I read that nothing with mass can travel at the speed of light. Therefor one can not ask what happens when an observer in a car moves with the speed of light. But, is it possible for a frame of reference to move with the speed of light? Is there something preventing that?
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is it possible for a frame of reference to move with the speed of light? Is there something preventing that?
This is not possible, and the first postulate of the special theory of relativity, is that the speed of light is a constant, which is $c \approx 3\times 10^8 ms^{-1}$, for all observers.
For example, if you are moving toward me at velocity $v$ and at some instant you switch on a light, both you and I will measure the speed of this light-pulse to be moving at $c$ and not the sum of speeds. That is, $$v' \ne c +v$$ but instead $$v'=c$$
Regardless of your motion as the observer, and regardless of the motion of the source, the speed of light will always be measured at this value.
This principle, the constancy of the speed of light, is one of the foundations of relativity.
joseph h
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