Rose: Really though, Doctor, tell me, who are you?
The Doctor: Do you know, like we were saying, about the Earth revolving? It's like when you were a kid, the first time they tell you that the world's turning and you just can't quite believe it because it looks like it's standing still. I can feel it. The turn of the Earth. The ground beneath our feet is spinning at a thousand miles an hour, the entire planet is hurtling around the sun at sixty-seven thousand miles an hour, and I can feel it. We're falling through space, you and me, clinging to the skin of this tiny little world, and if we let go... That's who I am. Now forget me, Rose Tyler. Go home.