According to Einstein’s theory, as an object approaches the speed of light time slows down and I assume it stops if an object were to obtain the speed of light. Since a photon, by definition, is traveling at the speed of light, does that mean that in the frame of reference of a photon, time stands still? Thus, when a photon travels from point A to point B, as far as it is concerned, it is emmitted and absorbed at the same instant of time regardless of how far appart point A and B happen to be? If so, this could have some wierd implications.
I would think that it wouldn’t. Just think… if you see a light from only 3 miles away, you are not seeing the light that is currently being emmitted. Instead, you are seeing the light that has been put off moments before. Therefore, light does not travel so fast as to escape time. In fact, nothing, my dear, as we have been able to capture the essential mechanisms of, has been able to escape time.
Light always travels at the same speed relative to any inertial frame. You can’t have a reference frame travelling at the speed of light. If we take the limit as the speed approaches c of a moving frame, then time slows to a standstill as observed by a “stationary” frame. The problem with this is the limit is unreachable by any material object and photons don’t approach c, they are already travelling at c.
Yes. There is no elapsed time in the photon’s frame between creation and absorbtion.
But because of the length contraction that also occurs at high speeds A and B are actually separated by zero space in the frame of the photon. So, of course it takes no time to travel between them from the photon’s perspective.
Of course, those equations don’t really work for v = c very well, just for v < c.
Also, isn’t the c where time stops the speed of light in a vacuum? Light slows down somewhat when it enters earths gravity well. There are probably also a hundred other things that slow light down that I’m clueless about.
Not exactly. The speed of light slows trying to leave a gravity well; it speeds up falling into a gravity well. The speed of light is constant in an inertial reference frame. In order to have an inertial reference frame where you have gravity, your frame must be free-falling.
Jdeforrest wrote:
You’re mixing up two different things here. You can have a vacuum in a strong gravity field, or a non-vacuum with hardly any gravity. A non-vacuum means that it’s travelling through some substance, such as air, water, or teflon (these are things for which I happen to know the approximate speed). I’ve heard that the reason light slows down going through things is that it still travels from sub-atomic particle to sub-atomic particle at c, but it gets delayed some when it interacts with the particles, being absorbed and re-emitted.