Big Bang 'Low Moan'
Universe started with a Hiss
Universe started with a Hiss
The Universe began not with a bang but with a low moan, building into a roar that gave way to a deafening hiss. And those sounds gave birth to the first stars.
Cosmologists do not usually think in terms of sound, but this aural picture is a good way to think about the Universe's beginnings, says astronomer Mark Whittle of the University of Virginia in Charlottesville. Whittle has reconstructed the cosmic cacophony from data teased out over the past couple of years from the high-resolution mapping by NASA's WMAP spacecraft of the cosmic microwave background radiation, the afterglow of the hot early Universe.
The variations in the cosmic background radiation expose the relative clumpiness of the early cosmos at a variety of different scales. These density variations began as quantum fluctuations in the moments after the big bang, and then propagated out as sonic waves. The denser regions became the seeds of galaxies and stars, which is why astronomers are so interested in them.
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Whittle played the soundtrack at the American Astronomical Society meeting in Denver last week. Contrary to its name, the big bang began in absolute silence. But the sound soon built up into a roar whose broad-peaked notes corresponded, in musical terms, to a "majestic" major third chord, evolving slowly into a "sadder" minor third, Whittle explained.
For those worried that you cannot have sounds in space, that is true today, but it was not so in the Universe's infancy. For perhaps its first million years, the Universe was small and dense enough that sound waves could indeed travel through it - so efficiently, in fact, that they moved at about half the speed of light.