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What is the speed of light? Here’s the history, discovery of the cosmic speed limit

On one hand, the speed of light is just a number: 299,792,458 meters per second. And on the other, it’s one of the most important constants that appears in nature and defines the relationship of causality itself.

As far as we can measure, it is a constant. It is the same speed for every observer in the entire universe. This constancy was first established in the late 1800’s with the experiments of Albert Michelson and Edward Morley at Case Western Reserve University . They attempted to measure changes in the speed of light as the Earth orbited around the Sun. They found no such variation, and no experiment ever since then has either.

Observations of the cosmic microwave background, the light released when the universe was 380,000 years old, show that the speed of light hasn’t measurably changed in over 13.8 billion years.

In fact, we now define the speed of light to be a constant, with a precise speed of 299,792,458 meters per second. While it remains a remote possibility in deeply theoretical physics that light may not be a constant, for all known purposes it is a constant, so it’s better to just define it and move on with life.

How was the speed of light first measured?

In 1676 the Danish astronomer Ole Christensen Romer made the first quantitative measurement of how fast light travels. He carefully observed the orbit of Io, the innermost moon of Jupiter. As the Earth circles the Sun in its own orbit, sometimes it approaches Jupiter and sometimes it recedes away from it. When the Earth is approaching Jupiter, the path that light has to travel from Io is shorter than when the Earth is receding away from Jupiter. By carefully measuring the changes to Io’s orbital period, Romer calculated a speed of light of around 220,000 kilometers per second.

Observations continued to improve until by the 19 th century astronomers and physicists had developed the sophistication to get very close to the modern value. In 1865, James Clerk Maxwell made a remarkable discovery. He was investigating the properties of electricity and magnetism, which for decades had remained mysterious in unconnected laboratory experiments around the world. Maxwell found that electricity and magnetism were really two sides of the same coin, both manifestations of a single electromagnetic force.

As Maxwell explored the consequences of his new theory, he found that changing magnetic fields can lead to changing electric fields, which then lead to a new round of changing magnetic fields. The fields leapfrog over each other and can even travel through empty space. When Maxwell went to calculate the speed of these electromagnetic waves, he was surprised to see the speed of light pop out – the first theoretical calculation of this important number.

What is the most precise measurement of the speed of light?

Because it is defined to be a constant, there’s no need to measure it further. The number we’ve defined is it, with no uncertainty, no error bars. It’s done. But the speed of light is just that – a speed. The number we choose to represent it depends on the units we use: kilometers versus miles, seconds versus hours, and so on. In fact, physicists commonly just set the speed of light to be 1 to make their calculations easier. So instead of trying to measure the speed light travels, physicists turn to more precisely measuring other units, like the length of the meter or the duration of the second. In other words, the defined value of the speed of light is used to establish the length of other units like the meter.

How does light slow down?

Yes, the speed of light is always a constant. But it slows down whenever it travels through a medium like air or water. How does this work? There are a few different ways to present an answer to this question, depending on whether you prefer a particle-like picture or a wave-like picture.

In a particle-like picture, light is made of tiny little bullets called photons. All those photons always travel at the speed of light, but as light passes through a medium those photons get all tangled up, bouncing around among all the molecules of the medium. This slows down the overall propagation of light, because it takes more time for the group of photons to make it through.

In a wave-like picture, light is made of electromagnetic waves. When these waves pass through a medium, they get all the charged particles in motion, which in turn generate new electromagnetic waves of their own. These interfere with the original light, forcing it to slow down as it passes through.

Either way, light always travels at the same speed, but matter can interfere with its travel, making it slow down.

Why is the speed of light important?

The speed of light is important because it’s about way more than, well, the speed of light. In the early 1900’s Einstein realized just how special this speed is. The old physics, dominated by the work of Isaac Newton, said that the universe had a fixed reference frame from which we could measure all motion. This is why Michelson and Morley went looking for changes in the speed, because it should change depending on our point of view. But their experiments showed that the speed was always constant, so what gives?

Einstein decided to take this experiment at face value. He assumed that the speed of light is a true, fundamental constant. No matter where you are, no matter how fast you’re moving, you’ll always see the same speed.

This is wild to think about. If you’re traveling at 99% the speed of light and turn on a flashlight, the beam will race ahead of you at…exactly the speed of light, no more, no less. If you’re coming from the opposite direction, you’ll still also measure the exact same speed.

This constancy forms the basis of Einstein’s special theory of relativity, which tells us that while all motion is relative – different observers won’t always agree on the length of measurements or the duration of events – some things are truly universal, like the speed of light.

Can you go faster than light speed?

Nope. Nothing can. Any particle with zero mass must travel at light speed. But anything with mass (which is most of the universe) cannot. The problem is relativity. The faster you go, the more energy you have. But we know from Einstein’s relativity that energy and mass are the same thing. So the more energy you have, the more mass you have, which makes it harder for you to go even faster. You can get as close as you want to the speed of light, but to actually crack that barrier takes an infinite amount of energy. So don’t even try.

How is the speed at which light travels related to causality?

If you think you can find a cheat to get around the limitations of light speed, then I need to tell you about its role in special relativity. You see, it’s not just about light. It just so happens that light travels at this special speed, and it was the first thing we discovered to travel at this speed. So it could have had another name. Indeed, a better name for this speed might be “the speed of time.”

Related: Is time travel possible? An astrophysicist explains

We live in a universe of causes and effects. All effects are preceded by a cause, and all causes lead to effects. The speed of light limits how quickly causes can lead to effects. Because it’s a maximum speed limit for any motion or interaction, in a given amount of time there’s a limit to what I can influence. If I want to tap you on the shoulder and you’re right next to me, I can do it right away. But if you’re on the other side of the planet, I have to travel there first. The motion of me traveling to you is limited by the speed of light, so that sets how quickly I can tap you on the shoulder – the speed light travels dictates how quickly a single cause can create an effect.

The ability to go faster than light would allow effects to happen before their causes. In essence, time travel into the past would be possible with faster-than-light travel. Since we view time as the unbroken chain of causes and effects going from the past to the future, breaking the speed of light would break causality, which would seriously undermine our sense of the forward motion of time.

Why does light travel at this speed?

No clue. It appears to us as a fundamental constant of nature. We have no theory of physics that explains its existence or why it has the value that it does. We hope that a future understanding of nature will provide this explanation, but right now all investigations are purely theoretical. For now, we just have to take it as a given.

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16.1 Traveling Waves

Learning objectives.

By the end of this section, you will be able to:

• Describe the basic characteristics of wave motion
• Define the terms wavelength, amplitude, period, frequency, and wave speed
• Explain the difference between longitudinal and transverse waves, and give examples of each type
• List the different types of waves

We saw in Oscillations that oscillatory motion is an important type of behavior that can be used to model a wide range of physical phenomena. Oscillatory motion is also important because oscillations can generate waves, which are of fundamental importance in physics. Many of the terms and equations we studied in the chapter on oscillations apply equally well to wave motion ( Figure 16.2 ).

Types of Waves

A wave is a disturbance that propagates, or moves from the place it was created. There are three basic types of waves: mechanical waves, electromagnetic waves, and matter waves.

Basic mechanical wave s are governed by Newton’s laws and require a medium. A medium is the substance mechanical waves propagate through, and the medium produces an elastic restoring force when it is deformed. Mechanical waves transfer energy and momentum, without transferring mass. Some examples of mechanical waves are water waves, sound waves, and seismic waves. The medium for water waves is water; for sound waves, the medium is usually air. (Sound waves can travel in other media as well; we will look at that in more detail in Sound .) For surface water waves, the disturbance occurs on the surface of the water, perhaps created by a rock thrown into a pond or by a swimmer splashing the surface repeatedly. For sound waves, the disturbance is a change in air pressure, perhaps created by the oscillating cone inside a speaker or a vibrating tuning fork. In both cases, the disturbance is the oscillation of the molecules of the fluid. In mechanical waves, energy and momentum transfer with the motion of the wave, whereas the mass oscillates around an equilibrium point. (We discuss this in Energy and Power of a Wave .) Earthquakes generate seismic waves from several types of disturbances, including the disturbance of Earth’s surface and pressure disturbances under the surface. Seismic waves travel through the solids and liquids that form Earth. In this chapter, we focus on mechanical waves.

Electromagnetic waves are associated with oscillations in electric and magnetic fields and do not require a medium. Examples include gamma rays, X-rays, ultraviolet waves, visible light, infrared waves, microwaves, and radio waves. Electromagnetic waves can travel through a vacuum at the speed of light, v = c = 2.99792458 × 10 8 m/s . v = c = 2.99792458 × 10 8 m/s . For example, light from distant stars travels through the vacuum of space and reaches Earth. Electromagnetic waves have some characteristics that are similar to mechanical waves; they are covered in more detail in Electromagnetic Waves .

Matter waves are a central part of the branch of physics known as quantum mechanics. These waves are associated with protons, electrons, neutrons, and other fundamental particles found in nature. The theory that all types of matter have wave-like properties was first proposed by Louis de Broglie in 1924. Matter waves are discussed in Photons and Matter Waves .

Mechanical Waves

Mechanical waves exhibit characteristics common to all waves, such as amplitude, wavelength, period, frequency, and energy. All wave characteristics can be described by a small set of underlying principles.

The simplest mechanical waves repeat themselves for several cycles and are associated with simple harmonic motion. These simple harmonic waves can be modeled using some combination of sine and cosine functions. For example, consider the simplified surface water wave that moves across the surface of water as illustrated in Figure 16.3 . Unlike complex ocean waves, in surface water waves, the medium, in this case water, moves vertically, oscillating up and down, whereas the disturbance of the wave moves horizontally through the medium. In Figure 16.3 , the waves causes a seagull to move up and down in simple harmonic motion as the wave crests and troughs (peaks and valleys) pass under the bird. The crest is the highest point of the wave, and the trough is the lowest part of the wave. The time for one complete oscillation of the up-and-down motion is the wave’s period T . The wave’s frequency is the number of waves that pass through a point per unit time and is equal to f = 1 / T . f = 1 / T . The period can be expressed using any convenient unit of time but is usually measured in seconds; frequency is usually measured in hertz (Hz), where 1 Hz = 1 s −1 . 1 Hz = 1 s −1 .

The length of the wave is called the wavelength and is represented by the Greek letter lambda ( λ ) ( λ ) , which is measured in any convenient unit of length, such as a centimeter or meter. The wavelength can be measured between any two similar points along the medium that have the same height and the same slope. In Figure 16.3 , the wavelength is shown measured between two crests. As stated above, the period of the wave is equal to the time for one oscillation, but it is also equal to the time for one wavelength to pass through a point along the wave’s path.

The amplitude of the wave ( A ) is a measure of the maximum displacement of the medium from its equilibrium position. In the figure, the equilibrium position is indicated by the dotted line, which is the height of the water if there were no waves moving through it. In this case, the wave is symmetrical, the crest of the wave is a distance + A + A above the equilibrium position, and the trough is a distance − A − A below the equilibrium position. The units for the amplitude can be centimeters or meters, or any convenient unit of distance.

