August 2011 Meeting Notes
This month we had a full business meeting, including a reminder of officer elections in October, a brief summary of our Summer Star Party efforts, an update on dark sites, discussion of a future Beginner Stargazing Program, a request for ideas and volunteers for future meeting programs and announcement of a Cub Scout stargazing event. Daryl Doughty showed some exceptional lightning photos he took when skies turned out to be less than optimal for astrophotography. Our program was a DVD lecture provided by Mike Woods, entitled "In Defense of the Big Bang" by Neil deGrasse Tyson.
In Defense of the Big Bang - A DVD Lecture by Professor Neil deGrasse Tyson
In his lecture, Neil deGrasse Tyson states the the Big Bang Theory is the best supported in all of science. He presents an array of compelling evidence that demonstrates the strong case for the Big Bang. This evidence includes
• clear indications of the expansion of the universe from the observation that galaxies in all directions are receding from us,
• precise agreement between prediction of the relative abundances of hydrogen, helium and lithium created by nucleosynthesis in the Big Bang, and the abundances actually observed,
• the temperature of the Cosmic Microwave Background radiation (the heat left over after the Big Bang),
• and the precise match between predicted light curves of distant supernovae and actual observations.
Early in the 20th Century, Edwin Hubble discovered that galaxies in every direction were moving rapidly away from Earth, as if we were in the center of an explosion. This discovery was made by observing that the spectra of these galaxies are "red shifted" by the doppler effect. The rapid separation between us and the galaxies stretches the wavelengths of light we observed from them. This means that characteristic frequencies of light, such as those emitted by hydrogen, appear to have longer wavelengths, making them redder. By measuring the amount of shift toward the red, it was a simple calculation to determine the speed of separation between us and the receding galaxies. It became clear that the further away we look, the faster things are moving away; again, the hallmark of an explosion. But Einstein's Theory of Relativity demonstrated that this expansion was not due to everything in the Universe flying away, through space from a central point, but rather due to the expansion of space itself, between the galaxies.
The rapid pace of discoveries and developments in atomic and particle physics during and after World War II set the stage for the suggestion by George Gamow that nuclear reactions caused by the immense heat of the Big Bang would lead to creation of specific elements (nucleosynthesis) in specific ratios. Calculations predicting the relative abundances of hydrogen, helium and lithium were in excellent agreement with that actual observed abundances of these elements throughout the Universe.
Shortly after the Big Bang, the Universe was a sea of seething particles that eventually cooled enough to form atoms. When this happened, photons (light) that had been bouncing between particles was suddenly able to begin a billions of years long journey through space. These high energy photons represented the high temperature of the Universe, but as time past and the Cosmos expanded, the photons cooled. The temperature that we should observe now, after 13.7 billion years of expansion, is precisely what was detected as the Cosmic Microwave Background radiation in 1964. The exceptional homogeneity and even more exceptional minor deviations have been critical in furthering details of the expansion of the Universe.
Supernovae are stars that completely destroy themselves in a final, cataclysmic explosion. They have a characteristic time for their light to brighten and then fade over a period of weeks. However, if such an event occurs in a galaxy that is receding from us at high velocity, the light from the later, fading portion of the supernova's light curve will have further to travel (because it's now further from the Earth), than the initial brightening (which occurred when the star was closer to Earth). This means that the further away the galaxy in which a supernova occurs, the more it's light curve will be stretched. This is exactly what is observed, and the degree of stretching precisely matches that predicted by the expansion of the universe.
Following Tyson's DVD lecture, meeting attendees engaged in a vigorous and very interesting discussion of the Big Bang and related topics. Not only were we exploring the ideas about the creation of the universe and the Big Bang, but questions about the expansion of space, whether there can be an expansion without a center, and the possibility that time and space themselves did not exist before the Big Bang. We even ventured into such topics as quantum mechanics and string theory. With the interest expressed, perhaps we should return to some of these topics again, in a few months.
Tuesday, September 6,
in the Bartlesville Public Library Meeting Room
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