CMBR Cosmic Microwave Background Radiation Hot Big Bang

CMBR Cosmic Microwave Background Radiation

Hot Big Bang theory • Universe expanded from a very condensed state • Initially constituents not known • Expanded and cooled rapidly • Suggested by Alpher, Bethe and Gamow

Consequences of the Big Bang • Too hot to form nucleons for the first microsecond • Nuclei of hydrogen and helium formed after 3 minutes • A plasma of nuclei and electrons for 300 000 years; opaque as photons absorbed continually • Becomes transparent at a temperature of about 3 000 K at this time • Photons at 3 000 K are infrared

The expanding Universe • Galaxies carried apart by the expanding Universe • Waves are also ‘stretched’ • The Universe is 1000 × larger since it became transparent • The infrared photons should be stretched into microwave photons (temperature about 3 K)

They looked for it in Princeton • Robert Dicke’s group was trying to find this cosmic microwave background radiation, predicted to be in every direction

They found it in Bell Labs (just down the road) • Working on microwave communication systems • Couldn’t get rid of the ‘noise’ in the aerial • Penzias and Wilson realised they had found what Dicke was looking for… NOBEL PRIZE 1978!!

COBE • The Cosmic Microwave Background Explorer • Confirmed the temperature of the microwave background (2. 73 K) • Revealed variation in the temperature of the early Universe

WMAP • Wilkinson Microwave Anisotropy Probe • Built to investigate the variations found by COBE • Confirmed and refined COBE findings

Smoot and Mather • Led the COBE team and analysed the data • Linked the temperature variation in the early Universe with the clumping of galactic clusters today NOBEL PRIZE 2007!!