UNDER ALIEN SKIES

A lively, technically accurate account of what future tourists would experience at various interesting parts of the universe.

Astronomer Plait, author of Bad Astronomy and Death From the Skies, chooses 10 places and begins with the familiar, describing what we would encounter on the moon and Mars. With no atmosphere, the sun heats the moon to 250 degrees at noon. It may drop to minus 200 at night, but the scenery is beautiful. Moving slowly across the sky, the huge Earth occupies 14 times the area of the moon seen from our planet and appears about 40 times brighter. Possessing air and weather, Mars seems tolerable, but this is deceptive. With less than 1% of Earth’s atmosphere, breathing “isn’t really an option.” More distant from the sun, Mars gets only 40% of the heat that the Earth does, making it a barren desert with nights so cold that carbon dioxide freezes out of the air. Long ago, however, it was warm, with a thick atmosphere, rivers, and oceans, so optimistic readers look forward to a visit, which could happen by the middle of the century. As the author shows, beyond Mars, matters are increasingly complex. A small asteroid is probably a pile of rubble, so rather than walk on it, “you’d plunge right through the surface,” and Saturn “has no land to land on.” Readers expecting an easy science-fiction romp will discover that Plait teaches serious astronomy. Provided they pay attention, they will learn why Charon, Pluto’s largest moon, remains motionless in the sky. All other moons move. How do stars and planets form? A visit to a gigantic nebula answers that question. Gravity from a black hole is so great that light cannot escape, but a black hole isn’t invisible. As in the rest of this entertaining book, Plait shows us why. The book includes an eight-page full-color insert and other illustrations.

Amusing experiences of a space armchair traveler and a good astronomical education.