Ancient shock waves may reveal creation

Feb. 12, 2002 at 4:58 PM
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BOZEMAN, Mont., Feb. 12 (UPI) -- A new project to find ancient echoes from the birth of the universe -- gravitational shock waves left over from the Big Bang -- may help astronomers determine what happened at the moment of creation.

"The next new window on the universe in astronomy will surely be gravitational waves," University of Chicago astrophysicist and cosmology expert Michael Turner told United Press International.

Studying gravity waves, Turner said, could allow us a glimpse of the universe "when it was only 10 to the minus-32 years old."

Presently, astronomers cannot see farther back than about 300,000 years after the Big Bang, since present-day detectors are simply not sensitive enough to pick up the extremely low-frequency waves that still linger from the first nano-seconds after the Big Bang.

As a solution, astrophysicists at Princeton University, the Goddard Space Flight Center and Montana State University have proposed to NASA the GREAT project -- for Gravitational Echoes Across Time.

"The mission proposal is completely new," physicist Neil Cornish told UPI from Bozeman. "The idea extends an existing mission concept -- the Laser Interferometer Space Antenna or LISA -- to much higher sensitivity and into a different frequency range."

Missions such as LISA are designed to study another Big Bang relic-- the Cosmic Microwave Background, or CMB. These lukewarm, low-intensity light waves are "the after-glow of the Big Bang," Cornish said.

"The CMB originated from the hot charged plasma of the early universe as it cooled and expanded into a hot neutral gas, roughly 300,000 years after the Big Bang," he told UPI.

The GREAT mission, he added, targets a much older Big Bang relic -- the Cosmic Gravitational Wave Background or CGB.

"Neither LIGO nor LISA have the sensitivity required to detect the cosmic gravitational wave background," Turner said. LIGO, the Laser Interferometer Gravitational-Wave Observatory, is a ground based project designed to study non-background gravity waves from large scale, recent phenomena such as exploding or collapsing stars.

"The cosmic gravitational wave background is thought to have been produced in the first tiny fraction of a second after the Big Bang," Cornish told UPI.

Measuring the CGB, Cornish explained, might well be the only way to discriminate between the two leading theories of creation -- inflation and string theory.

In standard inflation models, the size or amplitude of gravity waves is independent of wave frequency. In string models, however, "the amplitude of the wave goes up and down, depending on the frequency," Cornish said. "By measuring the amplitude of the CGB at different frequencies, we can figure out what caused the waves and thereby what processes governed the creation of the universe."

Constructing an apparatus to perform the measurements, however, will be a complex and expensive feat.

"The GREAT observatory works by using lasers to monitor the distance between a constellation of spacecraft," Cornish said. This distance -- tens of thousands of times larger than the radius of the Earth -- changes when a gravitational wave passes the spacecraft, stretching the fabric of space-time.

"Imagine a collection of dots on a rubber sheet," Cornish said. "The distance between the dots, like the spacecraft, increases and decreases with every stretch."

Unlike the rubber sheet, however, "the gravitational waves we are looking for will change these distances by less than the radius of an atom," Cornish said. "GREAT will use lasers focused by large mirrors to make these precise distance measurements."

Turner told UPI: "The payoff is really worth it. GREAT is a very ambitious goal, but we have a lot of clever minds and the rest of the century to make gravity waves the newest window on the universe."

(Reported by Mike Martin in Columbia, Mo.)

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