Parallel Worlds (42 page)

COMPENSATING FOR THERMAL FLUCTUATIONS

Yet another way
that optical telescopes have been revitalized is through lasers to compensate
for the distortion of the atmosphere. Stars do not twinkle because they
vibrate; stars twinkle mainly because of tiny thermal fluctuations in the
atmosphere. This means that in outer space, far from the atmosphere, the stars
glare down on our astronauts continuously. Although this twinkling gives much
of the beauty of the night sky, to an astronomer it is a nightmare, resulting
in blurry pictures of celestial bodies. (As a child, I remember staring at the
fuzzy pictures of the planet Mars, wishing there was some way to obtain crystal
clear pictures of the red planet. If only the disturbances from the atmosphere
could be eliminated by rearranging the light beams, I thought, maybe the
secret of extraterrestrial life could be solved.)

One way to
compensate for this blurriness is to use lasers and high-speed computers to
subtract out the distortion. This method uses "adaptive optics,"
pioneered by a classmate of mine from Harvard, Claire Max of the Lawrence
Livermore National Laboratory, and others, using the huge W. M. Keck telescope
in Hawaii (the largest in the world) and also the smaller 3-meter Shane
telescope at the Lick Observatory in California. For example, by shooting a
laser beam into outer space, one can measure tiny temperature fluctuations in
the atmosphere. This information is analyzed by computer, which then makes tiny
adjustments in the mirror of a telescope which compensate for the distortion
of starlight. In this way, one can approximately subtract out the disturbance
from the atmosphere.

This method was
successfully tested in 1996 and since then has produced crystal-sharp pictures
of planets, stars, and galaxies. The system fires light from a tunable dye
laser with 18 watts of power into the sky. The laser is attached to the 3-meter
telescope, whose de- formable mirrors are adjusted to make up for the
atmospheric distortion. The image itself is caught on a CCD camera and
digitalized. With a modest budget, this system has obtained pictures almost comparable
to the Hubble space telescope. One can see fine details in the outer planets
and even peer into the heart of a quasar using this method, which breathes new
life into optical telescopes.

This method has
also increased the resolution of the Keck telescope by a factor of 10. The
Keck Observatory, located at the summit of Hawaii's dormant volcano Mauna Kea,
almost 14,000 feet above sea level, consists of twin telescopes that weigh 270
tons each. Each mirror, measuring 10 meters (394 inches) across, is composed of
thirty-six hexagonal pieces, each of which can be independently manipulated by
computer. In 1999, an adaptive optics system was installed into Keck II,
consisting of a small, deformable mirror that can change shape 670 times per
second. Already, this system has captured the image of stars orbiting around the
black hole at the center of our Milky Way galaxy, the surface of Neptune and
Titan (a moon of Saturn), and even an extrasolar planet which eclipsed the
mother star 153 light-years from Earth. Light from the star HD 209458 dimmed
exactly as predicted, as the planet moved in front of the star.

LASHING RADIO
TELESCOPES TOGETHER

Radio telescopes
have also been revitalized by the computer revolution. In the past, radio
telescopes were limited by the size of their dish. The larger the dish, the
more radio signals could be gathered from space and analyzed. However, the
larger the dish, the more expensive it becomes. One way to overcome this
problem is to lash several dishes together to mimic the radio-gathering
capability of a super radio telescope. (The largest radio telescope that can be
lashed together on Earth is the size of Earth itself.) Previous efforts to lash
together radio telescopes in Germany, Italy, and the United States proved
partially successful.

One problem with
this method is that signals from all the various radio telescopes must be
combined precisely and then fed into a computer. In the past, this was
prohibitively difficult. However, with the coming of the Internet and cheap
high-speed computers, costs have dropped considerably. Today, creating radio
telescopes with the effective size of the planet Earth is no longer a fantasy.

