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What if Earth had several moons or massive rings like Saturn?  What if the Sun were but one star in a double-star or triple-star system?  What if Earth were the only planet circling the Sun? 

These and other imaginative scenarios are the subject of Arthur Upgren's inventive book Many Skies: Alternative Histories of the Sun, Moon, Planets, and Stars. Although the night sky as we know it seems eternal and inevitable, Upgren reminds us that, just as easily, it could have been very different.

Had the solar sytem happened to be in the midst of a star cluster, we might have many more bright stars in the sky.  Yet had it been located beyond the edge of the Milky Way galaxy, we might have no stars at all.  If Venus or Mars had a moon as large as ours, we would be able to view it easily with the unaided eye.  Given these or other alternative skies, what might Ptolemy or Copernicus have concluded about the center of the solar sytem and the Sun?

This book not only examines the changes in science that these alternative solar, stellar, and galactic arrangements would have brought, it also explores the different theologies, astrologies, and methods of tracking time that would have developed to reflect them. Our perception of our surroundings, the number of gods we worship, the symbols we use in art and literature, even the way we form nations and empires are all closely tied to our particular (and accidental) placement in the universe.

Many Skies, however, is not merely a fanciful play on what might have been.  Upgren also explores the actual ways that human interferences such as light pollution are changing the night sky.  Our atmosphere, he warns, will appear very different if we have belt of debris circling the globe and blotting out the stars, as will happen if advertisers one day pollute space with brilliant satellites displaying their products.

From fanciful to foreboding, the scenarios in Many Skies will both delight and inspire reflection, reminding us that ours is but one of many worldviews based on our experience of a universe that is as much a product of accident as it is of intention.

The planet Mars has been a subject of wonder for millennia, as attested by its place in mythology, by later speculation about its canals, and by the scientific and public excitement over the Viking mission. Although the scientific literature about the planet is voluminous, no comprehensive treatment of the results of modern spacecraft exploration has yet been made available. This volume fills that gap by providing a summary of what is presently known about Mars and identifying many puzzles such as polar cap variance, occurrence of dust storms, and the possible location of water. The introductory chapter cites questions, controversies, and milestones in the study of Mars, and also includes an annotated book list, basic data about the planet, and a guide to Martian seasons. A chapter on telescopic observation credits the contributions made by many amateurs that have advanced our knowledge of variations observed on Mars. A chapter on spacecraft exploration, by an American and a Russian author who have participated in all Mars missions, includes a revelation of an additional Soviet attempt. Twenty-nine technical articles cover geophysics; bedrock geology; surface; atmosphere; exosphere and magnetic field; and climate history. Two chapters address the search for life on Mars; three concluding chapters consider the Martian satellites. An indispensable reference for scientists, Mars will also serve as a complete sourcebook for serious amateur astronomers.

Measuring the Universe is the first history of the evolution of cosmic dimensions, from the work of Eratosthenes and Aristarchus in the third century B.C. to the efforts of Edmond Halley (1656—1742).

"Van Helden's authoritative treatment is concise and informative; he refers to numerous sources of information, draws on the discoveries of modern scholarship, and presents the first book-length treatment of this exceedingly important branch of science."—Edward Harrison, American Journal of Physics

"Van Helden writes well, with a flair for clear explanation. I warmly recommend this book."—Colin A. Ronan, Journal of the British Astronomical Association

They range in size from microscopic particles to masses of many tons. The geologic diversity of asteroids and other rocky bodies of the solar system are displayed in the enormous variety of textures and mineralogies observed in meteorites. The composition, chemistry, and mineralogy of primitive meteorites collectively provide evidence for a wide variety of chemical and physical processes. This book synthesizes our current understanding of the early solar system, summarizing information about processes that occurred before its formation. It will be valuable as a textbook for graduate education in planetary science and as a reference for meteoriticists and researchers in allied fields worldwide.