Cosmology, Page 106: [Previous Page] [Next Page] [Class Home Page] Textbook pages 479 - 484

The Cosmic Background Radiation

When the universe was formed 15 billion years ago, it was incredibly small, incredibly dense, and incredibly HOT. But the expansion has cooled this hot bubble to a temperature of just 2.7K above absolute zero! It is seen today as the Cosmic Background Radiation (CMB). The CMB, most strongly emits at millimeter wavelengths. It has been mapped using several satellite telescopes specially designed to look for structure in the CMB. A lot of attention has been given to mapping out the CMB because it allows us to measure some pretty incredible things..

Everywhere we see the CBR. We live IN it. It envelopes us. It keeps everything in the Universe at a temperature of at least 2.7 K degrees. Does it vary?? (is it homogenous and isotropic???)
Depends how closely you look. If you measure the temperature more accurately you get THIS: One side of the Universe is HOTTER than the other side! This is because we see our motion (the Earth, Sun, Galaxy, Local Group, and Local Super Cluster) moving relative to absolute space.
If we remove our motion relative to space and look even deeper we find blotchy areas of HOT and COLD. However, we also see a flat equitorial structure: we see the plane of our Galaxy, its always in the way!

Beyond the galactic plane we do see structure. This is what evolves to be objects we see today: Galaxies, Stars, Planets.. Cold (blue) regions are rarified, hot (red) regions are more dense.