Jim (jazzmanjim) wrote, @ 2004-04-09 01:12:00

Cool Science Stuff
I read this morning about a rather neat experiment that's going into orbit very soon.

Gravity Probe B is scheduled for launch from Vandenberg AFB on April 19. The satellite will be carrying four very precise gyroscopes - perhaps the most precise and frictionless gyroscopes ever made. The purpose of GPB is to verify part of Einstein's General Theory of Relativity.

Okay, so let's see if I can explain why this is cool. It's going to be kind of quick and dirty, so I'll leave some of the really detailed things out. And I'm not a physics major either (my physics major friend isn't available to proof this either) so you'll have to settle for the explanation of an amateur science-geek.

The General Theory of Relativity is one of the really big theories we have out there. it explains exactly how and why things in the universe act they way they act. The GTR is all mathematical formulas, though, and at the time much of it wasn't scientifically verifiable because we just didn't have the technology to do so. The math was sound, though, and what experiments could be run bore it out every time. Scientists can't really rest, though, until they can verify all of a Theory with direct experiments, though, and that's what the GPB is intended to do.

The GTR deals with large objects - really large objects. For "normal" objects like falling apples, buildings, and airplanes we use the old Newtonian Physics that the GTR supplanted because for the most part, Newtonian Physics works. When you get out into space and start dealing with things the size of planets and moons, though, Newtonian Physics just doesn't work. There are all sorts of imprecisions and conflicts and things that it just can't handle. So we have to use the GTR.

The biggest thing the GTR did was to say that there was no such thing as separate notions of time and space, but one thing called "spacetime". Spacetime is flexible. It bends and warps substantially when something large gets involved. How this happens is a really neat trick. Before Einstein, folks believed that gravity was a force that something gave off. Einstein showed that it didn't quite work that way.

Let's do a little visualization. Imagine that space is a nice, flat piece of rubber. Now roll a ping pong ball along the rubber sheet in a straight line. No problem. Now let's put a bowling ball in the middle of the sheet. It's going to make a dent in the sheet that, when we roll the ping pong ball again, is going to cause the ball to move toward the bowling ball if it gets close. That's the analogy Einstein used for how spacetime works. Before that, there were no "dents. Planets and starts just exerted a force called gravity that reached out and grabbed something. Einstein said that there was no reaching and grabbing, but that spacetime was warped by the gravity of a massive thing. It was a change in thinking that proved to be huge, to say the least.

But what about this time thing? How does that figure into it? Well, here's where the "relativity" part of the GTR fits in. Let's say you're on a spaceship with a perfectly tuned watch orbiting the Earth. I have the partner to your watch on my wrist standing on the surface of the planet. You orbit for an hour or so then come back and we compare watches. You'll find that our watches are now out of sync and that yours will be slightly faster than mine. You can even do that experiment by having one person to to the bottom of Death Valley and one staying at the top. The difference will be very slight, but it will be there. That's because Einstein found that time was a relative notion. You get even more extreme effect as gravity itself becomes stronger and stronger or as an object's speed gets closer to the speed of light.

These two discoveries (and an awful lot of math and experimentation that followed) put space and time together in one single unit. Convenient, huh? Except that proving it to a very precise degree is difficult. You have to be able to get experiments out into space and free of as many other influences (like flaws in the material, friction, etc) as possible before you can have any confidence in them.

What scientists believe will happen is that the gyroscopes in the GPB will be influenced by the curvature of spacetime around the earth in a very precise and predictable direction. The phenomenon they're looking at is called "frame dragging" and the satellite should be accurate to within 0.01 percent which is the most precise experiment ever done.

Very cool indeed.