The Astronomy Book PDF Free Download
Throughout history, the aim of astronomy has been to make sense of the universe. In the ancient world, astronomers puzzled over how and why the planets moved against the backdrop of the starry sky, the meaning of the mysterious apparition of comets, and the seeming remoteness of the sun and stars. Today, the emphasis has changed to new questions concerning how the universe began, what it is made of, and how it has changed. The way in which its constituents, such as galaxies, stars, and planets, fit into the larger picture and whether there is life beyond Earth are some of the questions humans still endeavor to answer. Understanding astronomy The baffling cosmic questions of the day have always inspired big ideas to answer them. They have stimulated curious and creative minds for millennia, resulting in pioneering advances in philosophy, mathematics, technology, and observation techniques. Just when one fresh breakthrough seems to explain gravitational waves, another discovery throws up a new conundrum. For all we have learned about the universe’s familiar constituents, as seen through telescopes and detectors of various kinds, one of our biggest discoveries is what we do not understand at all: more than 95 percent of the substance of the universe is in the form of “dark matter” and “dark energy.”
The origins of astronomy In many of the world’s most populated areas today, many of us are barely aware of the night sky. We cannot see it because the blaze of artificial lighting overwhelms the faint and delicate light of the stars. Light pollution on this scale has exploded since the mid-20th century. In past times, the starry patterns of the sky, the phases of the moon, and the meanderings of the planets were a familiar part of daily experience and a perpetual source of wonder. Few people fail to be moved the first time they experience a clear sky on a truly dark night, in which the magnificent sweep of the Milky Way arches across the sky. Our ancestors were driven by a mixture of curiosity and awe in their search for order and meaning in the great vault of the sky above their heads. The mystery and grandeur of the heavens were explained by the spiritual and divine.