issues concerning causation are discussed—and then, issues in the metaphysics of time and change. We end with a discussion of the question why, if backwards time travel will ever occur, we have not been visited by time travellers from the future.

1.1 Time Discrepancy

1.2 changing the past, 2.1 can and cannot, 2.2 improbable coincidences, 2.3 inexplicable occurrences, 3.1 backwards causation, 3.2 causal loops, 4.1 time travel and time, 4.2 time travel and change, 5. where are the time travellers, other internet resources, related entries, 1. what is time travel.

There is a number of rather different scenarios which would seem, intuitively, to count as ‘time travel’—and a number of scenarios which, while sharing certain features with some of the time travel cases, seem nevertheless not to count as genuine time travel: [ 1 ]

Time travel Doctor . Doctor Who steps into a machine in 2024. Observers outside the machine see it disappear. Inside the machine, time seems to Doctor Who to pass for ten minutes. Observers in 1984 (or 3072) see the machine appear out of nowhere. Doctor Who steps out. [ 2 ] Leap . The time traveller takes hold of a special device (or steps into a machine) and suddenly disappears; she appears at an earlier (or later) time. Unlike in Doctor , the time traveller experiences no lapse of time between her departure and arrival: from her point of view, she instantaneously appears at the destination time. [ 3 ] Putnam . Oscar Smith steps into a machine in 2024. From his point of view, things proceed much as in Doctor : time seems to Oscar Smith to pass for a while; then he steps out in 1984. For observers outside the machine, things proceed differently. Observers of Oscar’s arrival in the past see a time machine suddenly appear out of nowhere and immediately divide into two copies of itself: Oscar Smith steps out of one; and (through the window) they see inside the other something that looks just like what they would see if a film of Oscar Smith were played backwards (his hair gets shorter; food comes out of his mouth and goes back into his lunch box in a pristine, uneaten state; etc.). Observers of Oscar’s departure from the future do not simply see his time machine disappear after he gets into it: they see it collide with the apparently backwards-running machine just described, in such a way that both are simultaneously annihilated. [ 4 ] Gödel . The time traveller steps into an ordinary rocket ship (not a special time machine) and flies off on a certain course. At no point does she disappear (as in Leap ) or ‘turn back in time’ (as in Putnam )—yet thanks to the overall structure of spacetime (as conceived in the General Theory of Relativity), the traveller arrives at a point in the past (or future) of her departure. (Compare the way in which someone can travel continuously westwards, and arrive to the east of her departure point, thanks to the overall curved structure of the surface of the earth.) [ 5 ] Einstein . The time traveller steps into an ordinary rocket ship and flies off at high speed on a round trip. When he returns to Earth, thanks to certain effects predicted by the Special Theory of Relativity, only a very small amount of time has elapsed for him—he has aged only a few months—while a great deal of time has passed on Earth: it is now hundreds of years in the future of his time of departure. [ 6 ] Not time travel Sleep . One is very tired, and falls into a deep sleep. When one awakes twelve hours later, it seems from one’s own point of view that hardly any time has passed. Coma . One is in a coma for a number of years and then awakes, at which point it seems from one’s own point of view that hardly any time has passed. Cryogenics . One is cryogenically frozen for hundreds of years. Upon being woken, it seems from one’s own point of view that hardly any time has passed. Virtual . One enters a highly realistic, interactive virtual reality simulator in which some past era has been recreated down to the finest detail. Crystal . One looks into a crystal ball and sees what happened at some past time, or will happen at some future time. (Imagine that the crystal ball really works—like a closed-circuit security monitor, except that the vision genuinely comes from some past or future time. Even so, the person looking at the crystal ball is not thereby a time traveller.) Waiting . One enters one’s closet and stays there for seven hours. When one emerges, one has ‘arrived’ seven hours in the future of one’s ‘departure’. Dateline . One departs at 8pm on Monday, flies for fourteen hours, and arrives at 10pm on Monday.

A satisfactory definition of time travel would, at least, need to classify the cases in the right way. There might be some surprises—perhaps, on the best definition of ‘time travel’, Cryogenics turns out to be time travel after all—but it should certainly be the case, for example, that Gödel counts as time travel and that Sleep and Waiting do not. [ 7 ]

In fact there is no entirely satisfactory definition of ‘time travel’ in the literature. The most popular definition is the one given by Lewis (1976, 145–6):

What is time travel? Inevitably, it involves a discrepancy between time and time. Any traveller departs and then arrives at his destination; the time elapsed from departure to arrival…is the duration of the journey. But if he is a time traveller, the separation in time between departure and arrival does not equal the duration of his journey.…How can it be that the same two events, his departure and his arrival, are separated by two unequal amounts of time?…I reply by distinguishing time itself, external time as I shall also call it, from the personal time of a particular time traveller: roughly, that which is measured by his wristwatch. His journey takes an hour of his personal time, let us say…But the arrival is more than an hour after the departure in external time, if he travels toward the future; or the arrival is before the departure in external time…if he travels toward the past.

This correctly excludes Waiting —where the length of the ‘journey’ precisely matches the separation between ‘arrival’ and ‘departure’—and Crystal , where there is no journey at all—and it includes Doctor . It has trouble with Gödel , however—because when the overall structure of spacetime is as twisted as it is in the sort of case Gödel imagined, the notion of external time (“time itself”) loses its grip.

Another definition of time travel that one sometimes encounters in the literature (Arntzenius, 2006, 602) (Smeenk and Wüthrich, 2011, 5, 26) equates time travel with the existence of CTC’s: closed timelike curves. A curve in this context is a line in spacetime; it is timelike if it could represent the career of a material object; and it is closed if it returns to its starting point (i.e. in spacetime—not merely in space). This now includes Gödel —but it excludes Einstein .

The lack of an adequate definition of ‘time travel’ does not matter for our purposes here. [ 8 ] It suffices that we have clear cases of (what would count as) time travel—and that these cases give rise to all the problems that we shall wish to discuss.

Some authors (in philosophy, physics and science fiction) consider ‘time travel’ scenarios in which there are two temporal dimensions (e.g. Meiland (1974)), and others consider scenarios in which there are multiple ‘parallel’ universes—each one with its own four-dimensional spacetime (e.g. Deutsch and Lockwood (1994)). There is a question whether travelling to another version of 2001 (i.e. not the very same version one experienced in the past)—a version at a different point on the second time dimension, or in a different parallel universe—is really time travel, or whether it is more akin to Virtual . In any case, this kind of scenario does not give rise to many of the problems thrown up by the idea of travelling to the very same past one experienced in one’s younger days. It is these problems that form the primary focus of the present entry, and so we shall not have much to say about other kinds of ‘time travel’ scenario in what follows.

One objection to the possibility of time travel flows directly from attempts to define it in anything like Lewis’s way. The worry is that because time travel involves “a discrepancy between time and time”, time travel scenarios are simply incoherent. The time traveller traverses thirty years in one year; she is 51 years old 21 years after her birth; she dies at the age of 100, 200 years before her birth; and so on. The objection is that these are straightforward contradictions: the basic description of what time travel involves is inconsistent; therefore time travel is logically impossible. [ 9 ]

There must be something wrong with this objection, because it would show Einstein to be logically impossible—whereas this sort of future-directed time travel has actually been observed (albeit on a much smaller scale—but that does not affect the present point) (Hafele and Keating, 1972b,a). The most common response to the objection is that there is no contradiction because the interval of time traversed by the time traveller and the duration of her journey are measured with respect to different frames of reference: there is thus no reason why they should coincide. A similar point applies to the discrepancy between the time elapsed since the time traveller’s birth and her age upon arrival. There is no more of a contradiction here than in the fact that Melbourne is both 800 kilometres away from Sydney—along the main highway—and 1200 kilometres away—along the coast road. [ 10 ]

Before leaving the question ‘What is time travel?’ we should note the crucial distinction between changing the past and participating in (aka affecting or influencing) the past. [ 11 ] In the popular imagination, backwards time travel would allow one to change the past: to right the wrongs of history, to prevent one’s younger self doing things one later regretted, and so on. In a model with a single past, however, this idea is incoherent: the very description of the case involves a contradiction (e.g. the time traveller burns all her diaries at midnight on her fortieth birthday in 1976, and does not burn all her diaries at midnight on her fortieth birthday in 1976). It is not as if there are two versions of the past: the original one, without the time traveller present, and then a second version, with the time traveller playing a role. There is just one past—and two perspectives on it: the perspective of the younger self, and the perspective of the older time travelling self. If these perspectives are inconsistent (e.g. an event occurs in one but not the other) then the time travel scenario is incoherent.

This means that time travellers can do less than we might have hoped: they cannot right the wrongs of history; they cannot even stir a speck of dust on a certain day in the past if, on that day, the speck was in fact unmoved. But this does not mean that time travellers must be entirely powerless in the past: while they cannot do anything that did not actually happen, they can (in principle) do anything that did happen. Time travellers cannot change the past: they cannot make it different from the way it was—but they can participate in it: they can be amongst the people who did make the past the way it was. [ 12 ]

What about models involving two temporal dimensions, or parallel universes—do they allow for coherent scenarios in which the past is changed? [ 13 ] There is certainly no contradiction in saying that the time traveller burns all her diaries at midnight on her fortieth birthday in 1976 in universe 1 (or at hypertime A ), and does not burn all her diaries at midnight on her fortieth birthday in 1976 in universe 2 (or at hypertime B ). The question is whether this kind of story involves changing the past in the sense originally envisaged: righting the wrongs of history, preventing subsequently regretted actions, and so on. Goddu (2003) and van Inwagen (2010) argue that it does (in the context of particular hypertime models), while Smith (1997, 365–6; 2015) argues that it does not: that it involves avoiding the past—leaving it untouched while travelling to a different version of the past in which things proceed differently.

