Quote (Gurby @ Sep 5 2010 05:57pm)
The sensitivity and resolution of the measurement of these anisotropies was greatly advanced by WMAP. The fact that the CMB was measured to be so isotropic, in line with the predictions of the big bang model, was subsequently heralded as a major confirmation of the Big Bang model to the detriment of alternatives. These measurements showed the "acoustic peaks" were fit with high accuracy by the predictions of the Big Bang model and conditions of the early universe. (from Wikipedia on Plasma Cosmology)
Here's some stuff about the WMAP and how the the big bang is wrong: The hypothetical process of “inflation” is a crucial part of the current Big Bang model. Without this early period of super-fast expansion, the theory predicts that different parts of the sky should have widely differing intensities of the CBR, in contradiction to observations. While inflation is a purely ad-hoc hypothetical process, based on no known laws of physics, it does make one firm prediction. This is that the small anisotropies or fluctuations in the CBR should be distributed entirely randomly—in a Gaussian distribution.
Yet almost since the first results of the WMAP satellite were released four years ago, it has been clear that the small anisotropies in the CBR are not random, there are patterns. Especially at large angular sale in the sky, there are regions where the CBR is smoother and where it is lumpier. In addition there are too many “hot” and “cold” spots in the sky for a Gaussian distribution.
There have been a number of efforts to try to attribute this non-randomness to a limited section of the sky which is “anomalous” and in particular to the “WMAP cold spot” a region of the sky with the least intense CBR. Lawrence Rudnick et al published a widely noted paper in which they tried to attribute the cold spot to a huge void, 280 Mpc in diameter, that has been observed in the distribution of radio galaxies. The idea was that the gravitational effects of such a void could slightly redshift CBR photons from that direction.
However, Pavel Naselsky et al, among others demonstrated statistically that the non-Gaussian patterns on the sky are not just limited to the Cold Spot. Aleksandar Rakic, and Dominik J. Schwarz showed convincingly that the patterns are incompatible with the hypothesis of Guassianity, and Amit Yadav and Benajmin Wandelt, using a different method of analysis, ruled out the inflationary prediction at the 99.5% confidence level. The hot and cold spots themselves are not circular and show alignments on the sky as P. Vielva et al demonstrate.
Despite all this contradictory evidence, in only one paper, that of Y. Wiaux et al, is the validity of the inflationary hypothesis explicitly questioned. By contrast, Yadav and Wandelt conclude, not that the inflationary theory is wrong, but only that it is too simple and that more “exotic theories” with “multiple scalar fields, features in inflation potential, non-adiabatic fluctuations, non-canonical kinetic terms, deviations from the Bunch-Davies vacuum” will be needed.
To complicate the picture further, Gerrit L Verschuur finds that much of the anisotropy correlates with plasma clouds within the Milky Way, although the statistical significance of these correlations is still in some dispute.