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Nov. 18 - Dr. Isler - Origin/Evolution of Universe
"The Greatest Story Ever Told - The Origin and Evolution of the Universe" - Dr. Ralph Isler - Oak Ridge National Laboratory, Fusion Energy Division (retired ... but still collaborating on research) - Sunday, November 18th, 2007; 10:30 a.m. - Pellissippi State



Sunday, November 18th, 2007; 10:30 a.m.
Pellissippi State Technical Community College, Goins Administration Building, Cafeteria Annex

All societies have developed creation stories to explain how the universe came into being through supernatural events. But for the first time in history, we live in an age when it is not only possible to propose natural explanations for origins but to test those explanations through experiments. The first major step in formulating the present standard model of cosmology came in 1929. By studying the wavelength shifts of spectral lines from distant galaxies, Edwin Hubbell concluded that the universe was expanding. This observation implied that the cosmos may actually have had a beginning in time where everything was once concentrated in a minuscule volume at a very high temperature. The sudden onset of expansion from this singularity became known as the “big bang.” A major observation supporting this picture came in 1964 when the predicted cold remnant of the thermal radiation, the cosmic microwave background (CMB), was discovered to permeate all space. The third pillar supporting the big-bang theory was (in addition to expansion and the CMB emission) put into place by calculations showing that the observed ratios of hydrogen, helium, and lithium isotopes agreed quite accurately with the theoretical predictions.

Nevertheless, several problems plagued the standard big-bang theory. For example, how could the CMB look so uniform across the sky, since, based on the measured expansion rate of the universe, it can be shown that only distances about 1Âş of arc apart could ever have been in causal contact. This is called the horizon problem. In 1981 Alan Guth proposed that at very early times the universe was much smaller than deduced by just extrapolating the big-bang expansion rate back to t = 0, so that all parts could, indeed, be in causal contact. Around 10E-35 seconds it underwent a rapid expansion, doubling in size 100 times every 10E-37 seconds. This event is termed inflation, and several variations of the theory exist. The hypothesis, if true, solves not only the horizon problem but also other puzzles concerning geometry, the lack of magnetic monopoles, and the creation of density seeds for galaxy formation. Following inflation the universe settles into the currently observed big-bang expansion rate. In the past two decades this picture has been strongly supported by measurements of the small variations in the CMB temperature. Nevertheless, alternative proposals, such as cyclic universes, make predictions similar to those of inflation and cannot be ruled out. Among the major problems of cosmology at this time are the nature of so-called dark matter and dark energy. These constitute 95% of the mass-energy content of the universe, but their composition is unknown.



Posted by pking
Nov. 12, 2007