5 y/o DS and I were talking about the Air Force today (he asked and I explained what it was) and he said he was going to learn to fly. Then he said "And I'm going to learn how to gravitate. I try, and I get up on my tippy-toes, and almost off the ground but it doesn't work". I almost told gravitation is only on TV and he won't ever be able to (theoretically). I caught myself. Why squash his little scientific dreams? He'll figure out limitations soon enough :(