Sound of the first million years

If you can ignore the initial ultra-cheesy graphic (not the one above, which is the Cosmic Microwave Background), Mark Whittle’s article on the unpacking of the sound of the universe after the Big Bang is fascinating.  It turns out that in space, people can hear you scream… at least, during the first million years you can.  A few interesting quotes (emphasis Whittle’s), and a simulation of the sound:

… the Big Bang started out utterly silent! The initial expansion was absolutely pure and “radial” – no parts were catching up any other parts, and hence there were no pressure waves, and hence no sound. All was quiet.

… [at the time of the Big Bang] the Universe was much smaller (by at least a factor of 1000), and all the matter we now find in stars and galaxies was spread out uniformly. Add to this the fact that the young Universe was also much hotter, and we learn that over the first million years, all of space was filled with a hot thin uniform glowing gas, a billion times denser than the current cosmic density. Not only did the Universe have an atmosphere – in a sense, it was an atmosphere. It was within this atmosphere that sound waves could form and move in the young Universe.

… How do we measure the pressure variations in the primordial atmosphere? Simple: we look at the brightness variations on the CMB. These variations tell us the strength of the pressure waves were between one ten-thousandth (10-4) and one hundred thousandth (10-5). So these correspond to around 110 decibels. This is neither inaudibly quiet nor lethally loud: it is powerfully loud — it is about as loud as a rock concert!

This is what the universe sounded like, shifted up 50 octaves (to be audible) and compressed into 10 seconds.

Via: Mark Whittle

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