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.

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.

I think life on Earth must be about more than just solving problems... It's got to be something inspiring, even if it is vicarious.

You could warm Mars up, over time, with greenhouse gases.

With artificial intelligence, we are summoning the demon. In all those stories where there's the guy with the pentagram and the holy water, it's like, yeah, he's sure he can control the demon. Didn't work out.

If anyone has a vested interest in space solar power, it would have to be me.

I think we should be very careful about artificial intelligence. If I had to guess at what our biggest existential threat is, it's probably that. So we need to be very careful...With artificial intelligence we're summoning the demon.