Cosmic Microwave Background (CMB)


  • The Cosmic Microvave Background A theoretical blackbody curve with 34 COBE data points equally spaced along the curve: the data matches the curve so closely that curve and data and not distinguishable. The temperature is T=2.73 K.
  • COBE Full Sky Map of the Variations in the Cosmic Microwave Background This is the final 4-year map of the CMB. Blue are points of low temperature, high density. Red are points of high temperature, low density. The high density regions are "colder" because of a gravitational redshift effect (Frak576). The largest varitions are only about 1/10000.
  • Boomerang Map of the Variations in the CMB Boomerang is a balloon mission in Antarctica that studied detailed the CMB. It flew in 1998dec and the first results published 2000apr27. The image (25 X 10 degrees) is dominated by cold and hot spots (which color is which?) of about 1 degree size on the sky. The temperature variation is about 1/10000 of the T=2.73 K, modern CMB blackbody temperature. The bottom three panels show 3 model simulations for three space-time geometries: hyperspherical, flat (Euclidean), and hyperbolic. These images suggest and detailed modeling show that the data is consitent with a flat universe to a high degree. The cosmic density in units of the critical density for flatness is Omega_0 in range 0.88 to 1.12. Simple inflation predicts Omega=1 to 1/10**4?????
  • The Omega_Lambda-Omega_Mass Plane with SN Ia and Boomerang Data Omega is the mass-energy density density of the universe in units of the critical density: Omega < 1 and universe is hyperbolic and open (infinite?) and Omega > 1 and the universe is hyperspherical and closed (finite?): Omega=1 and the universe is flat (Euclidean) and open (infinite?). Two kinds of Omega have considered: Omega_M is ordinary mass-energy which we understand well; Omega_Lambda is cosmological constant energy which was introduced by Einstein to create a cosmic repulsive force. Omega_Lambda is poorly understood and may be just a fudge factor subsuming a lot of unknown physics. But the simplest cosmologies have the two Omegas as parameters and these cosmologies guide our interpretation of observations. This map shows 95 % confidence intervals for data from SN Ia and Boomerang data. If both are correct, then universe lies in the green region. Thus Omega_M=~.35 (Omega_luminous=~.01) and Omega_Lambda=~.65. The universe is close to being flat: Omega_0 in range 0.88 to 1.12. Simple inflation predicts Omega=1 to 1/10**4????? Close to flat is not as exactly flat as inflation predicts, but so far inflation looks good. The age of the universe is in the range .85/H_0--1.05/H_0 or about 14 Gyr for H_0=70. The universal expansion is accelerating. Note that the parameters of the universe discussed here only have exact meaning within the modified Friedmann models of the universe: if those models are wrong or approximations (as there are in inflationary cosmology), then parameters may not mean quite or anything like what it is thought they do.