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.

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.

Ironically, the Big Bang started out silent! Only with the passage of time did sound begin to grow. The second noticable feature of the sound is a dramatic transition at about 400,000 years. After this time, a hiss becomes apparent, at first almost imperceptible, but as time passes it builds to cacophonous levels and completely drowns out the earlier notes of the deep chord. This transition marks an important moment in cosmic history: the Universe suddently turns transparent. >from *Primordial Sounds: Big Bang Acoustics*. june 1, 2004

related context
> big bang acoustics: movie and sound files.
> a brief history of matter.

imago
> the cosmic concerto