2. The Grandfather Paradox

The most important objection to the logical possibility of backwards time travel is the so-called Grandfather paradox. This paradox has actually convinced many people that backwards time travel is impossible:

The dead giveaway that true time-travel is flatly impossible arises from the well-known “paradoxes” it entails. The classic example is “What if you go back into the past and kill your grandfather when he was still a little boy?”…So complex and hopeless are the paradoxes…that the easiest way out of the irrational chaos that results is to suppose that true time-travel is, and forever will be, impossible. (Asimov 1995 [2003, 276–7]) travel into one’s past…would seem to give rise to all sorts of logical problems, if you were able to change history. For example, what would happen if you killed your parents before you were born. It might be that one could avoid such paradoxes by some modification of the concept of free will. But this will not be necessary if what I call the chronology protection conjecture is correct: The laws of physics prevent closed timelike curves from appearing . (Hawking, 1992, 604) [ 14 ]

The paradox comes in different forms. Here’s one version:

If time travel was logically possible then the time traveller could return to the past and in a suicidal rage destroy his time machine before it was completed and murder his younger self. But if this was so a necessary condition for the time trip to have occurred at all is removed, and we should then conclude that the time trip did not occur. Hence if the time trip did occur, then it did not occur. Hence it did not occur, and it is necessary that it did not occur. To reply, as it is standardly done, that our time traveller cannot change the past in this way, is a petitio principii . Why is it that the time traveller is constrained in this way? What mysterious force stills his sudden suicidal rage? (Smith, 1985, 58)

The idea is that backwards time travel is impossible because if it occurred, time travellers would attempt to do things such as kill their younger selves (or their grandfathers etc.). We know that doing these things—indeed, changing the past in any way—is impossible. But were there time travel, there would then be nothing left to stop these things happening. If we let things get to the stage where the time traveller is facing Grandfather with a loaded weapon, then there is nothing left to prevent the impossible from occurring. So we must draw the line earlier: it must be impossible for someone to get into this situation at all; that is, backwards time travel must be impossible.

In order to defend the possibility of time travel in the face of this argument we need to show that time travel is not a sure route to doing the impossible. So, given that a time traveller has gone to the past and is facing Grandfather, what could stop her killing Grandfather? Some science fiction authors resort to the idea of chaperones or time guardians who prevent time travellers from changing the past—or to mysterious forces of logic. But it is hard to take these ideas seriously—and more importantly, it is hard to make them work in detail when we remember that changing the past is impossible. (The chaperone is acting to ensure that the past remains as it was—but the only reason it ever was that way is because of his very actions.) [ 15 ] Fortunately there is a better response—also to be found in the science fiction literature, and brought to the attention of philosophers by Lewis (1976). What would stop the time traveller doing the impossible? She would fail “for some commonplace reason”, as Lewis (1976, 150) puts it. Her gun might jam, a noise might distract her, she might slip on a banana peel, etc. Nothing more than such ordinary occurrences is required to stop the time traveller killing Grandfather. Hence backwards time travel does not entail the occurrence of impossible events—and so the above objection is defused.

A problem remains. Suppose Tim, a time-traveller, is facing his grandfather with a loaded gun. Can Tim kill Grandfather? On the one hand, yes he can. He is an excellent shot; there is no chaperone to stop him; the laws of logic will not magically stay his hand; he hates Grandfather and will not hesitate to pull the trigger; etc. On the other hand, no he can’t. To kill Grandfather would be to change the past, and no-one can do that (not to mention the fact that if Grandfather died, then Tim would not have been born). So we have a contradiction: Tim can kill Grandfather and Tim cannot kill Grandfather. Time travel thus leads to a contradiction: so it is impossible.

Note the difference between this version of the Grandfather paradox and the version considered above. In the earlier version, the contradiction happens if Tim kills Grandfather. The solution was to say that Tim can go into the past without killing Grandfather—hence time travel does not entail a contradiction. In the new version, the contradiction happens as soon as Tim gets to the past. Of course Tim does not kill Grandfather—but we still have a contradiction anyway: for he both can do it, and cannot do it. As Lewis puts it:

Could a time traveler change the past? It seems not: the events of a past moment could no more change than numbers could. Yet it seems that he would be as able as anyone to do things that would change the past if he did them. If a time traveler visiting the past both could and couldn’t do something that would change it, then there cannot possibly be such a time traveler. (Lewis, 1976, 149)

Lewis’s own solution to this problem has been widely accepted. [ 16 ] It turns on the idea that to say that something can happen is to say that its occurrence is compossible with certain facts, where context determines (more or less) which facts are the relevant ones. Tim’s killing Grandfather in 1921 is compossible with the facts about his weapon, training, state of mind, and so on. It is not compossible with further facts, such as the fact that Grandfather did not die in 1921. Thus ‘Tim can kill Grandfather’ is true in one sense (relative to one set of facts) and false in another sense (relative to another set of facts)—but there is no single sense in which it is both true and false. So there is no contradiction here—merely an equivocation.

Another response is that of Vihvelin (1996), who argues that there is no contradiction here because ‘Tim can kill Grandfather’ is simply false (i.e. contra Lewis, there is no legitimate sense in which it is true). According to Vihvelin, for ‘Tim can kill Grandfather’ to be true, there must be at least some occasions on which ‘If Tim had tried to kill Grandfather, he would or at least might have succeeded’ is true—but, Vihvelin argues, at any world remotely like ours, the latter counterfactual is always false. [ 17 ]

Return to the original version of the Grandfather paradox and Lewis’s ‘commonplace reasons’ response to it. This response engenders a new objection—due to Horwich (1987)—not to the possibility but to the probability of backwards time travel.

Think about correlated events in general. Whenever we see two things frequently occurring together, this is because one of them causes the other, or some third thing causes both. Horwich calls this the Principle of V-Correlation:

if events of type A and B are associated with one another, then either there is always a chain of events between them…or else we find an earlier event of type C that links up with A and B by two such chains of events. What we do not see is…an inverse fork—in which A and B are connected only with a characteristic subsequent event, but no preceding one. (Horwich, 1987, 97–8)

For example, suppose that two students turn up to class wearing the same outfits. That could just be a coincidence (i.e. there is no common cause, and no direct causal link between the two events). If it happens every week for the whole semester, it is possible that it is a coincidence, but this is extremely unlikely . Normally, we see this sort of extensive correlation only if either there is a common cause (e.g. both students have product endorsement deals with the same clothing company, or both slavishly copy the same influencer) or a direct causal link (e.g. one student is copying the other).

Now consider the time traveller setting off to kill her younger self. As discussed, no contradiction need ensue—this is prevented not by chaperones or mysterious forces, but by a run of ordinary occurrences in which the trigger falls off the time traveller’s gun, a gust of wind pushes her bullet off course, she slips on a banana peel, and so on. But now consider this run of ordinary occurrences. Whenever the time traveller contemplates auto-infanticide, someone nearby will drop a banana peel ready for her to slip on, or a bird will begin to fly so that it will be in the path of the time traveller’s bullet by the time she fires, and so on. In general, there will be a correlation between auto-infanticide attempts and foiling occurrences such as the presence of banana peels—and this correlation will be of the type that does not involve a direct causal connection between the correlated events or a common cause of both. But extensive correlations of this sort are, as we saw, extremely rare—so backwards time travel will happen about as often as you will see two people wear the same outfits to class every day of semester, without there being any causal connection between what one wears and what the other wears.

We can set out Horwich’s argument this way:

• If time travel were ever to occur, we should see extensive uncaused correlations.
• It is extremely unlikely that we should ever see extensive uncaused correlations.
• Therefore time travel is extremely unlikely to occur.

The conclusion is not that time travel is impossible, but that we should treat it the way we treat the possibility of, say, tossing a fair coin and getting heads one thousand times in a row. As Price (1996, 278 n.7) puts it—in the context of endorsing Horwich’s conclusion: “the hypothesis of time travel can be made to imply propositions of arbitrarily low probability. This is not a classical reductio, but it is as close as science ever gets.”

Smith (1997) attacks both premisses of Horwich’s argument. Against the first premise, he argues that backwards time travel, in itself, does not entail extensive uncaused correlations. Rather, when we look more closely, we see that time travel scenarios involving extensive uncaused correlations always build in prior coincidences which are themselves highly unlikely. Against the second premise, he argues that, from the fact that we have never seen extensive uncaused correlations, it does not follow that we never shall. This is not inductive scepticism: let us assume (contra the inductive sceptic) that in the absence of any specific reason for thinking things should be different in the future, we are entitled to assume they will continue being the same; still we cannot dismiss a specific reason for thinking the future will be a certain way simply on the basis that things have never been that way in the past. You might reassure an anxious friend that the sun will certainly rise tomorrow because it always has in the past—but you cannot similarly refute an astronomer who claims to have discovered a specific reason for thinking that the earth will stop rotating overnight.

Sider (2002, 119–20) endorses Smith’s second objection. Dowe (2003) criticises Smith’s first objection, but agrees with the second, concluding overall that time travel has not been shown to be improbable. Ismael (2003) reaches a similar conclusion. Goddu (2007) criticises Smith’s first objection to Horwich. Further contributions to the debate include Arntzenius (2006), Smeenk and Wüthrich (2011, §2.2) and Elliott (2018). For other arguments to the same conclusion as Horwich’s—that time travel is improbable—see Ney (2000) and Effingham (2020).

