Galaxy quest
by Ian Simmons
[ people - august 02 ]
Martin Rees has been Britain's Astronomer Royal since 1995. He has contributed to the theories of galaxy formation and clustering, and the origin of the cosmic background radiation. He was an early proponent of the idea that enormous black holes power quasars, and his study of their distribution helped discredit the steady state cosmological theory.
Ian Simmons (IS): Creationism has recently been introduced into science teaching in some UK faith schools. What do you feel about that?
Martin Rees (MR): Darwin himself said of his theory of natural selection: "There is grandeur in this view of life". It's a sad deprivation if some young people are not being exposed to this marvellous idea and, indeed, to the amazing world-view opened up by modern science, which should be - if nothing else - part of everyone's culture. But in expressing this view, I offer no criticism of 'faith schools' as such, most of which have traditionally offered an excellent education.
IS: What are the most interesting things in astronomy at the moment?
MR: 2002 was a remarkable year for astronomy, marked by new discoveries on all cosmic scales, from asteroids uncomfortably close to us, right out to quasars at record-breaking distances, whose light has taken more then 10 billion years to reach us.
From the parochial perspective of the UK, an important and gratifying development took place in July, when we signed up as full members of the European Southern Observatory (ESO). British astronomers now have access to the world's best optical facility - the VLT array of four eight-metre telescopes in Chile. The UK has been restored to the strong competitive position in optical astronomy that the Anglo Australian Telescope and the William Herschel Telescope gave us in the 1980s, a position which we dissipated during the 1990s when the Keck Telescopes and its successors came on line. We, in the UK, will now be able to collaborate fully with our European partners in future projects, with every expectation that Europe can fully match - and indeed, I'd hope, surpass - the US effort in 'flagship' projects in ground-based astronomy.
The fastest-surging branch of our subject is undoubtedly the study of other planetary systems. Almost 100 are already known. Within a few years, systems of planets will have been found around hundreds of stars. Astronomers will no doubt classify them (in their habitually unimaginative way) as Type 1, Type 2 and so forth. By studying these systems, we'll learn more about how our own Solar System formed. And when we've discovered other Earth-like planets, the new science of exobiology may surge forward excitingly. Planets are among the smallest objects that astronomers study, but the historic advance during the last year has been on the largest scale of all - in cosmology. We have learnt that our universe is 'flat' in the sense that the angles of even the largest triangle add up to 180 degrees. But it's made up of a surprising mixture of ingredients. Ordinary atoms - of which we, the stars, and the galaxies are made - contribute no more than five per cent. About 25 per cent is 'dark matter', whose nature is unknown (though probably it consists of some kind of electrically-neutral particles made in the big bang, along with the atoms and radiation). And the other 70 per cent is even more mysterious and unexpected: dark energy latent in empty space itself. A wide range of observations have contributed to this discovery: optical studies of very distant galaxies and supernovae; mapping of clusters of galaxies by X-ray telescopes in space; and precise measurements, from high-flying balloons and from Antarctica, of the cosmic background radiation (the 'afterglow' of the big bang).
This exemplifies two characteristics of our subject that render it especially fascinating and fruitful: it advances on a broad front, exploiting many different techniques; and each new advance, while bringing some issues into clearer focus, raises further questions and opens up new mysteries.
IS: What problems in astronomy have we yet to solve?
MR: I'm fortunate to work in a branch of science that fascinates a wide public. The important ideas can be conveyed very simply, but the most fascinating questions are still unanswered: What happened before the beginning? How will the universe end? Is there life on other planets? Are there other universes? When I lecture and write for general audiences, I try to share my bafflement about these questions with people who may have no background in science at all. In my most recent book, 'Our Cosmic Habitat', I also emphasise the links between the very large (the inner space of atoms) and the very small (the outer space of galaxies) and the fact that our entire universe seems to be strangely 'biophilic', attuned to the emergence of life, which is the most interesting and important thing in it. We need to understand the very beginning of the universe and the nature of the laws governing it. This demands some fundamentally new concepts (and, perhaps, will be forever beyond our grasp). We need also to understand cosmology as an environmental science: How, from simple beginnings, did our universe transform itself, over 13 billion years, into the complex cosmic habitat we see around us and of which we are a part?
IS: Searches of other stars are revealing more and more systems with planets. What are the chances that we will find life among them or elsewhere in our own system?
MR: As I describe in 'Our Cosmic Habitat', there are two different questions, which it is important to distinguish. First, how did life begin? I think there's a real chance of making progress here by searching on Mars and under the frozen ocean of Europa, and also by achieving a better understanding of how life on Earth began. We will then know whether life is a 'fluke' or near-inevitable in the kind of initial 'soup' expected on a young planet.
