Professor, Department of Astronomy and Astrophysics
University of Chicago

Group Contact CV SnapShots
CMB Introduction '96   Intermediate '01   Polarization Intro '01   Cosmic Symphony '04   Polarization Primer '97   Review '02   Power Animations   Lensing   Power Prehistory   Legacy Material '96   PhD Thesis '95 Baryon Acoustic Oscillations Cosmic Shear Clusters
Transfer Function WMAP Likelihood Reionization PPF for CAMB Halo Mass Conversion Cluster Abundance
Intro to Cosmology [243] Cosmology I [legacy 321] Cosmology II [321] Current Topics [282] Galaxies and Universe [242] Radiative Processes [305] Research Preparation [307] GR Perturbation Theory [408] CMB [448] Cosmic Acceleration [449]

Seeing Sound

Key Concepts

What we see on small scales is actually sound. The photons behave as a gas just like air. Ordinary sound waves are just travelling compressions and rarefactions of the gas which we hear as sound as they strike our ear drum. The photons also carry sound waves as gravity tries to compress the gas and pressure resists it. The reason why we see it rather than hear it is that when we compress the gas it becomes hotter. We see the sound waves as hot and cold spots on the sky.

The result is a spectrum of sound waves that are useful in determining the origin, evolution and fate of objects in the universe.