(At the start of class in astronomy, I put up a picture of the day and ask my students to try to guess what’s happening. Sometimes it’s easy: a picture of Jupiter or Mars. Sometimes it’s harder: I don’t actually expect my students to recognize, for instance, Tethys, but they can make observations and narrow down the possibilities. And sometimes it’s just weird. The previous day’s was a NASA poster “advertising” tourism on Kepler 16b, the world where your shadow always has a companion!)

Student: “Miss, how many suns does Mars have?”

Me: “One. Why do you ask?”

Student: “Huh, guess I was wrong. Sorry, [Friend]. I really thought it had two.”

Classmate: “Wait, Mars orbits the same sun we do. Why would you think it had two?”

Me: “Did you mean to say moons? Mars does have two moons…”

Classmate: “No, I meant that picture from yesterday. With the two suns. Wasn’t that Mars?”