It will not be humans who watch the sun's demise, six billion years from now. Any creatures that then exist will be as different from us as we are from bacteria or amoebae.

Devastation could arise insidiously, rather than suddenly, through unsustainable pressure on energy supplies, food, water and other natural resources. Indeed, these pressures are the prime 'threats without enemies' that confront us.

I'm not a specialist in the science but I have followed it fairly closely and it seems to me that there is among the experts a clear consensus that potential climate change is something to worry about.

God invented space so that not everything had to happen in Princeton.

In the case of climate change, the threat is long-term and diffuse and requires broad international action for the benefit of people decades in the future. And in politics, the urgent always trumps the important, and that is what makes it a very difficult and challenging issue.

If we ever establish contact with intelligent aliens living on a planet around a distant star ... They would be made of similar atoms to us. They could trace their origins back to the big bang 13.7 billion years ago, and they would share with us the universe's future. However, the surest common culture would be mathematics.

It will not be humans who watch the sun's demise, six billion years from now. Any creatures that then exist will be as different from us as we are from bacteria or amoebae.