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SHOW 101 TRANSCRIPT
What Are the Grand Questions of Science?

HOW about a grand tour, not of the continents but of science? We seek truth, where it may change. We view the cosmic spectrum of science, the Big Picture--of the fundamental structure of matter and energy, the beginnings and ends of the universe, the global changes on our planet, the evolution of life, and the essence of brain and mind. What discoveries lie ahead? What surprises are in store? Grand science requires grand questions. We brought together five leading scientists and thinkers and asked them to make a list.

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PARTICIPANTS

Dr. Francisco Ayala, who is sometimes called the Renaissance man of evolutionary biology, is a geneticist and philosopher at the University of California at Irvine (UCI). For Francisco, biology poses the most interesting and diversified questions.

Dr. Patricia Churchland is a professor of philosophy at the University of California at San Diego (UCSD), where she focuses on neuroscience, the study of the brain. Her books include Neurophilosophy: Toward a Unified Science of Mind-Brain. Pat cautions that before we deal with the large questions of brain and mind, we need to understand how nerve cells work.

Timothy Ferris is an award-winning author, a commentator for National Public Radio, and a consultant to NASA on long-term space policy. His best-selling books include Coming of Age in the Milky Way and The Whole Shebang: A State-of-the-Universe(s) Report. Tim sees physics and astronomy, which together reach from the subatomic to the cosmological scale, as embracing the grand questions.

Dr. Steven Koonin is vice president and provost of Caltech, where he is a professor of theoretical physics. He has also written on subjects as diverse as Earth's atmosphere and the human genome. Steve explains how the process of science works and draws a distinction between questions of fundamental physics and those of biology. 

Dr. Neil de Grasse Tyson is the director of the Hayden Planetarium of the American Museum of Natural History, in New York, and the author of several popular books on astronomy, including Just Visiting This Planet. Neil shows how the fun of science is as much process as results--and that the answers we find often lead to new questions.

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ROBERT: Steve, as provost of Caltech, one of the world's great scientific institutions, you are responsible for overseeing all kinds of research. Do great questions drive great scientists? 

STEVE: Yes, they do. Science is about figuring out how the world works, and there are really two kinds of science. One is where you know the rules but have to figure out how they apply in specific situations. The other is where you try to figure out the rules themselves. In this second category there have been revolutions--such as thermodynamics, quantum mechanics, relativity, the genetic code--that change the whole game. My late colleague [Nobel Laureate] Dick Feynman used to say, "Once you know the rules, everything else is just chess." The great questions lie in figuring out the rules. 

ROBERT: Your own research ranges broadly from computational physics of atoms to global phenomena like the earth's magnetic field and the composition of the atmosphere. What drives you?

STEVE: Gee, what does drive me? Interesting questions, I think, and the possibility of being able to answer them. But you can't ask questions that are too far out there.

ROBERT: Neil, you're a public scientist: why are the grand questions of science important for the public to know about? And how important are they in the day-to-day conduct of science?

NEIL: First of all, few scientists ever have the privilege of addressing, much less answering, the grand questions of science, but these are the carrots, the intellectual carrots, that seduce people into wanting to do science in the first place. And these questions do keep you going throughout your career-long journey. But often the fun of doing science is the path you take along the way, the progressive exploration that gets you closer to the machinery of how the world works.

ROBERT: What happens to the ambitious aspirations of these idealistic young scientists?

NEIL: You learn that once you've solved one question, there's another on the far side of it. So don't be fooled by how close you seem. 

ROBERT: Tim, you've written a number of elegant and insightful books on astronomy. Why astronomy?

TIM: Well, it's perhaps the oldest science. Long before history began, people were looking up at the night sky--and until quite recently, of course, most people had access to the night sky on clear nights. The tremendous urbanization and lighting up of the Western world is a recent phenomenon, and it has really hampered amateur astronomy and ordinary people's appreciation of the wider universe. Astronomy was my original interest--after all, it's the science of everything there is, on the largest scale. 

ROBERT: Why do so many of the grand questions have to do with physics and astronomy? 

