Quick Review of the 16 Sections

1. Introduction sets the stage: we will focus on the sound of creation.
    
   
2. For the first million years, the Universe was uniformly filled with hot thin bright gas, which cooled with cosmic expansion.
    
   
3. Looking far far away we can now see that glowing gas – redshifted – as the Cosmic Microwave Background (CMB).
    
   
4. The CMB is slightly patchy; the patches are, in part, sound waves. The sound is loud & deep (about 110 decibels & 50 octaves below A440).
    
   
5. The quality of sound is revealed by its "Sound Spectrum", which shows a fundamental & broad harmonics: these give a deep roar.
    
   
6. The sounds arise from gas falling into and bouncing out of dark matter clumps. Whole number bounces give discrete harmonics.
    
   
7. Other kinds of Universe would sound different. Models matching the observed sound yield several cosmic parameters (with uncertainties around 5%).
    
   
8. The CMB patchiness contains several distortions. Computer simulations can recover the "pure" sound, with its clean harmonics.
    
   
9. The simulations also generate an evolving sound: a descending scream which settles into a deep roar.
    
   
10. The "chord" of harmonics contains several intervals, including a major & minor 3rd. The chord changes somewhat over time.
     
    
11. After fog clearing, sound changes: gas falls into small dark matter clumps ⇒ growing hiss. These collapse to become the first stars.
     
    
12. Movies show the sound spectra developing over the first 100 Myr.
     
    
13. The expanding cosmic horizon accounts for the drop in pitch. Patches larger than the horizon are unmodified and non-acoustic.
     
    
14. All patches are thought to arise from quantum fluctuations amplified by a very early burst of inflation. The "initial sound spectrum" emerging from inflation is simple pure noise.
     
    
15. The CMB image contains two fundamentally different scales: sub-horizon acoustic patches which will become galaxy tapestry; super-horizon patches of pre-inflation quantum origin.
     
    
16. We finally follow the subsequent gravitational growth of sound waves across cosmic history, to form four fundamental structures:
    1. stars form first – massive, luminous and explosive. The first 100 Myr period of darkness ends with a brilliant firework display.
        
       
    2. galaxies form next, as groups of stars merge together into ever larger groups in a growing hierarchy of structures.
        
       
    3. clusters of galaxies begin to assemble after a few Gyr, indeed some are now still forming, and some have yet to form.
        
       
    4. finally, the tapestry of large scale galaxy distribution slowly emerges as gravity gives form to the longest primordial waves.