Is anything faster than the speed of light?

If it was possible to travel faster than the speed of light, would time reverse itself (like backwards time travel) or just not exist?

Your question is a very interesting one, and it is great to see that you are thinking about Professor Einstein’s theory in this way, but unfortunately, you’re probably not going to like the response. When you assume that it’s possible to travel faster than the speed of light, you’re taking the laws of physics and punching them in the stomach and throwing them down the stairs.

The problem is that you can’t say, ‘Hey, what would happen if you could go faster than the speed of light?’ because that’s totally physically impossible. It’s not possible to go faster than the speed of light, so the laws of physics can’t possibly say what would happen if you imagine things that way in some hypothetical universe. Physics is a complete package: once you decide to ignore one physical law, you’re ignoring them all.

You run into a similar problem when you ask ‘What if I could divide by zero?’ or ‘What if I could build a perpetual motion machine?’ or ‘What if I went back in time and killed my grandfather before I was born?’ There’s no answer, because the question doesn’t make any sense.

Of course, this doesn’t bother the writers of Star Trek. They go faster than the speed of light every show and travel into the past like it’s a trip to Disneyland. This brings up an interesting point, however: The idea of a space-warping engine is NOT entirely a bad one! Warping space would allow you to travel as if you were moving faster than light by changing the structure of the universe, at least temporarily. You would end up in a certain location much faster than if you travelled there the ‘normal way,’ kind of like a secret passage. Happily for relativity, you would STILL not actually be travelling faster than the speed of light in local space, so Einstein’s ‘speed limit’ still holds.

The point is that though it’s fun to think about and enjoy in science fiction, truly going faster than the speed of light is a violation of the laws of physics and therefore can not really be discussed by physics. I can’t say time would reverse itself or not exist or anything because those aren’t even options. It’s like if I invited you out to dinner and you told me you absolutely couldn’t come, but then I asked you whether you were going to have the soup or the salad!
Answered by: Steve Healey, Physics student, Rutgers University, New Jersey

One of the reasons that prevent any object with a mass going at or faster than the speed of light is that the mass is not constant — it increases with velocity and it goes to infinity at the speed of light. So that eventually you need infinite amounts of energy to accelerate infinite mass past the speed of light mark! (and as far as I know we have yet to find an infinite source of energy 🙂

However if you would still like to choose if you are having the soup or the salad at the dinner you will not attend here is a thought.

We really do not know what would happen to time when an object passes the speed of light. The only thing we have to rely on is the Special Theory of Relativity (Einstein 1905) and according to it time in a moving reference frame (say your space ship) goes slower as compared to a stationary frame (say Earth) the faster you go. In fact the equation that governs this so called time dilation is given below:

So you see when you start off — at zero speed (0% of speed of light) your time is just regular i.e. the time slowing factor (xt) is equal to 1. As you speed up your time runs slower by the factor shown on the y-axis. As you are approaching 100% of the speed of light your time slows more and more until it is infinitely slowed down. (You should realize that everything slows down including your heart beats, your thoughts, etc.) So for an example if your ship goes at 98% of the speed of light and you take a one year journey, when you return to Earth five years have gone by.

This region of speeds below 100% of the speed of light is the region of our regular time or Real Time.

Now say somehow you were able to go faster than the speed of light (i.e. the v in the above equation is now greater than c the speed of light). The equation will then give us a square root of a negative number on the right hand side (which is an imaginary number.) Well I can factor out the imaginary unit number (i or the square root of minus one) and plot the result on the same graph. This region I call Imaginary Time since it is some weird time with an imaginary unit attached to it (so I don’t really know what this time means.)

However you see that time in this imaginary region will speed up from infinity to the regular time speed of 1 and continue speeding up. At 140% or higher speed of light, time slowdown factor is less than one, i.e. time will go faster than in the stationary frame! So for an example if your ship goes at 200% of the speed of light and you take a one year journey, when you return to Earth only about 7 months have gone by. However I need to stress again that this is just a crazy thought experiment which produces some weird imaginary time and has no physical meaning.
Answered by: Anton Skorucak, M.S. Physics, PhysLink.com Editor

Can Some Objects Travel Faster Than Light?

