Martin Rees photographed at the Royal Society in London in August

Lord Martin Rees, Britain’s Astronomer Royal, is taking me on a mind-blowing trip through the universe. In two minutes we travel 2.4bn light years, past galaxies swirling spectacularly into existence from primordial dust and mysterious dark matter, all from the comfort of one of London’s finest old offices.

This micro-odyssey on Rees’s laptop illustrates a technology that he says is transforming astronomy: computer simulation. “One reason I feel a bit of a dinosaur in my research is that I’ve worked on various phenomena where computer simulations were not reliable enough, until about 10 years ago,” he says. “Now you can compute what happens, for example, when black holes collide – the magnetic fields, jets and so on – in a realistic way. That has been a huge boost for the field.”

Rees is one of the great polymaths of contemporary physics. His research has been outstanding, focusing particularly on high-energy events such as gamma-ray bursts and the formation of black holes. But more remarkable is his overall contribution first to cosmology and then to science as a whole.

We meet at the Royal Society, the national academy of science, which Rees led for five years until 2010. His successor as Britain’s “top scientist”, Paul Nurse, is away, so for our interview we borrow the president’s office at the society’s headquarters in Carlton House Terrace overlooking St James’s Park.

With sun streaming into the room through John Nash’s Regency windows, I remark that it is one of London’s most splendid offices. “It was [Joachim] von Ribbentrop’s when the German embassy was here in the 1930s,” he remarks. “Angela Merkel came to lecture when I was president, and I gave her tea here. She knew its history.”

At 71, Rees is an almost exact contemporary of two other British scientists who have made global names for themselves: cosmologist Stephen Hawking and the evolutionary biologist Richard Dawkins. The trio share, too, a family background in the English professional middle classes. Rees’s parents were teachers; he went to public school (Shrewsbury) followed by Trinity College, Cambridge.

Yet Hawking and Dawkins, who have both just published memoirs, are in their different ways individualists – mavericks, even. Rees, in contrast, epitomises orthodoxy and convention. He does not push himself forward and, though he is a good communicator, hates appearing on television.

In his public speeches Rees has a loud, confident voice. Speaking one-to-one he sounds soft and gentle, almost hesitant. His demeanour is patient, modest and courteous – matching his appearance. Rees is slight in build and bold in profile.

Even if there’s no life beyond Earth now, we can imagine a post-human species spreading far beyond it

“My research has been fairly broad and piecemeal,” he says, looking back at his career. “My main satisfaction is having been involved in a lot of debates which have clarified many issues. The issues we debated in the 1960s have been settled and the issues we’re discussing now could not even have been posed then.

“The 1960s were an exciting time to start because that was when the first evidence emerged for the Big Bang, and for black holes, neutron stars and quasars,” he adds. “It was a good time to be a young researcher. When everything is new, the experience of the old guys does not count for so much.”

So what advice does he give to young scientists today? “Go into a field where there are new data and new techniques. Otherwise you’re banging your head against the problems the old guys have failed to solve.”

Rees mentions extrasolar planets (planets around other stars) as the field of astronomy that has made most progress in recent years. Less than 20 years after the discovery of the first planet beyond our solar system, the number found through surveys from telescopes in space and on the ground has reached 1,000 – and scientists estimate that altogether our galaxy has billions of planets.

So far planets have been detected indirectly by the slight darkening or gravitational wobble they induce on their parent star. But the next generation of telescopes will enable astronomers to obtain direct images of potentially habitable Earthlike planets many light years away and to analyse the chemical signature of their atmosphere for evidence of life.

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We know too little about the origin of life on Earth to set the odds for its existence on faraway planets. “Even if simple life is common, it is a separate question whether it’s likely to evolve into anything we might recognise as intelligent or complex – and where this might happen,” Rees says. But he warns: “If there’s advanced life elsewhere we must not be too anthropomorphic about it. It may be something that we would not recognise.”

Rees is not averse to drawing ideas from science fiction, regretting the snooty attitude of many scientists towards the genre. “I tell my students that it’s better to read first-rate science fiction than second-rate science,” he says. “It’s more stimulating – and no more likely to be wrong.”

Martin Rees and the Queen with Newton's telescope at the Royal Festival Hall in London, June 2010

Sci-fi ideas worth considering include balloon-like creatures floating in the dense atmospheres of heavy planets, intelligent insectlike swarms, nanoscale robots. “There could be diffuse living structures, freely floating in interstellar clouds,” he speculates. “Such entities would live (and, if intelligent, think) in slow motion but nonetheless may come into their own in the long-range future.”