The water wave in the figure moves through the medium with a propagation velocity v → . v → . The magnitude of the wave velocity is the distance the wave travels in a given time, which is one wavelength in the time of one period, and the wave speed is the magnitude of wave velocity. In equation form, this is

This fundamental relationship holds for all types of waves. For water waves, v is the speed of a surface wave; for sound, v is the speed of sound; and for visible light, v is the speed of light.

Transverse and Longitudinal Waves

We have seen that a simple mechanical wave consists of a periodic disturbance that propagates from one place to another through a medium. In Figure 16.4 (a), the wave propagates in the horizontal direction, whereas the medium is disturbed in the vertical direction. Such a wave is called a transverse wave . In a transverse wave, the wave may propagate in any direction, but the disturbance of the medium is perpendicular to the direction of propagation. In contrast, in a longitudinal wave or compressional wave, the disturbance is parallel to the direction of propagation. Figure 16.4 (b) shows an example of a longitudinal wave. The size of the disturbance is its amplitude A and is completely independent of the speed of propagation v .

A simple graphical representation of a section of the spring shown in Figure 16.4 (b) is shown in Figure 16.5 . Figure 16.5 (a) shows the equilibrium position of the spring before any waves move down it. A point on the spring is marked with a blue dot. Figure 16.5 (b) through (g) show snapshots of the spring taken one-quarter of a period apart, sometime after the end of` the spring is oscillated back and forth in the x -direction at a constant frequency. The disturbance of the wave is seen as the compressions and the expansions of the spring. Note that the blue dot oscillates around its equilibrium position a distance A , as the longitudinal wave moves in the positive x -direction with a constant speed. The distance A is the amplitude of the wave. The y -position of the dot does not change as the wave moves through the spring. The wavelength of the wave is measured in part (d). The wavelength depends on the speed of the wave and the frequency of the driving force.

Waves may be transverse, longitudinal, or a combination of the two. Examples of transverse waves are the waves on stringed instruments or surface waves on water, such as ripples moving on a pond. Sound waves in air and water are longitudinal. With sound waves, the disturbances are periodic variations in pressure that are transmitted in fluids. Fluids do not have appreciable shear strength, and for this reason, the sound waves in them are longitudinal waves. Sound in solids can have both longitudinal and transverse components, such as those in a seismic wave. Earthquakes generate seismic waves under Earth’s surface with both longitudinal and transverse components (called compressional or P-waves and shear or S-waves, respectively). The components of seismic waves have important individual characteristics—they propagate at different speeds, for example. Earthquakes also have surface waves that are similar to surface waves on water. Ocean waves also have both transverse and longitudinal components.

Example 16.1

Wave on a string.

• The speed of the wave can be derived by dividing the distance traveled by the time.
• The period of the wave is the inverse of the frequency of the driving force.
• The wavelength can be found from the speed and the period v = λ / T . v = λ / T .
• The first wave traveled 30.00 m in 6.00 s: v = 30.00 m 6.00 s = 5.00 m s . v = 30.00 m 6.00 s = 5.00 m s .
• The period is equal to the inverse of the frequency: T = 1 f = 1 2.00 s −1 = 0.50 s . T = 1 f = 1 2.00 s −1 = 0.50 s .
• The wavelength is equal to the velocity times the period: λ = v T = 5.00 m s ( 0.50 s ) = 2.50 m . λ = v T = 5.00 m s ( 0.50 s ) = 2.50 m .

Significance

Check your understanding 16.1.

When a guitar string is plucked, the guitar string oscillates as a result of waves moving through the string. The vibrations of the string cause the air molecules to oscillate, forming sound waves. The frequency of the sound waves is equal to the frequency of the vibrating string. Is the wavelength of the sound wave always equal to the wavelength of the waves on the string?

Example 16.2

Characteristics of a wave.

• The amplitude and wavelength can be determined from the graph.
• Since the velocity is constant, the velocity of the wave can be found by dividing the distance traveled by the wave by the time it took the wave to travel the distance.
• The period can be found from v = λ T v = λ T and the frequency from f = 1 T . f = 1 T .
• The distance the wave traveled from time t = 0.00 s t = 0.00 s to time t = 3.00 s t = 3.00 s can be seen in the graph. Consider the red arrow, which shows the distance the crest has moved in 3 s. The distance is 8.00 cm − 2.00 cm = 6.00 cm . 8.00 cm − 2.00 cm = 6.00 cm . The velocity is v = Δ x Δ t = 8.00 cm − 2.00 cm 3.00 s − 0.00 s = 2.00 cm/s . v = Δ x Δ t = 8.00 cm − 2.00 cm 3.00 s − 0.00 s = 2.00 cm/s .
• The period is T = λ v = 8.00 cm 2.00 cm/s = 4.00 s T = λ v = 8.00 cm 2.00 cm/s = 4.00 s and the frequency is f = 1 T = 1 4.00 s = 0.25 Hz . f = 1 T = 1 4.00 s = 0.25 Hz .

Check Your Understanding 16.2

The propagation velocity of a transverse or longitudinal mechanical wave may be constant as the wave disturbance moves through the medium. Consider a transverse mechanical wave: Is the velocity of the medium also constant?

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Why is the speed of light the way it is?

It's just plain weird.

Paul M. Sutter is an astrophysicist at SUNY Stony Brook and the Flatiron Institute, host of Ask a Spaceman and Space Radio , and author of " How to Die in Space ." He contributed this article to Space.com's Expert Voices: Op-Ed & Insights . 

We all know and love the speed of light — 299,792,458 meters per second — but why does it have the value that it does? Why isn't it some other number? And why do we care so much about some random speed of electromagnetic waves? Why did it become such a cornerstone of physics? 

Well, it's because the speed of light is just plain weird.

Related: Constant speed of light: Einstein's special relativity survives a high-energy test

Putting light to the test

The first person to realize that light does indeed have a speed at all was an astronomer by the name of Ole Romer. In the late 1600s, he was obsessed with some strange motions of the moon Io around Jupiter. Every once in a while, the great planet would block our view of its little moon, causing an eclipse, but the timing between eclipses seemed to change over the course of the year. Either something funky was happening with the orbit of Io — which seemed suspicious — or something else was afoot.

After a couple years of observations, Romer made the connection. When we see Io get eclipsed, we're in a certain position in our own orbit around the sun. But by the next time we see another eclipse, a few days later, we're in a slightly different position, maybe closer or farther away from Jupiter than the last time. If we are farther away than the last time we saw an eclipse, then that means we have to wait a little bit of extra time to see the next one because it takes that much longer for the light to reach us, and the reverse is true if we happen to be a little bit closer to Jupiter.

The only way to explain the variations in the timing of eclipses of Io is if light has a finite speed.

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Making it mean something

Continued measurements over the course of the next few centuries solidified the measurement of the speed of light, but it wasn't until the mid-1800s when things really started to come together. That's when the physicist James Clerk Maxwell accidentally invented light.

Maxwell had been playing around with the then-poorly-understood phenomena of electricity and magnetism when he discovered a single unified picture that could explain all the disparate observations. Laying the groundwork for what we now understand to be the electromagnetic force , in those equations he discovered that changing electric fields can create magnetic fields, and vice versa. This allows waves of electricity to create waves of magnetism, which go on to make waves of electricity and back and forth and back and forth, leapfrogging over each other, capable of traveling through space.

And when he went to calculate the speed of these so-called electromagnetic waves, Maxwell got the same number that scientists had been measuring as the speed of light for centuries. Ergo, light is made of electromagnetic waves and it travels at that speed, because that is exactly how quickly waves of electricity and magnetism travel through space.

And this was all well and good until Einstein came along a few decades later and realized that the speed of light had nothing to do with light at all. With his special theory of relativity , Einstein realized the true connection between time and space, a unified fabric known as space-time. But as we all know, space is very different than time. A meter or a foot is very different than a second or a year. They appear to be two completely different things.

So how could they possibly be on the same footing?

There needed to be some sort of glue, some connection that allowed us to translate between movement in space and movement in time. In other words, we need to know how much one meter of space, for example, is worth in time. What's the exchange rate? Einstein found that there was a single constant, a certain speed, that could tell us how much space was equivalent to how much time, and vice versa.

Einstein's theories didn't say what that number was, but then he applied special relativity to the old equations of Maxwell and found that this conversion rate is exactly the speed of light.

Of course, this conversion rate, this fundamental constant that unifies space and time, doesn't know what an electromagnetic wave is, and it doesn't even really care. It's just some number, but it turns out that Maxwell had already calculated this number and discovered it without even knowing it. That's because all massless particles are able to travel at this speed, and since light is massless, it can travel at that speed. And so, the speed of light became an important cornerstone of modern physics.

But still, why that number, with that value, and not some other random number? Why did nature pick that one and no other? What's going on?

Related: The genius of Albert Einstein: his life, theories and impact on science

Making it meaningless

Well, the number doesn't really matter. It has units after all: meters per second. And in physics any number that has units attached to it can have any old value it wants, because it means you have to define what the units are. For example, in order to express the speed of light in meters per second, first you need to decide what the heck a meter is and what the heck a second is. And so the definition of the speed of light is tied up with the definitions of length and time.

In physics, we're more concerned with constants that have no units or dimensions — in other words, constants that appear in our physical theories that are just plain numbers. These appear much more fundamental, because they don't depend on any other definition. Another way of saying it is that, if we were to meet some alien civilization , we would have no way of understanding their measurement of the speed of light, but when it comes to dimensionless constants, we can all agree. They're just numbers.

One such number is known as the fine structure constant, which is a combination of the speed of light, Planck's constant , and something known as the permittivity of free space. Its value is approximately 0.007. 0.007 what? Just 0.007. Like I said, it's just a number.

So on one hand, the speed of light can be whatever it wants to be, because it has units and we need to define the units. But on the other hand, the speed of light can't be anything other than exactly what it is, because if you were to change the speed of light, you would change the fine structure constant. But our universe has chosen the fine structure constant to be approximately 0.007, and nothing else. That is simply the universe we live in, and we get no choice about it at all. And since this is fixed and universal, the speed of light has to be exactly what it is.

So why is the fine structure constant exactly the number that it is, and not something else? Good question. We don't know.

Learn more by listening to the episode "Why is the speed of light the way it is?" on the Ask A Spaceman podcast, available on iTunes and on the Web at http://www.askaspaceman.com. Thanks to Robert H, Michael E., @DesRon94, Evan W., Harry A., @twdixon, Hein P., Colin E., and Lothian53 for the questions that led to this piece! Ask your own question on Twitter using #AskASpaceman or by following Paul @PaulMattSutter and facebook.com/PaulMattSutter.

