Saturday, August 11, 2007

The Easy Way

I took a pretty hefty Modern Physics course back at the University. It was designed to be an overview of all the stuff you don't learn in early physics courses; essentially, it was about everything since Newton. All that stuff that doesn't make one damn bit of intuitive sense.

Now, I liked Dr. Gleeson. He was fun, and he was obviously a pretty smart dude, if a little weird... but I was willing to let weird slide, because physicists are always weird. It's just part of the job description. Anyway, he was pretty cool.

But I don't know why he was so resistant to explaining things the easy way. Don't get me wrong: I want to know the hard stuff too. I want to know all the math. I want to know the nitty-gritty.

But it really helps to learn all that if you understand what you're learning first, dammit! When we started learning Maxwell's equations, I didn't even understand what the hell a field was! Last I had heard, we were being told that you couldn't have action at a distance, and that there emphatically was not any sort of aether. Now, to jump from that to the electromagnetic field...? How was I supposed to take that? All of a sudden we can have action at a distance, and there is something light propagates through? What? But...

Anyway: the easy way.

There really is a way to explain most difficult concepts without getting into the technical stuff. For the dilettante, that's usually enough; if you're just curious, well, the casual explanation will probably sate you. But for the serious student - whether he intends to learn just the basics, or whether he intends to go on to a career in the stuff - it makes an excellent start.

Example: relativity.

Relativity is weird at first glance. I had the fact, but not the reason or the mechanism, explained to me many times over the years, and it's so counterintuitive that most often I just assumed that the person explaining it to me - and generally doing a bad job of it, I might add - had misunderstood it. It just didn't make sense that speed through space could have anything to do with time! And I wasn't alone in that fallacy, either; in fact, I was in company with the exalted likes of Sir Isaac Newton, who asserted quite matter-of-factly that time and space were absolute! It's simply borne out by human experience!

Human experience is limited.

Relativity is a brilliant, simple concept, and it's very, very true (except in quantum situations, but we won't get into those for now). Experiments bear it out. As you go faster in space, you go slower in time... sort of. Relative to a stationary observer. Or him to you. It's... well, it's relative. It has to do with frames of reference.

Anyway, here's the thing: due to conditions at the beginning of the universe that I'm really not qualified to enumerate, we are all hurtling through spacetime - the four dimensions in which we exist - at the speed of light, which is, as we know, the ultimate speed limit. It's as fast as things go. (Note that I didn't say it's the fastest things can go, but rather that it's as fast as things do go. That's important.)

We are going the speed of light, in four dimensions. How? Easy: if you're not moving in space, the three dimensions we're used to, then you're moving in time. If you start to move through space, you divert some of your total velocity from moving through time, and lo and behold... you slow down in time.

It's that simple! It's as if you were driving at 65 mph northward, and then turned to the northeast. You'd still be going 65 mph, but not moving northward at 65 mph - some of your velocity would now be moving eastward. When you move through space, you're not moving as much through time.

Okay, it's not really that simple. That's actually kind of a gross, oversimplified, slightly inaccurate summation. But it nonetheless conveys a good sense of the idea! It's the easy way to get a handle on what relativity means! As a starting point, it's absolutely invaluable!

So why did it take this damn long for me to learn it?!?

1 comment:

skyen said...

Maybe you're not as smart as you think you are. Ever think of that, Sherlock?

Heh. Hey, doing things the hard often makes a person really appreciate what they've gone through. At the very least you can tell us plebeians about the easy way.