Astronomers bring an awareness of the far future. “Thinking about life on Earth, most people see us as the culmination but we know the sun is only halfway through its life,” he says. “There is no reason to think that we’re the culmination. Even if there’s no life beyond Earth now, we can imagine a post-human species spreading far beyond Earth. Moreover, any [human] evolution in the future will be on the technological timescale of centuries rather than the Darwinian timescale of millions of years.”

First, however, human civilisation has to survive the perils of the next century or so. Ten years ago, Rees wrote Our Final Century: Will the Human Race Survive the Twenty-first Century?, a book that analysed the factors that could wipe out civilisation. Now he is co-founder of the new Cambridge Centre for the Study of Existential Risk, which will assess threats to the existence of human civilisation, from runaway climate change to a super-lethal pandemic, from nuclear war to artificially intelligent computers taking over the world. The aim is to compile a register of “events with low probability but catastrophic consequences … and assess how to enhance resilience against the more credible ones.”

The European Research Council has shortlisted the centre’s proposal for a five-year grant to create “a new science of existential risk”. “Those of us in the developed world fret too much about minor hazards of everyday life,” Rees says. “But we are less secure than we think. It seems to me that our political masters should worry far more about events that could arise as unexpectedly as the 2008 financial crisis but which could cause worldwide disruption.”

Although Rees has been portrayed as a predictor of doom, he rejects that label: “I estimate that there’s a 50 per cent chance of a major setback within the next century, like a nuclear war, but I don’t think we’ll be wiped out.”

After giving up his main administrative duties as president of the Royal Society and (last year) the master of Trinity College Cambridge, Rees hoped to do more research at Cambridge’s Institute of Astronomy. He has been associated with the university for almost all of his professional life and is married to another distinguished Cambridge professor, the anthropologist Dame Caroline Humphrey.

I tell my students that it’s better to read first-rate science fiction than second-rate science. It’s more stimulating – and no more likely to be wrong

But Rees miscalculated the amount of time he would gain after his retirement, as he has taken on a lot of writing and lecturing and, as a member of “the great and the good” of British science, agreed to chair several worthy committees and organisations. One initiative about which he is enthusiastic is the establishment of a multimillion-pound challenge prize fund for innovation, to mark next year’s tercentenary of the famous Longitude Prize that saw John Harrison win a fortune for developing an accurate chronometer for navigation at sea.

“The idea seems to have got a bit of traction,” says Rees, chairman of its managing committee. “The idea is to have something to announce by June 2014. We have identified seven areas for prizes and we’ll get sponsorship for each one, including a public consultation to see what people think of them.”

Physics globally is in good health, Rees feels. The US still leads in smaller, lab-scale research while Europe is becoming pre-eminent in huge international projects such as telescopes and, above all, Cern, the high-energy physics centre outside Geneva. “The message for Europe is that when we work together we can do as well as the Americans,” he says.

The $8bn Large Hadron Collider at Cern is the shining example of “big physics” catching the public imagination, following its successful hunt for the Higgs boson – the subatomic particle which, to oversimplify grossly, is responsible for the fundamental property of mass.

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Rees is gratified and surprised that the LHC and particle physics have received so much attention. “Astronomy has become much more exciting than it was in the 1960s, while particle physics is more arcane than it was then,” he says. “I think I could explain planets around stars – and how we find them – to someone with a sixth-form education but you can’t possibly explain the Higgs particle like that.” But then, as he concedes, you can’t predict popular appeal on the basis of relevance to people’s lives or even comprehensibility. One issue catching the imagination of the public and cosmologists alike is whether our universe is part of a possibly infinite “multiverse” of other universes.

Perhaps surprisingly, Rees believes that with more observations, computing and thinking, “this is a question we might find the answer to. It’s a heresy to think you have to test all the consequences of a theory to confirm it – you just need to test enough consequences to gain confidence in it. Then you believe the other consequences that you can’t test. We may be able to say with some confidence whether or not there are other Big Bangs and, if so, whether each one is governed by different laws [of nature].”

Mind-boggling concepts such as the multiverse, string theory, dark energy, supersymmetry and hidden dimensions of space and time raise the question of whether we can ever grasp the deep realities of nature. Rees thinks not.

“It is remarkable that our brains, which have changed little since our ancestors roamed the African savannah, have allowed us to understand the counterintuitive worlds of the quantum and the cosmos,” he says. “But there is no reason to think that our comprehension is matched to an understanding of all key features of reality.

“Some of these insights may have to wait for post-human intelligence. There may be phenomena, crucial to our long-term destiny, which we are not aware of – any more than a monkey comprehends the nature of stars and galaxies.”

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