My 7-year old daughter asks out of the blue, "What's 149 +137?" I pull up a sheet of paper and start to show her how to figure it out, but she waves me away, thinks a bit, and says, "It's 286, isn't it?"
"That's right! Yay!"
That afternoon my husband comes home talking about his chemistry students, "When I mentioned the Chinese working on a space elevator for a lunar colony, a 17-year old senior in the class started laughing so hard he couldn't sit up straight. 'It'll never work! What will they do when the moon isn't in the sky? It goes down in the daytime!' Seventeen years old, a high school senior, and no one had ever taught him that the moon orbits around the earth."