That's a possibility that arises from another of my main interests, which is the most powerful explosion in the universe—gamma ray bursts. These represent the violent end of a particular kind of supernova explosion. They're so powerful that they could be readily detected, even from the era when the very first stars were born. If some of these very first stars end their lives as gamma ray bursts, then we can use them to probe the earliest phases of galaxy formation—how the dark age ended and how the structures gradually built up. Big telescopes will offer snapshots of what the universe was like at various stages in the past.

There have been these amazing developments of the structure of the universe. But if I was asked to think of what else has been exciting in astronomy recently, the undoubted other highlight has been the discovery of large numbers of planets around other stars. Only in 1995 did astronomers find the first evidence for a planet orbiting another star like the sun. Now there are more than a hundred, and there's every expectation that a large proportion of the stars you can see in the sky have retinues of planets orbiting them.

Ten or 20 years from now, looking up at the sky will be a more interesting experience, because the stars won't just be twinkling points of light, but for each of them we'll be able to say something about the planets it has orbiting around it, their masses, their orbits, and perhaps the topographical features of the largest planets. That will make the night sky a lot more interesting and make everyone appreciate the universe as a much more rich and diverse place. Most of those planets will be inhospitable to life, but astronomers will have found planets which are rather like the earth. And that will give a focus for addressing the questions of life in the universe. We will be able to analyze the light from these earth-like planets, and test whether there is for instance ozone in its atmosphere which would be a signal for biological processes. And that would give us a clue as to whether there might be life. This enterprise will be complemented by progress by biologists in understanding the origin of life on earth—by experiments and perhaps also computer simulations. I'm very hopeful that 20 years from now we'll understand the origin of life; we'll have a feel for whether life is widespread in the universe; we might be able to point to particular other planets, orbiting other stars that might have life on them.

There is then a rather separate question: whether simple life is likely to evolve into anything we might recognize as intelligent or complex. That may be harder to decide. Some people say that there are many hurdles to be surmounted in going from simple life to complex life, and life on earth is lucky to surmount those hurdles but others suspect that life would somehow find its way to great complexity. Among my friends and colleagues there's a disparity of belief.

As an astronomer, I'm often asked: isn't it a bit presumptuous to try to say anything with any level of confidence about these vast galaxies or the Big Bang, etc? My response is that what makes things hard to understand isn't how big they are, but how complicated they are. There's a real sense in which galaxies and the Big Bang and stars are quite simple things. They don't have the same intricate layer upon layer of structure that an insect does, for instance. And so the task of understanding the complexities of life is in some respects more daunting than the challenge of understanding our Big Bang and of understanding the micro-world of atoms, as challenging as they are too.

It's rather interesting that the most complicated thing to develop in the universe, namely human beings, are in a well-defined sense midway between atoms and stars. It would take about as many human bodies to make up the mass of the sun as there are atoms in each of us. That's a surprisingly precise statement: the geometric mean of the mass of a proton and the mass of the sun, is about 55 kilograms—not far off the mass of an average person. It's surprising that this is such a close coincidence, but it's not surprising that the most complicated things are on this intermediate scale between cosmos and micro world. Anything complicated has to be made of huge numbers of atoms with many layers of structures: it's got to be very very big compared to an atom. On the other hand there's a limit because any structure that gets too big is crushed by gravity. You couldn't have a creature a mile high on the earth—even Galileo realized that. And something as big as a star or a planet is completely molded by gravity and no internal structures survive, so it's clear that complexity exists on this intermediate scale.

Looking forward to the next decade I expect development of the fundamental understanding of the Big Bang, I expect development in understanding the emergence and structure of the universe, using computer simulation observation, and I expect at least the beginnings of an integration between computer simulations, observations and biological thought in the quest to understand how planets formed and how they developed biospheres.


Cosmology has remained lively, and the focus my interest. It's not only developing fast, and of fundamental importance, but it's also one which has a positive and non-threatening public image. That makes it different from other high-profile sciences like genetics and nuclear science, about which there's public ambivalence. It's also one in which there is wide public interest. I'd derive less satisfaction from my research if I could only talk to a few fellow specialists about it. It's a bonus that there is a wide public which is interested in origins. Just as Darwinism has been since the 19th century, cosmology and fundamental physics are now part of public culture.

Darwin tried to understand how life evolved on this earth. I and other cosmologists try to set the entire earth into cosmic context—to trace the origin of the atoms that make it up, right back to a simple beginning in the Big Bang. There's public interest in how things began, was there a beginning, will the universe have an end, and so forth.

It's good for us as researchers to address a wider public. It makes us realize what the big questions are. What I mean by this is that in science the right methodology is often to focus on a  piece of the problem which you think you can solve. It's only cranks who try to solve the big problems at one go. If you ask a scientist what they're doing, they won't say trying to cure cancer or trying to understand the universe; they'll point at something very specific, progress is made by solving bite-sized problems one at a time. But the occupational risk for scientists is that even though that's the right methodology, they sometimes lose sight of the big picture. Members of a lay audience always ask the big questions, the important questions, and that helps us to remember that our piecemeal efforts are only worthwhile insofar as they're steps towards answering those big questions.

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