Thursday, December 1, 2011

Higher Dimensions and Multiple Universes

by Richard Crews
Theoretical physics used to talk about sensible things like billiard balls knocking each other around on a billiards table and baseballs arcing through the air. Then along came the 20th century with Relativity for very big stuff and Quantum Physics for very small stuff. Things didn't seem quite so reasonable: time slowed or sped up depending on gravity, nothing could travel faster than the speed of light, infinitesimal particles harbored whopping big amounts of energy, something could be in two different places at the same time, and more.

We couldn't really imagine such things. Our brains, after all, grew up dealing with wolves and trees and edible berries, all of which live in the "sensible" middle world (the "reasonable" world of Goldilocks--neither too hot nor too cold, too big nor too small). But we came to accept them--unimaginable as they were--because of two things: for one thing, smart people talked about them all the time as if they were so, and for another, we could see their results from atom bombs to computers, from worldwide air travel to watches that were accurate to a few seconds a year and ran forever on light or invisibly tiny batteries.

Yes, the 20th century presented some severe challenges to straight, reasonable thinking. But hold on, here comes the 21st century and theoretical physics is making things even stranger. It seems that quarks (that make up neutrons and protons, which make up atoms and molecules, which make up all the things we see and touch in the world around us) are not the ultimate building blocks--they are composed of even smaller entities, vibrating strings. And--hold on even harder--these tiny strings vibrate not just in the four dimensions we know and love, but in eleven dimensions.

How on earth can there be eleven dimensions around us? How come we don't see and feel them? Here's an analogy: You are sitting in a movie theater watching a film of a car racing down a highway. Three dimensions (plus time), right? Nope, just two (plus time)--it's all on the two-dimensional surface of the movie screen. The third spatial dimension is an optical illusion.

Then the car crashes into another car, and thanks to slow motion the action seems to slow down. The parts of the two cars sail slowly and gracefully away through the air. There's a distortion of the orderly tick-tock progression of time. Although you are still watching this in "real time," the time dimension on the screen has slowed considerably. It could even stop--or reverse. Yes, distortions in space and time dimensions can be quite taken for granted.

A universe of eleven dimensions with seven of them hidden from view is hard to imagine--well, OK, impossible to imagine. But if you want to live in the 21st century, you have to learn to smile and nod wisely when people talk about them.

But that's not all--try to imagine this: huge, high-dimensional structures (called membranes or "branes") having, say, six or eight dimensions and drifting around in still higher dimensional space (with, say, eight or ten dimensions). Two of them bump into one another releasing a tremendous amount of energy in three or four of their mutual dimensions. There's a big bang--in fact, a "Big Bang"--a universe is born. And, with another collision, another universe is born--and another, and another.

As theoretical physicists have untangled the mathematical implications of string theory, they have been forced to admit that there may be many, many universes--perhaps, the mathematics says, ten-to-the-five-hundredth (that's a ten followed by 500 zeroes)--perhaps more--perhaps an infinite number. Most of them are quite different from our universe--they have different physical constants, different properties; many cannot form any atoms, any matter, any life. But some (well, perhaps many--perhaps even an infinite number) are very much like our universe.

Could there be intelligent creatures living in parallel universes a fraction of an inch away from us? Yup. Could we communicate with them? Probably not; nothing gets across. Well, maybe gravity waves do. But that's 22nd century stuff. I'll leave that for another essay a hundred years or so from now.