Monday, March 20, 2006

WMAPping the Universe, part 2

Last week I talked about how new results from the Wilkinson Microwave Anisotropy Probe (WMAP) find that the first stars formed about 400 million years after the Big Bang, and that this was the major result from the newest data. So, boy, was I surprised when all the press stories talked about how the new evidence supports the theory of inflation.

Inflation in astronomy has nothing to do with the value of the dollar (though some would say it explains how the costs of rocket launches seem to be much more than the first estimates). Astrophysical inflation explains a phenomenon that may have occurred in the tiniest fraction of a second after the Big Bang -- we are talking one ten-millionth of a billionth of a billionth of a billionth of a second (1x10^-34 seconds, for those of you who can read scientific notation), and lasting until the universe was only one hundred thousandth of a billionth of a billionth of a billionth of a second (1x10^-32 seconds). I hope I got those billionths and millionths correct!

During this time, the Universe expanded faster than the speed of light (don't worry, it is allowed by Einstein! Just trust me, you don't want me to try and explain it!) from a size much smaller than an atom to something about the size of a grapefruit. (During such a time, a ray of light would only make it about one billionth of the way across the nucleus of an atom).

As the Universe stopped inflating this rapidly and settled down to a more leisurely speed-of-light expansion, some tiny imprints of this transition would be left on the universe. And it is these imprints that WMAP supposedly saw in its data.

If this result holds, it marks a big victory for the theory of inflation. Until now, inflation worked great at explaining what we already knew about the universe, but none of its predictions had been tested. Any scientist worth her salt knows that until a theory makes predictions that hold up under testing, that theory is nothing more than a good idea. It is almost always possible to make theories that can explain what we know, but a correct theory can also explain what we don't know about. And it looks like inflation has possibly passed its first true test. If you would like to know more about the theory of inflation and aren't scared of a little physics jargon (probably introductory college physics level), check out this article.

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