Return again to the original version of the Grandfather paradox and Lewis’s ‘commonplace reasons’ response to it. This response engenders a further objection. The autoinfanticidal time traveller is attempting to do something impossible (render herself permanently dead from an age younger than her age at the time of the attempts). Suppose we accept that she will not succeed and that what will stop her is a succession of commonplace occurrences. The previous objection was that such a succession is improbable . The new objection is that the exclusion of the time traveler from successfully committing auto-infanticide is mysteriously inexplicable . The worry is as follows. Each particular event that foils the time traveller is explicable in a perfectly ordinary way; but the inevitable combination of these events amounts to a ring-fencing of the forbidden zone of autoinfanticide—and this ring-fencing is mystifying. It’s like a grand conspiracy to stop the time traveler from doing what she wants to do—and yet there are no conspirators: no time lords, no magical forces of logic. This is profoundly perplexing. Riggs (1997, 52) writes: “Lewis’s account may do for a once only attempt, but is untenable as a general explanation of Tim’s continual lack of success if he keeps on trying.” Ismael (2003, 308) writes: “Considered individually, there will be nothing anomalous in the explanations…It is almost irresistible to suppose, however, that there is something anomalous in the cases considered collectively, i.e., in our unfailing lack of success.” See also Gorovitz (1964, 366–7), Horwich (1987, 119–21) and Carroll (2010, 86).

There have been two different kinds of defense of time travel against the objection that it involves mysteriously inexplicable occurrences. Baron and Colyvan (2016, 70) agree with the objectors that a purely causal explanation of failure—e.g. Tim fails to kill Grandfather because first he slips on a banana peel, then his gun jams, and so on—is insufficient. However they argue that, in addition, Lewis offers a non-causal—a logical —explanation of failure: “What explains Tim’s failure to kill his grandfather, then, is something about logic; specifically: Tim fails to kill his grandfather because the law of non-contradiction holds.” Smith (2017) argues that the appearance of inexplicability is illusory. There are no scenarios satisfying the description ‘a time traveller commits autoinfanticide’ (or changes the past in any other way) because the description is self-contradictory (e.g. it involves the time traveller permanently dying at 20 and also being alive at 40). So whatever happens it will not be ‘that’. There is literally no way for the time traveller not to fail. Hence there is no need for—or even possibility of—a substantive explanation of why failure invariably occurs, and such failure is not perplexing.

3. Causation

Backwards time travel scenarios give rise to interesting issues concerning causation. In this section we examine two such issues.

Earlier we distinguished changing the past and affecting the past, and argued that while the former is impossible, backwards time travel need involve only the latter. Affecting the past would be an example of backwards causation (i.e. causation where the effect precedes its cause)—and it has been argued that this too is impossible, or at least problematic. [ 18 ] The classic argument against backwards causation is the bilking argument . [ 19 ] Faced with the claim that some event A causes an earlier event B , the proponent of the bilking objection recommends an attempt to decorrelate A and B —that is, to bring about A in cases in which B has not occurred, and to prevent A in cases in which B has occurred. If the attempt is successful, then B often occurs despite the subsequent nonoccurrence of A , and A often occurs without B occurring, and so A cannot be the cause of B . If, on the other hand, the attempt is unsuccessful—if, that is, A cannot be prevented when B has occurred, nor brought about when B has not occurred—then, it is argued, it must be B that is the cause of A , rather than vice versa.

The bilking procedure requires repeated manipulation of event A . Thus, it cannot get under way in cases in which A is either unrepeatable or unmanipulable. Furthermore, the procedure requires us to know whether or not B has occurred, prior to manipulating A —and thus, it cannot get under way in cases in which it cannot be known whether or not B has occurred until after the occurrence or nonoccurrence of A (Dummett, 1964). These three loopholes allow room for many claims of backwards causation that cannot be touched by the bilking argument, because the bilking procedure cannot be performed at all. But what about those cases in which it can be performed? If the procedure succeeds—that is, A and B are decorrelated—then the claim that A causes B is refuted, or at least weakened (depending upon the details of the case). But if the bilking attempt fails, it does not follow that it must be B that is the cause of A , rather than vice versa. Depending upon the situation, that B causes A might become a viable alternative to the hypothesis that A causes B —but there is no reason to think that this alternative must always be the superior one. For example, suppose that I see a photo of you in a paper dated well before your birth, accompanied by a report of your arrival from the future. I now try to bilk your upcoming time trip—but I slip on a banana peel while rushing to push you away from your time machine, my time travel horror stories only inspire you further, and so on. Or again, suppose that I know that you were not in Sydney yesterday. I now try to get you to go there in your time machine—but first I am struck by lightning, then I fall down a manhole, and so on. What does all this prove? Surely not that your arrival in the past causes your departure from the future. Depending upon the details of the case, it seems that we might well be entitled to describe it as involving backwards time travel and backwards causation. At least, if we are not so entitled, this must be because of other facts about the case: it would not follow simply from the repeated coincidental failures of my bilking attempts.

Backwards time travel would apparently allow for the possibility of causal loops, in which things come from nowhere. The things in question might be objects—imagine a time traveller who steals a time machine from the local museum in order to make his time trip and then donates the time machine to the same museum at the end of the trip (i.e. in the past). In this case the machine itself is never built by anyone—it simply exists. The things in question might be information—imagine a time traveller who explains the theory behind time travel to her younger self: theory that she herself knows only because it was explained to her in her youth by her time travelling older self. The things in question might be actions. Imagine a time traveller who visits his younger self. When he encounters his younger self, he suddenly has a vivid memory of being punched on the nose by a strange visitor. He realises that this is that very encounter—and resignedly proceeds to punch his younger self. Why did he do it? Because he knew that it would happen and so felt that he had to do it—but he only knew it would happen because he in fact did it. [ 20 ]

One might think that causal loops are impossible—and hence that insofar as backwards time travel entails such loops, it too is impossible. [ 21 ] There are two issues to consider here. First, does backwards time travel entail causal loops? Lewis (1976, 148) raises the question whether there must be causal loops whenever there is backwards causation; in response to the question, he says simply “I am not sure.” Mellor (1998, 131) appears to claim a positive answer to the question. [ 22 ] Hanley (2004, 130) defends a negative answer by telling a time travel story in which there is backwards time travel and backwards causation, but no causal loops. [ 23 ] Monton (2009) criticises Hanley’s counterexample, but also defends a negative answer via different counterexamples. Effingham (2020) too argues for a negative answer.

Second, are causal loops impossible, or in some other way objectionable? One objection is that causal loops are inexplicable . There have been two main kinds of response to this objection. One is to agree but deny that this is a problem. Lewis (1976, 149) accepts that a loop (as a whole) would be inexplicable—but thinks that this inexplicability (like that of the Big Bang or the decay of a tritium atom) is merely strange, not impossible. In a similar vein, Meyer (2012, 263) argues that if someone asked for an explanation of a loop (as a whole), “the blame would fall on the person asking the question, not on our inability to answer it.” The second kind of response (Hanley, 2004, §5) is to deny that (all) causal loops are inexplicable. A second objection to causal loops, due to Mellor (1998, ch.12), is that in such loops the chances of events would fail to be related to their frequencies in accordance with the law of large numbers. Berkovitz (2001) and Dowe (2001) both argue that Mellor’s objection fails to establish the impossibility of causal loops. [ 24 ] Effingham (2020) considers—and rebuts—some additional objections to the possibility of causal loops.

4. Time and Change

Gödel (1949a [1990a])—in which Gödel presents models of Einstein’s General Theory of Relativity in which there exist CTC’s—can well be regarded as initiating the modern academic literature on time travel, in both philosophy and physics. In a companion paper, Gödel discusses the significance of his results for more general issues in the philosophy of time (Gödel 1949b [1990b]). For the succeeding half century, the time travel literature focussed predominantly on objections to the possibility (or probability) of time travel. More recently, however, there has been renewed interest in the connections between time travel and more general issues in the metaphysics of time and change. We examine some of these in the present section. [ 25 ]

The first thing that we need to do is set up the various metaphysical positions whose relationships with time travel will then be discussed. Consider two metaphysical questions:

• Are the past, present and future equally real?
• Is there an objective flow or passage of time, and an objective now?

We can label some views on the first question as follows. Eternalism is the view that past and future times, objects and events are just as real as the present time and present events and objects. Nowism is the view that only the present time and present events and objects exist. Now-and-then-ism is the view that the past and present exist but the future does not. We can also label some views on the second question. The A-theory answers in the affirmative: the flow of time and division of events into past (before now), present (now) and future (after now) are objective features of reality (as opposed to mere features of our experience). Furthermore, they are linked: the objective flow of time arises from the movement, through time, of the objective now (from the past towards the future). The B-theory answers in the negative: while we certainly experience now as special, and time as flowing, the B-theory denies that what is going on here is that we are detecting objective features of reality in a way that corresponds transparently to how those features are in themselves. The flow of time and the now are not objective features of reality; they are merely features of our experience. By combining answers to our first and second questions we arrive at positions on the metaphysics of time such as: [ 26 ]

• the block universe view: eternalism + B-theory
• the moving spotlight view: eternalism + A-theory
• the presentist view: nowism + A-theory
• the growing block view: now-and-then-ism + A-theory.