Join our Space Forums to keep talking space on the latest missions, night sky and more! And if you have a news tip, correction or comment, let us know at: [email protected].

Paul M. Sutter is an astrophysicist at SUNY Stony Brook and the Flatiron Institute in New York City. Paul received his PhD in Physics from the University of Illinois at Urbana-Champaign in 2011, and spent three years at the Paris Institute of Astrophysics, followed by a research fellowship in Trieste, Italy, His research focuses on many diverse topics, from the emptiest regions of the universe to the earliest moments of the Big Bang to the hunt for the first stars. As an "Agent to the Stars," Paul has passionately engaged the public in science outreach for several years. He is the host of the popular "Ask a Spaceman!" podcast, author of "Your Place in the Universe" and "How to Die in Space" and he frequently appears on TV — including on The Weather Channel, for which he serves as Official Space Specialist.

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• voidpotentialenergy This is just my opinion but i think L speed is it's speed because the particle part of it is the fastest it can interact with the quanta distance in quantum fluctuation. Light is particle and wave so the wave happens in the void between quanta. Gravity probably travels in that void and why gravity seems instant. Reply
• rod The space.com article wraps up the discussion with, "So on one hand, the speed of light can be whatever it wants to be, because it has units and we need to define the units. But on the other hand, the speed of light can't be anything other than exactly what it is, because if you were to change the speed of light, you would change the fine structure constant. But our universe has chosen the fine structure constant to be approximately 0.007, and nothing else. That is simply the universe we live in, and we get no choice about it at all. And since this is fixed and universal, the speed of light has to be exactly what it is. So why is the fine structure constant exactly the number that it is, and not something else? Good question. We don't know." It seems that the *universe* made this decision, *But our universe has chosen the fine structure constant to be...* I did not know that the universe was capable of making decisions concerning constants used in physics. E=mc^2 is a serious constant. Look at nuclear weapons development, explosive yields, and stellar evolution burn rates for p-p chain and CNO fusion rates. The report indicates why alpha (fine structure constant) is what it is and c is what it is, *We don't know*. Reply

Admin said: We all know and love the speed of light, but why does it have the value that it does? Why isn't it some other number? And why did it become such a cornerstone of physics? Why is the speed of light the way it is? : Read more

rod said: The space.com article wraps up the discussion with, "So on one hand, the speed of light can be whatever it wants to be, because it has units and we need to define the units. But on the other hand, the speed of light can't be anything other than exactly what it is, because if you were to change the speed of light, you would change the fine structure constant. But our universe has chosen the fine structure constant to be approximately 0.007, and nothing else. That is simply the universe we live in, and we get no choice about it at all. And since this is fixed and universal, the speed of light has to be exactly what it is. So why is the fine structure constant exactly the number that it is, and not something else? Good question. We don't know." It seems that the *universe* made this decision, *But our universe has chosen the fine structure constant to be...* I did not know that the universe was capable of making decisions concerning constants used in physics. E=mc^2 is a serious constant. Look at nuclear weapons development, explosive yields, and stellar evolution burn rates for p-p chain and CNO fusion rates. The report indicates why alpha (fine structure constant) is what it is and c is what it is, *We don't know*.

• rod FYI. When someone says *the universe has chosen*, I am reminded of these five lessons from a 1982 Fed. court trial. The essential characteristics of science are: It is guided by natural law; It has to be explanatory by reference to natural law; It is testable against the empirical world; Its conclusions are tentative, i.e., are not necessarily the final word; and It is falsifiable. Five important points about science. Reply
• Gary If the universe is expanding , how can the speed of light be constant ( miles per second , if each mile is getting longer ) ? Can light's velocity be constant while the universe expands ? So, with the expansion of the universe , doesn't the speed of light need to increase in order to stay at a constant velocity in miles per second ? Or, do the miles in the universe remain the same length as the universe 'adds' miles to its diameter ? Are the miles lengthening or are they simply being added / compounded ? Reply
• Gary Lets say we're in outer space and we shoot a laser through a block of glass. What causes the speed of the laser light to return to the speed it held prior to entering the block of glass ? Is there some medium in the vacuum of space that governs the speed of light ? Do the atoms in the glass push it back up to its original speed. If so, why don't those same atoms constantly push the light while it travels through the block of glass ? Reply

Gary said: Lets say we're in outer space and we shoot a laser through a block of glass. What causes the speed of the laser light to return to the speed it held prior to entering the block of glass ? Is there some medium in the vacuum of space that governs the speed of light ? Do the atoms in the glass push it back up to its original speed. If so, why don't those same atoms constantly push the light while it travels through the block of glass ?

Gary said: If the universe is expanding , how can the speed of light be constant ( miles per second , if each mile is getting longer ) ? Can light's velocity be constant while the universe expands ? So, with the expansion of the universe , doesn't the speed of light need to increase in order to stay at a constant velocity in miles per second ? Or, do the miles in the universe remain the same length as the universe 'adds' miles to its diameter ? Are the miles lengthening or are they simply being added / compounded ?

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NASA’s Guide to Near-light-speed Travel

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Watch this video to learn about near-light-speed safety considerations, travel times and distances between popular destinations around the universe. You can also download shorter clips from the video and printable postcards to send to your friends.

Can anything travel faster than the speed of light?

Does it matter if it's in a vacuum?

In 1676, by studying the motion of Jupiter's moon Io, Danish astronomer Ole Rømer calculated that light travels at a finite speed. Two years later, building on data gathered by Rømer, Dutch mathematician and scientist Christiaan Huygens became the first person to attempt to determine the actual speed of light, according to the American Museum of Natural History in New York City. Huygens came up with a figure of 131,000 miles per second (211,000 kilometers per second), a number that isn't accurate by today's standards — we now know that the speed of light in the "vacuum" of empty space is about 186,282 miles per second (299,792 km per second) — but his assessment showcased that light travels at an incredible speed.

According to Albert Einstein 's theory of special relativity , light travels so fast that, in a vacuum, nothing in the universe is capable of moving faster. 

"We cannot move through the vacuum of space faster than the speed of light," confirmed Jason Cassibry, an associate professor of aerospace engineering at the Propulsion Research Center, University of Alabama in Huntsville.

Question answered, right? Maybe not. When light is not in a vacuum, does the rule still apply?

Related: How many atoms are in the observable universe?

"Technically, the statement 'nothing can travel faster than the speed of light' isn't quite correct by itself," at least in a non-vacuum setting, Claudia de Rham, a theoretical physicist at Imperial College London, told Live Science in an email. But there are certain caveats to consider, she said. Light exhibits both particle-like and wave-like characteristics, and can therefore be regarded as both a particle (a photon ) and a wave. This is known as wave-particle duality.

If we look at light as a wave, then there are "multiple reasons" why certain waves can travel faster than white (or colorless) light in a medium, de Rham said. One such reason, she said, is that "as light travels through a medium — for instance, glass or water droplets — the different frequencies or colors of light travel at different speeds." The most obvious visual example of this occurs in rainbows, which typically have the long, faster red wavelengths at the top and the short, slower violet wavelengths at the bottom, according to a post by the University of Wisconsin-Madison . 

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When light travels through a vacuum, however, the same is not true. "All light is a type of electromagnetic wave, and they all have the same speed in a vacuum (3 x 10^8 meters per second). This means both radio waves and gamma rays have the same speed," Rhett Allain, a physics professor at Southeastern Louisiana University, told Live Science in an email.

So, according to de Rham, the only thing capable of traveling faster than the speed of light is, somewhat paradoxically, light itself, though only when not in the vacuum of space. Of note, regardless of the medium, light will never exceed its maximum speed of 186,282 miles per second.

Universal look

According to Cassibry, however, there is something else to consider when discussing things moving faster than the speed of light.

"There are parts of the universe that are expanding away from us faster than the speed of light, because space-time is expanding," he said. For example, the Hubble Space Telescope recently spotted 12.9 billion year-old light from a distant star known as Earendel. But, because the universe is expanding at every point, Earendel is moving away from Earth and has been since its formation, so the galaxy is now 28 billion light years away from Earth.

In this case, space-time is expanding, but the material in space-time is still traveling within the bounds of light speed.

Related: Why is space a vacuum?

So, it's clear that nothing travels faster than light that we know of, but is there any situation where it might be possible? Einstein's theory of special relativity, and his subsequent theory of general relativity, is "built under the principle that the notions of space and time are relative," de Rham said. But what does this mean? "If someone [were] able to travel faster than light and carry information with them, their notion of time would be twisted as compared to ours," de Rham said. "There could be situations where the future could affect our past, and then the whole structure of reality would stop making sense."

This would indicate that it would probably not be desirable to make a human travel faster than the speed of light. But could it ever be possible? Will there ever be a time when we are capable of creating craft that could propel materials — and ultimately humans — through space at a pace that outstrips light speed? "Theorists have proposed various types of warp bubbles that could enable faster-than-light travel," Cassibry said.

But is de Rham convinced?

"We can imagine being able to communicate at the speed of light with systems outside our solar system ," de Rham said. "But sending actual physical humans at the speed of light is simply impossible, because we cannot accelerate ourselves to such speed.

"Even in a very idealistic situation where we imagine we could keep accelerating ourselves at a constant rate — ignoring how we could even reach a technology that could keep accelerating us continuously — we would never actually reach the speed of light," she added. "We could get close, but never quite reach it."

Related: How long is a galactic year?

This is a point confirmed by Cassibry. "Neglecting relativity, if you were to accelerate with a rate of 1G [Earth gravity], it would take you a year to reach the speed of light. However, you would never really reach that velocity because as you start to approach lightspeed, your mass energy increases, approaching infinite. "One of the few known possible 'cheat codes' for this limitation is to expand and contract spacetime, thereby pulling your destination closer to you. There seems to be no fundamental limit on the rate at which spacetime can expand or contract, meaning we might be able to get around this velocity limit someday."

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Allain is similarly confident that going faster than light is far from likely, but, like Cassibry, noted that if humans want to explore distant planets, it may not actually be necessary to reach such speeds. "The only way we could understand going faster than light would be to use some type of wormhole in space," Allain said. "This wouldn't actually make us go faster than light, but instead give us a shortcut to some other location in space."

Cassibry, however, is unsure if wormholes will ever be a realistic option.

"Wormholes are theorized to be possible based on a special solution to Einstein's field equations," he said. "Basically, wormholes, if possible, would give you a shortcut from one destination to another. I have no idea if it's possible to construct one, or how we would even go about doing it." Originally published on Live Science.

Joe Phelan is a journalist based in London. His work has appeared in VICE, National Geographic, World Soccer and The Blizzard, and has been a guest on Times Radio. He is drawn to the weird, wonderful and under examined, as well as anything related to life in the Arctic Circle. He holds a bachelor's degree in journalism from the University of Chester. 

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A Groundbreaking Scientific Discovery Just Gave Humanity the Keys to Interstellar Travel

In a first, this warp drive actually obeys the laws of physics.

