A Theory Of Everything?
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The SSC is projected to cost over $8 billion (which is large compared to
the science budget, but insignificant compared to the Pentagon budget).
By every measure, it will be a colossal machine. It will consist of a
ring of powerful magnets stretched out in a tube over 50 miles in
diameter. In fact, one could easily fit the Washington Beltway, which
surrounds Washington D.C., inside the SSC. Inside this gigantic tube,
protons will be accelerated to unimaginable energies.
At present, it is scheduled to be finished near the turn of the century
in Texas, near the city of Austin. When completed, it will employ
thousands of physicists and engineers and cost millions of dollars to
operate.
At the very least, physicists hope that the SSC will find some exotic
sub-atomic particles, such as the "Higgs boson" and the "top quark," in
order to complete our present-day understanding of the quantum theory.
However, there is also the small chance that physicists might discover
"supersymmetric" particles, which may be remnants of the original
superstring theory. In other words, although the superstring theory
cannot be tested directly by the SSC, one hopes to find resonances from
the superstring theory among the debris created by smashing protons
together.
Parable of the Gemstone
To understand the intense controversy surrounding superstring theory,
think of the following parable.
Imagine that, at the beginning of time, there was once a beautiful,
glittering gemstone. Its perfect symmetries and harmonies were a sight
to behold. However, it possessed a tiny flaw and became unstable,
eventually exploding into thousands of tiny pieces. Imagine that the
fragments of the gemstone rained down on a flat, two-dimensional world,
called Flatland, where there lived a mythical race of beings called
Flatlanders.
These Flatlanders were intrigued by the beauty of the fragments, which
could be found scattered all over Flatland. The scientists of Flatland
postulated that these fragments must have come from a crystal of
unimaginable beauty that shattered in a titanic Big Bang. They then
decided to embark upon a noble quest, to reassemble all these pieces of
the gemstone.
After 2,000 years of labor by the finest minds of Flatland, they were
finally able to fit many, but certainly not all, of the fragments
together into two chunks. The first chunk was called the "quantum," and
the second chunk was called "relativity."
Although they Flatlanders were rightfully proud of their progress, they
were dismayed to find that these two chunks did not fit together. For
half a century, the Flatlanders maneuvered these two chunks in all
possible ways, and they still did not fit.
Finally, some of the younger, more rebellious scientists suggested a
heretical solution: perhaps these two chunks could fit together if they
were moved in the third dimension.
This immediately set off the greatest scientific controversy in years.
The older scientists scoffed at this idea, because they didn't believe
in the unseen third dimension. "What you can't measure doesn't exist,"
they declared.
Furthermore, even if the third dimension existed, one could calculate
that the energy necessary to move the pieces up off Flatland would
exceed all the energy available in Flatland. Thus, it was an untestable
theory, the critics shouted.
However, the younger scientists were undaunted. Using pure mathematics,
they could show that these two chunks fit together if they were rotated
and moved in the third dimension. The younger scientists claimed that
the problem was therefore theoretical, rather than experimental. If one
could completely solve the equations of the third dimension, then one
could, in principle, fit these two chunks completely together and
resolve the problem once and for all.
We Are Not Smart Enough
That is also the conclusion of today's superstring enthusiasts, that the
fundamental problem is theoretical, not practical. The true problem is
to solve the theory completely, and then compare it with present-day
experimental data. The problem, therefore, is not in building gigantic
atom smashers; the problem is being clever enough to solve the theory.
Edward Witten, impressed by the vast new areas of mathematics opened up
by the superstring theory, has said that the superstring theory
represents "21th century physics that fell accidentally into the 20th
century." This is because the superstring theory was discovered almost
by accident. By the normal progression of science, we theoretical
physicists might not have discovered the theory for another century.
The superstring theory may very well be 21st century physics, but the
bottleneck has been that 21st century mathematics has not yet been
discovered. In other words, although the string equations are perfectly
well-defined, no one is smart enough to solve them.
This situation is not entirely new to the history of physics. When
Newton first discovered the universal law of gravitation at the age of
23, he was unable to solve his equation because the mathematics of the
17th century was too primitive. He then labored over the next 20 years
to develop a new mathematical formalism (calculus) which was powerful
enough to solve his universal law of gravitation.
Similarly, the fundamental problem facing the superstring theory is
theoretical. If we could only sharpen our analytical skills and develop
more powerful mathematical tools, like Newton before us, perhaps we
could solve the theory and end the controversy.
