Einstein's relativity

Was watching an old documentary about Einstein while riding BART today... (there aren't too many videos I can choose from online that I can convert to put onto my portable video player)

So here's what I learned:

Einstein accepted the fact that speed of light was a constant, so how could two observers see the same speed? well if speed = d/t, and d and speed are const, than time must be a variable.

Also, this means that time is not absolute - ie: if an observer sees two lightning strikes around him, vs a moving observer at the same point - they will not agree on the time of those lightning strikes (since one was moving).

Also, since E = mc^2, then mass has energy and energy has mass. The sun sends out 4.5 pounds of light at us per day.