So much for positions on time itself. Now for some views on temporal objects: objects that exist in (and, in general, change over) time. Three-dimensionalism is the view that persons, tables and other temporal objects are three-dimensional entities. On this view, what you see in the mirror is a whole person. [ 27 ] Tomorrow, when you look again, you will see the whole person again. On this view, persons and other temporal objects are wholly present at every time at which they exist. Four-dimensionalism is the view that persons, tables and other temporal objects are four-dimensional entities, extending through three dimensions of space and one dimension of time. On this view, what you see in the mirror is not a whole person: it is just a three-dimensional temporal part of a person. Tomorrow, when you look again, you will see a different such temporal part. Say that an object persists through time if it is around at some time and still around at a later time. Three- and four-dimensionalists agree that (some) objects persist, but they differ over how objects persist. According to three-dimensionalists, objects persist by enduring : an object persists from t 1 to t 2 by being wholly present at t 1 and t 2 and every instant in between. According to four-dimensionalists, objects persist by perduring : an object persists from t 1 to t 2 by having temporal parts at t 1 and t 2 and every instant in between. Perduring can be usefully compared with being extended in space: a road extends from Melbourne to Sydney not by being wholly located at every point in between, but by having a spatial part at every point in between.

It is natural to combine three-dimensionalism with presentism and four-dimensionalism with the block universe view—but other combinations of views are certainly possible.

Gödel (1949b [1990b]) argues from the possibility of time travel (more precisely, from the existence of solutions to the field equations of General Relativity in which there exist CTC’s) to the B-theory: that is, to the conclusion that there is no objective flow or passage of time and no objective now. Gödel begins by reviewing an argument from Special Relativity to the B-theory: because the notion of simultaneity becomes a relative one in Special Relativity, there is no room for the idea of an objective succession of “nows”. He then notes that this argument is disrupted in the context of General Relativity, because in models of the latter theory to date, the presence of matter does allow recovery of an objectively distinguished series of “nows”. Gödel then proposes a new model (Gödel 1949a [1990a]) in which no such recovery is possible. (This is the model that contains CTC’s.) Finally, he addresses the issue of how one can infer anything about the nonexistence of an objective flow of time in our universe from the existence of a merely possible universe in which there is no objectively distinguished series of “nows”. His main response is that while it would not be straightforwardly contradictory to suppose that the existence of an objective flow of time depends on the particular, contingent arrangement and motion of matter in the world, this would nevertheless be unsatisfactory. Responses to Gödel have been of two main kinds. Some have objected to the claim that there is no objective flow of time in his model universe (e.g. Savitt (2005); see also Savitt (1994)). Others have objected to the attempt to transfer conclusions about that model universe to our own universe (e.g. Earman (1995, 197–200); for a partial response to Earman see Belot (2005, §3.4)). [ 28 ]

Earlier we posed two questions:

Gödel’s argument is related to the second question. Let’s turn now to the first question. Godfrey-Smith (1980, 72) writes “The metaphysical picture which underlies time travel talk is that of the block universe [i.e. eternalism, in the terminology of the present entry], in which the world is conceived as extended in time as it is in space.” In his report on the Analysis problem to which Godfrey-Smith’s paper is a response, Harrison (1980, 67) replies that he would like an argument in support of this assertion. Here is an argument: [ 29 ]

A fundamental requirement for the possibility of time travel is the existence of the destination of the journey. That is, a journey into the past or the future would have to presuppose that the past or future were somehow real. (Grey, 1999, 56)

Dowe (2000, 442–5) responds that the destination does not have to exist at the time of departure: it only has to exist at the time of arrival—and this is quite compatible with non-eternalist views. And Keller and Nelson (2001, 338) argue that time travel is compatible with presentism:

There is four-dimensional [i.e. eternalist, in the terminology of the present entry] time-travel if the appropriate sorts of events occur at the appropriate sorts of times; events like people hopping into time-machines and disappearing, people reappearing with the right sorts of memories, and so on. But the presentist can have just the same patterns of events happening at just the same times. Or at least, it can be the case on the presentist model that the right sorts of events will happen, or did happen, or are happening, at the rights sorts of times. If it suffices for four-dimensionalist time-travel that Jennifer disappears in 2054 and appears in 1985 with the right sorts of memories, then why shouldn’t it suffice for presentist time-travel that Jennifer will disappear in 2054, and that she did appear in 1985 with the right sorts of memories?

Sider (2005) responds that there is still a problem reconciling presentism with time travel conceived in Lewis’s way: that conception of time travel requires that personal time is similar to external time—but presentists have trouble allowing this. Further contributions to the debate whether presentism—and other versions of the A-theory—are compatible with time travel include Monton (2003), Daniels (2012), Hall (2014) and Wasserman (2018) on the side of compatibility, and Miller (2005), Slater (2005), Miller (2008), Hales (2010) and Markosian (2020) on the side of incompatibility.

Leibniz’s Law says that if x = y (i.e. x and y are identical—one and the same entity) then x and y have exactly the same properties. There is a superficial conflict between this principle of logic and the fact that things change. If Bill is at one time thin and at another time not so—and yet it is the very same person both times—it looks as though the very same entity (Bill) both possesses and fails to possess the property of being thin. Three-dimensionalists and four-dimensionalists respond to this problem in different ways. According to the four-dimensionalist, what is thin is not Bill (who is a four-dimensional entity) but certain temporal parts of Bill; and what is not thin are other temporal parts of Bill. So there is no single entity that both possesses and fails to possess the property of being thin. Three-dimensionalists have several options. One is to deny that there are such properties as ‘thin’ (simpliciter): there are only temporally relativised properties such as ‘thin at time t ’. In that case, while Bill at t 1 and Bill at t 2 are the very same entity—Bill is wholly present at each time—there is no single property that this one entity both possesses and fails to possess: Bill possesses the property ‘thin at t 1 ’ and lacks the property ‘thin at t 2 ’. [ 30 ]

Now consider the case of a time traveller Ben who encounters his younger self at time t . Suppose that the younger self is thin and the older self not so. The four-dimensionalist can accommodate this scenario easily. Just as before, what we have are two different three-dimensional parts of the same four-dimensional entity, one of which possesses the property ‘thin’ and the other of which does not. The three-dimensionalist, however, faces a problem. Even if we relativise properties to times, we still get the contradiction that Ben possesses the property ‘thin at t ’ and also lacks that very same property. [ 31 ] There are several possible options for the three-dimensionalist here. One is to relativise properties not to external times but to personal times (Horwich, 1975, 434–5); another is to relativise properties to spatial locations as well as to times (or simply to spacetime points). Sider (2001, 101–6) criticises both options (and others besides), concluding that time travel is incompatible with three-dimensionalism. Markosian (2004) responds to Sider’s argument; [ 32 ] Miller (2006) also responds to Sider and argues for the compatibility of time travel and endurantism; Gilmore (2007) seeks to weaken the case against endurantism by constructing analogous arguments against perdurantism. Simon (2005) finds problems with Sider’s arguments, but presents different arguments for the same conclusion; Effingham and Robson (2007) and Benovsky (2011) also offer new arguments for this conclusion. For further discussion see Wasserman (2018) and Effingham (2020). [ 33 ]

We have seen arguments to the conclusions that time travel is impossible, improbable and inexplicable. Here’s an argument to the conclusion that backwards time travel simply will not occur. If backwards time travel is ever going to occur, we would already have seen the time travellers—but we have seen none such. [ 34 ] The argument is a weak one. [ 35 ] For a start, it is perhaps conceivable that time travellers have already visited the Earth [ 36 ] —but even granting that they have not, this is still compatible with the future actuality of backwards time travel. First, it may be that time travel is very expensive, difficult or dangerous—or for some other reason quite rare—and that by the time it is available, our present period of history is insufficiently high on the list of interesting destinations. Second, it may be—and indeed existing proposals in the physics literature have this feature—that backwards time travel works by creating a CTC that lies entirely in the future: in this case, backwards time travel becomes possible after the creation of the CTC, but travel to a time earlier than the time at which the CTC is created is not possible. [ 37 ]

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• Vranas, Peter B.M., 2005, “Do cry over spilt milk: Possibly you can change the past”, Monist (Special Issue on Time Travel), 88: 370–87.
• –––, 2009, “Can I kill my younger self? Time travel and the retrosuicide paradox”, Pacific Philosophical Quarterly , 90: 520–34.
• –––, 2010, “What time travelers may be able to do”, Philosophical Studies , 150: 115–21.
• Wasserman, Ryan, 2018, Paradoxes of Time Travel , Oxford: Oxford University Press.
• Williams, Donald C., 1951, “The myth of passage”, Journal of Philosophy , 48: 457–72.
• Wright, John, 2006, “Personal identity, fission and time travel”, Philosophia , 34: 129–42.
• Yourgrau, Palle, 1999, Gödel Meets Einstein: Time Travel in the Gödel Universe , Chicago: Open Court.

How to cite this entry . Preview the PDF version of this entry at the Friends of the SEP Society . Look up topics and thinkers related to this entry at the Internet Philosophy Ontology Project (InPhO). Enhanced bibliography for this entry at PhilPapers , with links to its database.

• Time Travel , entry by Joel Hunter (Truckee Meadows Community College) in the Internet Encyclopedia of Philosophy .

causation: backward | free will: divine foreknowledge and | identity: over time | location and mereology | temporal parts | time | time machines | time travel: and modern physics

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Time travel: five ways that we could do it

Cathal O’Connell

Cathal O'Connell is a science writer based in Melbourne.

In 2009 the British physicist Stephen Hawking held a party for time travellers – the twist was he sent out the invites a year later (No guests showed up). Time travel is probably impossible. Even if it were possible, Hawking and others have argued that you could never travel back before the moment your time machine was built.

But travel to the future? That’s a different story.