Ironically, the superstring equations stand before us in perfectly
well-defined form, yet we are too primitive to understand why they work
so well and too dim witted to solve them. The search for the theory of
the universe is perhaps finally entering its last phase, awaiting the
birth of a new mathematics powerful enough to solve it.
Imagine a child gazing at a TV set. The images and stories conveyed on
the screen are easily understood by the child, yet the electronic
wizardry inside the TV set is beyond the child's ken. We physicists are
like this child, gazing in wonder at the mathematical sophistication and
elegance of the superstring equations and awed by its power. However,
like this child, we do not understand why the superstring theory works.
In conclusion, perhaps some of the readers will be inspired by this
story to read every book in their libraries about the superstring
theory. Perhaps some of the young readers of this article will be the
ones to complete this quest for the Theory of the Universe, begun so
many years ago by Einstein.
Dr. Kaku is author of Beyond Einstein (Bantam) and the forthcoming book,
Hyperspace, upon which this article is based.
BLACK HOLES, WORMHOLES, AND THE 10Th DIMENSION
Dr. Kaku is professor of theoretical physics at the City Univ. of New
York and author of Hyperspace: A Scientific Odyssey Through Parallel
Universe, Time Warps, and the 10th Dimension (Oxford Univ. Press).
Last June, astronomers were toasting each other with champagne glasses
in laboratories around the world, savoring their latest discovery. The
repaired $2 billion Hubble Space Telescope, once the laughing stock of
the scientific community, had snared its most elusive prize: a black
hole.
But the discovery of the Holy Grail of astrophysics may also rekindle a
long simmering debate within the physics community. What lies on the
other side of a black hole? If someone foolishly fell into a black hole,
will they be crushed by its immense gravity, as most physicists believe,
or will they be propelled into a parallel universe or emerge in another
time era?
To solve this complex question, physicists are opening up one of the
most bizarre and ttantalizing chapters in modern physics. They have to
navigate a minefield of potentially explosive theories, such as the
possibility of "wormholes," "white holes," time machines, and even the
10th dimension!
This controversy may well validate J.B.S. Haldane's wry observation that
the universe is "not only queerer than we sup- pose, it is queerer than
we can suppose."
This delicious controversy, which delights theoretical physicists but
boggles the mind of mere mortals, is the subject of my recent book,
Hyperspace.
BLACK HOLES: COLLAPSED STARS
A black hole, simply put, is a massive, dead star whose gravity is so
intense than even light cannot escape, hence its name. By definition, it
can't be seen, so NASA scientists focused instead on the tiny core of
the galaxy M87, a super massive "cosmic engine" 50 million light years
from earth.
Astronomers then showed that the core of M87 consisted of a ferocious,
swirling maelstrom of superhot hydrogen gas spinning at l.2 million
miles per hour. To keep this spinning disk of gas from violently flying
apart in all directions, there had to be a colossal mass concentrated at
its center, weighing as much as 2 to 3 billion suns! An object with that
staggering mass would be massive enough to prevent light from escaping.
Ergo, a black hole.
THE EINSTEIN-ROSEN BRIDGE
But this also revives an ongoing controversy surrounding black holes.
The best description of a spinning black hole was given in 1963 by the
New Zealand mathematician Roy Kerr, using Einstein's equations of
gravity. But there is a quirky feature to his solution. It predicts that
if one fell into a black hole, one might be sucked down a tunnel (called
the "Einstein-Rosen bridge") and shot out a "white hole" in a parallel
universe!
Kerr showed that a spinning black hole would collapse not into a point,
but to a "ring of fire." Because the ring was spinning rapidly,
centrifugal forces would keep it from collapsing. Remarkably, a space
probe fired directly through the ring would not be crushed into
oblivion, but might actually emerge unscratched on the other side of the
Einstein-Rosen bridge, in a parallel universe. This "wormhole" may
connect two parallel universes, or even distant parts of the same
universe.
THROUGH THE LOOKING GLASS
The simplest way to visualize a Kerr wormhole is to think of Alice's
Looking Glass. Anyone walking through the Looking Glass would be
transported instantly into Wonderland, a world where animals talked in
riddles and common sense wasn't so common.
The rim of the Looking Glass corresponds to the Kerr ring. Anyone
walking through the Kerr ring might be transported to the other side of
the universe or even the past. Like two Siamese twins joined at the hip,
we now have two universes joined via the Looking Glass.
