I actually encountered an old man climbing over the chain-link fence at 22nd Street Station in San Francisco. The rest is imaginary. Except, of course, for entropy and the heat death of the universe. Those are real, I’m sorry to say. My father really did try to explain difficult physics concepts to me when I was ten or so. Not the heat death of the universe exactly, but I remember a long discussion related to the conservation of energy. As a ten-year-old, I contended that if I put some heat in the freezer, I could destroy it.