[The antenna at Bell Lab ]

[The 2.725 +- 0.001 K CMB spectrum]

[The idea of the big bang ]

A rough estimate of the age of the universe ~ 1/

[The dipole moment in CMB, an excess of 0.00337 K in the direction of Leo ]

Our solar system is moving toward Leo at 371 km/sec. The whole Local Group is heading (at 620 km/sec) toward Hydra-Centaurus supercluster. So are many other galaxies. This Great Attractor is about 50 Mpc away.

- Density of radiation

r_{r}= u/c^{2}= 4s T^{4}/c^{3}

where s = 5.67 x 10^{-5}erg/sec/m^{2}/K^{4}is the Stefan-Boltzmann constant.

for T = 2.725 K**r**_{r}= 4.6 x 10^{-34}g/cm^{3}

- Average density of matter

Difficult to estimate, but one can measure halo gas temperature of galaxy clusters to count mass, which includes dark matter:**r**_{m}= 2.4 x 10^{-30}g/cm^{3}

(The density of luminous matter is about only 10% of that.)

- At present, it is a
**matter-dominated universe**(later you will see it is actually a 'dark-energy-dominated universe'), but in earlier days it was a**radiation-dominated universe**.

The transition occurred at about 24,000 years after the Big Bang, corresponding to a redshift of z = 5200; so temperature is about 2.725K x 5200 = 14000 K.

at t = 380,000 years, z = 1100 (T ~ 2.725 K x 1100 = 3000 K).

[Era of recombination, after which the universe became transparent. ]

At the scale of one degree or so, there are fluctuations less than 300 mK, i.e. < 10

[COBE map with resolution of about 7 degrees (1992)]

[BOOMERANG at the Antarctica]

[A patch of sky mapped by BOOMERANG (1998)]

[WMAP map with resolution of about 0.3 degrees (2003); new and more accurate results are coming ... Check the LAMBDA site at NASA and also the PLANCK mission (launched 2009) at ESA.]

[The power spectrum of CMB anisotropy (from WMAP)]