TIM: They have to do with physics because physics looks at the foundations and structure of matter, the very smallest things on the smallest scales, and with astronomy because astronomy looks at the structure of the universe, the very largest thing on the largest scale. Within this framework is every phenomenon that we know about and that we are. 

ROBERT: Francisco, Pat, how does that sit with you? Have physics and astronomy subsumed the bulk of the grand questions, or are these questions moving toward the life sciences?

FRANCISCO: Only after Darwin--after that major breakthrough in the nineteenth century--could we ask fundamental questions about biology. Before Darwin, there were no explanations of why birds had wings, say, or humans had lungs. These things were attributed to the Creator. Since Darwin's theory of evolution by natural selection, we have been able to ask all the important biological questions--questions about where we come from, why we function as we do, how we relate to one another. 

ROBERT: Aren't an increasing number of the grand questions biologically based?

FRANCISCO: Absolutely. With all due respect to physicists and astronomers, biological organisms are the most interesting and diversified phenomena in the world. That's why we study them. 

ROBERT: Pat, you're one of the leading thinkers about what's traditionally known as the mind-body problem. I'm revealing my bias here, but could you tell us why the brain and the mind are among the grand questions of science?

PAT: Two major questions need to be distinguished here. One has to do with whether psychological states--our mental life of remembering, thinking, creating--are really a subset of brain activity. And on that major question, although there are residual problems, I think most people agree that it's all only the brain--that there isn't anything in addition to the brain, such as a nonphysical soul.

ROBERT: Most people agree? Or most scientists agree? 

PAT: Scientists do, by and large. And I think that's the way the evidence stacks up now, in neuroscience. It's possible that there is a nonphysical soul, but it doesn't really look like that's the way things work. The other major question you need to ask, given that [materialist] framework, is, How do high-level psychological processes come about from basic neurophysiological effects? How do these brain cells, organized in this complex way, give rise to my watching something move, or seeing color, or smelling a rose. These are the kinds of questions that preoccupy me. 

ROBERT: Let's try enumerating the grand questions of science by category, from the most fundamental to the most complex. And let's start with physics. 

STEVE: There are several interesting questions at the forefront right now. One is that we have a picture of how the physical world is constructed at the most fundamental subatomic level. It's called the Standard Model and it includes quarks [the constituents of protons and neutrons, which themselves make up the nucleus of the atom], it includes electrons, it includes bosons [particles that carry the fundamental forces, or interactions]. And the question is, To what extent is this Standard Model valid? So far it has proved maddeningly valid. Everywhere we look to test it, it seems to be right. But it has some free parameters in it that we have to measure. We would like to know how many free parameters there are. What are those values? Are they all related in some way? And can we get them all into the Standard Model?

ROBERT: Tim, what are some quantum questions in physics? 

TIM: Physics at the beginning of the twenty-first century is composed of quantum physics and relativity. One problem is that they're not quite compatible. Another is that there are aspects of the quantum world that are very difficult--even confounding--to understand. Some physicists feel that these problems won't ever be of any functional importance. Others feel that through this keyhole there may be a great deal to be learned. If you look at the whole universe in quantum terms, it's interesting to think about light traveling vast distances over eons of time and then striking your eye and suddenly turning into something different--that is, into a kind of perception, or knowledge. And when we try to understand the two ends of this spectrum, the questions that naturally arise--and they're equally important--center on how the whole thing originated. How did the universe originate--and, completing the loop, how did human intelligence originate?

ROBERT: "Loop" is a good metaphor for thinking about these questions--better than the traditional hierarchies or levels. Francisco, I know physics is not your field, but what questions do you ask about physics? 

FRANCISCO: Not very many, because as a biologist I assume that the atoms are stable, the molecules react, and the laws of physics apply. And then I can start asking my kinds of questions--I don't have to know the details. 

ROBERT: I see. You don't need to reduce biology to physics to enable you to answer very sophisticated questions.

FRANCISCO: That's right.

STEVE: These are different kinds of questions. The biological questions deal with complexity, operate at a higher level. As an analogy, in order to build a computer I don't need to know the internal makeup of each of its parts--that is, the fundamental physics. But I do need to know how its constituents are interconnected and work together--that is, the engineering. 

