In the nearer term, the likeliest source of risk is a conflict between China and the U.S. These are now the two largest economies in the world, and the combination of their economic interdependence, the sharp differences in their political and economic values, and the growing divergence in their interests makes this relationship potentially dangerous for everyone who might be affected by it - which means pretty much everyone.

Berlin is a very edgy place, a very cosmopolitan place. It's a place where completely different ideas and cultures come together and clash in a very warm way. In a very warm-hearted way.

I absolutely am an environmentalist. I am probably more of an environmentalist than most people who live in the world, but I think that comes from my position in the world and that doesn't make me a better person.

Berlin is still a very edgy place, a very cosmopolitan place. It's a place where completely different ideas and cultures come together and clash in a very warm way. In a very warm-hearted way. It's a very young city. It's a vibrant city. It's an exciting city. It's a city that's also scarred by history. I think that's to be celebrated and graffiti is to be celebrated. Graffiti in Berlin is very different than when they spray something on the wall dividing the west bank and Israel. And should be treated as such in Berlin.

I think graffiti is part of Berlin culture. You think about what the Berlin wall meant and how visible that was in everyone's life. How it was a part of their very identity.

We're wealthy people. We're sitting here in New York, Washington. We live in a fantastically wealthy country. We don't have to worry about food. We don't have to worry about clothing. We wore the same shirt. We don't have to worry about our safety. It's very easy for us to be environmentalists. It's very easy for me to be an environmentalist. It's very easy for me to care about making sure that we protect the forests and the whales, and all that stuff. It's very hard for someone who makes $1,000 a year or some who makes less than $1 a day to care about the environment.

NASA is increasingly not the future of space exploration. I love the fact that we have private sector folks devoting a lot of money to stimulate innovation in space technology.