Physicists Attempt to Create Event Horizon in Lab
January 24, 2002 08:00 CDT
Even as scientists have questioned the existence of black holes in space,
others are attempting to produce the event horizon associated with them in a
laboratory. At an event horizon, light and time appear to stand still.
"It's very difficult to do experiments at real black holes," physicist Ulf
Leonhardt of the University of St. Andrews in Scotland told Nature. Leonhardt
developed a method to build a simulated event horizon using a device about
the size of a tabletop that halts light in the lab.
Simulation through the device theoretically would produce a form of "Hawking
radiation," weak electromagnetic waves thought to occur when light reaches
the event horizon, but hidden by other emissions. "We might even be able to
see it with the naked eye," says astronomer Fulvio Melia of the University of
Arizona in Tucson.
Hawking radiation has never been observed. Last week during the space
symposium in Washington, D.C., a team of scientists revealed the general
color of the universe as a pale turquoise. The scientists working on the
event horizon hope they will find a similar universal color for Hawking
radiation.
"If it's true it's tremendously interesting," cosmologist Bernard Carr of
Queen Mary and Westfield College, London., told Nature. Imitation event
horizons lead to understanding quantum effects of gravity, and resolve
conflicts that have developed between general relativity (the theory of the
biggest bodies in the Universe) and quantum theory (the rules governing its
tiniest constituents). General relativity predicts that nothing can escape a
black hole; quantum theory says that Hawking radiation does.
A black hole supposedly forms from a dying star when its mass compresses to a
tiny point. As light waves hit the event horizon, they are thought to split
into pairs of particles called "quanta;" one falls into the black hole and
one escapes as Hawking radiation. At that point, "a pile-up occurs," Melia
said. Many light waves produce streams of quanta heading forward and backward.
The team of physicists hopes to replicate this barrier. A laser beam directed
into cold matter manipulates the rate that its constituent atoms absorb and
re-emit waves of a second beam, causing this second beam to slow or stop.
The point where light stands still is analogous to an event horizon, and,
according to Leonhardt, quanta will be emitted. The simulation would be a
membranous event horizon without the black hole beyond.
Source: University of Arizona; University of St. Andrews; Queen Mary and
Westfield College; Nature; Chandra; Weiss