1. Big Bang

2. 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.

3. 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

4. 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

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

6. 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.

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

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

9. 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.