Why is it impossible to travel faster then the speed of light?

Question

Is it a technology thing?.......I may sound stupid and I probably am but I would still like to know. Thank you

Answer 1

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.

Answer 2

Someone who has more of a physics background than I could probably explain it better, but it has to do with the fact that speed is defined in terms of how long light takes to go from one place to another, therefore it would make no sense to say something can travel faster than it -- any measurement is relative to something else.

Answer 3

Phnx has given a complete answer.

However I give the following answer.

Light and all electro magnetic radiation is transformation of energy from one place to another.

Once energy is liberated from some matter in the form of EM radiation, they travel in vacuum with a particular speed 3x 10^8 m/s. Light being one among the EM radiation it has this speed.

In universe we are having matter and vacuum (absence of matter).

All EM radiation has a constant speed in vacuum. When they enter a medium its speed is reduced.

Important thing is that the speed does not depend upon any of the properties of the materials from which these radiations are emitted.

Thus there is no way of changing the speed using the properties of any material.

The speed depends only upon the property of vacuum.

Unless one comes across any medium which is neither matter nor vacuum, we cannot think of changing the speed of EM radiations.

It is absurd to think about a medium which is neither matter nor vacuum.

The speed of EM radiation depends upon the permeability and permittivity of the medium through which it passes.

For vacuum we are having a constant value for these quantities. Based on this the value of speed is fixed and constant.

Consider a frame of reference which is at rest and another moving with respect to a fixed star.

These frames of references and all things are matter which is situated in vacuum.

The EM radiations emitted by this matter travel in vacuum with a constant speed.

As already explained there is no way of altering the speed of light. Hence any experiment conducted in this reference frame will yield the same value for the speed of EM radiations.

If they give different values, then the meaning of vacuum is lost and one has to think that vacuum is different for different observers.

This is the reason that Einstein postulated that the speed of light will be measured the same by different observers.

The consequence of this is that length; mass and time become relative to the reference frame and will be different for different observers in such a way that the measurement of speed of light will be the same.

After all such explanations if any one thinks that there is a possibility of increasing the speed of light, then length, mass and time will be absolute and one can think of going to the past which is absurd according to Physics.

Answer 4

Here's a rather good article that discusses this. As interesting as going faster than light might be, what is REALLY interesting is what SLOWS light down, like when it gets tangled up in the orderly atoms of a diamond. THERE'S where I think a greater discovery awaits, not just what we already know, but, in getting to see what photons really look like and what their little set of twelve vortexes are doing. Researchers at Harvard are actually stopping photons. The second link below is about that research.
http://www.physorg.com/news12084.html
http://science.nasa.gov/headlines/y2002/27mar_stoplight.htm

Answer 5

Speed of light is 3*10^8 m/s. Well, if an object attains a speed almost equal 2 that of light its mass becomes infinite. Till now it's not possible but u never know. It might happen in future. Let's see
...........!

Answer 6

Very interesting links here by Patios, with light bending and actually stopping light waves, only to release this light whenever they want . Wow I cant wait til computers operate with this technology, its coming....and that Star Trek "beam me up..." thing, may be a bit more realistic now they say theyve taken the first steps into this unknown. Awsome stuff!.

Answer 7

It's not impossible, I think it's actually demonstrated that is possible. It was one interesting report on NGtv. They put the guy in front of TV screen and they emitted violent pictures on screen. At the same time EEG was registering his brainwaves. On every violent picture EEG was showing amplitude changes, but interesting was that EEG was reacting few ms BEFORE the pictures appeared. What it proves? They didn't mention anything but in my opinion is very simple. Brainwaves were faster than light, they notice the picture before eye was able to see it actually.

Answer 8

Einstein's Theory of Relativity tells us that this is the limit we can go in the universe. Any object approaching that speed ceases to be an object and therefore cannot attain that speed. Science is like religion; you may believe this or you may choose not to believe. The choice is yours.

Answer 9

It's just an assumption that has turned out be true as far as we can observe. It's the only reason why relativity works.

Also, it's somewhat intuitive. Something called the principle of locality. Things very far off shouldn't be able to pass information instantly. Don't get me started on quantum entanglement though!

Answer 10

what we know explains an aweful lot of things in the universe and if you can go faster than light then what we think we know is all wrong and considering what we think we know explains it is very likely we are right

any way you can go faster than the speed of light so long as its for a short enought period of time (its alright that fits in with what we think we know)

Answer 11

Because Matter and Energy are interchangable according to E=MC2. For mass to accelrate to the speed of light would would take an infinite amount of energy in theory, in reality mass accelrated to light speed becomes energy.