He sure is a thinker. At bedtime, he lay down in his bed with the lights off, thinking quietly while I checked news on my phone. A plane flew overhead, and he said, "Do planes vibrate?" I said I thought they did, as their engines run. "Like that time I felt sick on the plane?", he said, remembering the time of intense turbulence in a plane last month that made him nauseous. "No, that was turbulence.", I said.
Then he lay thinking quietly again and eventually fell asleep.
It is interesting to watch him go through his phases before he falls asleep. First he talks a lot and asks lots of questions. Then he grows quieter and more thoughtful. Finally, his breathing goes heavy and he drifts off.