ABSTRACT

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 evolution 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.