Chapter+2+The+Setting - The Setting 1 Chapter Two The...

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The Setting 1 Chapter Two The Setting: The Big Bang and Galaxy Formation Earth is a minor member of a system of planets in orbit around a star we call the Sun. The Sun is one of about 100 billion stars that make up our Milky Way. The light from this myriad of stars allows observers in neighboring galaxies to deF ne our galaxy’s spiral form. The galaxy is the basic unit into which universe matter is subdivided Like its billions of fellow galaxies, ours is speeding out on the wings of a great explosion that gave birth to the universe. That these major pieces of the universe are fl ying away from each other is revealed by a shift toward red in the spectra of the light reaching us from distant galaxies. The close correlation between the magnitude of this shift and the distance of the galaxy tells us that about 15 billion years ago all the galaxies must have been in one place. The catastrophic beginning of the universe is heralded by a dull glow of background light. This glow is the remnant of the great fl ash that occurred when the debris from the explosion cooled to the point where the electrons could be captured into orbits around the hydrogen and helium nuclei. Contained in the galaxies lying within the range of our telescopes are about 100 billion billion stars. A sizable number of these stars are thought to have planetary systems. While planets with Earth’s highly favorable environment are surely exceptions, it is difF cult to believe that Earth is unique. Other equally suitable habitats for life must exist. Introduction Why are we here? Are others like us to be found elsewhere? Dif± cult questions indeed! Despite millennia of thought the answers available today are little more satisfying than those that were available to our distant ancestors. New insights have been more than counterbalanced by new puzzles. Religion tells us we were created by God. Science tells us we were created by chance. Yet neither theologians nor scientists are quite happy with these pat answers. Both probe for greater insight. Are we God’s only charges? Has chance operated successfully elsewhere? While we as yet have no way to know whether living beings who match or exceed our ability to appreciate, to reason, and to exploit reside elsewhere in the universe, science is providing some very valuable constraints on such speculations. Two approaches are being taken. One is geological. It has to do with the likelihood that habitats suitable to life have come into being elsewhere. The other is biological. It has to do with the likelihood that given a suitable environment, life will evolve. Although, to date, only a few steps have been taken along these long roads, important progress has been made. In this book we attempt to summarize the success of both approaches. In trying to assess the likelihood that other settings suitable for intelligent life exist, we must
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This note was uploaded on 02/08/2011 for the course EAS 1601 taught by Professor Lynch during the Spring '08 term at Georgia Tech.

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Chapter+2+The+Setting - The Setting 1 Chapter Two The...

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