Man, I really had some misconceptions about how the gravity of the Earth, Sun, and planets really works. I was very surprised by how many things I had been thinking about either in too simplistic a way or I was just wrong about.
I had not known that there was such a significant gravitational difference between cities, or that the big gaseous planets had so little pull, or that it’s best to think of astronauts in space as being in free-fall rather than in a low-gravity environment.