John S. Lewis
Worlds Without End: The Exploration of Planets Known and Unknown

"various schools of thought [hundreds and thousands of years ago] derived their opinions by logic from a set of philosophical and religious premises that were in no way based on observation or constrained by reality. They neither based their explanations of the Universe on quantitative observations nor thought to test them in this manner. In short, they speculated shamelessly, concerned more about their standards of logic than whether their initial assumptions or final conclusions matched reality." -- page 202
What a pleasant surprise this book turned out to be. I wasn't really looking forward to reading this one as I imagined it would just go over some of the fairly recent news items involving the discovery of planets in other parts of the Universe. Instead, Worlds Without End provides a breathtaking look at a number of issues--few of which I had ever before considered. This is the best book I've read in quite a while.

Perhaps I just haven't been reading the (similar) books that would make this one seem dull and repetitive. To me, it came across exceedingly fresh.

Lewis covers a major portion of the field known as planetary science. Although certainly not required for understanding this work, previous readings of books such as Venus Revealed and/or Blind Watchers of the Sky will prove useful. Conversely, if you enjoy this book, you'll probably want to check out the two aforementioned titles too.

Earthlet, Earth, and Earthissimo are described. The first and last are two hypothetical earths that begin with identical compositions but different masses. The changes based on size alone are amazing to ponder--from the enormous mountains on Earthlet to the completely underwater world of Earthissimo. The reader is also led to imagine what the sky would look like if they lived on Io (one of Jupiter's moons). Jupiter would appear to be much brighter than our own moon (by a factor of 380!) due to its size and reflective cloud cover. In addition, it would fill almost 40 times as much of the sky as a full moon in our sky does. Since Io has a 1:1 spin-orbit resonance with Jupiter, the rising and setting of Jupiter that we are accustomed to with respect to celestial bodies would not occur on Io with respect to Jupiter. Instead Jupiter would loom high overhead making a small circular pattern in the sky each day but never setting. Truly an amazing sight.

Somewhat similarly, in a chapter entitled "Starry Nights: Life in a Globular Cluster", Lewis describes what the sky would look like in a portion of the Universe vastly different from our own like a globular cluster (an elliptical rather than spiral galaxy like the one we live in). Such a viewer would see 40 times as many stars in the night sky and more than 280 times as many bright stars (those with a magnitude greater than 1). What a spectacular scene that would be! It seems a shame that we aren't able to enjoy such a view for ourselves. At the very least, it would be nice to hear a first-hand account of the scene from a good writer or story teller. Lewis' facts and descriptions give the reader the next best thing.

Although Worlds Without End will peak your imagination, it isn't limited to just pie-in-the-sky musings. There is a load of solid science behind the more fiction-like prose. I highly recommend this book to anyone even remotely interested in astronomy, planetary science, or even science fiction.

From the publisher:
The most exciting new discovery in modern astronomy must surely be the detection of planets orbiting distant stars; but what kinds of worlds these new planets are is yet to be determined with certainty. In this imaginatively written yet solidly scientific work, planetary scientist John S. Lewis explains how planets form, what they are made of, and how scientists know what they know about both the planets in our solar system and those orbiting distant suns. From solidly grounded knowledge to the latest theories of planetary science, Worlds Without End is essential reading for everyone thrilled by the latest discoveries in astronomy.

John S. Lewis, author of Rain of Iron and Ice and Mining the Sky, is Professor of Planetary Sciences and Co-director of the Space Engineering Research Center at the University of Arizona. He lives in Tucson, Arizona, with his wife and four children.