ROBERT: Neil, talk about the implications of the Copernican revolution for the grand questions of astronomy.

NEIL: In the sixteenth century--just to remind you--Copernicus restored the sun to the center of the known universe, and that dislodged our perception of our planet as the center and ourselves as so important. The earth became merely one of a number of other planets in the solar system. And later we learned that the sun is not the center of the universe, either, but just one of hundreds of billions of stars in a galaxy, which is itself one of perhaps a hundred billion other galaxies. Each time we thought we were special, scientific discovery demonstrated that we are in fact not. Every step has led in this direction--we're ordinary. Maybe one day this message will no longer apply, but it seems to work at every step we take.

ROBERT: Is there a limit to this process of demotion?

NEIL: No, I don't think so. I think it will continue even to the very chemistry of our bodies. We're carbon-based life, and carbon is one of the most abundant elements in the universe, formed in the crucible of high-mass stars that explode and spill their guts across interstellar space, generating all the stuff that makes planets and life and people. This commonality is a testament to the universality of the laws of physics. If the laws of physics were one way here and another way there, or one way this minute and something else the next, we'd all be out of a job. We'd have nothing to study. 

ROBERT: Commonality being a fundamental principle of science.

NEIL: It's a fundamental principle, but not because we like it that way. Evidence throughout eons has demonstrated it. 

ROBERT: It seems that we've merged seamlessly from questions of physics to questions of astrophysics--from fundamental particles, in other words, to cosmology.

NEIL: And that trend will continue.

ROBERT: It's the trend of the past thirty years or so. You can't explain the origin of the universe without referring to elementary-particle physics and the forces that operate on these particles--and it's becoming increasingly difficult to do the reverse, that is, study the most fundamental properties of particle physics without referring to the origin of the universe.

STEVE: That's right. We can't get to the scales needed to explain fundamental physics unless we look back at the initial conditions of the Big Bang. We don't have accelerators powerful enough to generate the required energy. 

TIM: Biology and neuroscience are going to be increasingly embedded in these questions, too. Biology began, as it were, on a tabletop--on one planet existing in a wider context about which very little is known. I think the future of biology will involve looking at the environments on other planets and determining to what extent the way things are here on Earth are accidents and to what extent they could not have been otherwise.

FRANCISCO: Why would that be interesting? I'm much more interested in studying life on this planet. And I know that we're not accidents. So I'm not so interested in what is happening all over the universe. Not at first.

TIM: But wouldn't you be interested in knowing whether evolution, for instance, is a universal law or a law peculiar to this planet?

FRANCISCO: Well, I'm not particularly interested in that. I'm much more interested in evolutionary questions right here.
STEVE: If we discovered an instance of life on another planet--say that we found that life there had a different chemistry, different cell structure, different body structure--wouldn't that be extraordinarily interesting?

FRANCISCO: Oh, it would be interesting, but I have many more interesting questions about life right here on this planet. 

NEIL: But comparative studies can be critical. Take our study of the solar system: for the longest time the only planets we knew were the ones in our own system, so theorists came up with models that explained why, say, you have a big planet here, a small planet there, rings here, moons there. You construct your whole paradigm based on the example of one system. That can be extremely limiting. Whereas just by looking over the fence, you can find other examples--in my analogy, other solar systems--so that a whole new field of comparative planetary science is born.

FRANCISCO: But that's the difference precisely. You can't compare simple, inanimate systems like solar systems with complex, living organisms like human beings. I don't expect to find human beings, or any intelligent life, over the fence--anywhere else in the universe. That won't be repeated. I want to understand what's happening here; I get all my universes, so to speak--as many as I want for now--here on this planet. 

ROBERT: Let's stay with the universe. Neil, what's happening with the expansion of the universe, certainly one of the great questions of science?

