Torchbearer: Summer 1998

Just a Matter Of Time

To physicists and nuclear scientists, turning matter into light, heat, and other forms of energy is nothing new. Now a team of 20 physicists–four of them from the UTK physics department–has demonstrated the inverse process-turning light into matter.

UTK's Dr. Bill Bugg, professor; Steve Berridge, engineer; Dr. Achim Weidemann, research associate; and Dr. Konstantin Shmakov, research assistant, took part in the experiment at the Stanford Linear Accelerator Center in California.

They joined scientists from Princeton University, the University of Rochester, and Stanford University to make history. The results were announced in the Sept. 1, 1997, issue of Physical Review Letters.

The physicists used colliding beams of radiation to create matter from nothingness. The lower energy beam was produced by a trillion-watt green laser, one of the world's most powerful. The second beam of light was created when the laser light collided with high energy electrons from the two-mile-long Stanford Linear Accelerator, 10 billion times as powerful as the green laser.

The collision, which has been likened to ping-pong balls hitting a speeding Mack truck, created real particles of matter.

The creation of matter by light has never been observed in laboratory experiments until now.

"Lack of adequate laser technology was the limiting factor," says Bugg. "It was not until five or six years ago that lasers became available with the power needed to do this experiment."

Scientists believe similar light-to-matter conversions take place on the surfaces of neutron stars. This experiment could shed light on this and other astronomical phenomena. On a practical level, the conversion of light into matter could give particle physicists a new source of exceptionally uniform positrons for more easily controlled accelerators and other experiments.

Ever since Einstein's Theory of Relativity, scientists have theorized that such an achievement was possible. In 1934, two American physicists, Dr. Gregory Breit and Dr. John A. Wheeler, predicted the "reaction could go the other way," Bugg says.

Six decades later, scientists have proven them right.

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