Of course, we are all time travellers as we are swept along in the current of time, from past to future, at a rate of one hour per hour.

But, as with a river, the current flows at different speeds in different places. Science as we know it allows for several methods to take the fast-track into the future. Here’s a rundown.

1. Time travel via speed

This is the easiest and most practical way to time travel into the far future – go really fast.

According to Einstein’s theory of special relativity, when you travel at speeds approaching the speed of light, time slows down for you relative to the outside world.

This is not a just a conjecture or thought experiment – it’s been measured. Using twin atomic clocks (one flown in a jet aircraft, the other stationary on Earth) physicists have shown that a flying clock ticks slower, because of its speed.

In the case of the aircraft, the effect is minuscule. But If you were in a spaceship travelling at 90% of the speed of light, you’d experience time passing about 2.6 times slower than it was back on Earth.

And the closer you get to the speed of light, the more extreme the time-travel.

Computer solves a major time travel problem

The highest speeds achieved through any human technology are probably the protons whizzing around the Large Hadron Collider at 99.9999991% of the speed of light. Using special relativity we can calculate one second for the proton is equivalent to 27,777,778 seconds, or about 11 months , for us.

Amazingly, particle physicists have to take this time dilation into account when they are dealing with particles that decay. In the lab, muon particles typically decay in 2.2 microseconds. But fast moving muons, such as those created when cosmic rays strike the upper atmosphere, take 10 times longer to disintegrate.

2. Time travel via gravity

The next method of time travel is also inspired by Einstein. According to his theory of general relativity, the stronger the gravity you feel, the slower time moves.

As you get closer to the centre of the Earth, for example, the strength of gravity increases. Time runs slower for your feet than your head.

Again, this effect has been measured. In 2010, physicists at the US National Institute of Standards and Technology (NIST) placed two atomic clocks on shelves, one 33 centimetres above the other, and measured the difference in their rate of ticking. The lower one ticked slower because it feels a slightly stronger gravity.

To travel to the far future, all we need is a region of extremely strong gravity, such as a black hole. The closer you get to the event horizon, the slower time moves – but it’s risky business, cross the boundary and you can never escape.

And anyway, the effect is not that strong so it’s probably not worth the trip.

Assuming you had the technology to travel the vast distances to reach a black hole (the nearest is about 3,000 light years away), the time dilation through travelling would be far greater than any time dilation through orbiting the black hole itself.

(The situation described in the movie Interstellar , where one hour on a planet near a black hole is the equivalent of seven years back on Earth, is so extreme as to be impossible in our Universe, according to Kip Thorne, the movie’s scientific advisor.)

The most mindblowing thing, perhaps, is that GPS systems have to account for time dilation effects (due to both the speed of the satellites and gravity they feel) in order to work. Without these corrections, your phones GPS capability wouldn’t be able to pinpoint your location on Earth to within even a few kilometres.

3. Time travel via suspended animation

Another way to time travel to the future may be to slow your perception of time by slowing down, or stopping, your bodily processes and then restarting them later.

Bacterial spores can live for millions of years in a state of suspended animation, until the right conditions of temperature, moisture, food kick start their metabolisms again. Some mammals, such as bears and squirrels, can slow down their metabolism during hibernation, dramatically reducing their cells’ requirement for food and oxygen.

Could humans ever do the same?

Though completely stopping your metabolism is probably far beyond our current technology, some scientists are working towards achieving inducing a short-term hibernation state lasting at least a few hours. This might be just enough time to get a person through a medical emergency, such as a cardiac arrest, before they can reach the hospital.

In 2005, American scientists demonstrated a way to slow the metabolism of mice (which do not hibernate) by exposing them to minute doses of hydrogen sulphide, which binds to the same cell receptors as oxygen. The core body temperature of the mice dropped to 13 °C and metabolism decreased 10-fold. After six hours the mice could be reanimated without ill effects.

Unfortunately, similar experiments on sheep and pigs were not successful, suggesting the method might not work for larger animals.

Another method, which induces a hypothermic hibernation by replacing the blood with a cold saline solution, has worked on pigs and is currently undergoing human clinical trials in Pittsburgh.

4. Time travel via wormholes

General relativity also allows for the possibility for shortcuts through spacetime, known as wormholes, which might be able to bridge distances of a billion light years or more, or different points in time.

Many physicists, including Stephen Hawking, believe wormholes are constantly popping in and out of existence at the quantum scale, far smaller than atoms. The trick would be to capture one, and inflate it to human scales – a feat that would require a huge amount of energy, but which might just be possible, in theory.

Attempts to prove this either way have failed, ultimately because of the incompatibility between general relativity and quantum mechanics.

5. Time travel using light

Another time travel idea, put forward by the American physicist Ron Mallet, is to use a rotating cylinder of light to twist spacetime. Anything dropped inside the swirling cylinder could theoretically be dragged around in space and in time, in a similar way to how a bubble runs around on top your coffee after you swirl it with a spoon.

According to Mallet, the right geometry could lead to time travel into either the past and the future.

Since publishing his theory in 2000, Mallet has been trying to raise the funds to pay for a proof of concept experiment, which involves dropping neutrons through a circular arrangement of spinning lasers.

His ideas have not grabbed the rest of the physics community however, with others arguing that one of the assumptions of his basic model is plagued by a singularity, which is physics-speak for “it’s impossible”.

The Royal Institution of Australia has an Education resource based on this article. You can access it here .

Related Reading: Computer solves a major time travel problem

Originally published by Cosmos as Time travel: five ways that we could do it

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A history of time travel: the how, the why and the when of turning back the clock

Pop on Aqua's 'Turn Back Time' and settle in

For most of human history, the world didn’t change very quickly. Until the 1700s, kids could largely expect their lives to be similar to their parents, and that their children would have an experience very similar to their own, too. There were obviously changes in how humans lived over longer stretches of time, but nothing that even different generations could easily observe.

My first introduction to science fiction was Valérian and Laureline. I was ten years old. Every Wednesday there was a magazine called Pilote in France, and there was two pages of Valerian every week. It was the first time I’d seen a girl and a guy in space, agents travelling in time and space. That was amazing.

The past is written. The present? We have to deal with it. But the future is a white page. So I don’t understand why people on this white page are putting all this darkness.

God! Let’s have some color! Let’s have some fun! Let’s at least imagine a better world. Maybe we won’t be able to do it, but we have to try.

The industrial revolution changed all of this. For the first time in human history, the pace of technological change was visible within a human lifespan. 

It is not a coincidence that it was only after science and technological change became a normal part of the human experience, that time travel became something we dreamed of.

Time travel is actually somewhat unique in science fiction. Many core concepts have their origins earlier in history. 

The historical roots of the concept of a 'robot' can be seen in Jewish folklore for example: Golems were anthropomorphic beings sculpted from clay. In Greek mythology, characters would travel to other worlds, and it's no coincidence that The Matrix features a character called Persephone. But time travel is different.

The first real work to envisage travelling in time was The Time Machine by HG Wells, which was published in 1895. 

The book tells the story of a scientist who builds a machine that will take him to the year 802,701 - a world in which ape-like Morlocks are evolutionary descendants of humanity, and have regressed to a primitive lifestyle. 

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The book was a product of its time - both in terms of the science played upon (Charles Darwin had only published Origin of the Species 35 years earlier), and the racist attitudes: it is speculated that the Morlocks were inspired by the Morlachs, a real ethnic group in the Balkans who were often characterised as “primitive”.

Real science

But of course, this was science fiction - what about science fact? The two have always been closely linked, and during the early days it was no different. In 1907, the physicist Hermann Minkowski first argued that Einstein’s Special Relativity could be expressed in geometric terms as a fourth dimension (to add to our known three) - which is exactly how Wells visualised time travel in his work of fiction.

The development of Special and then General Relativity was significant as it provided the theoretical backbone for how time travel could be conceived in scientific terms. In 1949 Kurt Gödel took Einstein’s work and came up with a solution which as a mathematical necessity included what he called “closed timelike curves” - the idea that if you travel far enough, time will loop back around (like how if you keep flying East, you’ll eventually end up back where you started).

In other words, using what became known as the Gödel Metric, it is theoretically possible to travel between any one point in time and space and any other. 

There was just one problem: for Gödel’s theory to be right, the universe would have to be spinning - and scientists don’t believe that it is. So while the maths might make sense, Gödel’s universe does not appear to be the one we’re actually living in. Though he never gave up hope that he might be right: Apparently even on this deathbed, he would ask if anyone has found evidence of a spinning universe. And if he does ever turn out to be right, it means that time travel can happen, and is actually fairly straightforward (well, as far as physics goes anyway).

Since Gödel, scientists have continued to hypothesise about time travel, with perhaps the best known example being tachyons - or particles that move faster than the speed of light (therefore, effectively travelling in time). So far, despite one false alarm at CERN in 2011, there is no evidence that they actually exist.

Chancers and hoaxes

Of course, the lack of real science when it comes to time travel has not stopped some people from claiming to have done it. With the likes of Marty McFly and Doctor Who on the brain, chancers and hoaxers have realised that time travel is immediately a compelling prospect. Here’s a couple of amusing examples.

At the turn of the millennium, when the internet was still in its infancy, forums were captivated by the story of John Titor. Titor claimed he was from the year 2036, and had been sent back in time by the government to obtain an IBM 5100 computer. The thinking appeared to be that by obtaining the computer, the government could find a solution to the UNIX 2038 bug - in which clocks could be reset, Millennium Bug-style, leading to chaos everywhere.

