Theoretically, what would happen if a car is going faster than the speed of light with the headlights on?

Question

i know its not actually possible to go the speed of light. im saying theoretically if you could.

Answer 1

Say the theory of relativity were not valid and Lorentz contraction and time dilation did not exist, this is what I would think would happen:

You are traveling faster than light.  Cool... so you turn on your headlights.  Light travels out in a cone from your headlights, the light (which we can think of as little billiard balls) each have their velocity (that of light) and the velocity of the car (that of more that the speed of light).  We are talking good old Galilean relativity, we just add the velocity of the car to the velocity of the light.  

The light shining in front of the car will be going very fast, faster than the car, well over twice the speed of light, while the light at the edge of the cone (the light billiard balls emitted at an angle) will have less velocity, but still have more than your car.

So, I'd assume that it would not be too strange for you.  But I can think of two odd scenarios:

I) If someone saw you coming:

Since the light you are emitting is traveling at well over twice the speed of light, your photons would arrive at an observer well before you did-- so if you were on your way to grandma's house, she'd see you at the house hours before you were really there.

II) If you were accelerating rather than going at a constant velocity:

If you were to accelerate just right, you would always overtake your light.  So, your headlights would not shine in front of you, but rather behind you, moreover, if you made the same trip to grandma's house she'd have to wait hours after you arrived to see you!

This is one of Einstein's Thought Experiments that he did.  He found the conclusions to be completely non-sense.  This, as well as Maxwell's equations became his basis of the Special Theory of Relativity.

Hope this tickles your brain =)

Answer 2

Actually, theoretically, it is not possible for any body to go on speed of light. At that speed, the mass of the body becomes infinite which is not possibe. So, it is impossible for car to go on that speed.

The formula for mass of body moving comparable to velocity of light is m = m0 / ( 1 - (v^2/c^2)

So at velocity of light, v^2 / c^2 = 1 and 1-1 = 0

therefore m0/0 = Infinity.

Here m0 = original mass

          v = velocity of bogy

          c = velocity of light

Answer 3

Theoretically the car, the lights would all be energy at that point, so headlights would be useless

Answer 4

First of all, you need to realize that when you say you are traveling at the speed of light, that has to be with respect to, or relative to, something else. It is an underlying fundamental assumption of Einstein's special theory of relativity that uniform, non-accelerated motion has no meaning of and by itself. That is, there is, by assumption, no meaning to the idea of moving uniformly at the speed of light in an empty universe. That state is completely equivalent to being at rest in an empty universe..

I preface my answer with this comment because it leads immediately to the answer to the question. Imagine that you are in your car 'traveling at the speed of light' and that you turn on your headlights. That state of motion is utterly equivalent to being at rest in an empty universe. Since, when at rest, the light from your headlights would be launched forward from your car at the speed of light, relative to you, with a certain color spectrum, that is exactly what would happen if somehow you could be moving instead at the speed of light.

In other words, the presence or absence of other objects or matter in the universe relative to which, if present, you could make a determination that you were moving at the speed of light makes absolutely no difference to your own experiences and experiments. The light that you launch behaves in exactly the same way whether the other referential matter exists or not.

This leads into another interesting question, however. And that is whether the rest of the matter (mass) in the universe in some way affects your own local observations. So far this question has come up in relation to theories of gravity. If effect, the question is how does the universal gravitational constant, G, which determines how strongly gravitating masses attract each other, know what value to assume if there is no other mass in the universe. Mach proposed, essentially on philosophical grounds, that G must be determined by the sum total of all of the mass in the universe. Einstein assumed in his General Theory of Relativity that G is simply a universal constant, independent of the specific mass distribution of the universe. On the other hand, Brans and Dicke later proposed a so-called scalar-tensor theory of gravity in which the local value of G depends upon the rest of the mass in the universe through an additional scalar field that does not appear in Einstein's theory.

Answer 5

"Theoretically," it is not possible to go faster than the speed of light. There are no such speeds.

>> "I know its not actually possible to go the speed of light. im saying theoretically if you could."

You keep using that word, "theoretically." I do not think it means what you think it means. Our theory of motion is Special Relativity. In that theory, it is impossible to travel at the speed of light. If you're not talking about SR, then you're not talking about science, and you're in the wrong section.