by Helen Gavaghan

When Martin Rees, Astronomer Royal and soon to be President of the Royal Society (PRS), opened the door of the Master's Lodge at Trinity College, Cambridge what struck me was that he is contained - guarded even, yet with an impish sense of humour. During lunch and our interview he spoke of astronomy and physics with the practised ease of someone who has spent a lifetime popularising theoretical astrophysics.

To take on the role of PRS Rees is stepping down as Astronomer Royal. He made this decision because being PRS will give him a role over the whole of science, and that, he says, "means I won't be able to be an advocate for astronomy to the extent that I think the person who holds the Astronomer Royal title ought to be."

So what did he bring to this historic role?

Both Rees's professional practices and his popularising advocacy have made him a notable Astronomer Royal - the fifteenth since Charles II created the title in 1675. A quick Internet search reveals that his colleagues internationally consider him to be one of the central figures in his field. In his own words he is by nature a synthesizer, an innovator: "I'm more likely to be the person to write the first paper rather than the definitive paper on a particular topic," he says.

It is an approach that has won him many professional plaudits, the most recent being the Crafoord prize awarded in January 2005 to himself and two Princeton-based astrophysicists for their contribution to theories of how, beginning with the big bang, dark matter contributed to the formation of the first galaxies.

Given his role as a populariser of astrophysics and cosmology and given that one would not expect from his web site or his academic record that he would be reticent it was oddly difficult to persuade him to talk about his work and its overall meaning in detail. Yet what he and many other astrophysicists and cosmologists are doing is very exciting.

His agenda and that of many colleagues is trying to understand through computer simulations and mathematics events that took place during the so-called dark age of the Universe. The temporal limits of this dark age are fixed by practical and theoretical particle physics and cosmology as being a time span from between 100 million and one billion years after the Big Bang. It is then that the first galaxies were formed and the first light emitted, but, as yet t=0, that is the time when the Big Bang itself occurred, whether 10 or 15 billion years ago from now is still not clear.

What happened within the totality of the dark age would seem to have the potential to lead to the holy grail of physics, a theory that binds all observations of known forces, energy and matter into one unifying theory.

The models can be constrained at the earlier period by the results of particle physics and at the later time by observations across the electromagnetic spectrum from radio to gamma rays at both known and estimated astrometric distances. Details such as spectral, temporal and intensity resolutions help refine the models. In other words he and astrophysicists and cosmologists around the world are looking to build bridges that link particle physics and cosmology, and to link dark matter and energy (the work that won him the Crafoord Prize) with the matter and energy visible to our current instrumentation.

When one looks down the list of his nearly 500 papers published in leading science journals during the past 30 years one sees that this work is a fitting culmination of a research agenda that began 30 years ago during his days as a doctoral student. The titles show a steadily accreting body of seemingly disparate pieces of knowledge about the physical reality or possible reality of our Universe. In their totality they are an ideal knowledge base for exploring the dark age of the Universe.

Rees began his intellectual exploration with work on the intergalactic medium and radio sources, questioning the nature of those sources and the manner in which what one observes relates to the physical nature, location of the emitter and the three-dimensional dissipative pattern of its emissions (eventually and after some persuasion he admitted that one of the papers to emerge from this research, which he published solo in Nature in 1966, was the work of which he was most proud).

He was working in an intellectually stimulating environment with a charismatic supervisor, Dennis Sciama (correct), and with contemporaries who included other luminaries such as Paul Davies and Stephen Hawkins.

Over the years he has explored also the tidal consequences of the motion of planets and stars, that is gravity, and after initially eschewing particle physics as a topic for his doctoral studies, he has tackled such esoteria as the behaviour of very high energy (multi giga-electron volts) neutrinos in gamma ray bursts in pursuit of an explanation of how matter at its most basic level is formed.

Amid this burgeoning of science I wondered if he had had any eureka moments or big intellectual surprises. As when I asked what his favourite piece of professional work was, he became unexpectedly less forthcoming. "I think," he said, "the main gratification has been that the subject has evolved so fast ... in the past 10 years ... you know black holes, neutron stars, evolution of the Universe, exoplanets, gamma-ray bursts all these things."

It is sharing such discoveries with the public that has clearly brought him great personal satisfaction. He has written many popular books and articles. In the Daily Mail earlier this year he asked the age old question, are we alone? Whether we are or not, he concluded, "we cannot be weighed down by the immensity of the Cosmos and our apparent irrelevance."

His popularising role began when as a math student at Cambridge in the early 1960s he did some broadcasting, but it was not until he was 22 that he knew he would become an astronomer. Until then he was discarding career ideas, deciding against economics and particle physics. Since then he has come full circle, as his work exploring the role of fundamental particles in the construction of matter attests.

Given such breadth of interests it is not surprising that in 1995 he was accorded the title of Astronomer Royal. "The existence of the title is of historic interest," he says, "because it reflects the fact that astronomy was the first publicly supported science, dating back to the establishment of the Royal Observatory. There was no physics or chemistry supported by the State until the nineteenth century and that is why there is no similar title for those subjects."

The job of PRS encompasses both. His new role, like that of Astronomer Royal, does not directly wield power or direct how money should be spent, but it is a prestigious title and influential with scientists and politicians.

I was curious to know, therefore, how he would respond if he were grilled about astronomy and his views of science in society with the scepticism that journalists commonly bring to their interviews with politicians. His response was that he would welcome such questioning, then gently he added, perhaps as a caution, that with politics journalists are at least as well informed as their interviewees.

Rees' future interviewers need to know that besides taking astronomy to a wider public he has also taken an active interest in organisations such as NATO and in Pugwash, a body established in 1957 by physicist, Joseph Rotblat, and the philosopher Bertrand Russell. Pugwash's aim was and is to explore practical ways of preventing a world that was clearly not going to disarm any time soon from blowing itself up, by keeping open lines of communication among the world's scientists and politicians with knowledge of and concern about how to manage nuclear weapons.

In the early 1990s Pugwash turned its attention to assessments of the risk of regional conflicts. What part, I wondered, could the organisation play in today's world. "Whether it is Pugwash as an organisation, what I have said in several lectures this year is that we are going to need counterparts of Joe Rotblat not just in physics, but in bio and cyber technology and in environmental science as well."

Towards the end of the interview Rees said, "I am a fox." It was not a reference I knew. It transpires that it comes from a fragment of poetry by the 7th century Greek poet, Archilocus: "The fox knows many things, the hedgehog one big thing." In an essay written in 1953, Isaiah Berlin takes the fragment and applies his understanding of the dichotomy it highlights to an analysis of the mind set of Russian writers, in particular to Tolstoy. To my mind the meaning and dichotomy for Rees, if there is one, would depend on what the individual holds within his or her personal understanding of the characteristics of those animals. So is Rees cunning, is he hunted, though by assertion a fox, is he really a hedgehog? I do not know.

I would rather think of him as a fusion of Aristotle and his teacher Plato, that is as someone with a penchant both for abstraction about the Universe and an awareness of its physical reality. Though a theoretical astrophysicists he is dipping into data from all aspects of physical reality, and as such is laying with others tantalising ground work for anyone aspiring to the creation of a grand unified theory of matter and energy.

I also concluded that he is kind, but that interviewers will need to be well briefed and ready for the kind of elegant and subtle sidestepping of the question that would put a politician to shame.

Top