NEIL: Well, we're expanding, and we've been expanding, and it looks now as though the expansion is a one-way trip. For decades, theorists felt that a philosophically attractive universe would be one in which we would expand and collapse and then expand again [in some infinite cycle], because that took away the worrisome issue of there being only one beginning to the universe. But it looks as if things are moving outward, never to reverse and come back into a Big Crunch. And it may well be that the universe is not just expanding but that its expansion is accelerating [i.e., the longer time goes on, the faster the flying apart becomes--though evidence is still equivocal and the question remains unresolved]. The temperature of the universe is dropping, the density of matter is diminishing, and it would seem that we're headed for what we call a thermal death, where everything falls to the same extremely cold temperature--close to absolute zero, which is the temperature at which all motion virtually stops.

ROBERT: Are you depressed about that?

NEIL: It's a few hundred billion years away.

ROBERT: Actually, cosmology is becoming even more complex. Tim, tell us about the theories of multi-universes and inflation. There's a whole new realm of reality out there. 

TIM: The original models of the Big Bang, after the expansion of the universe was first discovered [in 1929 by astronomer Edwin Hubble], lacked an explanation of why the universe should be expanding in the first place. The inflationary models contain physically plausible mechanisms that could have caused space itself to expand, which is indeed what seems to be happening in the actual universe that we inhabit. 

ROBERT: The inflationary model solves several problems inherent in the Big Bang, such as the horizon problem, the quandary that the universe appears the same in all directions even though light hasn't had enough time since the Big Bang to travel across the universe and link the horizons. 

TIM: In the various inflationary models, the universe began as a small bubble of space. These models are rather beautiful, and they seem to imply that the bubble occurred in pre-existing space of some sort. And this raises, to me, the marvelously stimulating notion of there being ensembles of many universes, of which ours is only one example. In that case, a question arises in cosmology similar to Jacques Monod's question about chance and necessity in biology: Which aspects of our universe are chance and which ones had to be the way they are because that was the only physically possible outcome?

ROBERT: And with regard to chance and necessity in biology, there are some questions about to be answered by the Human Genome Project: the massive, multiyear effort to sequence our DNA, the three billion chemical bases arranged into some hundred and forty thousand genes--the number of genes keeps changing. DNA is resident in the nucleus of virtually every cell of our bodies from where each gene--each working hereditary unit--determines an aspect of our physical mechanism.1 How is this enormous project faring at the moment?

{FOOTNOTE}1 The Human Genome Project, coordinated by the U.S. Department of Energy and the National Institutes of Health, is an international initiative to discover all the human genes (the human genome) and make them accessible for biological and medical study. A genome is all the DNA in an organism, including its genes. Genes are the functioning segments of the very long DNA molecule; they carry all information (code) for making all the proteins required by all organisms. These proteins determine specific biological functions, including how the organism appears, how its body metabolizes food or fights infection, what illnesses or defects it might have, and sometimes even how it behaves. DNA is made up of four similar chemicals (called bases and abbreviated A, T, C, and G) that are repeated, in different orders, millions or billions of times throughout a genome, depending on the species. The particular order of As, Ts, Cs, and Gs is what carries the information; the sequence is the code. This sequence underlies all of life's diversity, even determining whether an organism is human or another species such as yeast, rice, or fruit fly, all of which have their own genomes and are themselves the focus of genome projects. Human genes vary widely in length, often extending over thousands of bases, but only about ten percent of the three billion chemical bases of the human genome is known to include the protein-coding sequences of genes. The majority of base sequences, interspersed among the genes, are noncoding control regions, whose functions are regulatory (i.e., turning genes on or off), and other regions whose functions are obscure.

STEVE: We're getting the list of the parts--if you like--of the human genome. We'll have most of the sequence soon. But we also need to understand the configuration of all those parts, how they fit together and work together.2

{FOOTNOTE}2 The Human Genome Project estimated (at year end 1999) that the working draft sequence of the entire human genome would be ninety percent finished by mid 2000 and the final, high-quality sequence completed by 2003. It's become a race among competing scientific groups, accelerating the original timetable, so that the final map of the human genome--filling in the gaps--could come even sooner. 