If a superluminal—meaning faster than the speed of light—warp drive like Alcubierre’s worked, it would revolutionize humanity’s endeavors across the universe , allowing us, perhaps, to reach Alpha Centauri, our closest star system, in days or weeks even though it’s four light years away.

However, the Alcubierre drive has a glaring problem: the force behind its operation, called “negative energy,” involves exotic particles—hypothetical matter that, as far as we know, doesn’t exist in our universe. Described only in mathematical terms, exotic particles act in unexpected ways, like having negative mass and working in opposition to gravity (in fact, it has “anti-gravity”). For the past 30 years, scientists have been publishing research that chips away at the inherent hurdles to light speed revealed in Alcubierre’s foundational 1994 article published in the peer-reviewed journal Classical and Quantum Gravity .

Now, researchers at the New York City-based think tank Applied Physics believe they’ve found a creative new approach to solving the warp drive’s fundamental roadblock. Along with colleagues from other institutions, the team envisioned a “positive energy” system that doesn’t violate the known laws of physics . It’s a game-changer, say two of the study’s authors: Gianni Martire, CEO of Applied Physics, and Jared Fuchs, Ph.D., a senior scientist there. Their work, also published in Classical and Quantum Gravity in late April, could be the first chapter in the manual for interstellar spaceflight.

POSITIVE ENERGY MAKES all the difference. Imagine you are an astronaut in space, pushing a tennis ball away from you. Instead of moving away, the ball pushes back, to the point that it would “take your hand off” if you applied enough pushing force, Martire tells Popular Mechanics . That’s a sign of negative energy, and, though the Alcubierre drive design requires it, there’s no way to harness it.

Instead, regular old positive energy is more feasible for constructing the “ warp bubble .” As its name suggests, it’s a spherical structure that surrounds and encloses space for a passenger ship using a shell of regular—but incredibly dense—matter. The bubble propels the spaceship using the powerful gravity of the shell, but without causing the passengers to feel any acceleration. “An elevator ride would be more eventful,” Martire says.

That’s because the density of the shell, as well as the pressure it exerts on the interior, is controlled carefully, Fuchs tells Popular Mechanics . Nothing can travel faster than the speed of light, according to the gravity-bound principles of Albert Einstein’s theory of general relativity . So the bubble is designed such that observers within their local spacetime environment—inside the bubble—experience normal movement in time. Simultaneously, the bubble itself compresses the spacetime in front of the ship and expands it behind the ship, ferrying itself and the contained craft incredibly fast. The walls of the bubble generate the necessary momentum, akin to the momentum of balls rolling, Fuchs explains. “It’s the movement of the matter in the walls that actually creates the effect for passengers on the inside.”

Building on its 2021 paper published in Classical and Quantum Gravity —which details the same researchers’ earlier work on physical warp drives—the team was able to model the complexity of the system using its own computational program, Warp Factory. This toolkit for modeling warp drive spacetimes allows researchers to evaluate Einstein’s field equations and compute the energy conditions required for various warp drive geometries. Anyone can download and use it for free . These experiments led to what Fuchs calls a mini model, the first general model of a positive-energy warp drive. Their past work also demonstrated that the amount of energy a warp bubble requires depends on the shape of the bubble; for example, the flatter the bubble in the direction of travel, the less energy it needs.

THIS LATEST ADVANCEMENT suggests fresh possibilities for studying warp travel design, Erik Lentz, Ph.D., tells Popular Mechanics . In his current position as a staff physicist at Pacific Northwest National Laboratory in Richland, Washington, Lentz contributes to research on dark matter detection and quantum information science research. His independent research in warp drive theory also aims to be grounded in conventional physics while reimagining the shape of warped space. The topic needs to overcome many practical hurdles, he says.

Controlling warp bubbles requires a great deal of coordination because they involve enormous amounts of matter and energy to keep the passengers safe and with a similar passage of time as the destination. “We could just as well engineer spacetime where time passes much differently inside [the passenger compartment] than outside. We could miss our appointment at Proxima Centauri if we aren’t careful,” Lentz says. “That is still a risk if we are traveling less than the speed of light.” Communication between people inside the bubble and outside could also become distorted as it passes through the curvature of warped space, he adds.

While Applied Physics’ current solution requires a warp drive that travels below the speed of light, the model still needs to plug in a mass equivalent to about two Jupiters. Otherwise, it will never achieve the gravitational force and momentum high enough to cause a meaningful warp effect. But no one knows what the source of this mass could be—not yet, at least. Some research suggests that if we could somehow harness dark matter , we could use it for light-speed travel, but Fuchs and Martire are doubtful, since it’s currently a big mystery (and an exotic particle).

Despite the many problems scientists still need to solve to build a working warp drive, the Applied Physics team claims its model should eventually get closer to light speed. And even if a feasible model remains below the speed of light, it’s a vast improvement over today’s technology. For example, traveling at even half the speed of light to Alpha Centauri would take nine years. In stark contrast, our fastest spacecraft, Voyager 1—currently traveling at 38,000 miles per hour—would take 75,000 years to reach our closest neighboring star system.

Of course, as you approach the actual speed of light, things get truly weird, according to the principles of Einstein’s special relativity . The mass of an object moving faster and faster would increase infinitely, eventually requiring an infinite amount of energy to maintain its speed.

“That’s the chief limitation and key challenge we have to overcome—how can we have all this matter in our [bubble], but not at such a scale that we can never even put it together?” Martire says. It’s possible the answer lies in condensed matter physics, he adds. This branch of physics deals particularly with the forces between atoms and electrons in matter. It has already proven fundamental to several of our current technologies, such as transistors, solid-state lasers, and magnetic storage media.

The other big issue is that current models allow a stable warp bubble, but only for a constant velocity. Scientists still need to figure out how to design an initial acceleration. On the other end of the journey, how will the ship slow down and stop? “It’s like trying to grasp the automobile for the first time,” Martire says. “We don’t have an engine just yet, but we see the light at the end of the tunnel.” Warp drive technology is at the stage of 1882 car technology, he says: when automobile travel was possible, but it still looked like a hard, hard problem.

The Applied Physics team believes future innovations in warp travel are inevitable. The general positive energy model is a first step. Besides, you don’t need to zoom at light speed to achieve distances that today are just a dream, Martire says. “Humanity is officially, mathematically, on an interstellar track.”

Before joining Popular Mechanics , Manasee Wagh worked as a newspaper reporter, a science journalist, a tech writer, and a computer engineer. She’s always looking for ways to combine the three greatest joys in her life: science, travel, and food.

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How fast am I going?

More information, what is this, online gps speedometer to the rescue.

As drivers, we all know how important it is to be aware of our speed and heading while on the road. Whether we're cruising on the highway or navigating through busy city streets, knowing how fast we're going and in what direction can mean the difference between a safe journey and a dangerous one. Fortunately, with the help of modern technology, checking your speed and heading has never been easier. That's where a GPS speedometer comes in.

How does it work?

Before we dive into the features of a GPS speedometer, let's take a moment to understand how it works. GPS, or Global Positioning System, is a technology that uses satellites to determine your exact location on Earth. By calculating the time it takes for signals to travel from multiple satellites to your device, GPS can pinpoint your location with incredible accuracy.

A GPS speedometer uses this same technology to measure your speed and heading. By comparing your device's location at two different points in time, the website can calculate the distance you've traveled and divide it by the time it took to travel that distance to determine your speed. Additionally, by comparing your device's location and the direction it is facing at two different points in time, the website can determine your heading. The result is your speed and heading.

It's important to note that GPS measurements may not be as accurate as those from traditional instruments in your car. Factors like terrain, weather, and the quality of your device's GPS signal can all affect the accuracy of the measurement. However, for most everyday use cases, a GPS speedometer is more than sufficient.

The GPS speedometer website offers a variety of features to make checking your speed and heading as easy and convenient as possible. One of the most useful features is the ability to switch between different units of measurement. Whether you prefer miles per hour, kilometers per hour, meters per second, knots, or even mach, the website has you covered.

In addition to the unit of measurement, the website also provides real-time updates on your speed and heading. As you move, the display will update in real-time to show your current speed and the direction you are facing. This feature is especially useful for those who need to monitor their speed and heading while driving, such as truck drivers or delivery drivers.

Finally, the website also allows you to customize the display to your liking. You can choose between different color schemes and adjust the size of the display to fit your device's screen.

Using the GPS speedometer website is incredibly easy. Simply visit the website on your device and grant it access to your device's location. The website will then display your current speed and heading in the unit of measurement of your choice. You can leave the website open while you drive to monitor your speed and heading in real-time.

To get the most accurate readings, make sure your device has a clear view of the sky to ensure a strong GPS signal. Additionally, try to avoid using the website in areas with poor weather conditions or terrain that may interfere with the signal.

Benefits of using a GPS speedometer

There are several benefits to using a GPS speedometer. Firstly, it can help keep you safe on the road by making you aware of your speed and heading. By monitoring your speed and heading in real-time, you can adjust your driving behavior to stay within the speed limit and avoid accidents.

Using a GPS speedometer can also help you avoid speeding tickets and other legal issues. If you're pulled over for speeding, you can use the GPS speedometer data to prove your innocence and avoid costly fines.

Furthermore, GPS speed tracking on your smartphone can prove valuable for other modes of travel such as boating, skiing, horseback riding, and even while traveling on trains, ensuring you have a precise speed measurement across various outdoor adventures and modes of transportation.

There are several situations where you might want to check your speed using your phone's GPS, such as when you're cycling, running, or driving. For instance, if you're cycling through a scenic route and want to maintain a consistent pace, a GPS speedometer app can help you monitor your speed and make necessary adjustments. Similarly, while running, you can use your phone's GPS to track your current speed and analyze your performance. Additionally, drivers can also benefit from GPS speed tracking, especially when their vehicle's speedometer is malfunctioning or when driving through unfamiliar roads with varying speed limits. Overall, using your smartphone for GPS speed tracking is a convenient and versatile solution for various activities where monitoring your speed is essential.

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Can information travel faster than light?

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One of the tenets of Einstein's Theory of Special Relativity is that nothing can travel faster than the speed of light in a vacuum. Light speed is considered the universal speed limit of everything, and this is widely accepted by the scientific community. But in science, if you make a hard-and-fast rule, someone will try to disprove it, or at least find a loophole. And the speed of light is no exception.

Light, in a vacuum, travels at approximately 299,792 kilometers per second (186,282 miles per second). In September 2011, physicists working on the Oscillation Project with Emulsion-tRacking Apparatus (OPERA) created a frenzy in the scientific community when they announced that their experiments resulted in subatomic particles called neutrinos traveling from the European Organization for Nuclear Research (CERN) near Geneva, Switzerland to the Gran Sasso National Laboratory near L'Aquila, Italy and arriving around 60 nanoseconds earlier than a beam of light. Ideas as to either how these neutrinos could have actually broken the speed of light, or as to what errors could have caused the impossible results, abounded. Finally, equipment issues, including a loose cable, were discovered as likely culprits, and the results were declared erroneous. So no rewriting of Einstein's theories turned out to be necessary.

