Romana I: Newton? Who’s Newton? The Doctor: Old Isaac. Friend of mine on Earth. Discovered gravity. Well, I say he discovered gravity, I had to give him a bit of a prod. Romana I: What did you do? The Doctor: Climbed up a tree. Romana I: And? The Doctor: Dropped an apple on his head. Romana I: Ah, and so he discovered gravity? The Doctor: No, no. He told me to clear off out of his tree. I explained it to him afterwards at dinner.