FRANCISCO: The sequence of the genome will give us very interesting and important information, but this is only the beginning. The genome is a linearly organized molecule. Information is conveyed in the same way as in the sequence of letters in a sentence of English. You have a sentence, you read can it, but now you have to go from there to create the whole organism--that's where biology comes in. A human being, or any other kind of organism, is organized in four dimensions--the three spatial dimensions plus time. How an organism develops and changes over time is surely one of the grand questions.

ROBERT: Pat, what are some of the core questions of neuroscience?

PAT: The thing to remember about neuroscience is that we don't yet have what you might call an explanatory framework, and in this sense neuroscience really differs from physics, astronomy and even cell biology. Neuroscience is still very, very young. We don't have the strong, established paradigms within which the general explanations fit. Now, this makes brain research very exciting, but it also means that we can't expect from neuroscience the kinds of [coherent models] we can expect from physics.

ROBERT: What kinds of fundamental questions are we dealing with? Questions regarding cognition? Memory?

PAT: I like to think about the field in a slightly different way. Of course there are all those kinds of questions. But first you have to know what the basic structural units are. And it looks like neurons--the nerve cells in the brain--are those basic structural units. But there's a lot we don't really understand about a single nerve cell. So when we contemplate the larger questions--such as the nature of consciousness and the biological mechanisms for decision-making--we still have not satisfactorily answered the question of how individual neurons work. In particular, we don't know how neurons code information. There are a number of hypotheses; some of them look plausible and some have explanatory strength. But it's a fundamental question for which we have no answer. When you're thinking about the brain, you have to avoid going immediately to the grand, sexy questions and expecting good answers. It isn't going to be like that. Ultimately, I think we'll have an understanding of the neurobiological mechanisms for consciousness, for decision-making, and so on. But in the meantime we have to understand how individual neurons work and how they cooperate with other neurons. It's not a grand sexy question, but it is a grand question. 

ROBERT: Steve, are there any grand questions about our own planet Earth?

STEVE: Sure. For example, questions about the fluid earth--the ocean, the air, the various layers of the atmosphere. What is the extent of the natural variability of these systems? What causes that variability? What makes ice ages is one specific question we don't understand yet. Similarly, we don't understand what's going on in the deep oceans, which are an important component of the earth's atmospheric system. All this affects the long-term climate of the earth, which is obviously of great interest to us. 

TIM: We don't even know where the oceans came from.

STEVE: That's certainly true. I remember asking that question in third grade: Where did the water come from?

NEIL: It came from where everything comes from. We've had comets streaming throughout the solar system, and they've got tons of water in them. That's one way that the earth's oceans could have been brought here, though there are still unresolved problems with isotope ratios. But I beg to differ that questions related to Earth are in the category of grand questions, because Earth is just one planet. When I think of grand questions, I think of questions that apply everywhere, involving the future and evolution of the universe. 

ROBERT: If you had a massive glacier creeping down toward New York--

NEIL: Don't get me wrong. I love Earth--it's our home.

STEVE: Well, there are questions about Earth that are generic questions. Ice ages are an example because they elicit questions regarding the origin of planetary magnetic fields.

NEIL: Good, there you go. 

STEVE: Some planets have magnetic fields and others don't. The earth's magnetic field reverses about every hundred thousand years or something like that. We don't understand how that happens. So it's a grand question of sorts. But I also think that climate is a grand question--for one thing, because we really care about the answer. 

NEIL: I'd think of the climate question not so much as it applies to Earth, but how it's generalized to conditions on other planets. Why, for instance, has Jupiter's red spot survived for at least three hundred years?

STEVE: You may get very different answers on different planets. Planetary science is going to be like biology; there's a different answer in each system. 

NEIL: You hope not. But on the other hand, if some phenomenon on other planets requires a different explanation from that here on Earth, that's critical to know. 

ROBERT: Francisco, what are the grand questions in biology?

FRANCISCO: I'd say there are three. The ape-human transformation. The gene-soma [cell] transformation. And the brain-mind transformation. What I mean by the ape-human transformation is: Why is it that we are so similar to apes and yet something happened in our evolution to produce our minds and our culture. By the gene-soma transformation, as I touched on earlier, I mean, How does the linear information in the genetic code generate highly complex, multidimensional organisms, with innumerable parts and always changing. As for the brain-mind transformation, Pat [Churchland] can answer that one much better than I can.

