“How can a Big Bang have been the start of the universe, since intense explosions destroy everything?” — Tristan S., age 8, Newark, Delaware Pretend you’re a perfectly flat chess piece in a game of chess on a perfectly flat and humongous chessboard. One day you look around and ask: How did I get here? …

“Why does time change when traveling close to the speed of light?” — Timothy, age 11, Shoreview, Minnesota Imagine you’re in a car driving across the country watching the landscape. A tree in the distance gets closer to your car, passes right by you, then moves off again in the distance behind you. Of course, …