A battery by definition is a collection of cells. So the cell is a little can of chemicals. And the challenge is taking a very high-energy cell, and a large number of them, and combining them safely into a large battery.

There's nothing - I've bought everything I want. I don't like yachts or anything; you know, I'm not a yacht person, and I've got pretty much the nicest plane I'd want to have.

I would like to fly in space. Absolutely. That would be cool. I used to just do personally risky things, but now I've got kids and responsibilities, so I can't be my own test pilot. That wouldn't be a good idea. But I definitely want to fly as soon as it's a sensible thing to do.

Life is too short for long-term grudges.

The future of humanity is going to bifurcate in two directions: Either it's going to become multiplanetary, or it's going to remain confined to one planet and eventually there's going to be an extinction event.

The extension of life beyond Earth is the most important thing we can do as a species.

My vision is for a fully reusable rocket transport system between Earth and Mars that is able to re-fuel on Mars - this is very important - so you don't have to carry the return fuel when you go there.