NEIL: As you were talking, I was thinking that physics has counterparts to these deep transformation questions. For example, as we understand the laws of physics, there's a reversibility in the laws of motion in terms of collisions of molecules. Yet if a drop of ink falls into a glass of water, that ink doesn't reassemble itself into a drop. It's dissolved, never to return to the drop it once was. So things change as you go to different scales. These transitions from how things work at microscopic levels to how things work in their complex forms at macroscopic levels are fundamental.

STEVE: That is perhaps the pervasive character of all these grand questions. How do you go from small pieces to large phenomena? 

ROBERT: A stunning example is: How can a hundred billion neurons generate the grandeur of consciousness--or, in the vernacular, How can meat make mind? This is the first time in history when we can even begin to answer this question. 

PAT: There are a number of reasons why it took neuroscience a lot longer to get going than, say, astronomy. In astronomy, you could make certain fundamental observations with very simple devices, very simple technology--like a ground lens. In neuroscience, you need much more knowledge. You need to understand electricity; you need to understand cell biology; you have to have the technology to put something under a microscope and see all the tiny bits and pieces. If you want to understand neuron function, you need very advanced technology to probe these very, very tiny cells. And so we had only a sort of speculative psychology for a long time, and not much neuroscience, because other science and technology had to be in place first. We now see remarkable developments in the study of the brain, because the technology is coming on-line. But there are still fundamental things we haven't been able to do. For example, although imaging is a set of great new technologies, it still gives us only broad portraits. This picks up on what Steve [Koonin] said about going from small pieces to large phenomena--in this case, between what single cells [neurons] do and what [brain] imaging shows us. We have no technology for accessing this gap in function.

NEIL: As we know, physics has had a long string of greats, like Newton and Galileo, who laid a foundation for centuries of discoveries. Could it be that neuroscience needs a counterpart?

PAT: There was a lot of physics before Newton. In order to have great insight and great synthesis, you've got to have lots of bits and pieces, and that's especially true in neuroscience. We're seeing tremendous progress in neuroscience at all levels of organization. But ultimately we'll have some great figure or figures, I suppose, who will put it all together and tell us what the fundamental principles are. 

STEVE: You can't have Newton before you have Kepler.

PAT: You can't have Newton before you have Galileo. 

FRANCISCO: There's another issue here. We're never going to find a universal law or simple equation like f=ma [force equals mass times acceleration] for the human brain. We're going to need much more complex explanations.

TIM: How do you know we'll never find a Newtonian-level law for the function of the brain?

FRANCISCO: That's a very interesting question, because I never like to say "never" in science.

ROBERT: He does anyway.

FRANCISCO: It's the complexity.

STEVE: How do we describe complexity? A gas, for example, consists of billions of molecules--

FRANCISCO: It's not only complexity, it's the complexity of the brain. I can have simple laws to explain complexity, but how can I explain the brain?

STEVE: Ultimately we'll have simple laws to explain it.

NEIL: The solar system was complex, too, before its laws were discovered.

ROBERT: But the kind of complexity Francisco [Ayala] is talking about in the brain is orders of magnitude greater than that of planetary motion.

PAT: Here I think I do disagree. It simply depends on how things go in our study of the brain. At the moment, it's hard to see what the fundamental principles are going to be, if any. But I'm not so sure there aren't going to be fundamental principles. Bear in mind that before the discovery of the structure of DNA, many people said we'd never be able to get a fundamental principle that explained the inheritability of traits. 

FRANCISCO: But we've already discovered that. Biology has already had its Galileo and its Kepler. Mendel discovered the laws of inheritance--how genes act--before we even knew that DNA was the genetic material and how it acts.

PAT: We do have comparable discoveries in neuroscience--fundamental discoveries we can build on.

FRANCISCO: Yes. I think you're downplaying the brilliance of many great neurobiologists who have made many important discoveries.

