Gresham College Lectures

“In space, no one can hear you scream”. The chillingly accurate tagline of Ridley Scott’s 1979 space horror classic, Alien, is often belied in science fiction movies, forgetting that in space there is no air, and hence no sound. Space today is terrifyingly silent. But it wasn’t always thus: the early universe was filled with hot plasma in which sound waves could travel. The cosmos was quivering with the aftershocks of the Big Bang. It is one of the greatest achievements of modern physics that we are able to pick up the cosmic harmony of the baby universe. These sounds were not meant to be heard by human ears: the base note has a wavelength of 450 million light years. Nevertheless, this triumph of science (and music) rivals in beauty anything written by Bach. This lecture will investigate the many, surprising ways in which sound waves of various kinds are found in the cosmos: from the relic radiation form the Big Bang, to the distribution of galaxies in the sky; from the trembling of stars to gravitational