Colloquia

Cosmology's extraordinary development shows no signs of slowing down. With the evolution of the Universe's average properties now fairly well understood, the focus has switched to the evoution of perturbations -- how an extremely smooth infant Universe changes into an extremely lumpy old Universe, with galaxies strewn to the horizon. Remarkably, the roots of present day structure can be traced back to sound waves in the early Universe. Even more remarkable, the power spectrum of the sound shows a fundamental and harmonics, as if the Universe were a kind of primitive musical instrument. This talk aims to unpack the relatively new subject of "Big Bang Acoustics", using reproductions of the primordial sound as a vehicle for discussing the physics of that remote time. It turns out that, as with many vibrating objects, the nature of the sound reveals much about the nature of the object as well as the nature of the stimulus.