Other researchers are trying to bend the rules rather than break them. In fact, bending space-time is one theory of how superluminal – faster-than-light -- speeds in space travel might be reached. The idea is that space time could be contracted in front of a spaceship and expanded behind it, while the ship would remain stationary in a warp bubble that itself was moving faster than the speed of light. This concept was originally modeled by Mexican theoretical physicist Miguel Alcubierre in 1994 as a theoretical possibility, but one that would require a universe-sized amount of negative energy to power the phenomenon. It was later refined to requiring a planet-sized amount and then again to needing an amount around the size of the Voyager 1 space probe. Unfortunately, the negative energy would have to come from exotic matter that is difficult to come by, and we're currently only at the level of miniature lab experiments on warp drives. The math behind these theories is based on the laws of relativity, so theoretically it wouldn't be breaking the rules. The technology, if it ever exists, could also be used for going slower than light, but much faster than we can go now, which might be more practical.

Space travel is just one of the possible applications of reaching or exceeding the speed of light. Some scientists are working on doing the same for the purposes of much faster data transfer. Read on to find out about current data speeds and the potential for faster-than-light information.

Can data even travel at the speed of light?

The possibility of superluminal data transfer.

Currently, most of our data travels through either copper wire or fiber optic cable. Even when we send data via our cell phones over radio waves, which also travel at light speed, it ends up traversing the wired networks of the Internet at some point. The two most common types of copper wire for long-distance information transfer are twisted pair (used first for telephony, and later for dial-up Internet and DSL ), and coaxial cable (used for cable TV initially, then Internet and phone). Coaxial cable is the faster of the two. But still faster is fiber optic cable. Rather than using copper to conduct data in the form of electrical signals, fiber optic cable moves data as pulses of light.

The "in a vacuum" reference on the previous page regarding the speed of light is important. Light through fiber optic is not as fast as light through a vacuum. Light, when moving through just about any medium, is slower than the universal constant we know as the speed of light. The difference is negligible through air, but light can be slowed down considerably through other media, including glass, which makes up the core of most fiber optic cabling. The refractive index of a medium is the speed of light in a vacuum divided by the speed of light in the medium. So if you know two of those numbers, you can calculate the other. The index of refraction of glass is around 1.5. If you divide the speed of light (approximately 300,000 kilometers, or 186,411 miles, per second) by this, you get around 200,000 kilometers (124,274 miles) per second, which is the approximate speed of light through glass. Some fiber optic cabling is made of plastic, which has an even higher refractive index, and therefore a lower speed.

Part of the reason for the decrease in speed is the dual nature of light. It has the attributes of both a particle and a wave. Light is actually made up of particles called photons , and they do not move in a straight line through the cabling. As the photons hit molecules of material, they bounce in various directions. Light refraction and absorption by the medium eventually lead to some energy and data loss. This is why a signal can't travel indefinitely and has to be boosted periodically to cover long distances. However, the slowing of light isn't all bad news. Some impurities are added to fiber optics to control the speed and aid in channeling the signal effectively.

Fiber optic cable is still far faster than copper wire, and isn't as susceptible to electromagnetic interference. Fiber can achieve speeds of hundreds of Gigabits per second, or even Terabits. Home Internet connections don't achieve those super high speeds, at least partially because wiring is being shared by many households over entire areas, and even networks that use fiber optics generally have copper running the last stretch into people's homes. But with fiber running all the way to your neighborhood or home, you can get something in the range of 50 to 100 Megabits per second of data transfer, compared to 1 to 6 Megabits per second from average DSL lines and 25 or so Megabits per second from cable. Actual data speeds vary greatly by location, provider and your chosen plan, of course.

There are also other things that cause signal latency (delay), such as the back and forth communication required when you access a Web page or download data (handshaking). Your computer and the server housing the data are communicating to make sure they are synchronized and data transfer is successful, causing a delay, albeit a brief and necessary one. The distance your data has to travel will also affect how long it takes to get there, and there could be additional bottlenecks at any hardware and cabling the data has to travel through to get to its destination. A system is only as fast as its slowest component, and every millisecond counts in the days of seemingly (but not really) instant communication.

There have been recent breakthroughs in transferring data over copper wiring at nearly fiber optic speeds via reducing interference and other techniques. And researchers are also working on transmitting data via light through the air, say using lightbulbs for WiFi, or transmitting laser beams from building to building. Again, light through the air does move at close to light speed, but nothing we have now is surpassing the speed limit. Can we achieve actual faster-than-light transfer?

The use of fiber optic cable wasn't the first attempt to harness light for data transfer. Alexander Graham Bell himself invented the photophone, which was essentially the first wireless telephone, but using light rather than the radio waves used by modern cell phones. It worked by projecting a voice toward a mirror, which caused the mirror to vibrate. Light from the sun was bounced off the vibrating mirror into a selenium receiver that converted it into an electrical current for transmission via telephone (his most famous invention). Its major flaw was that direct sunlight was necessary, so clouds or other objects could block the signal. Never mind making a call in the middle of the night. But it actually worked, and served as a predecessor to fiber optics.

Scientists at the National Institute of Standards and Technology (NIST) are claiming to have achieved faster-than-light transfer of quantum data using something called four-wave mixing, which incidentally is a phenomenon that's considered a form of interference in fiber optic lines. The experiment involves sending a short 200-nanosecond seed pulse through heated rubidium vapor and at the same time sending in a second pump beam at a different frequency to amplify the seed pulse. Photons from both beams interact with the vapor in a way that generates a third beam. Apparently, the peaks of both the amplified seed pulse and the newly generated pulse can exit faster than a reference beam traveling at the speed of light in a vacuum. The speed differences they reported were 50 to 90 nanoseconds faster than light through a vacuum. They even proclaimed being able to tune the speed of the pulses by altering the input seed detuning and power.

Another fast data transfer technology in the works is quantum teleportation , which relies on the existence of entangled pairs: two particles that are in tune with each other to the point that if you measure one, the other ends up with the same quality that you found in the first one, no matter their distance from one another. This also requires a third particle that contains the actual bits of data you are trying to transfer. A laser is used to teleport one of the entangled particles elsewhere, in a manner of speaking. It isn't really transporting a photon, but rather changing a new photon into a copy of the original. The photon in the entangled pair can be compared to the third photon to find their similarities or differences, and that information can be relayed to the other location and used for comparison with the twin particle to glean the data. This sounds like something that would result in instant transfer, but that's not the case. Laser beams only travel at the speed of light. But this has potential applications for sending encrypted data via satellite, and for networking quantum computers, should we ever invent them. And it's further along than any attempts at superluminal data transfer. It works over miles at this point, and researchers are trying to increase the teleportation distance.

The answer to whether meaningful information can travel faster than light is currently no. We're only at the level of moving a few quantum particles at speeds that may possibly be over the speed of light, if the data pans out on subsequent experiments. To have a practically applicable form of data transfer, you have to be able to send organized bits of data that mean something, uncorrupted, to another machine that can interpret it. The fastest transmission in the world will mean nothing otherwise. But you can be sure that if the speed of light is broken, we'll be applying it to our Internet transmissions far sooner than to interstellar travel. Our ability to watch the highest quality television and surf the net at the fastest speeds will be paramount. And perhaps for those purposes, even getting ourselves to truly as-fast-as-light transmission would do wonders.

Frequently Answered Questions

Is it possible for information to travel faster than light, lots more information, author's note.

Physics is a truly fascinating subject, as it attempts to find the answer to how everything in the universe works. Without the study of physics, we probably wouldn't have a lot of modern conveniences, for instance those that require electricity, or depend upon the behavior of waves of any sort (like just about every form of long distance communication). You certainly wouldn't be reading this right now. Without an understanding of physical laws, lifting a piano would be more difficult, video games wouldn't be as much fun (or exist), and cartoon animators wouldn't know what laws to break to make us laugh. And we certainly wouldn't have ventured into space, an ability we'll need if we discover, via astrophysics or a keen observer, that a planet-destroying asteroid is headed our way. Also, kudos to mathematics for making the study of physics possible. I will continue to sit back and reap the benefits made possible by all the hard-working mathematicians, physicists and engineers of the world.

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Please copy/paste the following text to properly cite this HowStuffWorks.com article:

• Speed Of Sound vs Speed Of Light

The speed of sound and the speed of light are two common concepts that most of us likely learn about at some point in life. Both are defined rather simply, with the speed of sound being the speed that sound travels, and the speed of light being the speed at which light travels. Although these two concepts may sound similar, they are in fact radically different from one another. What are some of the differences between them?

The first notable difference between the speed of sound and light is how fast they are. In Earth’s atmosphere , the speed of sound averages at about 761-miles per hour (1,225-kilometres per hour). That may seem fast, yet when compared to the speed of light, it seems quite small. Light travels at a staggering 670-million miles per hour (1.07-billion kilometres per hour). That’s around 880,000 times faster than the speed of sound. 

Sound Must Have A Medium

In order for sound to exist, it must have a medium to travel through. For sound, this medium is air, and that’s why sound does not exist in the emptiness of space. Meanwhile, light does not need a medium to exist. Rather, light travels independently of any medium, and thus it can travel through space, unlike sound. 

The Speed Of Light Is Constant

Another notable difference between light and sound is that the speed of light is constant while the speed of sound is not. Since the speed of sound requires air to exist, its speed is dependent upon the density and temperature of air. For example, when we say that sound travels at 761-miles per hour, this is only the case at sea level and when temperatures are around 59-degrees Fahrenheit (15-degrees Celsius). If you are at a higher elevation where the density of air is lower and temperatures are colder, the speed of sound will be different. Thus, the speed of sound varies. Light, however, has no such constraint. Rather, the speed of light is constant regardless of any other factor. No matter the conditions, it always travels at the same speed. 

Things That Can Move Faster Than Sound

The speed of sound is fast, yet it is by no means the fastest thing in the universe. It is not even the fastest thing on Earth . Human’s have broken the sound barrier countless times, a speed known as supersonic speed. Light is a different story, however. The speed of light is a fixed law of nature, and it represents the fastest possible speed anything can move at. No matter how hard we try or how advanced technology becomes, the current understanding of the cosmos is that the light barrier cannot be broken. Thus, the speed of light is like a cosmic speed limit. 

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October 26, 1998

How fast is the earth moving?

Rhett Herman, a physics professor at Radford University in Virginia, supplies the following answer

Getty Images

Questions about how fast the earth--or anything, for that matter--is moving are incomplete unless they also ask, "Compared to what?" Without a frame of reference, questions about motion cannot be completely answered.

