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Created: May 17, 2003
Latest Update: May 17, 2003

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From Hawking's Universe in a Nutshell

Strings and Branes: So What Do We Know?

Site Copyright: Jeanne Curran and Susan R. Takata and Individual Authors, May 2003.
"Fair use" encouraged.

What if? What if we're really trapped on a membrane from which neither light nor energy (except gravity) can escape or enter? What if that explains "dark matter." Ninety percent of the cosmos we have been able to identify is "dark matter." What if that "dark matter" is just the rest of the universe that we can't see because light can't escape from or enter into our membrane from the great bulk of the universe? Sounds like science fiction? It's not. It's the latest theory physicists are exploring in an attempt to somehow understand the relation between particle physics (very, very tiny bits of matter) and astrophysics (immense galactic bits of matter), for the laws of the two appear to be contradictory.

This brief essay is based on a Los Angeles Times article by K.C. Cole: A New Slice on Physics May 17, 2003. At p. A 1. Backup.

Because I started out with degrees in math and physics, I never really understood all the fascination with positivism. Physics is physics is physics, and it has always had to put up with its own ambiguities. Yes, there are those who fudge data. Some well known "hard" scientists have resorted to painting little black spots on their white mice, and telling us the spots came there naturally following their experiment. Some journalists have filed stories about people and places they'd never seen and never been, and faked the stories. People fake questionnaire data all the time, forcing survey institutes into expensive quality checks, some of which probably get faked, too. There's always dishonesty afoot, much of it hopefully dissuaded by a sincere interest in learning and knowing. Most of us are curious. We'd really like to know. Not only for a better world. But also because it feels good to "know," to be able to confirm to our own satisfaction that something we suspected is "true," is true, meaning that it's as close to true as what we presently know will let us come.

By 1957 I was using the binary system, in which there's no 2+2 to equal 4. So I'm always surprised that people are so anxious to get their paws on "real" numbers. The Times article that appeared today on string theory can't give us real numbers. It's physics; but we can't measure 10 dimensions. We have trouble with four. And there's no way for light to escape our "brane," (from "membrane," not from "brain") which means we can't see these other dimensions anyway. And physicists find that OK. My husband, Arnold, also a physicist, asked plaintively,

"Do you know what they're talking about?"

"Yeah, I kinda get it. That new collider they're building in Europe, they're hoping that it will be able to speed a particle up to give it enough energy that they'll be able to "see" a fifth dimension."

"So what will it look like?"

"Oh, well, you won't be able to see it. They just keep real accurate figures on the total energy, and when their numbers show that they have lost some energy, that the total energy doesn't add up, then they'll know they've got a fifth dimension."

"Where is it, if you can't see it?"

"That's what Hawking was trying to show with the glob under the plane. Sorry, he called it the "bulk," but I kinda like "glob." Our universe is trapped in the plane, or the brane, as they call it, but gravity is not glued down to this plane like the other major forces, like electromagnetism, so gravity slips off into the glob and we lose it. It's gone to another blane, and we can't see outside our own blane, remember?"

"gravity can't be glued to a particular brane. Gravity, as Einstein revealed, is the curving of space-time itself, so it wanders willy-nilly where it will, leaking off our brane into what physicists call "the bulk" -- the rest of space-time." . . .

"Experimental evidence could come in the next decade from two very different realms. A new particle collider under construction in Europe could reach high-enough energies to produce, say, a five-dimensional "particle" of gravity -- a telltale sign of brane worlds beyond. This particle might be detected as energy missing from a collision because it "leaks" into an extra dimension."
L. A. Times article

"You see, gravity can escape. "[I]t wanders willy-nilly where it will, leaking off our brane into what physicists call "the bulk" -- the rest of space-time." I can sort of imagine that. You speed everything up until it's going so fast it explodes into smaller particles. But Einstein's relativity showed us that e = mc2, that is, that when that much energy is expended you can find all of it, because energy and matter switch from one to the other. Energy is equal to mass times the speed of light squared. So you can kind of intuitively see that speed is involved, very fast speed, the speed of light, and the mass of the particles, and the energy of the particles. When they measure the mass of the particles produced and the energy released and put it in the equation for relativity (between energy and mass) they should be able to see that the energy equals the mass times the speed of light squared. But if something goes wrong, and there's not enough energy to make both sides of the equation equal, then some energy has escaped somewhere. Where? Well, it wandered off will-nilly and slipped into a fifth dimension, which is "the rest of space-time" or the glob."

"Now, that's perfectly clear, isn't it?"

Gee, Arnold wasn't there anymore. So I finished the article, which ends with:

"In the end, there's always the chance that all these ideas will turn out to be too, well, off-the-wall. "Who knows?" said University of Chicago physicist Sean Carroll. But even if brane worlds aren't real, Carroll said, "they will have taught us a useful lesson that we should have known all along, which is that we don't have a clue to what's going on."
L.A. Times article.

We want to "know." It feels good to "know." Few of us are really satisfied by "faking" it. But as good as our understanding gets, when it comes to the real issues that matter, "we don't have a clue to what's going on." That's OK. Everyday we learn more. And getting there is most of the fun, anyway. May we just learn to tolerate that ambiguity, so when people we think are supposed to know what they're talking about tell us that gravity just slipped off the brane into the glob, and is now in the fifth dimension, we won't hurl epithet's like "stupid, magic, black magic, superstition." We'll just nod and remember that "knowingness" trips us up every time. Just when I thought I knew the world was flat, oops, round, off goes gravity slipping off the edge into the fifth dimensions. And if you think I'm joking, take a look at what that particle collider in Europe is going to cost.

love and peace, and don't "know" too quickly, jeanne