There are a few statements in science that are absolutely true. One such statement is that nothing can travel faster than the speed of light. Such assertions are backed by assumptions that are often not expressed. Read on to find how statements about the speed of light can be confusing.

While nothing can go faster than light in vacuum, it is pretty easy for particles to move faster than light in matter through some medium like glass. Assume a photon beam and high energy muon beam point in the same direction and travel at the same speed as light. Though it has been established that the speed of light would slow down inside glass, the muon does not slow down when it passes through the glass and still maintains the speed of light inside.

The Cherenkov Effect

While working with uranium salts dissolved in sulfuric acid, a young Russian physicist named Pavel Cherenkov noticed a glowing light. Initially, the light was attributed directly to radioactivity but when Cherenkov tried to isolate the effect, he realized that radiation made the sulfuric acid glow. Eventually, he was able to show that even water would glow in the presence of a lot of radiation. Named after the student, the Cherenkov radiation occurs when a particle carrying an electric charge travels faster than light through an optically transparent medium such as glass. When these particles travel faster, the glass emits a stunning yet dangerous blue color.

This is a transcript from the video series Understanding the Misconceptions of Science. Watch it now, on Wondrium.

How Does Cherenkov Radiation Work?

Cherenkov shared his findings with his thesis advisor, Sergey Vavilov. Vavilov mentioned the effect to Igor Tamm and Ilya Frank, who figured out what was going on. Cherenkov, Tamm, and Frank went on to win the Nobel Prize in Physics in 1958. The Cherenkov radiation is analogous to a sonic boom that occurs when a jet flies faster than the speed of sound. If the jet flies slower than the speed of sound, then the sound waves propagate ahead of the plane. But when the speed of the jet exceeds the speed of sound, it compresses the air in front of it. As the jet moves ahead faster and faster, the compressed energy also moves ahead. When the compressed air passes over, it results in an extremely loud noise similar to an explosion as all sound arrives at once. When the jet generates a sound from pushing the air out of its way, it creates a series of circles appearing at each point the jet passes. The circles add up and make a cone of sound that surrounds the path of the plane.

Cherenkov Effect in Nuclear Physics

Cherenkov effect is similar to the sonic boom but occurs when a charged particle passes through a transparent material at a speed greater than the speed of light. The charged particle shakes up the molecules of the material and they give off light as it moves. As in the case of sound waves, the light emitted travels outwards in a circular pattern at the speed of light, resulting in a conical pattern called Cherenkov Effect. Physicists use the concept of Cherenkov radiation in nuclear physics or particle physics experiments to distinguish the quickly moving particles from the slower ones. This is because the Cherenkov light is emitted only by electrically charged particles moving faster than light.

What Can Travel Faster than Light?

Edwin Hubble combined his distance measurements of the galaxies with the velocity measurements of American astronomer Vesto Slipher to draw an interesting graph in 1929. Hubble postulated that there was a linear relationship between the distance of galaxies as measured from Earth and recessional velocity. This correlation was taken as a clear evidence of an expanding universe and the big bang.

However, the expansion of universe has significantly changed over time. From the fast expanding universe about 14 billion years ago to the era of dark energy about 5 billion years and speeding up of expansion now, the changes have been dramatic. We know that Pluto is not expanding away from us at the speed of light nor is the Milky Way or the Andromeda galaxy. According to the Hubble’s hypothesis, the recessional velocity is 70 kilometers per second per mega parsec. So, a galaxy that’s a mega parsec away will be moving away from the Milky Way at a speed of 70 kilometers per second while a galaxy at a distance of 2 mega parsecs will be moving away at a speed of 140 kilometers per second. So, the farther we move away, the faster the objects are moving. Hence, the common theory that the universe is expanding at the speed of light is obviously incorrect and a misconception.

Now let us assume that the universe is indeed expanding at the speed of light and it is calculated that objects 14 billion light years away from us were travelling at the speed of light but objects 28 billion light years away are travelling at twice the speed. So, the entire argument of ‘expanding faster than the speed of light’ is quite mushy. However, the argument that the speed of light is the ultimate speed is within the theory of special relativity.

So, the question whether two galaxies separated by 14 billion light years are moving away from each other at the speed of light can’t be answered objectively. The distance between these galaxies are growing at the speed of light but relative to their little local bit of space, they’re not even moving. Hence, it would be more accurate to say that though objects cannot move through space faster than light, but space itself can move faster than light. The superluminal expansion of the distant universe is really astounding but what we may never get know is the answer to the simple question how big is the universe really?

