Nobel Prize 2006: The Cosmic Microwave Background

News flash: John Mather and George Smoot, two of the scientists behind the COBE Satellite, have won the 2006 Nobel Prize in Physics for their measurements of the average temperature of the CMB and the fluctuations about that average. (Here’s one self-aggrandizing reason why I find this particularly exciting.)

The average, measured by the FIRAS instrument, proves that the CMB is a “black body” to an accuracy actually better than the instrument was capable of measuring, which in turn proves that the Universe started out in a hot, dense state and has been expanding ever since — the hot Big Bang.

The CMB Spectrum measured by COBE/FIRAS—with error bars!

The DMR instrument measured tiny — one part in 100,000 — fluctuations on top of that average. These hot and cold spots trace the tiny initial lumps and voids that eventually grew into the so-called large-scale structure of galaxies and clusters of galaxies that we see today.

CMB Fluctuations measured by COBE/DMR

Of course these measurements open up some very big questions: why is the Universe so very nearly homogeneous (i.e., why is the temperature the same in every direction?)? What caused those tiny inhomogeneities that became everything that we can see in the Universe today? Unfortunately I’ve got lectures to prepare, so I can’t tell you about cosmological inflation, currently our best idea for solving both of these problems in one swoop….

(Images courtesy Lambda and the COBE Team.)