In the United
States, the most advanced device employing this interference technology is the
VLBA (very long baseline array), which is a collection of ten radio antennas
located at different sites, including New Mexico, Arizona, New Hampshire,
Washington, Texas, the Virgin Islands, and Hawaii. Each VLBA station contains a
huge, 82-foot-diameter dish which weighs 240 tons and stands as tall as a
ten-story building. Radio signals are carefully recorded at each site on tape,
which is then shipped to the Socorro Operations Center, New Mexico, where they
are correlated and analyzed. The system went online in 1993 at a cost of $85
million.

Correlating the
data from these ten sites creates an effective, giant radio telescope that is
5,000 miles wide and can produce some of the sharpest images on Earth. It is
equivalent to standing in New York City and reading a newspaper in Los Angeles.
Already, the VLBA has produced "movies" of cosmic jets and supernova
explosions and the most accurate distance measurement ever made of an object
outside the Milky Way galaxy.

In the future,
even optical telescopes may use the power of in- terferometry, although this is
quite difficult because of the short wavelength of light. There is a plan to
bring the optical data from the two telescopes at the Keck Observatory in
Hawaii and interfere them, essentially creating a giant telescope much larger
than either one.

MEASURING THE ELEVENTH DIMENSION

In addition to
the search for dark matter and black holes, what is most intriguing to
physicists is the search for higher dimensions of space and time. One of the
more ambitious attempts to verify the existence of a nearby universe was done
at the University of Colorado at Boulder. Scientists there tried to measure
deviations from Newton's famous inverse square law.

According to
Newton's theory of gravity, the force of attraction between any two bodies
diminishes with the square of the distance separating them. If you double the
distance from Earth to the Sun, then the force of gravity goes down by 2
squared, or 4. This, in turn, measures the dimensionality of space.

So far, Newton's
law of gravity holds at cosmological distances involving large clusters of
galaxies. But no one has adequately tested his law of gravity down to tiny
length scales because it was prohibitively difficult. Because gravity is such
a weak force, even the tiniest disturbance can destroy the experiment. Even
passing trucks create vibrations large enough to nullify experiments trying to
measure the gravity between two small objects.

The physicists
in Colorado built a delicate instrument, called a high-frequency resonator,
that was able to test the law of gravity down to a 10th of a millimeter, the
first time this had ever been done on such a tiny scale. The experiment
consisted of two very thin tungsten reeds suspended in a vacuum. One of the
reeds vibrated at a frequency of 1,000 cycles per second, looking somewhat
like a vibrating diving board. Physicists then looked for any vibrations that
were transmitted across the vacuum to the second reed. The apparatus was so
sensitive that it could detect motion in the second reed caused by the force of
a billionth of the weight of a grain of sand. If there was a deviation in
Newton's law of gravity, then there should have been slight disturbances
recorded in the second reed. However, after analyzing distances down to 108
millionths of a meter, the physicists found no such deviation. "So far,
Newton is holding his ground," said C. D. Hoyle of the University of
Trento in Italy, who analyzed the experiment for
Nature
magazine.

This result was
negative, but this has only whetted the appetite of other physicists who want
to test deviations to Newton's law down to the microscopic level.

Yet another
experiment is being planned at Purdue University. Physicists there want to
measure tiny deviations in Newton's gravity not at the millimeter level but at
the atomic level. They plan to do this by using nanotechnology to measure the
difference between nickel 58 and nickel 64. These two isotopes have identical
electrical and chemical properties, but one isotope has six more neutrons than
the other. In principle, the only difference between these isotopes is their
weight.

These scientists
envision creating a Casimir device consisting of two sets of neutral plates
made out of the two isotopes. Normally, when these plates are held closely
together, nothing happens because they have no charge. But if they are brought
extremely close to each other, the Casimir effect takes place, and the two
plates are attracted slightly, an effect that has been measured in the
laboratory. But because each set of parallel plates is made out of different
isotopes of nickel, they will be attracted slightly differently, depending on
their gravity.

