About principle of relativity?

Question

if i'm travelling in a train at the speed of light then i wont be able to look at the back of the compartment because those light rays wont reach me and this may prove principal of relativity maybe wrong. but einstein assumes that speed of light is constant for everyone so i'll be able to see the back of the train. i'm just confused over this assumption. how does the light ray reach me? and how does the assumption change this?

Answer 1

Everything in the train should stay constant because its not only the train thats moving its everything in it. The question is, are you gonna be fast enough to observe everything around you before you get to your destination? Time is constant when your travelling at the speed of light while everything else stays variable. (i got a headache now)

Also I got this from a website:
In his Special Theory of Relativity, Einstein stated that Newton's idea that space, mass, and time were absolute and unchanging was wrong when put to extreme tests. Because the speed of light is constant under any circumstance -- that is, for moving and stationary observers alike -- Einstein reasoned that space, mass, and time become variable.

That time in the moving reference frame passes more slowly than time in the stationary reference frame is a concept known as time dilation. This means that a clock in motion with respect to a stationary observer is perceived by the observer to run more slowly than a stationary clock. The closer the moving clock's velocity to the speed of light, the more its seconds appear to get stretched out. It's not the mechanics of the clock that get stretched out; it's that time itself gets dilated. Applying this to a biological clock, then, a person traveling on a rocket ship at great speed -- like the twin who travels through space in the "Time Traveler" activity on this Web site -- would age more slowly relative to an observer on Earth.

Though it seems far-fetched, time dilation is a real phenomenon, proven by experiment. In 1971, scientists tested Einstein's theory on time dilation using atomic clocks, which are capable of measuring time to the billionth of a second. One clock was set to record time on the ground, while another traveled around the world at 600 miles per hour on board a jet. Though both clocks showed the same time at the start of the experiment, the jet's on-board clock was behind by a few billionths of a second at the completion. Just as Einstein would have predicted, time had passed more slowly for the clock traveling at a fast speed. Projecting these results over a much greater speed -- like c, the speed of light -- the time difference would be much more exaggerated.

Answer 2

If the speed of light is constant for everyone, then the state of the observed universe has to change as the speed of light is approached. What Einstein worked out and then supported mathematically was that the energy poured into approaching the speed of light increases the mass of the object and the object changes dimensions, getting shorter in the direction of travel. When you get near the speed of light (you can't reach it if you have mass), you measure the time it takes light to travel from the rear of the car to you and conclude it is the same as always, but an observer outside, standing still (who can somehow see this) would consider your ruler and measurement to be much shorter. That's what makes it relativity - between observers.
As has been demonstrated repeatedly with atomic clocks in orbit, designs of synchrotrons and light passing the sun - relativity works.

Answer 3

The speed of light is constant for all observers so you should see the back of the train.
Assume you are on the train and your friend Sid is stood watching from the side of the tracks.
As the train approaches the speed of light your time will slow down so despite the light taking longer to get to you (from Sid`s point of view) you will now see any difference in the light coming from the back of the carriage.
When the train hits the speed of light your personal time will have stopped in relation to Sid`s time and the light will never catch up with you. ie From the moment you hit the speed of light you will never age and the light will never catch up with you .
From your point of view the light will catch up with you like normal but an infinite length of time outside the train will have passed and the world you started out on will no longer exist.