Common Questions about Can Objects Travel Faster Than Light?

Q: Who was Pavel Cherenkov?

Pavel Cherenkov was a Russian physicist who was awarded the Nobel Prize in Physics for the discovery of Cherenkov radiation . The Cherenkov effect was of great consequence to experimental work in nuclear physics.

Q: How does the speed of light vary in different medium?

The velocity is about 2/3rd the speed of light in glass and plastic, while in water it is about 3/4th the speed of light. However, light travels at just 40% of its normal speed in diamond.

Q: Which object travels faster than light?

The controversial hypothetical particles Tachyons are said to travel faster than light. However, according to Einstein’s special theory of relativity particles regarding speed of light , they can never travel faster than light in the real world.

Keep Reading
Wave or Particle—What Is Light?
How We Observe Light Determines Whether It’s a Particle or a Wave
Early Research on Unified Field Theory

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Study Shows How The Universe Would Look if You Broke The Speed of Light, And It’s Weird

(Omar Jabri/EyeEm/Getty Images)

Nothing can go faster than light. It’s a rule of physics woven into the very fabric of Einstein’s special theory of relativity. The faster something goes, the closer it gets to its perspective of time freezing to a standstill.

Go faster still, and you run into issues of time reversing, messing with notions of causality.

But researchers from the University of Warsaw in Poland and the National University of Singapore have now pushed the limits of relativity to come up with a system that doesn’t run afoul of existing physics, and might even point the way to new theories.

What they’ve come up with is an «extension of special relativity» that combines three time dimensions with a single space dimension («1+3 space-time»), as opposed to the three spatial dimensions and one time dimension that we’re all used to.

Rather than creating any major logical inconsistencies, this new study adds more evidence to back up the idea that objects might well be able to go faster than light without completely breaking our current laws of physics.

«There is no fundamental reason why observers moving in relation to the described physical systems with speeds greater than the speed of light should not be subject to it,» says physicist Andrzej Dragan, from the University of Warsaw in Poland.

This new study builds on previous work by some of the same researchers which posits that superluminal perspectives could help tie together quantum mechanics with Einstein’s special theory of relativity – two branches of physics that currently can’t be reconciled into a single overarching theory that describes gravity in the same way we explain other forces.

Particles can no longer be modelled as point-like objects under this framework, as we might in the more mundane 3D (plus time) perspective of the Universe.

Instead, to make sense of what observers might see and how a superluminal particle might behave, we’d need to turn to the kinds of field theories that underpin quantum physics.

Based on this new model, superluminal objects would look like a particle expanding like a bubble through space – not unlike a wave through a field. The high-speed object, on the other hand, would ‘experience’ several different timelines.

Even so, the speed of light in a vacuum would remain constant even for those observers going faster than it, which preserves one of Einstein’s fundamental principles – a principle that has previously only been thought about in relation to observers going slower than the speed of light (like all of us).

«This new definition preserves Einstein’s postulate of constancy of the speed of light in vacuum even for superluminal observers,» says Dragan.

«Therefore, our extended special relativity does not seem like a particularly extravagant idea.»

However, the researchers acknowledge that switching to a 1+3 space-time model does raise some new questions, even while it answers others. They suggest that extending the theory of special relativity to incorporate faster-than-light frames of reference is needed.

That may well involve borrowing from quantum field theory: a combination of concepts from special relativity, quantum mechanics, and classical field theory (which aims to predict how physical fields are going to interact with each other).

If the physicists are right, the particles of the Universe would all have extraordinary properties in extended special relativity.

One of the questions raised by the research is whether or not we would ever be able to observe this extended behavior – but answering that is going to require a lot more time and a lot more scientists.

«The mere experimental discovery of a new fundamental particle is a feat worthy of the Nobel Prize and feasible in a large research team using the latest experimental techniques,» says physicist Krzysztof Turzyński, from the University of Warsaw.

«However, we hope to apply our results to a better understanding of the phenomenon of spontaneous symmetry breaking associated with the mass of the Higgs particle and other particles in the Standard Model, especially in the early Universe.»