Imagine for a moment that you lived on another planet. Not Tatooine, Trantor or another fictional orb, but a real-deal planet circling a star somewhere in our real-deal galaxy. What would your world look like? Would there be a rocky surface? An atmosphere? How long would a day last? How about a year? What special physiology might you need to survive there? There’s no single scenario, of course. Starting with some basic facts, you can speculate in all sorts of surprising directions. That’s the fun of the exercise.
Over the last quarter century or so, astronomers have confirmed more than 3,600 exoplanets — that’s 3,600-plus worlds in addition to the planets, moons and other heavenly bodies known in our own solar system. People have long imagined what it would be like to live on Mars, and bold thinkers have dared to