If you're in a vehicle going the speed of light, what happens when you turn on the headlights?

Answer 1

This question comes up very regularly. If you do a search you will find it has been answered dozens of times in the past few months.

The thing you need to relaise is that the speed of light is an absolute constant. It doesn't matter what speed you are travelling at, the light will always be travelling away from you at the same speed: the speed of light.

The freaky part is that the light from your headlights would seem to be travelling away form you at the speed of light (C), but to an observer who was sitting still the light would also appears to be travelling away from them at the speed of light. How can that happen? Well it's one of the tricky bits of relativity, but part of the solution lies in understanding that although light never slows down or speeds up relative to any observer it does change frequency.

So to you the light from your headlights will look quite normal, but to someone sitting still your headlights will appear to be emitting x-rays. The light would be invisible to them.

The corrolary of that is that any light approaching your windshield will be equally shifted into the x-ray part of the spectrum. Although the headlights will be emitting visible light, any time they strike an object and reflect back they will reflect back extremely low frequency light that is invisible to the human eye.


So yes, you most ceratinly would need headlights if a car is travelling at the speed of light. Unfortunately it won't do a damn bit of good to turn on your headlights. That's not because the light won't travel, it will travel just fine. The problem will be that any light that reflects back off the road will be invisible to the human eye.

Answer 2

I believe if you are traveling at the speed of light and you turn on the headlights, then the headlights are also traveling at the speed of light. Thusly nothing changes because you cannot go faster than the speed of light and the headlights are at the front of the vehicle so you could never catch up to them. So, the distance between you and the front of the headlights is infinity.

Answer 3

Your hypothetical is based on an impossible situation. You cannot reach the speed of light, for your mass will reach infinity. The better question would be: what would happen if you turn on the headlights in a vehicle traveling just shy of the speed of light? Answer: the light would speed away at the speed of light, as it always does for all observers no matter how fast they are traveling. Light always travels at the same speed, regardless of the speed of its source. It's time that changes. This is a fundamental aspect of our universe.

Answer 4

Well, consider this... if you're going 9/10 the speed of light, and fire a bullet going 9/10 the speed of light, how fast does this bullett go? The answer, because of relativity, is 99/100 the speed of light, because the numbers don't just add up, you have to use an equation (which I'm too lazy to go find). I'm fairly certain that if you were going the speed of light, no matter what you did you couldn't shoot anything because using that equation it would always come out to 1/1 the speed of light.

Answer 5

if you're contained in the motorized vehicle, you nevertheless see the mild going from the headlight on the speed of light as widespread. if you're on the floor (table sure) you only see the mild under no circumstances comes out. It sounds contradictory. Does the mild ever comes out sort the headlight? it is because time contained in the motorized vehicle remains table sure with comprehend to the individuals on the floor. So if time remains table sure, mild doesn't flow no matter if it strikes a the speed of light.

Answer 6

Since you can't go at the speed of light, the question is academic. But, in fact, you could not turn on the headlights, because at the speed of light time is stationary: nothing can happen or change.

Answer 7

Even though I can only offer a pure guess, I would like to try.

"Star Trek: The next generation" did something similar to this and I'm inclined to believe its close to what would really happen.

In the episode "The Battle". Captain of the Enterprise Jean-Luc Picard rushed toward the enemy vessel at the speed of light. (It had its "headlights" turned on too but that is not important to the battle)

If you had been aboard the Enterprise and looked out the forward port window you would have seen the enemy ship rushing toward you at the speed of light. If you had been looking out the rear port window you would have seen a perfect light replica of the Enterprise from its original position.

If you were aboard the enemy ship and looked out the front port window you would see what appears to be two enterprises. One Enterprise that is farther away is actually and illusion created by the enterprise outrunning its only generated "headlights". The second Enterprise as it appears closer to you in a new position would be the real one, but of course by the time you see it, it has already fired its proton cannons, sorry.

Here is the link to a free site that better explains the battle and contains details pictures of the event.
http://en.wikipedia.org/wiki/Picard_maneuver
or
http://www.memory-alpha.org/en/wiki/Picard_Maneuver
(Has pictures)

Answer 8

The lights would shine on as if you weren't moving at all. However, your perception at the speed of light is different from a sub-light perception. You should only be able to clearly see what is behind you because by looking forward you would be staring into a different visual plane. Thus the fact that your headlights are shining forward doesn't matter because they aren't serving any purpose for you.

Answer 9

The light from your headlights will travel away from you at the speed of light. Also you will hit the stopped car in front of you that you could'nt see till you turned on you're lights very hard.

Answer 10

The lights would come on just as normal. Do you mean how would the headlights look to you if you were travelling at the speed of light in a vacuum and sitting in the driver's seat (everything else being as usual)? As they normally would, because the speed of light is constant in a vacuum (of course you have to remember that something travelling at the speed of light experiences the whole history of the universe simultaneously, ie, time stops, so I guess you'd be "seeing" quite a lot things LOL). How would they look to someone else? Well presuming you were travelling in the same direction as the light towards your poor mate, he wouldn't see anything because the light would get to his eyes at the same time as your car slams into him and kills him (because, the headlights, and the car they're attached to would be travelling at the same speed as the light they're emitting.)
If he were standing at an angle to your car, all he'd see is one almighty blur: after all you're travelling at the speed of light - I assume the human brain wouldn't be able to process an object travelling at the speed of light in a very meaningful way. The light from the headlights would hit his eyes and he'd see the blur of your car after you'd already passed him and were tens of thousands of kilometres away (Remember your car travelling at the speed of light would be 300,000 km away one second after passing your friend.)

Remember too it would take an infinite amount of energy for a car to get to the speed of light, so you'd have to have used the whole universe as a source of fuel first and then you still wouldn't be at the speed of light, as well as having nowhere left to drive to.