If I'm on a train going the speed of light...?

Question

and I turn on the headlights the same instance I pass by someone outside the train...
I'm guessing the light travels away from me at the speed of light...
Does the light travel away from the person outside the train at double the speed of light, or is the light non existant to them since I'm stopped in time and the train is already moving away from them as fast as anything can travel.

Answer 1

OK, what you just asked is a very straightforward special relativity question. Before Einstein, there wouldn't have been a really satisfying answer to this question, but one of his "assumptions" for relativity is that the speed of light travels at the same speed (in a vacuum of space) no matter what speed the object itself is moving at (as long as it doesn't speed up, slow down or change directions). The strangest part about the whole thing is that both the person outside the train and the person on the train see the light moving at the exact same speed.

Now, about being "stopped in time," that would only be true for the person watching you fly by at the speed of light. You would feel like you were aging, and time was passing, normally. But that's a topic for another discussion.

Answer 2

If you are travelling at the speed of light and you turn on the headlights the light will not come out of the headlight as it is already travelling at the speed of light. Put another way, the light will come out of the headlight, however, since the headlight itself is already moving at lightspeed, the light will travel along with the headlight (same speed), therefore if you were in front of the train you would not see it. A person standing beside the train would only see it as you pass them just as if you were standing still on the tracks at that point and suddenly switched on the lights.

Answer 3

The following will make no sense at all to most people but it is what theory says would happen and the math, which is a bit complicated, all hangs together.

At the speed of light, time stops. So you would appear frozen and unmoving to that person outside the train. To you, in the train, you seem normal yourself but that other person standing by the track is frozen in time. Not only that, but the entire universe has shrunk to no distance in the direction you are moving.

So the person standing by the track sees your light beam moving at the speed of light and you following it at the speed of light and not cataching up or falling behind. You are just keeping pace with the light from your own headlight. But you yourself see the light move away from you at the speed of light. But that has no real meaning since time has stopped and distance has shrunk to zero. Speed, which is distance divided by time, like miles per hour, becomes zero divided by zero.

This is why no physical matter can ever travel at the speed of light. It is not a technology problem, it is a physical property of the universe.

Answer 4

The person standing outside the train (which, according to Einstein, would have to be moving at a speed at least slightly lower than light) would perceive a vast mass of light, still moving a C, but blueshiftted into the ultraviolet, if not beyond that.

Answer 5

It's an interesting question. Of course you know that it will not be possible for the train to travel at the speed of light (since if you do you will have infinite mass).

Nevertheless, as far as I know there is no such thing as "double the speed of light". This concept does not exist (last I heard). The fastest thing in existance is speed of light itself. Can you reword the question?

Answer 6

You can't add to light speed....so the headlights would never appear to have been turned on from the external observer.

Answer 7

Where did you get that train ? Kool.........:)