'Birth cry' of the cosmos heard
<URL:http://news.bbc.co.uk/1/hi/sci/tech/3832711.stm>

By Dr David Whitehouse
BBC News Online science editor

Astronomers have recaptured the sounds of the early Universe showing
it was born not with a bang but a quiet whisper that became a dull
roar.

Mark Whittle of the University of Virginia has analysed the so-called
background radiation that was born 400,000 years after the Big Bang.

Ripples in the radiation are like sound waves bouncing through the
cosmos.

Over the first million years the music of the cosmos changed from a
bright major chord to a sombre minor one.

Below human hearing

"It really is a very obvious thing to do," Professor Whittle told BBC
News Online. "I was a little surprised that someone had not done it
before."

He took the latest data about the Cosmic Microwave Background
radiation (CMB) which comes from an era just after the Big Bang.

They show ripples in the CMB which are subtle variations in the
density of matter which can, in one sense, be thought of as sound
waves.

These cosmic sound waves are 30,000 light-years wide and are 55
octaves below what humans can hear.

But when they are shifted to regions of the audible spectrum, the cry
from the birth of the cosmos can be heard.

Unique perspective

One sound compresses the first million years of the Universe into just
five seconds.

The Big Bang would have taken place in complete silence but as the
Universe expanded sound waves would have been able to grow.

"For the first 400,000 years it sounds like a scream declining to a
dull roar," says Professor Whittle.

He believes that hearing the sounds of the cosmos provides a unique
perspective on the evolution of the Universe.

"It draws the listener closer to the subject in a different way from
what images do," he told BBC News Online.

During the expansion there is a change in the frequencies of the sound
waves that results in the characteristic sound of the Universe
changing from a major third chord to a minor third.

"Listening to it I have to say that the Universe is a lousy musical
instrument," says Professor Whittle.

© BBC MMIV

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