In order to
maximize the Casimir effect, the plates have to be brought extremely close
together. (The effect is proportional to the inverse fourth power of the
separation distance. Hence, the effect grows rapidly as the plates are brought
together.) The Purdue physicists will use nanotechnology to make plates
separated by atomic distances. They will use state-of-the-art
microelectromechanical torsion oscillators to measure tiny oscillations in the
plates. Any difference between the nickel 58 and nickel 64 plates can then be
attributed to gravity. In this way, they hope to measure deviations to Newton's
laws of motion down to atomic distances. If they find a deviation from Newton's
famed inverse square law with this ingenious device, it may signal the presence
of a higher-dimensional universe separated from our universe by the size of an
atom.

LARGE HADRON COLLIDER

But the device
that may decisively settle many of these questions is the LHC (Large Hadron
Collider), now nearing completion near Geneva, Switzerland, at the famed CERN
nuclear laboratory. Unlike previous experiments on strange forms of matter that
naturally occur in our world, the LHC might have enough energy to create them
directly in the laboratory. The LHC will be able to probe tiny distances, down
to i0
^-19
meters, or 10,000 times smaller than a proton, and create
temperatures not seen since the big bang. "Physicists are sure that nature
has new tricks up her sleeve that must be revealed in those collisions—perhaps
an exotic particle known as the Higgs boson, perhaps evidence of a miraculous
effect called supersymme- try, or perhaps something unexpected that will turn
theoretical particle physics on its head," writes Chris Llewellyn Smith,
former director general of CERN and now president of the University College in
London. Already, CERN has seven thousand users of its equipment, which amounts
to more than half of all the experimental particle physicists on the planet.
And many of them will be directly involved in the LHC experiments.

The LHC is a
powerful circular machine, 27 kilometers in diameter, large enough to
completely encircle many cities around the world. Its tunnel is so long that it
actually straddles the French- Swiss border. The LHC is so expensive that it
has taken a consortium of several European nations to build it. When it is
finally turned on in 2007, powerful magnets arranged along the circular tubing
will force a beam of protons to circulate at ever-increasing energies, until
they reach about 14 trillion electron volts.

The machine
consists of a large circular vacuum chamber with huge magnets placed
strategically along its length to bend the powerful beam into a circle. As the
particles circulate in the tubing, energy is injected into the chamber,
increasing the velocity of the protons. When the beam finally hits a target, it
releases a titanic burst of radiation. Fragments created by this collision are
then photographed by batteries of detectors to look for evidence of new, exotic,
subatomic particles.

The LHC is truly
a mammoth machine. While LIGO and LISA push the envelope in terms of
sensitivity, the LHC is the ultimate in sheer brute strength. Its powerful
magnets, which bend the beam of protons into a graceful arc, generate a field
of 8.3 teslas, which is 160,000 times greater than Earth's magnetic field. To
generate such monstrous magnetic fields, physicists ram 12,000 amps of
electrical current down a series of coils, which have to be cooled down to —271
degrees C, where the coils lose all resistance and become superconducting. In
all, it has 1,232 15-meter-long magnets, which are placed along 85 percent of
the entire circumference of the machine.

In the tunnel,
protons are accelerated to 99.999999 percent of the speed of light until they
hit a target, located at four places around the tube, thereby creating billions
of collisions each second. Huge detectors are placed there (the largest is the
size of a six-story building) to analyze the debris and hunt for elusive
subatomic particles.

As Smith
mentioned earlier, one of the goals of the LHC is to find the elusive Higgs
boson, which is the last piece of the Standard Model that has still eluded
capture. It is important because this particle is responsible for spontaneous
symmetry breaking in particle theories and gives rise to the masses of the
quantum world. Estimates of the mass of the Higgs boson place it somewhere
between 115 and 200 billion electron volts (the proton, by contrast, weighs
about 1 billion electron volts). (The Tevatron, a much smaller machine located
at Fermilab outside Chicago, may actually be the first accelerator to bag the
elusive Higgs boson, if the particle's mass is not too heavy. In principle, the
Tevatron may produce up to 10,000 Higgs bosons if it operates as planned. The
LHC, however, will generate particles with seven times more energy. With 14
trillion electron volts to play with, the LHC can conceivably become a
"factory" for Higgs bosons, creating millions of them in its proton
collisions.)