Any discussion about finding life elsewhere in the universe always leads us to analyze the factors that make life possible on Earth. What would the earth and life on it be like if our planet had formed under different circumstances?What if the earth were less massive, or if the sun had ended up with more mass when the solar system was formed? What would happen if a star exploded near the earth, or passed through our solar system right now? What if a black hole passed through the earth? What if our ozone layer became depleted? What would happen to life on Earth?In this engaging and accessible exploratory work, accomplished astronomer Neil F. Comins shows how these and other hypothetical situations would affect our planet and the life it sustains, by extrapolating from our present condition and applying plausible astronomical and geological theories.What if the moon didn't exist, for example? Well, Comins explains, the earth would rotate more than three times faster than it currently does, and our tides would be much lower. There would be recurrent gale-force winds like those on Jupiter, making it a challenge for "tall" beings (like humans) to evolve. And the atmosphere would have taken millions of years longer to convert from one dominated by carbon dioxide to the life-giving nitrogen/oxygen atmosphere of today (if it could at all - the atmosphere surrounding moonless Venus is still predominantly composed of carbon dioxide).By following up its initial imaginative leaps with careful analysis, What If the Moon Didn't Exist? offers the reader a fresh understanding of our place in the solar system, and a deep appreciation of how fragile a habitat the earth is. Read Less