Everything today is "transient." Technology and its ability to empower actors large and small evolve so quickly that we have to get used to living in a world that exists in a more or less constant state of flux.

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.

The United States is not longer going to be the world's policemen and our days of determining you're in or you're out around the world no matter what the level of direct American interest or connection are going to be very limited. Increasingly, Africa will be doing that.

The real question is not are there other forms of life in the universe, but are there other intelligent forms of life out there right now. Because the universe is not only really big but it's also really long. It's been around for a long time; it's going to be around for a long time.

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.

There is always the risk that a conflagration in the Middle East becomes larger and more dangerous. In this scenario, we discover that the Arab Spring was merely the prelude to a deeper and much farther-reaching upheaval in the region that has greater impact on countries like Iran and Saudi Arabia.

Climate is a global issue. Coal is still the energy that is being used more than anything else to make electricity. The United States is using less as we're turning more to gas. But, around the world, that's what they're using.