Today, we take the risk of nuclear war quite seriously, climate change not so much and epidemics least of all. But no single country, not even the United States, is well prepared. And even if one country is doing the right things to protect itself, it has to be a global thing.

You need to understand things in order to invent beyond them.

The trouble with energy farming is that the energy isn't always where you want to use it, and it isn't always when you want to use it.

Make it just like a Mac.

Security is, I would say, our top priority because for all the exciting things you will be able to do with computers - organizing your lives, staying in touch with people, being creative - if we don't solve these security problems, then people will hold back.

The outpouring of support from millions of people in the immediate aftermath of the earthquake in Haiti has been impressive.

I think if you talk to the experts in any field where you have to take on a unknown challenge, where you're going to be working on it for a long time you'd find that to work themselves up to their best performance and really throw themselves into it, you know, spend all these hours in there and ah, give it their... give it their best that optimism plays a role.