Consider the movement of the earth's surface with respect to the planet's center. The earth rotates once every 23 hours, 56 minutes and 4.09053 seconds, called the sidereal period, and its circumference is roughly 40,075 kilometers. Thus, the surface of the earth at the equator moves at a speed of 460 meters per second--or roughly 1,000 miles per hour.

As schoolchildren, we learn that the earth is moving about our sun in a very nearly circular orbit. It covers this route at a speed of nearly 30 kilometers per second, or 67,000 miles per hour. In addition, our solar system--Earth and all--whirls around the center of our galaxy at some 220 kilometers per second, or 490,000 miles per hour. As we consider increasingly large size scales, the speeds involved become absolutely huge!

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The galaxies in our neighborhood are also rushing at a speed of nearly 1,000 kilometers per second towards a structure called the Great Attractor, a region of space roughly 150 million light-years (one light year is about six trillion miles) away from us. This Great Attractor, having a mass 100 quadrillion times greater than our sun and span of 500 million light-years, is made of both the visible matter that we can see along with the so-called dark matter that we cannot see.

Each of the motions described above were given relative to some structure. Our motion about our sun was described relative to our sun, while the motion of our local group of galaxies was described as toward the Great Attractor. The question arises: Is there some universal frame of reference relative to which we can define the motions of all things? The answer may have been provided by the Cosmic Background Explorer (COBE) satellite.

In 1989, the COBE satellite was placed in orbit about the earth (again, the earth is the frame of reference!) to measure the long-diluted radiation echo of the birth of our universe. This radiation, which remains from the immensely hot and dense primordial fireball that was our early universe, is known as the cosmic microwave background radiation (CBR). The CBR presently pervades all of space. It is the equivalent of the entire universe "glowing with heat."

One of COBE's discoveries was that the earth was moving with respect to this CBR with a well-defined speed and direction. Because the CBR permeates all space, we can finally answer the original question fully, using the CBR as the frame of reference.

The earth is moving with respect to the CBR at a speed of 390 kilometers per second. We can also specify the direction relative to the CBR. It is more fun, though, to look up into the night sky and find the constellation known as Leo (the Lion). The earth is moving toward Leo at the dizzying speed of 390 kilometers per second. It is fortunate that we won't hit anything out there during any of our lifetimes!

GPS Speedometer

Download android app, download ios app, how fast am i going check online with this online gps speedometer.

Make sure you gave permissions to this website and the browser.

Check how fast you are going with this online speedometer by enabling location access. See How?

How to Track movement online using GPS speedometer?

1. Visit Google and search speedometeronline.com

2. After visit website show prompt message for GPS Access give Allow access

3. Then Track your free GPS Speedometer online on your phone/computer and share with your friends

How to enable website location on phone?

First, go to your device settings and turn on the location then follow the steps.

Step 1: Open SpeedoMeterOnline.com and click on the Lock icon at the top.

Step 2: Then click on the Permission option.

Step 3: Now Click on the Switch to enable location access.

Step 4: The button should look like this.

Step 5: After that Refresh the website it will start showing your traveling speed.

How many types of speeds this GPS speedometer website can track?

This website can track Three types of speeds first is meters per second, the second is Miles per hour and the third last tone is Kilometer per hour. You can access this by just click on the button below the speed

How fast am i Driving?

This Online Speedometer will get your Car, Train of Cycle current speed without installing any app. Just give GPS Permission to make accurate speed.

How fast am i going right now?

Speedometeronline.com show the exact traveling speed of your train, bus, car, cycle or anyother moving vehicle speed in Mph or Kph and also Meter per Second with the use of GPS on your phone.

What is GPS Speedometer?

GPS Speedometer has received a single from the satellite of orbit of earth and calculates how fast you are traveling on any surface like land, water, or Air. You can use our speedometeronline.com as a GPS boat speedometer, online speedometer for train, Boat GPS speedometer and you can use also for if you are traveling via bus, streetcars, cable cars, or on water via ferries and water taxis and on Air for plane GPS speedometer.

You no need to install any app just bookmark us and visit when you need

Where We Can Use online Speedometer?

Bike online speedometer.

A bike online speedometer is a digital tool used to measure the speed of a bicycle in real-time through a web or mobile application.

Boat Online Speedometer

You can find your boat speed while travelling in sea or lake, and share with your friends

Train speed Test Online

Are you looking for tool that show yout train speed online? Then no app required to install just visit speedometeronline.com and give gps access that's it!

Bicycle online speedometer

You can also use this speedometer for cycle because it's track gps speed and shows the meter ,miles and km.

Bus or Cable cars online speedometer

Want to know the Speed Of Bus or Cable cars. Then try this latest best bus speed tracker. TO know your speed correctly and tell your friends about it.

Speedometer online - check how fast am i going

What is online speedometer.

An online speedometer is a digital web compass tool used to measure the speed of an object or vehicle in real-time through a web or mobile application.

How fast am i going

To use an online speedometer to determine how fast you are going, you will first need to open the tool on your smartphone or other digital device. Once you have the tool open, make sure that it is set to the correct mode for your activity, whether you are driving a car, riding a bike, or jogging.

Next, start moving and wait for the tool to register your speed. The tool should display your current speed in real-time, typically in either miles per hour (mph) or kilometers per hour (km/h). As you continue to move, the tool will update your speed accordingly.

It's important to remember that online speedometers can be affected by a number of factors, including poor GPS reception, network congestion, or other issues. Additionally, the accuracy of the tool may be affected by the speed and direction of your movement, as well as the type of terrain you are on.

For this reason, it's a good idea to use an online speedometer as a general guide rather than relying solely on the displayed speed. Always exercise caution and use common sense when traveling at high speeds, and be sure to obey all traffic laws and regulations.

In summary, an online speedometer can be a useful tool for determining how fast you are going while driving, cycling, or jogging. However, it's important to keep in mind that the accuracy of the tool can be affected by a variety of factors, and should be used as a general guide rather than a definitive measure of speed.

Car Speedometer online

A car speedometer is an instrument that measures the speed of a vehicle in miles per hour (mph) or kilometers per hour (km/h). It is usually located on the dashboard of the car, directly in front of the driver.

There are two types of speedometers: analog and digital. Analog speedometers use a needle and a dial to indicate the speed, while digital speedometers display the speed numerically on a digital screen.

The speedometer measures the rotation of the vehicle's wheels and translates that into speed. Inside the speedometer is a mechanism that is connected to the car's driveshaft or transmission. As the car moves, the driveshaft or transmission rotates and turns the speedometer cable, which in turn moves the speedometer needle or sends a signal to the digital display.

In modern cars, the speedometer is often part of a larger instrument cluster that includes other gauges, such as the tachometer (which measures engine RPM), fuel gauge, and temperature gauge.

Many modern cars also have online versions of their speedometers, which can be accessed through a smartphone app or website. These online speedometers use GPS technology to track the car's speed and display it on the screen. This can be useful for monitoring speed and for navigation purposes. However, it is important to note that online speedometers may not always be accurate, and it is always safest to rely on the speedometer in the car itself.

Train speedometer online

An online train speedometer is a tool that allows users to track the speed and location of a train in real-time through a website or mobile app. It uses GPS technology to determine the train's current location, and then calculates the speed of the train based on the distance it has traveled over a certain period of time.

Online train speedometers are often used by train enthusiasts, passengers, and railway companies to track the progress of a train journey. By knowing the train's location and speed, passengers can estimate their arrival time at their destination and railway companies can monitor the train's progress to ensure it is running on schedule.

To use an online train speedometer, the user simply enters the train number or selects it from a list of available trains. The website or app then displays the train's location on a map, along with its speed, direction, and estimated time of arrival at its next destination. Some online train speedometers also provide additional information, such as the train's route, timetable, and any delays or disruptions that may be affecting its journey.

It's important to note that online train speedometers rely on GPS technology, which may not always be accurate due to factors such as poor satellite reception, signal interference, or network congestion. Additionally, some online train speedometers may not display real-time data, and instead provide estimated arrival times based on the train's scheduled timetable. Therefore, it's always best to confirm train times and schedules with the relevant railway company before making any travel plans.

Bike speedometer online

An online bike speedometer is a tool that allows users to track the speed and distance traveled on a bicycle ride in real-time through a website or mobile app. It uses GPS technology to determine the bike's current location, and then calculates the speed and distance traveled based on the distance and time elapsed between GPS coordinates.

Online bike speedometers are often used by cyclists to track their performance and progress, and to plan and analyze their training sessions. They can also be used to share rides with others and compare results with friends and other riders.

To use an online bike speedometer, the user simply starts the app or website on their smartphone or GPS-enabled bike computer before beginning their ride. The app or website then uses GPS technology to track the bike's location and speed, and calculates the distance traveled, average speed, and other data such as elevation and cadence.

Many online bike speedometers also allow users to save and share their rides with others, either through social media platforms or by linking to other online services such as Strava, Garmin Connect, or TrainingPeaks. This allows users to compare their performance with others, track their progress over time, and get feedback and support from the cycling community.

It's important to note that online bike speedometers rely on GPS technology, which may not always be accurate due to factors such as poor satellite reception, signal interference, or network congestion. Additionally, they may require a good internet connection or mobile data plan to function properly. Therefore, it's always best to double-check the accuracy of the data and to use common sense and caution while cycling, particularly when riding in traffic or unfamiliar areas.

If you're interested in buying an online bike speedometer, here are some buying advice tips to consider:

1.Compatibility: Make sure the online bike speedometer is compatible with your device and operating system. Some tools may only work with certain devices or require specific software versions.

2.Features: Consider what features you need or want in a bike speedometer. Some tools may offer additional data, such as elevation gain, cadence, or heart rate, while others may be more basic.

3.Accuracy: Look for online bike speedometers that are accurate and reliable. Read reviews and ratings from other users to get an idea of how well the tool performs.

4.Ease of use: Choose a tool that is easy to use and understand. A simple and intuitive interface can make a big difference when it comes to tracking your speed and progress.

5.Price: Consider the cost of the tool, as well as any ongoing fees or subscriptions. Some online bike speedometers may be free, while others may require a one-time or recurring payment.

Battery life: Check the battery life of the tool. Some online bike speedometers have a long battery life, while others may need to be charged frequently.

Water resistance: If you plan to use your online bike speedometer in wet weather, make sure it is water-resistant or waterproof.

Overall, an online bike speedometer can be a useful tool for tracking your speed and progress while cycling. Be sure to do your research and choose a tool that meets your needs and budget.

OR just but phone holder for your bike open speedometeronline.com and it's ready to ride

Digital speedometer online

An online digital speedometer is a tool that displays the speed of a vehicle or bicycle in real-time on a digital screen through a website or mobile app. Unlike analog speedometers that use a needle and dial to indicate speed, digital speedometers display speed numerically on a digital screen.

An online digital speedometer is a tool that displays the speed of a vehicle or bicycle in real-time on a digital screen through a website or mobile app. These tools are generally very accurate and reliable, and can be used by drivers, cyclists, and other users who want to monitor their speed and ensure they are not exceeding legal or safe limits.

