

The Sound of the Big Bang (Planck Version) - alexqgb
http://faculty.washington.edu/jcramer/BBSound_2013.html

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IvyMike
You would think it would be louder.

P.S. I fully admit this is a stupid joke but it makes me laugh so there ya go.

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igul222
Could somebody explain what I'm listening to?

~~~
elux
From the WMAP edition at:
<http://faculty.washington.edu/jcramer/BBSound_2003.html>

>Q: How can you represent it as a sound? Sound is supposed to be a wave that
travels through air, and there was no air in the early stages of the Big Bang?

>A: The Big Bang Sound in the simulation is derived from the sound propagating
as compression waves through the plasma/hydrogen medium of the early universe
some 100 to 700 thousand years after the initial Big Bang. The density of this
medium was changing as the universe expanded, but should have been
considerably more dense than air on our little planet. One does NOT need air
to have sound, only some medium in which compression/rarefaction waves can
propagate. The sound waves were very low in frequency and had wavelengths
comparable to some fraction of the size of the universe. For the convenience
of humans, who could not hear such low frequencies, I have increased them to
the audio range of the human ear.

Or... One could simply say it's a rendering of J.R.R. Tolkien's _Ainulindalë_.
;)

"The Music of The Ainur", strange and beautiful.

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teeja
Interesting speculation in light of the article I read earlier that the
universe may have started out with one time and one space dimension. No
"sound" then ... and no gravity.

[http://www.space.com/11470-universe-birth-1-dimension-
physic...](http://www.space.com/11470-universe-birth-1-dimension-physics-
theory.html)

[http://news.discovery.com/space/once-upon-a-time-the-
univers...](http://news.discovery.com/space/once-upon-a-time-the-universe-was-
really-weird-110321.htm)

~~~
3rd3
Isn’t one spatial and one temporal dimension enough for sound to exist?

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andrewflnr
It sounds oddly mechanical, like an overhead helicopter at times. Can anyone
give a not-too-technical explanation for that?

~~~
ISL
I haven't looked at his source yet, but my guess is that the power spectrum
was inverted directly back to real space/"time" domain, without randomizing
the phase.

Keep a grain of salt at the ready as you analyze the problem. It's a tricky
thing to do "right", and even when you're done, it's not clear that "right"
will be well-defined in this case.

Edit: Since the code is a *.nb form, I can't read it directly (insufficient
space/desire to install the Mathematica Reader), but from what I can glean
reading it as ASCII text, the sound is synthesized from in-phase cosines. Each
signal at every frequency starts together, leading to a spike in amplitude.
You can see each pop very clearly if you look at the wav file over a short
duration in the time domain.

The relative phases of the spectra, following the analysis that Cramer's used
(inverting the angular power spectrum into sound) actually are in the raw
WMAP/Planck data, and may be in print. If you have the raw temperature map and
are comfortable computing the angular power spectrum, you'll have access to
the phase too.

I can't find a perfect reference at the moment, but to emphasize the
importance of the phase in reconstructing real-space data, check out the
pictures in [1].

[1]
[http://homepages.inf.ed.ac.uk/rbf/CVonline/LOCAL_COPIES/OWEN...](http://homepages.inf.ed.ac.uk/rbf/CVonline/LOCAL_COPIES/OWENS/LECT4/node2.html)

