If your on a train going the speed of light and you run forward on the train, ...

Question

will you go faster than the speed of light? They say its impossible to go faster than the speed of light so what gives?

Answer 1

OK, a train can't be going at the speed of light for a start. For something to travel at the speed of light it needs to have no mass.

Also, things get very strange around the speed of light so even if there was a train travelling at the speed of light, you running forward on it, wouldn't mean that you were travelling faster than the speed of light.

The speed of light is an absolute limit. There's no way for it to be broken (in current scientific understanding anyway).

Actually, what would happen in your scenario is that the train would melt due to all sorts of friction, even air resistance long before it got anywhere near the speed of light. Remember space craft which  re-enter the atmosphere need to have highly specialised heat shielding to stop them burning up and they're only going about 30000 kph. The speed of light is about a billion 1000000000 kph.

Answer 2

the train will never reach the speed of light because it needs an unlimited amount of energy to reach that speed. and if you are in a train you are in a closed system so if you run you will run the exact same speed as you would if you weren't in the train. plus if you walk on earth you are not walking at the speed the earth is traveling around the sun. so you will never reach the speed of light

Answer 3

The train can't go at the speed of light, so the question is meaningless.

If you are on a train going nearly c (with respect to, say, the ground), and you walk forward, you do not hit any barriers. You can walk, run, bicycle, rocket forward just as normal. However, speeds in relativity do not combine simply by adding them together. The observer on the ground does not observe that your velocity is that of the train (vt) plus the velocity of your walking/running/etc. (vw). He observes your velocity as (vt+vw)/(1+vt*vw/c^2), which has the property that your total velocity is never c or greater.

Why is this? It is a logical conclusion from the proposition that the speed of light is c in all reference frames. If c is constant, then this must be true.