TIM: I've been listening to this, and I'm struck by a thought that hadn't occurred to me before. Two of these great questions that we've been describing involve codes or inscriptions. One is genetics, which is simply a linear molecular code that manifests itself in complex, living organisms. It occurred to me that coding is also an issue of intelligence. In searching for extraterrestrial intelligence, for example, we define intelligence pragmatically--as the ability to send an encoded message. We're the only species on Earth, and probably in the history of the earth, that's had that ability. So our one species came about from an encoded system and now uses an encoded system to signal or discern intelligence. So these two great questions are quite closely related, aren't they? 

FRANCISCO: In the first case, genetics, we're using the concept of information metaphorically. In the second case, communications and language, we're talking about real information. The relationship between the genetic code and the organism--what I've called the gene-soma question--is really a chicken-and-egg question. 

TIM: There's also a case at the intermediate level. How is information encoded in the brain? How do our synapses "remember," for example?

FRANCISCO: Here's what I mean by the chicken-egg question: If you put the DNA into the world all by itself, it's never going to produce a human being, not even the tiniest insect. To activate the DNA, you need the information provided by the mother in the egg.

TIM: All codes are context determined. 

FRANCISCO: That's right, and in this particular case calling DNA a code is purely metaphor.

ROBERT: Some physicists claim that information is more than metaphor--that it's actually more fundamental than matter or energy. But let's switch to practical questions. What are the grand questions of science that have practical applications? 

STEVE: About fifteen years ago, people discovered a new class of superconductors--high-temperature superconductors--with all sorts of interesting applications: everything from better MRI [Magnetic Resonance Imaging] machines to faster trains to more efficient power plants to better stereo speakers. And we still don't understand how these superconductors work, or what the highest temperatures can be. Another potentially practical area is stable atoms with superheavy nuclei. People have hypothesized that there could be nuclei with charge of about 114, stable and heavier than any of the known elements. Do they exist, and if so, are there interesting applications?

ROBERT: How about quantum computing, where the physics is different from digital computing. In digital computers, the so-called logic elements are bits, which can be in one of two states, either on or off. But the logic elements in quantum computers are something called qubits, which can be in both states at the same time? 

STEVE: That's right. The superposition principle of quantum mechanics allows a quantum computer to be in many states at once--at least until you ask it for the answer--and therefore it can explore a tremendously large set of solutions. 

ROBERT: Just how much more powerful could a quantum computer be?

STEVE: Well, we already know that quantum computers can in principle solve problems that aren't solvable by digital computers. Among these are problems whose difficulty increases rapidly with problem size, such as factoring large numbers. 

ROBERT: How about potential applications?

STEVE: The factoring I just mentioned is important in encrypting data to provide security. Theorists have produced quantum circuits for this task and also for looking up entries in a table. However, you should realize that these applications will require dealing with hundreds of qubits to be useful, and so far it's an experimental triumph to get just two qubits to work. The major task facing the field is finding the right quantum system that can be rigged to compute, whether it be atoms, electrons, nuclear spins, or something else. Dealing with the inevitable imperfections in a real system is also going to be a major challenge. But I think it's something that's going to happen in the next few decades.

ROBERT: What about the prospects of biological computing, using the chemical bases of DNA molecules as logic elements for the massive parallel processing of information?

STEVE: We've seen two demonstrations already of DNA computing. One is where all possible solutions to a problem were encoded in DNA molecules, and then chemical techniques were used to fish out the correct one from the test tube. A second is where small, specially constructed DNA molecules were induced to self-assemble into a large structure embodying the solution. While both of these demonstrations are extraordinarily clever and provocative, they run afoul of the fact that you can put only so much DNA into a reasonable volume of liquid. So I think DNA-based computing, like quantum computing, will be a niche technology. However, there's a very interesting potential application of the self-assembly of DNA. That is, you can induce DNA to self-assemble into a three-dimensional scaffolding, and that structure can then be turned into wires and electronic elements by suitable chemistry. So we'll soon have the ability to assemble 3-D circuits [circuits built vertically upward from the surface of a microchip] on the tiniest scale.

ROBERT: How do you see the development of computers and computation power in the new millennium?

