Well, he did say the universe was a lot smaller now. The difficult thing would be all the moving everything in the galaxy does, mixed with time. When you think about it, time is easy, that's always set. This moment in time of the universe will always be this moment in time in the universe. Where things ARE, when they're all moving, it a lot harder to pinpoint. The planets orbit the sun, the solar system orbits the galaxy, and the galaxy orbits through all of space.
He's used to that, and judging by the way he was still rambling, I don't think he was having the much trouble when it was just Earth.
I couldn't control something like that, I don't fly the TARDIS, the Doctor does. And he seemed pretty in control when he brought us to Venice. Said we were going there, and there we were.