What happens when a train traveling at the speed of light turns on its headlights?

[Pizzachu]

Light seems to go the speed of light, no matter how fast the observer is going. It's one of the weird things about relativity.

So a guy on the train would see his headlights working normally. A person standing near the tracks would see the train moving at the same speed as its light.

No, it would not be possible for a train to travel that fast. Nothing can move anywhere close to the speed of light on Earth where there's Air resistance.

In space it may be possible to accelerate a ship to near light-speed, but it would take a long time and a whole lot of energy.

 

[SantosOwen]

What happens when a train traveling at the speed of light turns on its headlights? If they illuminate anything, then wouldnt the light coming from then be going faster than the speed of light? Is it even possible for the train to go that fast in the first place?
Thoughtful answers only, please.

 

[odimwitdwon]

Brilliant. A train traveling at the speed of light... Well, since that can't happen in our Universe, you must be talking about a different one. For a different Universe with different physical laws it is literally impossible to guess what "would happen".
In our Universe, speed is relative. All trains are traveling *as close to* the speed of light you wish, but not "at" it, in a particular reference frame (determined for each train). So since you have witnessed objects traveling at these same speeds, you tell me: what happens?
(Hint: If you say anything other than the light from the headlight travels at the speed of light away from the train, then you are an idiot)
The speed of light (in a vacuum) is constant. Speed is distance divided by time. In order for this ratio to be constant, it is necessary that as the distance changes with reference frame, so does the time.

 

[Anne]

haha. I think the light will only show in the headlights and not actually illuminate anything.
Even though it's impossible for the train to go that fast, I don't think the lights would work.