Many Skies: Alternative Histories of the Sun, Moon, Planets, and Stars

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 t...