From: Stig Agermose <stig.agermose@post.cybercity.dk>
Date: Thu, 27 Jul 2000 05:56:40 +0200
Fwd Date: Thu, 27 Jul 2000 09:41:32 -0400
Subject: UpDate: Scientists Dream Of Parallel Worlds

Source: San Francisco Examiner,

http://www.sfgate.com/cgi-bin/article.cgi?file=/examiner/hotnews/stories/24/cosmos.dtl

Stig

**

Scientists dream of parallel worlds

By Keay Davidson

EXAMINER SCIENCE WRITER

July 24, 2000

©2000 San Francisco Examiner

*

Alien universes might be stacked alongside ours like slices of
ham and cheese in a Dagwood sandwich, according to a bizarre new
scientific theory.

This hypothesis is one possible implication of a radical concept
of physics championed by scientists from UC-Berkeley, Stanford
and New York University.

Part of this concept holds that our universe might be shaped
like a thin membrane - one slice of cheese, so to speak -
surrounded by higher dimensions that transcend the three
familiar dimensions of height, width and depth.

According to the notion, six to seven dimensions exist beyond
the three everyday dimensions, plus time. (Physicist Albert
Einstein recognized time as the fourth dimension in 1905.)

We live our lives confined to the surface of our
three-dimensional membrane, oblivious to other dimensions, "much
as the lives of (movie) actors unfold on a two-dimensional
(movie) screen in a larger three-dimensional world," says
UC-Berkeley physicist Nima Arkani-Hamed.

He and associates Savas Dimopoulos and Georgi Dvali describe
their "large extra dimensions" hypothesis and some of its wilder
possible implications in the forthcoming August issue of
Scientific American.

Arkani-Hamed is an assistant professor of physics at UC-Berkeley
and Lawrence Berkeley National Laboratory. He was born in
Houston, but spent his early years in Iran, the child of two
Iranian physicists. When he was 9, the family fled the ayatollah
on horseback: "My family had huge political problems with the
regime. We had no choice but to escape," he said.

Dimopoulos, of Stanford, is a veteran physicist famed for his
role in helping pioneer supersymmetry, an important modern
paradigm of theoretical physics. (The new book "Supersymmetry"
by Gordon Kane says the theory of supersymmetry "implies that
each of the fundamental particles has a "superpartner' that can
be detected at (particle beam) energies and intensities only now
being achieved in the giant (particle) accelerators.")

Dvali, at NYU, and Arkani-Hamed have reputations as bright young
up-and-comers in the profession.

In the past, other scientists, especially a camp of physicists
called string theorists, posited the existence of six to seven
extra dimensions. However, they assumed these extra dimensions
would be extremely small - too small to detect with instruments
called particle accelerators. Accelerators reveal the underlying
nature of matter and energy by bashing together subatomic
particles.

The notion of other dimensions really isn't all that strange.

For example, consider a pencil: If you see it from a great
distance, it appears to be a straight line, that is, a
one-dimensional object. Looking more closely, you can see that
it has not only length but height - two dimensions. Seen even
closer and from the side, the pencil displays a third dimension
- depth.

The assumption that extra dimensions exist is the latest blow to
humans' old assumption of being important inhabitants of the
cosmos, the three researchers say. That assumption was first
shaken in the 16th century when astronomer Nicolaus Copernicus
showed that Earth orbits the sun, not vice versa as
traditionally thought.

"The idea of extra dimensions in effect continues the Copernican
tradition in understanding our place in the world," the three
scientists write in Scientific American. "The Earth is not the
center of the solar system; the sun is not the center of our
galaxy. Our galaxy is just one of billions in a universe that
has no center, and now our entire three-dimensional universe
would be just a thin membrane in the full space of dimensions."

If that doesn't send a chill down your spine, consider this: Our
cosmos and alien universes might be like stacks of ham and
cheese in a sandwich, each slice only a millimeter from the
next.