STEVE: Obviously, we're going to ride silicon and Moore's Law [i.e., the storage capacity of a microchip doubles about every eighteen months] for all they're worth--probably for another ten to fifteen years for a factor [gain] of five hundred to a thousandfold. Important steps will be ever finer chip features, although there are fundamental limits there, and some exploitation of the third dimension. There are also new physical phenomena to explore, including the spin degrees of freedom in semiconductors.

ROBERT: And beyond that sort of obvious evolution?

STEVE: There will be increasingly broad searches for new substrates to make computers. Bucky tubes and Bucky balls [complex molecular assemblies composed of carbon-based hexagonal structures, also known as fullerenes, for their resemblance to the geodesic domes designed by the visionary architect R. Buckminster Fuller], individual organic molecules, quantum dots, and other devices might let us make smaller and faster computers. And even farther out would be ways to induce biological systems to compute. We know that information flow within a cell is important. Suppose we could somehow encode a problem in the chemicals of a bacterium and then let the bacterium reproduce under the appropriate selection pressure to evolve toward the solution. The possibility has already been demonstrated using artificial digital organisms, but we don't know how to do it with living organisms. Then, apart from the hardware, there's the very real challenge of learning how to exploit all this power: with the best algorithms, the right sort of storage and visualization, high-speed communication, usable software, and so on. Using computers effectively requires a lot more than just having great hardware.

TIM: Quantum computing is a possibility. Biological computing is also an interesting possibility. And if you take seriously the idea that the brain is a computer--and I'm not sure I do--it's by far the best computer we've ever encountered. So why not try to simulate it?

ROBERT: Pat, what do you see out there in the medical world, particularly in neuroscience? 

PAT: There are a number of diseases we're working on but which are still without a cure. One, of course, is Alzheimer's. And there are the various addictions, such as alcohol and drugs. It's also very important to get to the bottom of schizophrenia; roughly one percent of the population has a schizophrenic episode at some point. I think the practical implications of advances in neuroscience are going to be tremendous. But much more work needs to be done.

ROBERT: What needs to be done now is to ask a final question. If each of you could be given the absolute answer to one grand question, but only one, which one would you want it to be?

STEVE: How did life begin? Is there life elsewhere in the universe? 

TIM: How did intelligence originate? Because until I know that, I don't know whether Francisco [Ayala] is right in assuming that intelligence is rare in the cosmos.

FRANCISCO: Pat's sexy question: How is the brain-mind transformation effected? How, out of all these neurons, with their electrical signals and chemical flows, do we get a mind that can think, write poetry, appreciate music. 

PAT: Francisco has stolen my question. Out of meat, how do you get thought? That's the grandest question. 

NEIL: There are some grand questions on which I don't want to risk wasting my allotted opportunity, because they may be dead ends. But one that isn't a dead end is, What is the nature and what are the properties of dark matter in the universe? Dark matter is ubiquitous--there's more of it than all other matter put together--and yet we're in a state of complete ignorance about it. We know it's there, because its gravity manifests itself, but we know nothing else about it. Dark matter is the ultimate tangible frontier. 


ROBERT: CONCLUDING COMMENT

THE grand questions of science are compelling and overarching, awesome and exhausting; they provoke our curiosity, creativity, intellectual rigor, speculation, and even fantasy. They embrace subatomic structure and multi-universal inflation; the enormous diversity of biology; the prodigious capabilities of the human brain, the most complex organization of matter known; and the marvel of the human mind, creator of art and science and seeker of purpose and destiny. The position of our species in the universe is oddly extreme. On the one hand, humankind seems completely meaningless, an insignificant accident on an inconsequential galactic outpost among billions of galaxies; on the other, the universe is, to some thinkers and in some sense, human-centered--something the ancients thought obvious and we moderns think ancient. It's thrilling to skim the bits and pieces of heroic thinking; it puts one's own life into perspective. As for my own favorite questions, I'll pick two. First, what is the extent of reality--are there multiple universes? Second, can everything in the mind be explained by something in the brain? Whether the universe is grand design or random accident, our investigation of it amounts to an imperative; from consciousness to cosmology, our instinct is to get closer to truth.

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