But there is a second question. Even if simple life exists, what are the odds against its evolving into something that we would recognise as intelligent? This question is likely to prove far more intractable. Even if primitive life were common, the emergence of advanced life may not be. We know, in outline, the key stages in life's development here on Earth Simple life seems to have emerged quite quickly, whereas it took nearly three billion years for even the most basic multicellular organisms to come on the scene. This disparity of timescales suggests that there may be severe barriers to the emergence of any complex life. Intelligence could therefore be exceedingly rare, even if simple life were widespread. Certainly, our own emergence was the outcome of time and chance. If the Earth's history were re-run, the fauna might be quite different.
IS: And do you think any of it is actually trying to contact or visit us?
MR: Claims that advanced life is widespread must confront the famous question first posed by the great physicist Enrico Fermi: "Why aren't the aliens here?" Why haven't they visited Earth already, or at least manifested their existence in a way that leaves no doubt? Why aren't they, or their artefacts, staring us in the face?
This argument gains further weight when we realise that some stars are billions of years older than our Sun: if life were common, its emergence should have had a head-start on planets around these ancient stars. Even if we have not been visited (and of course we cannot be absolutely sure we haven't), we should not, despite Fermi's question, conclude that aliens don't exist. It would be far easier to send a radio or laser signal than to traverse the mind-boggling distances of interstellar space. It makes sense first to 'listen' rather than transmit. If a signal were detected, there would be time to send a measured response, but no scope for snappy repartee: any two-way exchange would take decades.
Searches for Extraterrestrial Intelligence (SETI) are a worthwhile gamble (even if one suspects that there are heavy odds against success) because of the huge philosophical import of any detection. A manifestly artificial signal - even if it were as boring as a set of prime numbers or the digits of 'pi' in binary notation - would convey the momentous message that intelligence (though not necessarily consciousness) wasn't unique to the Earth and had evolved elsewhere, and that concepts of logic and physics weren't peculiar to the kind of hardware that we carry around in our heads. The SETI Institute at Mountain View, California, is spearheading these searches, supported by hefty private benefactions.
Even if intelligence were widespread, we may never become aware of more than a small, and atypical, fraction of what is out there. Some brains may package reality in a fashion that we can't conceive. Others could be uncommunicative, living contemplative lives, perhaps deep under some planetary ocean, doing nothing to reveal their presence. There may be a lot more life out there than we could ever detect. Absence of evidence wouldn't be evidence of absence. The only type of intelligence we could detect would be one that led to a technology we could recognise. It would, in some ways, be disappointing if searches for alien intelligence were doomed to fail. On the other hand, it would give humans a pretext for a boost in self-esteem: if our tiny Earth were a unique abode of intelligence (at least in the domain accessible to our telescopes), it would have greater cosmic significance than it would merit if the Galaxy already teemed with complex life. And we'd have even stronger motives to cherish this 'pale blue dot' in the cosmos, and not foreclose life's future.
IS: There has been a lot of controversy recently over Stephen Wolfram's claim that we have been getting it all wrong. We've been looking at the universe using mathematics, when we should be using cellular automata. As someone who began as a mathematician, how do you rate this idea?
MR: Cellular automata are fascinating. It's amazing that 'artificial life' can be generated even by an algorithm as simple as that of John Conway's 'game of life', which was one of the pioneering ideas in this field. Wolfram's work, as mathematics, is exceedingly interesting and may, indeed, illuminate our understanding of biological systems. It's also undoubtedly true that the availability of computers has developed our scientific intuition in remarkable ways. (The whole idea of the transition to chaos was readily studied on the first pocket calculators, but was hard to study beforehand; and marvellous patterns like Mandelbrot's set lay unknown in the pre-computer age.) However, I'm worried that the hype built up around Wolfram's book may backfire: it manifestly isn't a fundamental and original answer to the deep problems of physics, but, for all that, it's a remarkable piece of work by an exceedingly talented thinker.
IS: After the end of the Cold War, everyone seemed to assume that arms control would become easier. It hasn't, especially with the ugly situation in Kashmir. Is there hope for the future or is the genie well and truly out of the bottle?
MR: I'm depressed about the prospects for nuclear arms control. More generally, I'm pessimistic because of chemical, biological and cyber weapons too. For 40 years, the main threat was from superpower confrontation - the Cold War. Since 1990, that's been replaced by a multipolar world with a wider range of threats from smaller nations. Now, especially since September 2001, we're concerned about terrorist groups. And in future, single dissident individuals - not even organised groups or terrorist cells - will pose serious threats, especially when they have access to dangerous chemical and biological technologies which may be far less readily controlled. Even if all nations imposed strict regulations on perilous applications of these advances, the chances of effective enforcement are no better than in the case of the drug laws. And even a single infringement could trigger catastrophe.
