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Mar13-10, 12:17 PM
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Quote Quote by welshvegan View Post
...and how a light year is not a light year for someone traveling at .99999c, but is a light year for a beam of light.
A light year for you isn't a light year for the guy on the rocket, but there's no such thing as "for a beam of light", so the last statement doesn't make sense.

I recommend that you study spacetime diagrams. That's the best way to learn about SR. (It's almost impossible to understand SR without them, and they are much easier to understand than the algebraic expressions representing Lorentz transformations).