Big Bang

Radio Noise Theory Hubble’s law suggests that any initial radiation would be extremely redshifted. If there was start to the universe then the radiation would have a blackbody spectrum. Experiment In 1964 Penzias and Wilson measured background radio noise. Cosmic microwave background The intensity was consistent with blackbody radiation at 3K.

Hot Radiation If the universe had a beginning there would be a start – Big Bang. An initial burst of light would be as hot as a star. Not as hot as a plasma About 3000 K

Stretching Light As the universe expands the wavelength of light stretches. Burst of light: 3000 K Peak radiation:1 micron Visible light Today the universe is 1000 times larger. Temperature: 3 K Peak radiation : 1 mm Microwaves 1 wavelength, small universe 1 wavelength, expanded universe

COBE In 1989 NASA launched the COBE satellite. Measure far infrared spectrum Black body temperature 2.728 K

Anisotropy COBE measured fluctuations in the CMB. One part in 100,000 Eliminate Earth’s motion Remove Milky Way noise The CMB is anisotropic – different by direction.

WMAP The Wilkinson Microwave Anisotropy Probe was designed to measure the CMB. Launched in 2001 Ended 2010 WMAP measured five microwave frequency bands.

More Precise WMAP improved COBE’s measurements. Blue 2.7249 K Red 2.7251 K The anisotropy points at the fraction of matter of different types. Ordinary matter 5% Cold dark matter 23% Dark energy 72%

Age of the Universe The Hubble constant is related to the age of the universe. H0 = (73.5 km/s)/Mpc; 1 Mpc = 3 x 1019 km 1/H0 = 4 x 1017 s = 13.7 billion years This is consistent with the most distant quasars. The Planck satellite is measuring the CMB with more precision.