Riding a bicycle around the solar system scale model in Peoria, Illinois, makes it clear just how big the solar system is. Our solar system is just one little corner of a galaxy containing hundreds of billions of stars, among some fifty billion galaxies in the universe, each containing hundreds of billions of stars of their own. It is staggering. The sun is the center of our little corner of the universe. An “ordinary” star, it is about five billion years old, and should shine for another five billion years before expanding, then contracting into a dim white dwarf no bigger than Earth. Understanding the movement of celestial bodies is no small feat, but the Maya were accomplished in determining the movements of Venus, a planet whose apparent appearance and disappearance were integral to Maya religion. Not long ago, scientists were able to find other planets orbiting other stars. Could there be any like Earth that support life? That is the question astronomers with SETI (Search for Extraterrestrial Intelligence) hope to answer. They use radio telescopes to listen for signals from other worlds. So far, the airwaves have been quiet, but if the Drake equation is accurate; there may be many other intelligent species out there.
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