The CAT is only sensitive to features in the sky of a certain angular size (about ½°), which is why all the blobs in the map appear the same size. The size of the blobs is about 25,000 light years at the time the radiation was emitted, but corresponds to features about 25,000,000 light years across now (because the universe has expanded by a factor of 1000 since then). Because the universe was only 100,000 years old at this time, features much bigger than these blobs cannot be causally connected (ie a light ray could not have travelled across them), and represent the fluctuations imprinted at the very earliest instant after the big bang. The features that CAT sees, however, are believed to be due sound waves in the hot gas that made up the universe at 100,000 years, and their detailed properties can tell us a great deal about how much matter there is in the universe, how fast it is expanding, and how the galaxies we see now came to be formed.
To make a better image, we need to have more antennas, with a bigger range of spacings between them - CAT has only three antennas. We plan to build a telescope to do this - the Very Small Array .
The CAT group at MRAO. 27/3/96