# If you're in a car which is on the speed of light, what happens when you turn on

1. 67
ahmed.bposted 13 years ago

If you're in a car which is on the speed of light, what happens when you turn on the headlights?

2. 39
slc334posted 13 years ago

I'm just guessing, but I think due to E=mc^2, the photons won't go any faster than the car, but they will have more mass due to relativity.

3. 64
topquarkposted 13 years ago

If you are in a car travelling at the speed of light, you would not experience the passage of time, so you wouldn't be able to measure the speed of the photons coming from the headlights.  Your watch would have stopped and the photons and the car would appear stationery.

If you are a stationery observer watching the car, you would measure the speed of the car and the speed of the photons to be the same (the speed of light).  From your point of view, the photons are travelling at the same speed as the car - so you won't see the headlights until the car hit you!

If you in a car travelling at 99% - or indeed any other fraction - of the speed of light, you would measure the speed of the photons coming from the headlights to be the speed of light.  The reason that you don't measure the speed of the photons to be "speed of light - speed of car" is because your perception of time is slowed down compared to a stationery observer (although you wouldn't be aware of this).

4. 39
110211posted 13 years ago

I have no idea dude,
but surely if your car was able to go at the speed of light, you would have adequate technology that would at least make the headlights work.
In theory your headlight would be travelling at the speed of light +1

110211

5. 59
Etaripposted 13 years ago

OK! Classical physics question which a very confusing answer. The front of the car would have entered into the speed of light before the rest of the car meaning that if you turned on the headlight the light would be seen almost smeared all over in front of you in almost every direction. The light would be traveling at the speed of light which means that time would have stopped for the light but because you are in a car that will not ever completely be traveling at the speed of light, you as the observer would be witnessing a type of radiation from being ejected out of another dimension as it the laws of physics break down the closer you get towards the speed of light.

6. 63
Manna in the wildposted 11 years ago

In the light of recent CERN LHA experimental data, we can now answer this with confidence in the following way:

Assuming that the Higgs boson is the new particle that has indeed been observed in the LHC:

1) In a car you cannot travel at the speed of light because a car and you have a non-zero rest-mass which means it must communicate with the Higgs field, and that causes you to ALWAYS travel less than the speed of light.

2) The speed of light is the same for all observers no matter how fast they are travelling relative to some other moving object.  The reason for this is that photons NEVER interact with the Higgs field. i.e. they not only have zero rest-mass, they MUST travel at the speed of light. (And so must every other massless particle).

These two statements are as near to facts as you will get. Therefore your question is not realistic.

working