What little I've read about Einstein, out of a textbook, regarded his theories on motion at the speed of light. I'm not sure if this is general or special relativity, but it involved observations such as time dilation and length contraction, as well as changes to momentum and energy. I realize his whole theory, just about, rests on the premise that light will move at the speed of light regardless of your reference frame's velocity. This is a very counter-intuitive notion, when we think of this in terms of classical/Newtonian physics. My question is, does his observations of time dilation and length contraction, or any other observations/realizations he made, serve to explain just why and how light always moves at the speed of light? I mean just thinking about traveling at the speed of light right next to a photon, how can it be that that photon still appears to be moving away at the speed of light while you're traveling at the same speed? Again, does time dilation or anything in his theory at all clarify these observations?