Lisa Yount, Modern Astronomy: Expanding the Universe
Chelsea House Publications | ISBN 081605746X | 2006 | PDF | 3 MB | 225 pages
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Astronomy poses many of the same questions that religion does, the deepest questions a human being can ask: What is the universe? How big is it? How did it begin? How will it end? What part do we play in it? Are we alone? Through most of history, in fact, astronomy was part of religion. The astronomers of ancient times usually were priests.
Astronomy in the 20th century changed humans’ understanding as profoundly as Copernicus and Galileo did. At the start of the century, soon after George Ellery Hale, the first astronomer covered in this book, built his first large telescope, people thought the solar system was essentially at the center of the universe, much as people of Copernicus’s time had believed the Earth was.
By the end of the century, that picture had altered completely. Astronomers had shown that the Sun is a rather average star, located on one of the Milky Way’s spiral arms rather than in the galaxy’s center. The solar system is one of an untold number of planetary systems. Similarly, the Milky Way is just one among billions of galaxies. Those galaxies, in turn, are mere specks compared to vast masses of invisible, or “dark,” matter surrounding them, whose nature is completely unknown.


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