At this moment, you might be one millimeter - about fract,1,25
1/25 inch - from, say, the frigid bottom of a dark ocean on an
extraterrestrial planet, or the dusty chill of a cosmic dust
cloud a million galaxies away, or the noisy interior of an alien
bar packed with blue-skinned octopoids.

You can't see these amazing sights. But - if the hypothesis is
correct - they're there, literally next to you, forever veiled
from view by your inability to perceive these dimensions.

It sounds like a rejected script from an old "Twilight Zone"
episode. Yet it's one reasonable - although far from proven -
extrapolation from one of the hottest activities in physics, the
effort to resolve an old conundrum: Why is gravity so much
weaker than the other forces?

That question might sound odd to nonphysicists. We're all
accustomed to gravity's pull: It holds our feet firmly to the
ground, plucks flowerpots off windowsills, drags hapless
airplanes to their doom. Gravity also keeps the moon orbiting
Earth, and Earth orbiting the sun.

Yet to physicists, gravity is a wimp because it is extremely
weak compared to the three other known physical forces -
electromagnetism, the strong nuclear force and the weak
interaction force.

Electromagnetism gives us phenomena as diverse as light,
electricity and magnetism. The strong nuclear force binds
together the building blocks of atoms, namely protons and
neutrons. The weak interaction force is responsible for
radioactive decay.

Consider a nail that lies on a table. It's held down by the
gravitational force of the entire Earth, which weighs almost 6
septillion tons.

Yet Earth's grip on the nail can be instantly broken by a toy
magnet that weighs just a few ounces. Just hold the magnet over
the nail and - click! - the nail rises to meet it, courtesy of
electromagnetic force. It's as if an ant could wrest an apple
from Goliath's fist.

Likewise, Arkani-Hamed and his colleagues point out, the
electrical pull between two electrons (negatively charged
subatomic particles) is
10,000,000,000,000,000,000,000,000,000,000,000,000,000,000 times
as much as the gravitational pull between them.

"The feebleness of gravity is dramatic," they write in Scientific
American.

But why should it be? They propose that the reason is that the
force of gravity, unlike the other forces, spreads through all
dimensions, including the six or seven extra dimensions.

Hence the gravitational force is immensely spread out, like a
dollop of mayonnaise on a slice of bread. This makes it
extremely weak on the "local" level, as compared with other
forces.

By contrast, the other forces are concentrated solely in the
three-dimensional membrane in which we live. Being so
concentrated, they're much stronger than gravity.

 From there, it's a short step to the speculation that our
membrane universe might repeatedly fold over on itself. The
result: multiple universe slices adjacent to each other.

Hence anyone at Point A in Universe One could be next to Point B
in Universe Two, and next to Point C in Universe Three, yet
they'd never be able to see or - as far as anyone knows -
communicate with each other because light and the strong nuclear
and weak interaction forces can't pass between universes.

But gravity can. In that regard, Arkani-Hamed and his associates
add, someday we might be able to detect the gravitational pull
of giant masses, like stars, in other universes.

Arkani-Hamed is "one of these guys who just has enormous fun
thinking," says an admirer, the noted theoretical physicist
Michael Peskin of Stanford Linear Accelerator Center in Palo
Alto, where Arkani-Hamed once worked. "It was just extremely
exciting to have him in the (physics) group here. Every day he
would have some idea that would be amazing."

Laboratory experiments are under way at Stanford University, the
University of Washington at Seattle and the University of
Colorado at Boulder to test the scientists' prediction that
gravity would become much more intense at very small scales -
say, over distances much less than a millimeter.

One of the experimenters, physics Professor Eric Adelberger of
Seattle, is using a laser to try to detect the changing
gravitational force between an aluminum ring suspended by a
tungsten thread and a rotating copper disk.

Gravity is such a subtle force that it's a tremendously hard
experiment to perform, Adelberger said. "Even the tiniest piece
of dust in there will goof you up."

*

©2000 San Francisco Examiner