What is the Royal Society's role in our age?
We support and promote excellent scientific research. But we also engage with the public and with political process. More and more often, policy issues have scientific aspects.

Do you ever feel politics holds science back?
It's our job as scientists to ensure that politicians' decisions are based on the best possible scientific advice, but obviously they have other criteria, too. The other problem is that many important long-term issues, such as population growth, don't have immediate impact. It's hard to keep them high on the political agenda.

How do you get people to engage with the concept of climate change?
It's difficult. The science is complicated and there's a lot of debate about what sacrifices we should make now for future generations. Also, it's global, so action has to be international. But the UK has shown political leadership, and we could and should take a lead in developing technologies needed for a low-carbon economy.

What are your thoughts on the politicians and scientists who fuel climate-change scepticism?
Essentially, all scientists who have looked into the evidence and understood it agree: there are uncertainties about the projections, but there
is undoubted evidence not only of climate change now, but of more drastic climate change in the future.

What about those who claim it's a conspiracy?
I think you should ask them.

What led you to astronomy?
To be honest, I specialised in science because I was bad at languages.

What does it tell us about the universe?
Charles Darwin gave us a perspective on how life had emerged from simple beginnings. We're trying to take his work further and ask where did the earth and the stars come from? We have developed, with fair confidence, a picture of how the first atoms, stars and planets evolved from some mysterious beginning 14 billion years ago. This grander picture, I think, is one of the triumphs of science in recent decades.

Some people dispute this picture. In the US, the creationists are a powerful force.
They're the sort of people who are intellectually deprived. They don't appreciate the wonderful story that science has opened up for us.

"Story" is an unusual way to describe it.
Science is really part of culture. One is culturally deprived if one is unaware of Darwinism and evolution, and DNA and all these things. And it's the most universal culture.

Science crosses borders, in other words?
Yes. Astronomy especially, because all cultures in all parts of the world throughout human
history have looked at the night sky. They've interpreted it differently, but it's the one thing that they've all wondered about.

Do your academic interests give you a strong sense of humans' insignificance?
My professional perspective on the cosmos doesn't make me worry any less about what will happen tomorrow, or next week.

Really? It doesn't alter your view?
There is one special perspective. Most educated people are aware that we're the outcome of billions of years of evolution, but they tend to feel we're somehow the end of it. But we are less than halfway through the sun's life - there is as much time ahead as it has taken for us to emerge from the primordial slime. So astronomy does give one a feeling about the long-range future.

In your book Our Final Century, you give an apocalyptic view of our time.
This century is the first in which human consumption puts pressure on the entire planet. And advances in technology, which have had benign effects overall, can pose new threats and challenges. In the old days, there was a limit to how much damage one could do, but a village idiot in the global village is more disquieting.

Was there a plan?
I knew I was going to do something academic, but the detail was unpredictable. I've been very fortunate, in many respects.

Did you vote, before you became a life peer?
I've always been more politically engaged than most scientists. When I finish as president of the Royal Society I shall spend more time in the House of Lords and on other political activity.

What will be your key issues?
The kind of issues where a scientific perspective is helpful.

Does politics need more scientists?
Politics involves many issues beyond science, but we do need scientist citizens, with different political views, to take part in public debate.

Are we all doomed?
I certainly hope not. I don't expect we are. This is the best time for young people to be alive.