Scientist Can now Create Matter Out
of Nothing
Scientist Can now Create Matter Out of Nothing
A trailblazing experiment at the Stanford Linear
Accelerator Center in California has confirmed a longstanding
prediction by theorists that light beams colliding with each other can
goad the empty vacuum into creating something out of nothing.
In a report published this month by the journal Physical
Review Letters, 20 physicists from four research institutions
disclosed that they had created two tiny specks of matter -- an
electron and its antimatter counterpart, a positron -- by colliding
two ultrapowerful beams of radiation.
The possibility of doing something like this was
suggested in 1934 by two American physicists, Dr. Gregory Breit and
Dr. John A. Wheeler. But more than six decades would pass before any
laboratory could pump enough power into colliding beams of radiation
to conjure up matter from nothingness. The Stanford accelerator
finally provided enough energy to do it.
Dr. Adrian C. Melissinos of the University of Rochester,
a spokesman for the group, said in an interview that the weaker of the
two light beams used in the experiment was produced by a trillion-watt
green laser. That in itself fell far short of the needed energy, even
though the pulsed green laser is one of the world's most powerful.
But the opposing beam of radiation was another story;
boosted by energy drawn from electrons whizzing down the two-mile-long
Stanford accelerator, this second beam of radiation was some 10
billion times as powerful as the green laser beam.
The paths of colliding electrons and photons in the
experiment were as complicated as those choreographed by an expert
pool player planning a difficult shot.
Photons of light from the green laser were allowed to
collide almost head-on with 47-billion-electronvolt electrons shot
from the Stanford particle accelerator. These collisions transferred
some of the electrons' energy to the photons they hit, boosting the
photons from green visible light to gamma-ray photons, and forcing the
freshly spawned gamma photons to recoil into the oncoming laser beam.
The violent collisions that ensued between the gamma photons and the
green laser photons created an enormous electromagnetic field.
This field, Melissinos said, "was so high that the
vacuum within the experiment spontaneously broke down, creating real
particles of matter and antimatter."
This breakdown of the vacuum by an ultrastrong
electromagnetic field was hypothesized in 1950 by Dr. Julian S.
Schwinger, who was awarded a Nobel Prize in physics in 1965. The
creation of matter by colliding photons of radiation is believed to
take place in some stars, but it was never observed in laboratory
experiments before, largely because the required
energy is beyond the reach of conventional laboratory equipment.
With his special theory of relativity, Einstein showed
that matter and energy are equivalent and can be transmuted through
the equation E equals mc2; that is, energy in ergs is equal to mass in
grams times the speed of light squared, in centimeters per second.
This accounts for the vast energy released by small amounts of matter
in nuclear explosions, but it also means that staggering amounts of
energy are required to
create even the tiniest particles of matter.
The hardest part of the project, in which scientists
employed by the Stanford Linear Accelerator Center collaborated with
colleagues from the University of Tennessee in Knoxville, Princeton
University and the University of Rochester, was synchronizing the
timing of laser and electron pulses, Melissinos said. The green laser
pulse, traveling at the speed of light, was only one half millimeter
long. That pulse had to be timed to collide with an electron pulse
almost as it emerged from the two-mile-long beam line.
The experiment, Melissinos said, is unlikely to have
many practical applications, although it might help in the design of a
new generation of research accelerators. Existing accelerators use
particles of matter as projectiles -- protons, electrons or entire
atoms. But a possible future accelerator that physicists call a
"gamma-gamma machine" might work by colliding opposing beams of
photons, especially gamma-ray photons.
Meanwhile, Melissinos and his colleagues expect to use
photon collisions as a way to explore the intricacies of quantum
electrodynamics -- a highly successful but complex theory explaining
the interactions of electromagnetic fields with matter.
Copyright 1997 The New York Times
By Malcom W. Browne
Scientists Use Light to Create Particles