Online digital speedometers are often used by drivers, cyclists, and other users who want to monitor their speed and ensure they are not exceeding legal or safe limits. They can also be used to track performance and progress over time, and to compare results with other users.

To use an online digital speedometer, the user simply opens the app or website on their smartphone or other digital device and starts the tool. The tool then uses GPS technology or other sensors to detect the vehicle or bicycle's speed and displays it on the digital screen in real-time. Some digital speedometers may also display additional data, such as distance traveled, time elapsed, or average speed.

If you're interested in buying an online digital speedometer, there are a few things to consider. Here are some buying advice tips:

1. Compatibility: Make sure the online digital speedometer is compatible with your device and operating system. Some tools may only work with certain devices or require specific software versions.

2. Features: Consider what features you need or want in a digital speedometer. Some tools may offer additional data, such as distance traveled, time elapsed, or average speed, while others may be more basic.

3. Accuracy: Look for online digital speedometers that are accurate and reliable. Read reviews and ratings from other users to get an idea of how well the tool performs.

4. Ease of use: Choose a tool that is easy to use and understand. A simple and intuitive interface can make a big difference when it comes to tracking your speed and progress.

5. Price: Consider the cost of the tool, as well as any ongoing fees or subscriptions. Some online digital speedometers may be free, while others may require a one-time or recurring payment.

Overall, an online digital speedometer can be a useful tool for tracking your speed and performance while driving or cycling. Be sure to do your research and choose a tool that meets your needs and budget.

If you see this site not showing your speed then make sure check your brower accessing GPS location in your phone settings. Click to Minimize this for now.

Speed, Distance & Time Calculator

Use this speed calculator to easily calculate the average speed, distance travelled and the trip duration of a vehicle: car, bus, train, bike, motorcycle, plane etc. Works with miles, feet, kilometers, meters, etc..

Related calculators

• Speed, Distance & Time Calculation
• Average Speed formula
• Distance formula
• Duration (Time) formula
• How to calculate the average speed of a car?

    Speed, Distance & Time Calculation

In order to use the above speed, distance & time calculator, or do such math on your own, you will need to know two out of three metrics: speed, distance, time. You will need to convert the metrics to the same time and distance units, e.g. miles, kilometers, meters, yards, feet, and hours, minutes or seconds. For example, if you have speed in mph (miles per hour), time should also be in hours. If you have distance in kilometers, then speed should also be in km/h (kilometers per hour).

The unit of the result will depend on the units you input, but our speed calculator will conveniently display additional units where appropriate.

    Average Speed formula

The formula for average speed, also called average velocity in physics and engineering, is:

where v is the velocity, d is the distance, and t is the time, so you can read it as Speed = Distance / Time . As noted above, make sure you convert the units appropriately first, or use our speed calculator which does that automatically. The resulting unit will depend on the units for both time and distance, so if your input was in miles and hours, the speed will be in mph. If it was in meters and seconds, it will be in m/s (meters per second).

Example: If you took a plane from New York to Los Angeles and the flight was 5 hours of air time, what was the speed of the plane, given that the flight path was 2450 miles? The answer is 2450 / 5 = 490 mph (miles per hour) average speed. If you want the result in km/h, you can convert from miles to km to get 788.58 km/h.

    Distance formula

The formula for distance, if you know time (duration) and the average speed, is:

Example: If a truck travelled at an average speed of 80 km per hour for 4 hours, how many miles did it cover in that time? To find the miles covered, first, calculate 80 * 4 = 320 km, then convert km to miles by dividing by 1.6093 or by using our km to miles converter to get the answer: 198.84 miles.

    Duration (Time) formula

The time, or more precisely, the duration of the trip, can be calculated knowing the distance and the average speed using the formula:

where d is the distance travelled, v is the speed (velocity) and t is the time, so you can read it as Time = Distance / Speed . Make sure you convert the units so both their distance and time components match, or use our trip duration calculator above which will handle conversions automatically. For example, if you have distance in miles and speed in km/h, you will need to convert speed to mph or distance to kilometers. The time unit of the result will match the time unit of the speed measure, so if it is measured in something per hour, the result will be in hours. If it is measured in some unit per second, the result will be in seconds.

Example: If a train can travel 500 miles with an average speed of 50 miles per hour, how long it would take it to complete a 500-mile route? To find the answer, use the formula and substitute the values, resulting in 500 / 50 = 10 hours.

    How to calculate the average speed of a car?

Say you travelled a certain distance with a car or another vehicle and you want to calculate what its average speed was. The easiest way to do that would be by using the calculator above, but if you prefer, you can also do the math yourself. Either way, you need to know the distance to a satisfactory approximation, for which you can use a map (e.g. Google Maps) to measure the distance from point to point. Make sure you measure closely to the path you took, and not via a straight line, unless you travelled by air in which case that would be a good approximation. Of course, having a GPS reading of the distance would be more precise. Then you need to know the travel time. Make sure you subtract any rests or stops you made from the total trip duration.

If the total distance travelled was 500 miles and the time it took you was 5 hours, then your average speed was 500 / 5 = 100 miles per hour (mph). If the distance was 300 kilometers and it took you 5 hours to cover it, your speed was 300 / 5 = 60 km/h (kilometers per hour).

Cite this calculator & page

If you'd like to cite this online calculator resource and information as provided on the page, you can use the following citation: Georgiev G.Z., "Speed Distance Time Calculator" , [online] Available at: https://www.gigacalculator.com/calculators/speed-calculator.php URL [Accessed Date: 03 Jun, 2024].

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Slow warp —

New warp drive concept does twist space, doesn’t move us very fast, while it won't make a useful spaceship engine, it may tell us more about relativity..

Paul Sutter - May 23, 2024 12:55 pm UTC

A team of physicists has discovered that it’s possible to build a real, actual, physical warp drive and not break any known rules of physics. One caveat: the vessel doing the warping can’t exceed the speed of light, so you’re not going to get anywhere interesting any time soon. But this research still represents an important advance in our understanding of gravity.

Moving without motion

Einstein’s general theory of relativity is a toolkit for solving problems involving gravity that connects mass and energy with deformations in spacetime. In turn, those spacetime deformations instruct the mass and energy how to move. In almost all cases, physicists use the equations of relativity to figure out how a particular combination of objects will move. They have some physical scenario, like a planet orbiting a star or two black holes colliding, and they ask how those objects deform spacetime and what the subsequent evolution of the system should be.

But it’s also possible to run Einstein’s math in reverse by imagining some desired motion and asking what kind of spacetime deformation can make it possible. This is how the Mexican physicist Miguel Alcubierre discovered the physical basis for a warp drive—long a staple of the Star Trek franchise.

The goal of a warp drive is to get from A to B in the time between commercial breaks, which typically involves faster-than-light motion. But special relativity expressly forbids speeds faster than light. While this never bothered the writers of Star Trek , it did irritate Alcubierre. He discovered that it was possible to build a warp drive through a clever manipulation of spacetime, arranging it so that space in front of a vessel gets scrunched up and the space behind the vessel stretched out. This generates motion without, strictly speaking, movement.

It sounds like a contradiction, but that’s just one of the many wonderful aspects of general relativity. Alcubierre’s warp drive avoids violations of the speed-of-light limit because it never moves through space; instead space itself is manipulated to, in essence, bring the spacecraft’s destination closer to it.

While tantalizing, Alcubierre’s design has a fatal flaw. To provide the necessary distortions of spacetime, the spacecraft must contain some form of exotic matter, typically regarded as matter with negative mass. Negative mass has some conceptual problems that seem to defy our understanding of physics, like the possibility that if you kick a ball that weighs negative 5 kilograms, it will go flying backwards, violating conservation of momentum. Plus, nobody has ever seen any object with negative mass existing in the real Universe, ever.

These problems with negative mass have led physicists to propose various versions of “energy conditions” as supplements to general relativity. These aren’t baked into relativity itself, but add-ons needed because general relativity allows things like negative mass that don’t appear to exist in our Universe—these energy conditions keep them out of relativity’s equations. They’re scientists’ response to the unsettling fact that vanilla GR allows for things like superluminal motion, but the rest of the Universe doesn’t seem to agree.

Warp factor zero

The energy conditions aren’t experimentally or observationally proven, but they are statements that concord with all observations of the Universe, so most physicists take them rather seriously. And until recently, physicists have viewed those energy conditions as making it absolutely 100 percent clear that you can’t build a warp drive, even if you really wanted to.

But there is a way around it, discovered by an international team of physicists led by Jared Fuchs at the University of Alabama in Huntsville. (The team is also affiliated with the Applied Propulsion Laboratory of Applied Physics, a virtual think tank dedicated to the research of, among many other things, warp drives.) In a paper accepted for publication in the journal Classical and Quantum Gravity , the researchers dug deep into relativity to explore if any version of a warp drive could work.

The equations of general relativity are notoriously difficult to solve, especially in complex cases such as a warp drive. So the team turned to software algorithms; instead of trying to solve the equations by hand, they explored their solutions numerically and verified that they conformed to the energy conditions.

The team did not actually attempt to construct a propulsion device. Instead, they explored various solutions to general relativity that would allow travel from point to point without a vessel undergoing any acceleration or experiencing any overwhelming gravitational tidal forces within the vessel, much to the comfort of any imagined passengers. They then checked whether these solutions adhered to the energy conditions that prevent the use of exotic matter.

The researchers did indeed discover a warp drive solution: a method of manipulating space so that travelers can move without accelerating. There is no such thing as a free lunch, however, and the physicality of this warp drive does come with a major caveat: the vessel and passengers can never travel faster than light. Also disappointing: the fact that the researchers behind the new work don’t seem to bother with figuring out what configurations of matter would allow the warping to happen.

reader comments

Channel ars technica.

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Beneath the Great Wall of China lies the world's deepest high-speed railway station

Preserving the great wall, will the great wall be making an appearance at the winter olympics, the winter olympics high-speed railway.

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Qantas group boarding overhaul an Australian-first move

The way you board on a major Australian airline is being shaken up, with the overhaul tipped to cut queue time and get you in your seat and in the air faster.

Emirates’ premium economy is best in world

‘Very close’: World’s best airline for 2024

Horror Singapore flight didn’t ‘suddenly’ drop

Qantas says a shake-up to how passengers board planes will cut standing-around time at the gate and on the tarmac.

A new system splits passengers into six groups, divided by class, frequent flyer status and seat location.

The airline reckons trials of the system across the country sped up queues at the gate and hastened seating.

Qantas Domestic chief executive Markus Svensson said the change should make more planes leave on time.

“We’re continuing to look for ways to respond to pain points and improve the travel experience for our customers,” Mr Svensson said.

“We know how important on time departure is to our customers, so this process is also about doing everything possible to ensure we depart on time.”

Virgin overtook Qantas as the most punctual carrier in Australia in April.

