Freesound Forums

“Sound waves that rang out in the early universe sculpted its structure.”

http://www.newscientist.com/article/dn21653-ancient-sound-waves-sculpted-galaxy-formation.html

It does not say what frequency it was but the waves had to be pretty long.

The frequency that is is implied in the figures they give is a 1/2 cycle per of 500 million light years or 1 cycle per 1000 million light years - or low harmonics thereof. Whichever it is it's to low in frequency for my ears. I can only sense down to around 15Hz or cycles per second with my ears, (for loud sounds), and maybe down to 5 or 6 Hz feeling it with my chest and stomach. The movement of air on earth that we call weather, is sound in the frequency range of perhaps 1 cycle per day down to a few cycles per year as high and low pressure regions move around.

0.0

Sound like my sort of thing

strangely_gnarled wrote:
The frequency that is is implied in the figures they give is a 1/2 cycle per of 500 million light years or 1 cycle per 1000 million light years - or low harmonics thereof. Whichever it is it's to low in frequency for my ears. I can only sense down to around 15Hz or cycles per second with my ears, (for loud sounds), and maybe down to 5 or 6 Hz feeling it with my chest and stomach. The movement of air on earth that we call weather, is sound in the frequency range of perhaps 1 cycle per day down to a few cycles per year as high and low pressure regions move around.

The point here is not whether they are audible or not, but the fact that shock waves and vibration waves travelling through the plasma in the early universe medium shaped its evolution and its structure as we see today. - These are the same phenomenon as sound. Just as Earthquakes are vibrations (i.e., sound waves) travelling through the Earth's crust, but with frequencies too low for us to hear.

The phenomenon here was that gas began to cluster together due to gravity. As it did so, it heated up (all gases heat up when compressed). The hot gas gave off heat in the form of radiation. So much radiation, in fact, that it created radiation pressure which pushed the outer gas that was in the process of falling in. - Much as the Solar wind (effectively radiation and high speed particles) can push small particles away from the Sun.

So, this gas was fllin in and is suddenly pushed out by radiation. It colides with more gas further out which was still falling in - creating a shock wave. The shock wave expands outwards.
The trick here is that the Universe itself is also expanding as a whole... and at some point these expanding shockwaves became standing waves.
At the crests of these waves, matter density was higher than in between the waves, and thus more galaxies were likely to form. Just as you can create standing (sound) waves on a box containing a fine powder (saw dust, sand,...) and the powder will form a pattern of 'clumps' and voids. Or like a glass of milk vibrating on top of the frigde can get standing ripples on the liquid surface.

This could also be of interest.
Scientists now have a good idea of how things would sound on plantes other than our own.
http://www.telegraph.co.uk/science/space/9181253/Scientists-replicate-sounds-on-Mars-and-Venus.html