light and time

Last one was about politics, now how about some science?

I'm reading (or trying to) The Elegant Universe , by Brian Greene, which attempts to lay out superstring theory for non-physicists like me. Well I found almost right away that I wanted to get a much better understanding of Enstein's relativity theories than I currently have, not to mention quantum mechanics, so I'm tripping through a little book called Physics for the Rest of Us. The first chapter is on the Special Theory of Relativity.

Now it seems that the key to this theory is light, or rather the speed of light. That's mainly because light has this weird unique property in that it does not seem to be bound by its frame of reference--that is, it appears to be moving the same speed whether you're watching it move away or whether it's coming right at you. Okay, I say to myself, and exactly how did someone figure this out? After all, watching light move is not exactly like watching cars along a freeway. So that's my first question: how did we figure out what the speed of light is? It seems we did it using the movement of stars (later Michelson used revolving mirrors and a strobe light but that just refined the number), but in order to use stars wouldn't we have to know the distances first? And if so, how did we figure out the distances?

Well that conundrum stopped me for a while, but at last I decided to accept it and move on. And now I'm working on the theory of relative simultaneity. This theory seems to simply postulate that movement in time is as relative (between frames of reference) as movement in the other three dimensions. But it seems that the only way we can measure the relativity of time is by measuring the movement of light.

This stopped me again. Is it completely moronic to wonder if light is not a function of the first 3 dimensions but rather of time? Is it possible that light is a physical manifestation of time? I read somewhere in my recent studies that light can only be observed in movement (that is across time) and only as it moves past us (kind of like the present time), which makes sense, because after all, unlike a beach ball, light does not fly past us to some destination, stop and take up residence somewhere. Also there's the question of the wave vs. particle debate--light hasn't even been classified yet. Okay, it bends around objects and changes speed in different mediums, but if I remember my college physics, Einsten postulates time does that as well, at least it distorts around large objects. This is something I'll learn later in the chapter, presumably. But really, you have to wonder, when watching a sunset, are we literally watching time pass by?

I know this is all kind of silly. My mind is racing ahead to prove my whimsies wrong before I even get them down in words. Sure would love to have an afternoon with a whiteboard and a physicist!