From Monday at Brisbane Airport, passengers on the flying kangaroo will get a boarding group number of one to six on their ticket.

Once your group number is called, you can board.

Anyone lucky enough to have travelled overseas may know similar systems are used internationally.

Qantas’ new system comes into effect at Brisbane today, Perth next week, and then Melbourne and Sydney later in the month.

Signs and announcements will help clarify which of the six groups is boarding at what times, the airline says.

The Dubai-based airline ranked fifth as the best airline in the world – but it came first in one category – and it’s easy to see why.

The wait is over – the winner of the world’s best airline for 2024 has been revealed, with two Aussie carriers scraping into the top ten.

A Sydney pilot has revealed the area with the worst turbulence in the world in a clip that has gone viral with two million likes.

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Global Entry Mobile App Now Available in More Airports

WASHINGTON – U.S. Customs and Border Protection (CBP) announced today that the Global Entry mobile application can now be used at eight additional airports, enabling more trusted travelers to complete their arrival processing on the plane instead of waiting in line to use a portal.  

“CBP has prioritized Global Entry arrival to enhance the speed, accuracy, and security of the arrival process for trusted travelers,” said CBP’s Senior Official Performing the Duties of the Commissioner Troy A. Miller. “CBP officers are often the first to welcome trusted travelers when they arrive home, and we want to continue to find ways to improve that experience through new technologies and innovations while maintaining the highest levels of security.”  

Travelers may now use the app at Austin–Bergstrom International Airport, Nashville International Airport, Houston International, Kansas City International Airport, Louis Armstrong New Orleans International Airport, San Antonio International Airport, St. Louis Lambert International Airport, and Toledo Express Airport. The app will be available to Trusted Traveler Programs members flying into all 77 U.S. international airports by the end of fiscal year 2024. A list of U.S. airports that currently accept the GE mobile app can be found here . 

The Global Entry app is available to be downloaded from the Google Play Store or Apple App Store, and can currently be used at 53 international ports of entry in the United States and all Preclearance locations. Upon landing at any of these airports, Global Entry members can complete their entry processing before leaving the plane, and then bypass the Global Entry portals to speak with a CBP officer.  

Global Entry is one of the Department of Homeland Security’s Trusted Traveler Programs , and is used at land, air, and seaports of entry into the United States at all major airports and all Preclearance airports. All applicants undergo rigorous and recurring background checks and an in-person interview before initial enrollment. To maintain Global Entry members as low-risk travelers, any violation of the program’s terms and conditions will result in appropriate enforcement action and termination of the traveler’s membership privileges. More information on Global Entry and CBP’s Trusted Traveler Programs is available here .   

U.S. Customs and Border Protection (CBP) is America's frontline: the nation's largest law enforcement organization and the world's first unified border management agency. The 65,000+ men and women of CBP protect America on the ground, in the air, and on the seas. We facilitate safe, lawful travel and trade and ensure our country's economic prosperity. We enhance the nation's security through innovation, intelligence, collaboration, and trust.

2024 Vision Zero Safe Streets and Speed Management Projects

Since 2020,  Vision Zero Madison has implemented safety improvement and speed management projects every year to enhance safe travel on City streets. These projects focus on incorporating  Proven Safety Countermeasures into our roadway infrastructure, such as high visibility crosswalks, green bike markings, rapid flashing beacon lights, and increased signal visibility, as well as lowering speed limits across the City in high injury zones.

“Traveling on our streets should be safe for everyone – regardless of their age, ability or travel mode”, said Mayor Satya Rhodes-Conway.  “Vision Zero strives to improve our streets and prevent serious and fatal crashes. While each of these projects may be small, they add up to a big impact, and a safer city.”

Vision Zero infrastructure improvements happen along with larger reconstruction projects, as well as through smaller improvements at critical locations as a part of the Safe Streets Madison Program.  Every infrastructure project in the City provides an opportunity to be proactive in building safer streets.

Some examples of Vision Zero safety improvements under construction or already completed include:

Segoe Rd and Sheboygan Ave Project (Under Construction)

• Fully protected bike facility (Segoe Rd) and buffered bike lanes (Sheboygan Ave)
• Bump-outs throughout the corridor (Segoe Rd) to shorten crossings and slow traffic
• Improved street lighting
• High visibility crosswalk markings and green bike markings

Atwood Avenue Project (Complete)

• Off Street two-way pedestrian bicycle path along Atwood Ave
• High visibility crosswalks
• Green bike path crossing
• Raised crossings
• Midblock crossing at high use location
• Improved lighting
• Improved intersections with safety measures for pedestrian bicycle crossing

Wilson Street project (Partially Complete)

• New protected bike facility
• High visibility crosswalk markings

2024 Safe Streets Projects

This year’s Safe Streets projects include many school safety, traffic calming, rectangular rapid flashing beacons (RRFBs), traffic signal safety, and other pedestrian bicycle improvements.

School safety projects include:

• Sandburg Elementary: Donald Dr -- new midblock crosswalk
• East High School: N Fourth St -- speed humps
• Kennedy Elementary: Meadowlark Dr -- speed humps
• Southside Elementary: Moorland Rd -- median island
• Mendota Elementary: School Rd -- speed humps
• Henderson Elementary: Tompkins Dr -- speed humps
• Leopold Elementary: Traceway Dr -- speed humps

Traffic calming projects include:

• Drake St -- an island and RRFB at Orchard St pedestrian crossing
• Drake St -- two speed humps at the Zoo area, just west of Randall Ave
• Great Gray Dr -- a series of pedestrian islands at Owl Creek Park
• Milky Way -- four total speed humps along roadway
• Moorland Rd at Dunwoody Dr -- pedestrian island and RRFB at school crosswalk
• Muir Field Rd at Cimarron Trl -- two traffic calming islands
• Odana Rd -- six additional center concrete islands between Grand Canyon Dr and S Whitney Way
• Traceway Dr -- four total speed humps near Aldo Leopold Park
• Jackson Quarry Ln -- one speed hump

Rectangular rapid flashing beacons (RRFBs) include:

• Cottage Grove Rd at Maher Ave -- completed in May 2024
• Regent St at Brooks St -- completed in May 2024
• Sprecher Rd at Dominion Dr -- design complete; to be installed this summer
• S Whitney Way at S Hill Dr -- design complete; to be installed this summer
• Northport Dr at Goodland Dr -- design complete; to be installed this summer
• Atwood Ave at Miller Ave/Waubesa St -- design complete; to be installed this summer
• E Washington Ave at Schmedeman Ave (Kwik Trip, Gooh Grocery Store) -- design in process; to be installed this summer/fall
• Seminole Hwy at Manitou Way -- installation this summer with City Engineering Bikeways Path project
• E Doty St at S Pinckney St -- installation with City Engineering resurfacing project this fall
• Portage Rd at Tomscot Trl -- design in process; to be installed this summer/fall
• E Washington Ave at Kedzie St -- design complete; to be installed after Bus Rapid Transit work done in area
• Odana Rd at Parman Terr/Gately Terr -- RRFB setup with temporary curbs this summer; permanent curb changes and sidewalk later

Traffic signal safety improvements include:

• Pedestrian countdown signals at Fish Hatchery Rd - S Park St - Parr St
• Protected left turns at N Frances St - University Ave
• Accessible Pedestrian Signals (APS) at Cedar St - S Park St
• Accessible Pedestrian Signals (APS) at Northport Dr - Dryden Dr

Additional pedestrian bicycle improvement projects include:

• Tennyson Ln crosswalks
• Green bike lanes at W Dayton St and N Randall Ave
• Green bike lanes at various multi-use path crossings
• Driver Feedback Board at 7900 block of Raymond Rd

2024 Speed Management Projects

Starting in June, the City will be continuing efforts to set safe speed limits with speed management projects on the following streets:

• Zeier Rd: E Washington Ave to Lien Rd (35 mph to 30 mph)
• Thierer Rd: E Washington Ave to Lien Rd (35 mph to 30 mph)
• Lien Rd: E Washington Ave to N Thompson Dr (35 mph to 30 mph)
• Sycamore Ave: Walsh Rd to N Thompson Dr (35 mph to 30 mph)
• Pflaum Rd/Agriculture Dr: S Stoughton Rd to Femrite Dr (35 mph to 30 mph)
• Campus Dr: (40 mph to 35 mph)
• Regent St: Midvale Blvd to Whitney Way (30 mph to 25 mph)
• Sheboygan Ave: Segoe Rd to Whitney Way, with reconstruction (30 mph to 25 mph)
• S High Point Rd:  Mineral Point Rd to Mid Town Rd (35 mph to 30 mph)

Data shows that Madison’s speed limit reductions are making a difference. 31 out of 38 locations studied had seen a decrease in the number of vehicles traveling 10+ mph over the speed limit. Even 5 mph can drastically change the likelihood of a serious injury or fatality crash, especially when the crash involves a pedestrian or bicyclist. The recently updated national standards support Madison’s new practice on setting safe speed limits in urban areas.

“We want to thank our residents and City officials for the support and collaboration in making our streets safer,” said Yang Tao, Director of the City of Madison Traffic Engineering Division. “To achieve safer streets, Madison needs to continue to improve walking, biking and accessibility to other transportation alternatives throughout the community. Everyone deserves to have safe streets to get to work, to school and to play and enjoy our city.” 

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Chinese Tesla rival BYD says its new hybrid cars can go 1,250 miles without stopping for gas or charging

• BYD says its new hybrid powertrain system lets cars go 1,250 miles without refueling or charging.
• That's nearly twice the range of some rival hybrids in the US.
• Hybrid popularity has surged as EVs remain expensive and largely unprofitable.

Driving 1,250 miles without stopping to fill up? That's a pipe dream for any car on the market right now, whether it's powered by gas or electricity.

But the Chinese EV maker BYD says it can happen thanks to upgrades in its new hybrid powertrain system, which is set to launch on two recently revealed midsize sedans, Bloomberg reported . It's the equivalent of about 81 miles per gallon, more than three times the US fuel-economy average for model-year-2022 cars. It's also about 500 more miles of range than a hybrid 2023 Lexus ES gets, which last year topped Kelley Blue Book's list of longest-range hybrids.

Related stories

A leap this big in hybrid technology would boost an already fervent interest in these cars , with their impressive fuel economies, lower up-front costs, and mitigated range anxiety . The models are wildly popular with both automakers and consumers as a bridge between traditional internal-combustion engines and fully electric models, especially as electric-vehicle sales plateau in many markets.

In BYD's case, hybrids make up the majority of its models sold, Reuters reported .

Toyota, a relative latecomer to EVs with a plethora of hybrid options, has seen its strategy vindicated by this softening of the market. Ford said in April that it would expand its hybrid offerings as the segment helped cushion EV losses. GM also plans to bring more hybrid models to North America in response to changing demand.

Just don't expect to buy a BYD car in the US anytime soon.

Watch: The true cost of turning America's school buses electric

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