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The Wilkinson Microwave Anisotropy Probe (WMAP) - The Cosmic Microwave Background
The Wilkinson Microwave Anisotropy Probe (WMAP) is a NASA Explorer mission that launched June 2001 to make fundamental measurements of cosmology -- the study of the properties of our universe as a whole. The second major thing that the big bang should produce is a characteristic radiation spectrum to be seen in the sky. If the universe were once much smaller and hotter than it is now, and if it has been expanding ever since the beginning, then it must also have been cooling down this whole time. (Imagine a gas that expands adiabatically, if the volume increases, the temperature must decrease). Thus, if we know roughly how old the universe is and what it's expansion rate is, we can form a pretty good guess of what it's current thermodynamic temperature must be. Measurements of these sorts first occured in the 1960's. In 1989, a satellite named COBE measured the spectrum of the left-over radiation from the big bang |
