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Tuesday, June 8, 2004 (SF Chronicle)
Big Bang echoes through time/Professor turns cosmic ripples into sound
New York Times
Denver -- If the universe is created with a bang but no one is around to
see it, does it still make a sound?
Some 13.7 billion years later, Mark Whittle, a professor of astronomy at
the University of Virginia, says yes.
Sound has played an important role in research on the Big Bang, the
explosive birth of the universe. In 1963, trying to track a mysterious
hiss generated by their microwave antenna, Arno Penzias and Robert Wilson
of Bell Labs discovered the cosmic microwave background, a faint glow of
photons left over from the Big Bang.
Satellites now show minuscule ripples in the cosmic microwaves. Whittle
realized that the ripples -- slight variations in density of matter that
would determine where stars and galaxies would form -- could be seen as
sound waves bouncing through the infant 380,000-year-old universe.
"I have done what is the obvious thing, turning the information into real
sounds," said Whittle, who presented his aural findings here at a meeting
of the American Astronomical Society.
Sound waves propagate with just the slightest disturbances. The sound of a
voice compresses air by one part in 5 million. The differences in pressure
in the primordial gases were one part in 10,000, and that corresponds to a
satisfyingly loud, but not lethal, 110 decibels -- rock concert volume.
Some massaging of the data was needed. The cosmic sound waves stretched
20,000 light-years, moved at half the speed of light, and were about 50
octaves below what people can hear. Whittle shifted the sounds to the
human audible range, producing a chord like the sound of a jet engine. He
used computer models to generate the cosmic chords for the first million
years and condensed them to five seconds.
The Big Bang actually erupted in complete silence. In the first instant,
the mass of the universe was spread out completely evenly. No pressure
differences, no sound.
Then, the quiet vanished.
"For the first 400,000 years," Whittle said, "it sounds like a descending
scream falling into a dull roar."
Over the first million years, Whittle said, the music of the cosmos also
shifted from a pleasant major chord to a more somber minor one.
On the Web
To listen to the Big Bang, go to www.astro.virginia.edu/~dmw8f ----------------------------------------------------------------------
Copyright 2004 SF Chronicle
Received on 2004-06-08 18:32:35