Some physicists have wondered whether black holes or worm- holes might
someday be used as shortcuts to another sector of our universe, or even
as a time machine to the distant past (making possible the swashbuckling
exploits in Star Wars). However, we caution that there are skeptics. The
critics concede that hundreds of wormhole solutions have now been found
to Einstein's equations, and hence they cannot be lightly dismissed as
the ravings of crack pots. But they point out that wormholes might be
unstable, or that intense radiation and sub-atomic forces surrounding
the entrance to the wormhole would kill anyone who dared to enter.
Spirited debates have erupted between physicists concerning these
wormholes. Unfortunately, this controversy cannot be re- solved, because
Einstein's equations break down at the center of black holes or
wormholes, where radiation and sub-atomic forces might be ferocious
enough to collapse the entrance. The problem is Einstein's theory only
works for gravity, not the quantum forces which govern radiation and
sub-atomic particles. What is needed is a theory which embraces both the
quantum theory of radiation and gravity simultaneously. In a word, to
solve the problem of quantum black holes, we need a "theory of
everything!"
A THEORY OF EVERYTHING?
One of the crowning achievements of 20th century science is that all the
laws of physics, at a fundamental level, can be summarized by just two
formalisms: (1) Einstein's theory of gravity, which gives us a cosmic
description of the very large, i.e. galaxies, black holes and the Big
Bang, and (2) the quantum theory, which gives us a microscopic
description of the very small, i.e. the microcosm of sub-atomic
particles and radiation.
But the supreme irony, and surely one of Nature's cosmic jokes, is that
they look bewilderingly different; even the world's greatest physicists,
including Einstein and Heisenberg, have failed to unify these into one.
The two theories use different mathematics and different physical
principles to describe the universe in their respective domains, the
cosmic and the microscopic.
Fortunately, we now have a candidate for this theory. (In fact, it is
the only candidate. Scores of rival proposals have all been shown to be
inconsistent.) It's called "superstring theory," and almost effortlessly
unites gravity with a theory of radiation, which is required to solve
the problem of quantum wormholes.
The superstring theory can explain the mysterious quantum laws of
sub-atomic physics by postulating that sub-atomic particles are really
just resonances or vibrations of a tiny string. The vibrations of a
violin string correspond to musical notes; likewise the vibrations of a
superstring correspond to the particles found in nature. The universe is
then a symphony of vibrating strings.
An added bonus is that, as a string moves in time, it warps the fabric
of space around it, producing black holes, wormholes, and other exotic
solutions of Einstein's equations. Thus, in one stroke, the superstring
theory unites both the theory of Einstein and quantum physics into one
coherent, compelling picture.
A 10 DIMENSIONAL UNIVERSE
The curious feature of superstrings, however, is that they can only
vibrate in 10 dimensions. This is, in fact, one of the reasons why it
can unify the known forces of the universe: in 10 dimensions there is
"more room" to accommodate both Einstein's theory of gravity as well as
sub-atomic physics. In some sense, previous attempts at unifying the
forces of nature failed because a standard four dimensional theory is
"too small" to jam all the forces into one mathematical framework.
To visualize higher dimensions, consider a Japanese tea garden, where
carp spend their entire lives swimming on the bottom of a shallow pond.
The carp are only vaguely aware of a world beyond the surface. To a carp
"scientist," the universe only consists of two dimensions, length and
width. There is no such thing as "height." In fact, they are incapable
of imagining a third dimension beyond the pond. The word "up" has no
meaning for them. (Imagine their distress if we were to suddenly lift
them out of their two dimensional universe into "hyperspace," i.e. our
world!)
However, if it rains, then the surface of their pond becomes rippled.
Although the third dimension is beyond their comprehension, they can
clearly see the waves traveling on the pond's surface. Likewise,
although we earthlings cannot "see" these higher dimensions, we can see
their ripples when they vibrate. According to this theory, "light" is
nothing but vibrations rippling along the 5th dimension. By adding
higher dimensions, we can easily accommodate more and more forces,
including the nuclear forces. In a nutshell: the more dimensions we
have, the more forces we can accommodate.
One persistent criticism of this theory, however, is that we do not see
these higher dimensions in the laboratory. At present, every event in
the universe, from the tiniest sub-atomic decay to exploding galaxies,
can be described by 4 numbers (length, width, depth, and time), not 10
numbers. To answer this criticism, many physicists believe (but cannot
yet prove) that the universe at the instant of the Big Bang was in fact
fully 10 dimensional. Only after the instant of creation did 6 of the 10
dimensions "curled up" into a ball too tiny to observe. In a real sense,
this theory is really a theory of creation, when the full power of 10
dimensional space-time was manifest.
Sheila Na Gig
Send e-mail to mapona@yahoo.com
Copyright © 1999 Sheila Na Gig.
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