President Theodore Roosevelt had a routine habit, almost a ritual. Every now and then, along with the naturalist William Beebe, he would step outside at dark, look into the night sky, find the faint spot of light at the lower left-hand corner of Pegasus, and one of them would recite: “That is the Spiral Galaxy of Andromeda. It is as large as our Milky Way. It is one of a hundred million galaxies. It is seven hundred and fifty thousand light years away. It consists of one hundred billion suns, each