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.

First published in November 1988, this work provided a coherent narrative about the known understandings of meteorites and the early solar system.

From the original publication:

Although the Earth was formed, together with the other planets, at the birth of the solar system, geological activity has since erased all but a hint of the processes that accompanied its formation. If we wish to explore the processes that occurred in the earliest solar system, and the nature of the environment in which they took place, we must turn to the record contained in more primitive material. Many meteorites appear to satisfy that criterion, and much effort has been applied in identifying those meteorites, or their constituents, that have retained a reliable record of the early solar system. This book provides a synthesis of what has been learned so far about the earliest stages of solar system history through the study of meteorites, and what, given our current level of understanding, remains to be learned.

Contents 1. Introduction 2. Source Regions 3. Secondary Processing 4. Irradiation Effects 5. Solar System Chronology 6. Chondrites and the Early Solar System 7. Elemental Composition of Chondrites 8. Magnetic Fields in the Early Solar System 9. Chondrules10. Primitive Material Surviving in chondrites11. Micrometeorites12. Inhomogencity of the Nebula13. Survival of Presolar Material in Meteorites14. Nucleosynthesis15. Nucleocosmochronology16. Summary

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.