What if the Earth had two moons?
and nine other thought-provoking speculations on the solar system
Explores how the earth would be different in ten alternative astronomical conditions, including how the planet would change if there was a second moon, if the moon orbited backwards, if the earth's crust were thicker, if there was a counter-Earth, if the sun were less massive, and if there were two suns.
St. Martin's Press
2010
9780312598921
book
