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Message: <blockquote data-quote="babomb" data-source="post: 2398034" data-attributes="member: 1316">Disclaimer: I am a college student majoring in computer science, and it's been at least a year since I've studied relativity.Well, maybe. Special relativity equations sort of break down at the speed of light, and you'd have to divide by zero. If you take the limit of the equation, however, the answer would be yes, time stops from the point of view of an observer. That may or may not have any meaning.Let's talk about what happens if the ship is moving at NEAR-light speed first. Let's say the ship is moving at 90% of the speed of light. And let's say the guy in the spaceship is moving at 5% of the speed of light. He is NOT moving at 95% of the speed of light relative to an outside observer. There is something called a Lorentz transformation involved. I'll spare you the equations, but an outside observer would say he was going just under 91% of the speed of light (10/11 of c, to be exact).Why? Well, for the same reason that time dialates at high speeds (e.g., things on the ship appear to move more slowly), length CONTRACTS (the ship appears to be shorter in the dimension of its motion). That is, an outside observer would measure the ship as being shorter than if it were at rest. Here's a picture:[CODE] ________          ____|        |        |    ||        |        |    |   --->|x_______|        |x___|Ship at rest     Ship moving to the right with repsect to observer[/CODE]So, not only does the guy walking in the ship take longer to get to the other end, he moves a shorter distance (again, from the POV of an outside observer).What happens AT the speed of light? Well, again, in the equations, you have to divide by zero. If we take the limit, we could say that time is stopped on the ship and that the ship has a length of 0. Assuming that were correct (and it isn't, since getting the ship to the speed of light is impossible to begin with), an outside observer would say that the man did not move at all relative to the ship.That's a good question, and one I can't adeqautely answer. The best I can do is say that I don't think the Special Relativity equations don't really apply to objects moving at the speed of light (whether general relativity is any more helpful, I don't know). The equations are, in a sense, derived from the postulate that the speed of light in a vacuum is constant, and so don't do a great job of describing motion OF light, if that makes any sense. They assume sub-light speed motion.I'll also point out that simultanity is ALSO relative. However, I do not believe that the photon would see itself as existing along the entire path at once, because that would create difficulties in describing, e.g., the emission and absorbtion of photons by atoms. I could be wrong, but I point here as a reference: <a href="http://www.madsci.org/posts/archives/nov2000/975451454.As.r.html" target="_blank">http://www.madsci.org/posts/archives/nov2000/975451454.As.r.html</a></blockquote>

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