Posting on the 'Time Travel Institute' forums, Titor went into details on how his time machine worked:  It was powered by “two top-spin, dual positive singularities”, and used an X-ray venting system. He also gave a potted history of what humanity could expect: A new American civil war in 2004, and World War III in 2015. He also claimed the “many worlds” interpretation of quantum physics was true, hence why he wasn’t violating the so-called “grandfather paradox”.

Titor claimed he was from the year 2036, and had been sent back in time by the government to obtain an IBM 5100 computer.

Okay, so he probably wasn’t a real time traveller, but in the early days of the internet, when anonymity was more commonplace, he truly captured the imaginations of nerdy early adopters who perhaps, just a little bit, hoped that he might be the real thing.

More recently, in 2013, an Iranian scientist named Ali Razeghi claimed to have invented a time machine of sorts. It was supposedly capable of predicting the next 5-8 years for an individual, with up to 98% accuracy. According to The Telegraph , Razeghi said the invention fits into the size of a standard PC case and “It will not take you into the future, it will bring the future to you”. The idea is that the Iranian government could use it to predict future security threats and military confrontations. So perhaps it is time to check in and see if he managed to predict Donald Trump?

So is this the best we can do? Will we ever manage to crack time travel? Some scientists are still sceptical that it could ever be possible. This includes Stephen Hawking, who proposed the 'Chronology Protection Conjecture' – which is what it sounds like. Essentially, he argues that the laws of physics are as they are to specifically make time travel impossible – on all but “submicroscopic” scales. Essentially, this is to protect how causality works, as if we are suddenly allowed to travel back and kill our grandfathers, it would create massive time paradoxes.

Hawking revealed to Ars Technica in 2012 how he had held a party for time travellers, but only sent out invitations after the date it was held. So did the party support his argument that time travel is impossible? Or did he end up spending the evening in the company of John Titor and Doctor Who?

“I sat there a long time, but no one came”, he said, much to our disappointment.

Huge thanks to Stephen Jorgenson-Murray for walking us through some of the more brain-mangling science for this article.

To celebrate the release of Valerian and the City of a Thousand Planets , Luc Besson is today behind the lens at TechRadar. Here’s what we’ve got in store for you:

• Luc Besson presents TechRadar
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• Luc Besson talks streaming, viral videos and cinema tech
• Star spangled glamour: making space travel cooler than ever before
• A history of time travel: the how, the why and the when
• 20 best sci-fi films on Netflix and Amazon Prime
• Amazing future tech from sci-fi films that totally exist now

Valerian and the City of a Thousand Planets is released in UK cinemas August 2nd, and is out now in the US.

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Have Powers, Will (Time) Travel: Superheroes and the Urge to Change the Past

Eileen Gonzalez

Eileen's primary literary love is comic books, but she’s always on the lookout for her next literary adventure no matter what form it takes. She has a Bachelor's in media studies, a Master's in digital communication, a smattering of published short stories, and a seriously cute dog. Follow her on Bluesky .

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In Alex Segura’s YA novel Ara ñ a and Spider-Man 2099: Dark Tomorrow , Anya/Araña is on the trail of a stolen artifact when said artifact unexpectedly blasts her into the early 22nd century. There, she meets Miguel, the former Spider-Man 2099, who is no stranger to time travel. But Miguel gave up being a hero after traumatic personal losses, and it will take the gravest crisis imaginable to convince him to put on his costume and be a hero one more time.

Since time travel is integral to the plot, reading this novel got me thinking about the different ways time travel has appeared in superhero stories — some good, some bad. Along the way, Segura was kind enough to answer my questions about Dark Tomorrow and time travel stories in general. If you care about spoilers, read freely: there are none here — at least, none for Dark Tomorrow .

Just a Jump to the Left…

Time travel stories predate comics by at least several decades. Encyclopedia Britannica cites books like H.G. Wells’s The Time Machine and even Charles Dickens’s A Christmas Carol as early classics in the genre. The Time Machine was adapted as a comic book in the Classics Illustrated series, which Segura cited to me as a story that resonated with him as a young reader.

“I love [time travel stories], honestly,” he said. “The idea of hopping around time has always been of interest”

It has also been a part of the superhero experience since the early days. In the 1940s, Batman traveled back in time to pal around with D’Artagnan and the Three Musketeers in Batman #32 and into the near future to show what the world might be like if the Nazis were to win World War II in Batman #15. (Granted, this last one was less a story and more an attempt to scare the audience into buying war bonds.)

Time travel became a common plot device in the 1950s and ’60s, when stringent self-censorship precluded more violent kinds of stories. That’s how we got nonsense like Action Comics #148, in which Superman travels back in time to cheat Indigenous people out of the land Metropolis sits on, and Green Lantern #8, in which Hal Jordan is drafted into fighting villains in the 58th century because humans of the future are too pathetic to do it themselves (but not too pathetic to kidnap a 20th-century man and give him amnesia).

But there were more serious stories too. In the poignant yet retroactively hilarious Avengers #56, Captain America traveled back to the 1940s to convince himself that his sidekick Bucky was really dead. (Bucky was not, in fact, dead.)

This versatility is part of what draws Segura to time travel stories: they “can range from the funny to the painfully emotional,” he told me, “and I love the idea of affecting your own future or going back in time to see what things were like. The story possibilities are endless.”

As superheroes made their way into other genres, they took their tales of time travel with them. An episode of Freakazoid! has the titular hero prevent the Pearl Harbor attack, which somehow results in Rush Limbaugh becoming a decent person. In his 1978 film, Superman reverses the Earth’s rotation, which also reverses time and allows him another chance to save Lois Lane. (It goes without saying that that’s not how science works , but okay, fine.)

And then there’s the star of The CW’s The Flash , Barry Allen. Oh, Barry. Damn it, Barry .

With Great Power Comes Great Irresponsibility

The Flash may be more closely associated with time travel than any other hero (which I’m sure upsets Booster Gold, a 25th century ne’er-do-well who traveled to our time to become a heroic gloryhound). Early on, he learned he could travel through time by running on the Cosmic Treadmill. Some of his biggest foes — Reverse-Flash and Abra Kadabra — and his closest allies — his wife Iris West and their grandson Bart Allen — come from the future. Barry would later abuse his ability to time travel in both the comic Flashpoint and the TV show The Flash , when he rewrote all of reality to bring his murdered mom back to life.

This storyline is where I started to view time travel tales differently. Even more than Ray Bradbury’s A Sound of Thunder , this is the story that made me realize the ethical pitfalls of time travel.

Unlike Eckels, the hapless protagonist of Bradbury’s classic story — or even grief-stricken Superman impulsively reversing the Earth’s rotation by a couple of minutes — Barry Allen makes a conscious decision to change the past. As Reverse-Flash gleefully puts it, “You traded the life of your mother for the rest of the world!”

And Barry’s action is not without consequences. In both the comic and the TV show, the lives of Barry’s friends turn out vastly different — and sometimes worse — than how they were before.

As Segura points out, consequences are another reason that time travel makes for such a fascinating subject. In particular, he cited the “emotional stakes” — the inevitability of revisiting painful events or dead loved ones, or of seeing future events you may not like — as being especially high and therefore especially interesting. I can certainly agree, but personally, I have trouble sympathizing with a supposedly heroic character who willingly (and, in the TV show, more than once) messes with something as dangerous as time because he can’t handle being sad or accept his mistakes.

Obviously, Barry has the right to be upset over his mother’s death, even years after the fact. But you don’t get to ruin countless lives just because you can (it seems unlikely that Barry’s friends are the only ones who got screwed over, out of all the billions of people in the world). He allows his grief to make him selfish, even villainous. Who else but a villain tries to remake the world as they see fit? Go to therapy like the rest of us, bud.

Fortunately, Dark Tomorrow is more judicious in its use of time travel: Anya doesn’t do it on purpose, and Miguel only did so when the world was in danger. But Segura acknowledges that Miguel’s pain, much like Barry Allen’s, could have driven him down a darker path.

“[I]t’d be weird if he wasn’t” tempted to go back in time and prevent his personal tragedies from occurring, Segura says. “But I think one of the lessons Miguel learned early on was the fragility of time travel, and how the timeline tends to right itself or protect itself against major attempts to alter it….At his heart, Miguel is a scientist, and has probably grappled with these questions regularly when caught up in his time travel adventures!”

In other words, the heroes of Dark Tomorrow are not trying to remake the world in their image, so to speak. They’re just trying to save it, and in the process of doing so, they could end up changing a few things — probably for the better, but who knows what tomorrow will bring?

In the Not-Too-Distant Future…

So why do we still like all these time travel tales? Or, in my case, all of these tales except for those starring Barry Allen?

I think it’s a combination of everything I’ve covered: it’s high-stakes, it’s emotional, and it’s just plain fun. The appeals and temptations of time travel may be stronger for a superhero than for your average character, making for even richer storytelling. Righting wrongs is the superhero’s main reason for existing. If presented with the chance to use time travel to fix past mistakes, they’re sure to feel pressure to do so — and, in some cases, succumb to that pressure.

In Dark Tomorrow , the time travel is in part a simple necessity: Araña and Spider-Man 2099 exist a century apart, so the only way that they — Marvel’s two Latine Spider-people — could go adventuring together is through time travel shenanigans. But Segura believes it serves another purpose: to compare two very different worlds with surprisingly similar problems.

“Miguel’s Nueva York might seem shinier and more convenient than our New York, but as we dig deeper, we see some of the same problems crop up — and some of the same class issues and social situations,” Segura says. “It really helps hammer home the theme that you can be a hero whenever you are, and it takes the same kind of passion, dedication, and sacrifice.”

