I have been thinking about the universe lately. The whole thing. After reading some of astronomer Chet Raymo’s elegiac prose (Starry Nights, The Soul of the Night), I have been craning my neck upward at odd angles when I encounter a rare pool of darkness between Chicago streetlights. Mostly, though, I see the moon, Venus, and the jets’ flight path into O’Hare Field, and must take Raymo’s word for what lies beyond.

Learning about the universe does little for earthly self-esteem. Our sun, powerful enough to turn white skin bronze and to coax oxygen from every plant on earth, ranks fairly low by galactic standards. If the giant star Antares were positioned where our sun is—93 million miles away—Earth would be inside it! And our sun and Antares represent just 2 of 500 billion stars that swim around in the vast, forlorn space of the Milky Way. A dime held out at arm’s length would block 15 million stars from view, if our eyes could see with that power.

Only one other galaxy, Andromeda, lies close enough (a mere 2 million light-years away) to see with the naked eye. It showed up on star charts long before the invention of the telescope, and until recently no one could know that the little blob of light marked the presence of another galaxy, one twice the size of the Milky Way and home to a trillion stars. Or that these next-door neighbors were but two of a hundred billion galaxies likewise swarming with stars.

One reason the night sky stays dark despite the presence of so many luminous bodies is that all the galaxies are hurtling away from each other with astonishing speed. Tomorrow, some galaxies will be 30 million miles farther away. In the time it takes to type this sentence, they’ll have receded another 5,100 miles.

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