Question

i know this has been used as a joke, but i'm curious. If a car was traveling the speed of light, what would happen when you turn the headlights on?

Answer 1

the gas mileage would go up :)

Answer 2

I recall a PBS show about something like this; well, it had this in it. At the speed of light, something odd happens to space and things appear to bend around each other ... the rest of the details are a bit fuzzy tho

Answer 3

Matter cannot travel at the speed of light, as due to relativity the time gets "slower" the faster you go. Speed of light (from the point of external observer) is the point where time would stop thus making the "internal speed" observed from the object itself infinite.

Answer 4

It is actually not a joke. This is a thought experiment Einstein proposed. The light would only still travel at the speed of light and if you assume the car drives at the speed (which is impossible, the faster the car goes the more mass it will accumulate, because of relativistic effects and the more energy it will take to propel it, and if you go in it will reach infinity) the light will stay in the headlights and won't move forward or won't illuminate the space in front of him.
Hope that helped :D

Answer 5

You are thinking speed of headlight = velocity of car + speed of headlight.. But its actually speed of headlight = (velocity of car + speed of headlight) / (1+(velocity of car * speed of headlight)/c^2(speed of light))

Answer 6

But if reality, isn't it true the closer something get to the speed of light, it starts transferring from a state of matter to a state of energy? Thus if that is the case, there is no car, nor headlight to produce a light beam, but a mass of energy traveling through space.

Answer 7

I know mass is impossible to go at the speed of light but, if it could the light would go out normally (believe it or not). The speed of light is the same to all observers and when one moves at that speed time seems slower and lengths seem shorter in order to accommodate for the velocity.

The light would come out normally.

Answer 8

Forget the mass conversion and all that nonsense for a second... it's not really relevant right now. If you are in the frame of the car, the light leaps ahead of you at the speed of light. If you are in the frame of the observer watching the car go by, nothing happens - because his relative velocity is c, the gamma factor goes to infinity, and no light can leave the car - check Lorentz Transformations, gamma factor on wikipedia.

Answer 9

cars travel nowhere near the speed of light so lets just forget about it.

Answer 10

To the traveler in the car, the light would seem to emit normally. To the observer standing still, he would only energy moving. Here is another thought experiment. Car A is traveling at 1/2 the speed of light. Car B is traveling towards Car A in the opposite direction at 1/2 the speed of light. Both cars turn on their lights. What will each driver observe?

Answer 11

You would see normal light emited. The light can still only travel at a maximum speed (the speed of light) and it is therefore travelling at 299 792 458 m/s in every direction, even ahead of you. it can't travel at 299 792 458 x2m/s.

A meter is still a meter but time changes depending on how fast your are moving. A second would still seem the same for someone moving close to the speed of light compared to someone stationary but time itself changes. A second for the person moving close to the speed of light may seem like hundreds or thousands of years to a person who is stationary.

Time is relative to your speed

Answer 12

It's worth noting that due to time dialation it would not be possible to "turn on" the headlights in the car if it were moving AT the speed of light because time within the frame of the car would essentially be stopped. The reason this seems paradoxical is because reaching the speed of light, according to our current understanding, is not possible and therefore any explanation of what happens at the speed of light doesn't really apply to our world.

Answer 13

imagine this: one car is at rest while another car travels 0.99c. The car at rest turns on its headlights so they shine right past the car traveling at 0.99c. A scientist in the passenger seat measures the speed of light beam going past him. He is surprised to find that the light is traveling past him at the speed of light. This is because REGARDLESS OF YOUR FRAME OF REFERENCE light will always travel at the same speed in a vacuum.