By opening a door to the past — or the future — time travel stories don’t just entertain us: they teach us the critical lesson that people are people, no matter where or when they were born.

For more time travelin’ superheroes, check out these lists about heroes wrecking the timestream and getting stuck in the past !

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Author Roy Huff

Bestselling science fiction and fantasy author Roy Huff. Amazing books and a sci-fi fantasy super-geek. Join the tribe. Read more.

24 Reasons Time Travel is the Ultimate Superpower

March 5, 2019 by Roy Huff

Hollywood has finally caught on with the Flash, Timeless, Frequency, and DC’s Legends of Tomorrow, but they’re only scratching the surface.

It took confronting a rabid pit bull in middle school to understand the awesomeness of superpowers and how not having them sucks when you’re in a bind.

Imagine staring down a beast foaming at the mouth, not knowing if it would chase you down and infect you with an insidious disease that drives you mad until you succumb to a horrible death. Fortunately, in this case, the only superpower I needed was patience to wait for animal control.

But all superpowers aren’t created equal. With all due respect to Scientologists’ who revere powers like  auditing  and the ability to hold one’s need to use the restroom, time travel is in a league of its own.

I don’t mean the limited power depicted in most fiction. I’m talking about time travel that avoids the nonsense of the paradox and encompasses slowing time, freezing time, looping time, and moving backward and forward through time at will.

And don’t let some content editor block you with a mysterious force that prevents you from changing too much just because he thinks it’s bad fiction or gives the protagonist too much power. It’s all or nothing, baby. Yes, it’s totally awesome, and you know it. In case you’re not convinced, try these reasons on for size.

Kill Hitler (or Any Other Ruthless Dictator) and See What Happens

Screw the consequences. And don’t tell me Hitler made the world a better place for some sick, twisted reason. Yes, the world would be totally different, but I’d bet it would be a very interesting and good different. Why not find out?

Cream the Kid Who Picked on You in School

If you’ve ever been bullied, you’ll appreciate this one. A few time loops will make you poetic with your jabs and punches, or you could just have a little fun and put them in an awkward position when time resumes at normal speed.

Ace Any Test

If you can’t get an A with the ultimate cheat sheet, it’s time to move on.

Try Out Different Lines on a Prospective Date Until One Works

50 First Dates  comes to mind, as does  Groundhog Day  (my personal favorite). But there’s so much to work with. Who wouldn’t want to know the most beautiful thing to say to that perfect person they’ve always wanted to impress?

Make a Ton of Cash

It’s so obvious, yet so many time travel stories don’t bother to make the most of this storyline. If you controlled time, how would you make a ton of cash? So many possibilities here:

Win the lottery, a hand at poker, or name your gambling vice. Play the stock market. Invest in real estate. Discover hidden loot, buried trinkets, lost relics, and sunken ships. The list is endless.

Invent Gadgets From the Future

Another personal favorite, but I digress. Why not accelerate things a bit? For the environmentally conscious, here’s an excellent way to make alternative energy a cheap efficient reality. Or invent a way to upload information to your brain. While you’re at it, throw in a holodeck and some replicators.

Save Books From the Library of Alexandria (Then Read Them All)

Bibliophiles rejoice! Even lovers of poetry and literary fiction should jump on the sci-fi bandwagon for this one,  seriously ! You’ll need to bring a translator, or at least a souped up version of Google Translate. The payoff would be enormous.

Rip Mega Hits From the Future

You may not sound as good, but then again, talent is overrated. It’s not stealing if it hasn’t been invented yet, so ignore the naysayers who complain about the ethics. If it’s fame you desire, this option is a must.

Find out if Your Significant Other is a Cheater

If you have suspicions, they probably are. But if you’ve just started dating, save yourself the headaches and skip ahead.

Buy the Perfect Gift

If you’ve found that perfect love, you know finding the perfect gift can be equally as hard. Those initial facial expressions don’t lie.

See What Happens to Your Kids

For maximum impact, foresight is necessary. Maybe your kid should study art. Find out now if that safe career path makes them miserable or that speed takes them to the Olympics  or prison .

Prevent the Death of Millions Before Natural Disasters

Even time travel stories constrained by the paradox should jump on this one. The butterfly effect may change most things, but natural disasters will outlast most storms of change. What could be better than saving thousands of lives from earthquakes and tsunamis?

Get the Appreciation you Know you Deserve

It’s okay to indulge every once in a while. Who wouldn’t want to know what those accolades from your boss, friends, or significant other will look like? It will save a heck of a lot of time if you discover you need to move on. Just make sure your clicker doesn’t share the same memory feature as Adam Sandler’s.

Change the Outcome of Elections

Whether you’re a Democrat, Republican, Tory, or Liberal, I’m sure there’ve been winners you’d like to see get crushed. Time travel takes opponent research to the next level. Have fun with it.

Visit Your Own funeral

Avoiding death is obvious, but a more practical reason is discovering who attends your funeral. Don’t waste any more time caring what people think if they don’t bother to show up. Life’s too short.

Visit the End of Civilization (if it Ever Comes)

Call me an optimist. I’m still planning on hopping into a cryo chamber by the  Alcor Life Extension Foundation  and hitching a ride to the future. Therapeutic cloning, gene modification, and singularity may extend life well beyond the realms of modern science. 

If we’ve survived this long, what’s a few more billion years? Yes, maybe we’ll all look like Lady Cassandra from  Doctor Who , but I think mankind will survive longer than most envision,  Skynet  be damned.

Visit the Death of the Universe

Our universe will eventually die. Everything down to the subatomic particles will be ripped apart as the expansion of the universe throttles at breakneck speeds. It may be boring to watch, but why not?

Prevent the Death of the Universe

If you can visit, why not stop it? You could do it the hard way by changing the laws of physics, like the Q in  Star Trek TNG . Or, you could do it the “easy” way by creating a stable wormhole to a parallel universe and hitching a ride.

Accelerate the Progress of Scientific Theories

Don’t know how to make a stable wormhole? No worries! A few hundred thousand time loops will do the trick, or you could just jump a century or two in the future and read the Cliff notes version.

Prove Once and for all What Happened in the Beginning of Time

After you’ve visited the end, take a trip to the beginning.

Hang Out With Jesus

I’m sure hanging out with JC would be a lot cooler than most people realize. Besides, good friends are hard to come by.

Empty Your Netflix Queue

I saved the best for last. I remember when this didn’t take that long, but since the advent of original content and A+ acquisitions, there’s never enough screen time.  

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Teleportation, ESP & Time Travel: 10 Tales of Superpowers

Teleportation and Other Fantastic Claims

The idea of people with superpowers is one that has long captivated audiences. Modern-day movies, graphic novels, TV shows and video games are full of fictional stories involving people who have acquired extraordinary and seemingly impossible abilities. The real world has plenty of fantastic claims as well spurring on debate and study.

One person who made fantastic claims was Pedro Ruiz Calderón, a Catholic priest who was brought to trial in Mexico City in 1540. Calderón claimed that he could teleport between continents, make himself invisible, predict the future , make women fall in love with him, find buried treasure, summon and exorcise demons among other abilities. Research by John Chuchiak IV, a professor at Missouri State University, sheds light on his trial.

LiveScience takes a look at superpowers throughout history. Some of them appear impossible while scientists are working on others to make them a reality.

Psychokinesis

Psychokinesis (PK) is the ability to move or otherwise manipulate objects using the human mind . There are two types of psychokinesis , the "macro" and "micro" level. Many have claimed macro abilities — to be able to manipulate of large objects — throughout history. A 19th-century example was Eusapia Palladino who, in an 1892 photograph taken in Milan, and shown here, supposedly levitated a table while researcher Alexandr Aksakov checked for fraud. 

The micro level involves the manipulation of random events using the human mind. Between 1979 and 2007 the PEAR (Princeton Engineering Anomalies Research) lab in New Jersey studied this phenomenon running detailed statistical analysis. Its researchers found that the human mind has a very slight ability to manipulate random events, a finding that is controversial and debated among scientists. 

Time Travel

Time Travel is an ability which is often featured in science fiction. Through time dilation it is theoretically possible to travel forward in time although the effect wouldn't be significant unless you traveled a vast distance on a very fast spacecraft.

Moving backwards in time is more difficult and scientists are still uncertain as to whether it is even theoretically possible.

There have been claims of people having encounters, of sorts, with the past. On August 4, 1951 two English women on holiday near Dieppe claimed to hear the sounds of the famous World War II battle throughout the night while in their hotel room. They took careful notes and an article describing their case was published in the May-June 1952 edition of the Journal of the Society for Psychical Research.

Reincarnation

Reincarnation is the belief that when someone dies they are reborn. It's featured in several religions including Hinduism, Jainism and Buddhism.

There have been cases where young children recall information which some believe to be from past lives they lived. The late Dr. Ian Stevenson, a medical doctor who was head of the Division of Perceptual Studies at the University of Virginia, documented and published an estimated 3,000 cases of this over a period of 40 years. He tried to match up these claimed experiences with people who actually died.  

Extra Sensory Perception (ESP)

Extra Sensory Perception, or ESP, is the ability to obtain information through means other than the five senses. Examples of it include telepathy or “mind reading,” as it’s more popularly known. Precognition is another form and involves knowing of a future event ahead of time. Another form is remote viewing, seeing a distant place through paranormal means.

