what if a train was travelling at the speed of light....?

Question

& a passenger walked up the carriage,would they be then be travelling faster than the speed of light?

theorectically speaking?

Answer 1

assuming the train could get to that speed, then the following acceleration laws would apply :

In Newton's mechanics, if we apply a constant force to an object of constant mass, the acceleration will be constant. In principle we can accelerate such an object to exceed the speed of light. Not so in relativistic mechanics. The following snippet out of the eBook Relativity 4 Engineers (the link refers to a special offer to CR4 readers) shows how to compute the acceleration for a relativistic scenario: (note that the symbol v here means 'normalized velocity', i.e., v=v/c, where v is velocity in m/s and c is the speed of light in m/s).

Here all the variables are as measured in a single inertial frame of reference, e.g., the reference system of a observer that is not accelerated in any way.

The crux of this matter is that as v increases, the acceleration drops off with the factor (1-v^2). As velocity approaches the speed of light, so that (1-v^2) approaches zero, the acceleration also approaches zero, unless the force is infinitely large (which is absurd).

This then, according to relativity theory, is why nothing can exceed the speed of light as measured in any inertial frame.


So you just couldnt put the amount of energy required to go any faster.


which raises another question which i think ill post, does it get harder to walk forwards in a moving train than to go backwards.
im sure everyone will say no, but that law seems to go against it.

Answer 2

That's a good question. But Einstein did come up with an answer:

No... It isn't possible...

The laws of relativity really state that nothing can look like its travelling faster than the speed of light. In this scenario this means:
Another passenger on the train watching the walking passenger would see him walking along normally at a few mph. All well and good... but what about someone watching the train go past the station? Surely if the train is travelling at the speed of light and the passenger at 4mph then he would look like he is moving at the speed of light plus 4 mph? Well no, due to time dilation he would appear to be stationary relative to the train! I.e. to the person on the platform everything on the train would appear to be frozen in time.

Answer 3

Let's assume that the train can travel at the speed of light. A passenger in the train walking at a speed of 3miles an hour STILL only travel at 3 miles an hour in the 'reference frame' of the train. This passenger would not be travelling faster than the speed of light. People in the train still see him/her travelling at the speed of 3 miles an hour.

An example: The earth is travelling at a speed of 60000 miles an hour around the sun, if you walk at 3 miles an hour do not mean your speed is 60003miles an hour ...Your friend still see you walk at a speed of 3 miles an hour.



Cheers.

Answer 4

Of course not, due to relativity. As it is travelling with the train and although someone walks towards the front of the train, that does not imply that the one walking is faster than the train. Since the one walking inside the train needs the same speed as the train to get from point A to point B, then the person cannot travel faster than the train itself.

Answer 5

If it was possible to travel at the speed of light, the passenger would only be travelling faster than the speed of light relative to the surroundings outside the train e.g. the track. relative to the train and contents the passenger would be travelling at walking pace.
I think!! - strange things happen at that speed.

Answer 6

No. And if this person would be sitting still, holding a flashlight, the light would also not travel at twice the light speed.

What happens is much too complicated to describe properly, but if boils down to that the train would appear to shrink to the person walking at light speed.


Edit: start here, and follow many links, to learn more about the subject:
http://en.wikipedia.org/wiki/General_relativity

Answer 7

confident, there's achievable of a custom to holiday on the cost of light yet, that practice has no longer yet been engineered. Hypothetically conversing, if a custom replaced into vacationing quicker than the cost of light on a gloomy night and the headlights have been grew to become on, the railroad music could nonetheless be darkish, basically as though the lights have been off because of the fact by utilising the time gentle reaches a undeniable evaluate front of the practice, the practice could have already surpassed that factor considering's vacationing quicker than gentle.

Answer 8

Ah, hello relativity.
Never mind the speed of light for now -
Supposing two people were playing ping-pong on a railway carriage. To them, the ball is going back & forth at say 40mph.
The train passes thriugh a station at 60mph, and the bloke on the platform thinks "that ball was moving between 20mph & 100mph"!
Who is correct ?
Both
Same with your train.
It's all relative to your place & view of the situation.
Anyway, a thing moving at "c" would have infinite mass, which would make a mess of the track at least.
Bob

Answer 9

Hmmmmm. Obviously, the answer is always going to be no, even theoretically, since nothing can ever travel faster than light.

But forgetting that for a moment, I can't see how anything can ever travel faster than the thing transporting it. That just wouldn't make sense.

The physics of this conundrum is beyond me, but the answer is no. Good question though, made me think.

Answer 10

No because the speed of the train is relative the the contents so even if you ran down the train you would be still traveling at the same speed as the train, and thats the speed of light. if yoou jumped up in the air on a train you would not fly backward at the speed of light because if that happened you would be left behind or crash into the carrage door