The U.S. military and CIA did research exploring the military and intelligence applications of ESP, particularly remote viewing. Project "Stargate" was a $20-million study started during the Cold War. It was spurred on by reports that the Soviet Union was investigating ESP. Although some claim that there were successful instances of remote viewing the project was shut down in 1995. [ The 10 Most Outrageous Military Experiments

The practice of "dowsing" or "divining" often features a person using twigs or a rod to find a water source. It can, however, be used for other things as well. Pedro Ruiz Calderón, the 16th-century priest, claimed to have been able to find buried treasure using supernatural means, and made a good amount of money selling his abilities. Needless to say modern-day scientists are skeptical that dowsing can actually be done.

(Shown here, an 18th-century depiction from the 1733 book "Histoire Critique des Practiques Superstitieuses.")

Predicting the Future

In many ways predicting the future is not a supernatural power. Economists, climatologists, demographers, all use scientific (or semi-scientific) methods to try to predict the future.

The use of supernatural powers to predict the future, however, has a much longer history. The use of horoscopic astrology, though not based in science, dates back more than 2,000 years and is tailored to the individual.

An ancient astrologer would determine the positions of the planets, sun and moon at the time their client was born. They would then use the information to determine their future.  Researchers reconstructed and published in 2012 the oldest known astrologer's board , found in a cave in Croatia.

Astral Projection

Invisibility

From HG Wells 1897 novel "The Invisible Man" to Harry Potter's invisibility cloak, the ability to make yourself invisible is one that has long fascinated science fiction writers.

Pedro Ruiz Calderón, the Catholic priest put on trial in 1540, claimed to be able to turn invisible. He said that the ability came in handy when he snuck in and out of the bedrooms of his mistresses.  

Although the power seems fantastic scientists are working on technologies that may one day be able to render large objects partly or entirely invisible. Using artificial metamaterials they are developing techniques to bend light. Another effort, published in 2011 in the journal Nature Communications, uses calcite to block off red and green lasers and ordinary white light .

Love Spells

The ability to use supernatural abilities to make someone fall in love with you has ancient origins.

Archaeology Magazine reported on a case from Roman Egypt in which two wax figurines were found in an "erotic embrace." They contained an inscription which read in part "seize Euphemia and lead her to me Theon, loving me with mad desire, and bind her with unloosable shackles, strong ones of adamantine, for the love of me..."

Although modern-day scientists don't believe in love spells some substances, like strawberries, are said to act as an aphrodisiac, increasing sexual desire. [Top 10 Aphrodisiacs]

Teleportation

Teleportation was made famous by the series "Star Trek." People, aliens included, could beam from the fictional starship Enterprise to the surface of a planet in one piece (although transporter malfunctions were occasionally used as a plot device).

In real life Pedro Ruiz Calderón, the priest who went on trial in 1540, claimed to be able to teleport from Mexico to Europe and back again. His claim was laughable since, if he could do that, he could have easily escaped his trial!

Today scientists working in the field of quantum physics are working on teleporting light , with some success . Whether we will ever be able to teleport spaceship crewmembers or warlock priests is another matter. [ Twisted Physics: 7 Mind-Blowing Findings ]

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Owen Jarus is a regular contributor to Live Science who writes about archaeology and humans' past. He has also written for The Independent (UK), The Canadian Press (CP) and The Associated Press (AP), among others. Owen has a bachelor of arts degree from the University of Toronto and a journalism degree from Ryerson University. 

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Superman’s Greatest Feat Just Got More Complicated

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An Iconic and Controversial Western Is Coming to Prime Video

10 cheesiest '80s movies, ranked, pixar's highest-grossing films of all time, ranked.

Superman: The Movie is one of the most iconic and beloved films both in cinema and in the sub-genre of comic book films. Not only has it maintained that title over the decades, but it also featured one of Superman's most impressive feats on screen, the ability to change history. For decades, audiences witnessed the character literally change time to save the life of Lois Lane , and the sheer spectacle of it has been enough to disregard the logic behind such a feat, but one theorist may have finally found an explanation that, while complicated, offers a nearly foolproof answer to Superman's time-traveling.

In the film, Lex Luthor enacted a plan to set off a massive bomb on the San Andreas fault to separate the west coast from the US and capitalize on the land as free real estate for him to claim. At first, the plan went off almost without a hitch, but Lois Lane, trapped in a crack in the Earth, was suffocated and buried under rubble. Enraged, Superman flew into the air, defied Jor-El's warning over tampering with human history and reversed time early enough to save his love . However, Reddit theorist Cilarnen believed that Superman never turned back time. Instead, he time-traveled to the past to reverse what had been done.

RELATED: A Batman Theory Connects The Joker to a Birds of Prey Villain

While confusing to decipher at a glance, the physics are explained to show that Superman traveled past the speed of light to succeed in his plan. Physics also explained that any object traveling at this rate would technically be traveling backward in time; hence, things occurred in reverse the faster he flew. This is why he traveled through time rather than reverse it, as the world and its populace would never survive the Earth's rotation if stopped and reversed.

As for the rotation, that is explained as an optical illusion as Supes traveled through time. To audiences, his time traveling is perceived as going backward in time, similar to Jules Verne's The Time Machine . Everything is happening at an accelerated rate backward to viewers, but Superman is only looking for the perfect point to stop traveling. This is why when he's shown going in the opposite direction, the planet isn't returning to a proper rotation. Instead, he's at a new point in time, and he's using his remaining speed to find Lois and help her before things could go wrong.

RELATED: Ta-Nehisi Coates' Superman Script Is Reportedly Close to Finished

The film then showed Superman saving Lois and apprehending Lex Luthor , but he seemingly averted the catastrophe that took place earlier in the film. It's a mild confusing moment but could've occurred before further issues could arise. Thanks to Superman, he now had more time to save lives, like Lois', and stop Luthor from succeeding in his plan. While it's the only aspect of the theory that made the least sense, it's thankfully not enough to debunk it entirely, as it could open up larger story inconsistencies.

Superman being a time-traveler isn't a title that he's worn in films before, but the idea that he did felt fitting for that era of the Man of Steel. Even better is the idea of the physics behind it. It maintained the film's integrity, but it also added another level of entertainment for many fans of the classic and further amplified just how intelligent this iteration of Clark Kent is, thanks to his time in the Fortress of Solitude. In the end, the theory changed entirely the idea of why Superman is the Man of Tomorrow.

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Screen Rant

Why superman time traveling in the 1978 movie was so controversial.

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We Asked You to Vote for Far Side's Funniest Superman Comic & the Winner Is a Perfect Movie Parody

Superman's new villain is a nightmare-fuel combination of doomsday & [spoiler], 10 times hollywood gave up on movie series.

Richard Donner’s 1978 film Superman is an almost universally beloved movie, but one of its few criticized aspects is its use of time travel in its finale. Superman was the first modern superhero blockbuster , adapting the Man of Steel to film with iconic performances, groundbreaking special effects, and one of John Williams’ finest film scores. Seemingly writing itself into a corner in the third act, however, Superman resolved a shocking moment with a surprising use of Superman’s abilities which viewers question or criticize to this day.

Starring Christopher Reeve as the titular hero, Margot Kidder as Lois Lane, and Gene Hackman as Lex Luthor, Superman instantly became the definitive version of the classic hero’s mythos, telling a story that was simultaneously a love letter to its comic source material and an earnestly-written epic. The film was famously marketed with the tagline “ You'll believe a man can fly ,” and while its effects made Superman’s abilities seem more tangible than ever before, the movie’s true strength came from its sheer sincerity. Christopher Reeve is still considered by many to be the best Superman and Clark Kent , believably switching between the two personas within the same scene and skillfully imbuing his dual identity with verisimilitude.

Related: Where General Zod Was In Superman: The Animated Series

In Superman’s action-packed finale, Lex Luthor hijacks two nuclear missiles, sending them to the United States East and West Coasts. While Superman stops the first missile and alleviates the damage from the second, he fails to save Lois Lane, prompting him, in grief-induced fury, to travel back in time and save Lois in addition to reversing the damage from the second missile. Superman’s ability to travel through time has precedent in the comics and thematic significance in the film, but some feel that the moment was abrupt and cheapened the impact of a major character’s death. Additionally, there were understandable question marks around the physical plausibility of the sequence, given its suddenness and crucial role in the narrative. However, while Superman’s use of time travel appeared to come out of nowhere in the film, it was actually a significant and deliberate choice on the parts of the character and filmmakers.

Having been released in 1978, the comics that Superman was largely based on were the Silver Age and Bronze Age issues of Action Comics and Superman . While Superman’s powers were quite tame in his earliest stories, he gradually grew in power until he could essentially invent new abilities on the fly, such as telepathy and shapeshifting. Superman’s ability to fly at relativistic speeds and travel through time appeared numerous times, particularly in the Silver Age, but his powers became far more limited following the Crisis on Infinite Earths event and subsequent continuity reboot.

While the climax may have been controversial, it did have greater narrative significance, beyond just saving Superman's love interest. Superman was instructed by Jor-El (via posthumous holograms) to never interfere with human history, but his frustration over failing to save Lois reminded him of a similar failure to save his father’s life, so he chose to follow his father’s words of encouragement, using his full power to save everyone, including the woman he loved. Superman was choosing Earth and humanity over Krypton.

While Superman’s use of time travel was a character-defining choice and nothing he hadn’t done in the comics, the moment did seem to come out of nowhere following an extremely surprising major character death. This would, understandably, feel a bit too abrupt of a way to ensure a tidy resolution, but the scene fit the tone of the film and the core of Superman’s character. 1978’s Superman was about its hero’s characterization , not his limits, and the film’s time-travel scene, while controversial, expressed his humanity as much as his abilities.

Next: All 3 Versions Of Zod's Superman 2 Ending Explained

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