All about strings: An interview with Leonard Susskind

Leonard Susskind

Leonard Susskind

Leonard Susskind is considered one of the fathers of string theory in physics. He is the Felix Bloch Professor of Theoretical Physics at Stanford University and Director of the Stanford Institute of Theoretical Physics.This is an edited transcript of an interview with Leonard Susskind (Stanford 13/04/2004)

GZ: What are the big questions in physics today?
LS: The connection between cosmology, gravitation, quantum mechanics and string theory (if it turns out to be the right theory which is probably). For me these are the central questions. Of course there are questions which divide the universe into before year 2000 and after year 2000. There are questions left over from the twentieth century. The questions from the twentieth century are how we understand the pattern of elementary particles and so forth, how we understand what’ s called the Standard Model, how does it fit into something bigger and more complete.
Under 21st century physics I would classify questions that have to do with the structure of universe, as well as the origin of our laws of nature, our laws of physics.

GZ: Could string theory be the “theory of everything” and give all the answers?
LS: I dislike the term “theory of everything” and I would never use it myself and if knew who had said it first I would shoot him. It’s an inflammatory term and all kinds of people correctly say that it is not a theory of everything. It doesn’t explain how the brain works and so it’s a term which I would not use. If it is a theory which can, at some point, explain the origin of the universe and the spectrum of elementary particles and so forth, it remains to be seen. My feeling is that there’s probably only one quantum theory of gravity and string theory appears to be a part of that theory of gravity.
What we are discovering about string theory is very different from what we had expected and hoped for. The original hope of string theory was that it would provide an absolutely unique set of answers to the questions such as: what is the particles’ spectrum, what are the masses of particles. It would have been a very elegant answer, a beautiful mathematical answer and extremely unique. Unique in that we would find that, basically, the world could not be any other way that the way it is. That was the hope. The reality is extremely different. The reality is that the more we study of the theory, the more possible kinds of things we discover it can describe. We discover it’s a theory with a vast number of solutions. We simply find that there are enormous numbers of possible worlds that string theory can describe.

GZ:String theory has often been called a “revolution in physics”…
LS: The word revolution has been tremendously overused. Super and revolution are the most overused words in physics. Everything is a revolution. Is string theory a revolution? We don’t know yet. I think we don’t know what string theory is yet. I think we’ve made very wrong guesses about what string theory will do for us. I think we got it completely wrong. We thought it would give us a unique theory of the elementary particles. Instead it’s giving us perhaps as many as 10500 different possibilities of what the universe could be like. This is very puzzling. What do we make out of it? Do we just randomly pick one of these possible universes? Or all of them are important? What’s going on? My own view for some time now, is that in an inflationary context you could have a patch of this universe, a patch of that, a patch of whatever else is possible. In string theory it looks like 10500 possibilities are possible, each with its own set of particles, set of interactions. My guess is that the universe is just exceedingly big, full of tremendous amount of diversity. All these different possibilities materialize at some place. We simply live where is possible to live, in that part of this giant structure which is not totally hostile or lethal to our existence.

GZ: String theory has captured the public imagination because it refers to hidden dimensions. Of course, science fiction stories have made a lot of hidden dimensions. Why do we need so many extra dimensions to explain nature?
LS: Wish I could give you a simple mathematical explanation, for I’m afraid nobody can explain it simply otherwise. It‘s a very complicated theory which fits together in a consistent way only if the number of dimensions are ten or eleven. Why does physics need them? Elementary particles in the ordinary view of things are point particles. A point can’t have many, many properties. A point is too simple to have properties. However, we know that elementary particles have a lot of properties. They have spin, they have electric charge, they have something called isotopic spin, they have a quantum number called color – it’s not got anything to do with ordinary color – they have generations that they belong to, there are whole catalogs of different kinds of quantum numbers, of different kinds of properties that quarks, electrons, netrinos, or photons have. It sounds unreasonable for a point to have that structure. So the feeling most of us have is that, at some level, if you look deeply enough into things, you‘ll discover that particles aren’t points. That they must have all kinds of internal machinery that gives them these properties. One of those machineries, one of the ingredients into understanding what the quantum numbers of particles are, is the idea of higher dimensions. I‘ll give you an example. The simplest and oldest theory of higher dimensions is called the Kaluza theory. It was invented by Kaluza in 1917. Einstein liked it very much. It postulated one extra dimension, i.e. a particle in the extra dimension could be regarded as a little circular dimension. The idea of Kaluza theory is that the particle can move not only in the usual three directions of space but it can also move around in this extra dimension. Well, the particle which moves around in the extra dimension is different than one that moves differently in the extra dimension. The amount of speed that is going in the extra dimension as well as the direction it goes matter a lot. What is this new option corresponds to? It corresponds to the electric charge of the particle in Kaluza’s theory. So, electric charge becomes motion in another direction, in a new direction. What’s going on now is that these extra directions – all of them – correspond in various kinds of ways to the extra properties that these points have. So I wouldn’t say that we needed the extra dimensions, but we needed the kind of structure, the kind of complexity in space that could explain why these other degrees of freedom are there.

GZ: Skeptics say that string theory will forever remain outside the realm of real science, because it’s not experimentally falsifiable.

LS: I would simply dismiss these people for lack of imagination. There are all these people who are constantly pontificating of what science is and what science isn’t. These people lack of imagination. I also lack of imagination but I have a lot of imagination to know that I lack of imagination. We do not know what people can do in the future. We do not know what the human intelligence is capable of collectively. True, we are in a new course of exploration s studying extremely remote things which are very, very difficult to establish experimentally. But we should not abandon our course.GZ: Let me take you back to what we discussed before about string theory predicting up to 10500 different possible universes. Is this perhaps an answer to the paradox that we live in a universe so finely-tuned. Is this the answer to the Anthropic principle?
LS: That may be. My view is that the fine-tuning of the universe, particularly with regards to the cosmological constant, is so exceptional that we can no longer ignore it. Nevertheless, we have to ask whether the Anthropic principle is really serious business. Different people mean different things by the anthropic principle. Some give a religious depth to that thing, that the Almighty created the universe for no other purpose than people to live there. That’s one theory to which I don’t subscribe. I think it’s the duty of physicists and scientists to take that theory only as an absolutely last resort, when everything else fails. Other people think it’s part of the weirdness of quantum mechanics that somehow we live in the one place we can.
My view is a little different. It’s similar to asking why we live on a planet which is so finely-tuned. Our planet is at just the right distance from the sun so that we do not get boiled or frozen. That’s a very small window of opportunity, it’s a fine tuning. To find the reason why this is so, you need at least two things: a set of very large alternative possibilities and a cosmology which creates all of these different possibilities. So, it wouldn’t be enough to know that the “planet equation” – whatever it is – has many, many solutions with different values of, say, the “right temperature”. I also want to know that the surrounding universe grew and expanded creating lots of planets. Those two ingredients make sense out of this anthropic idea. One, that the theory, whatever it is, has so many solutions that even though it takes a very fine tuning for life, there will still be enough other solutions, so that statistically there will be one. And that, whatever the cosmology of the universe is, it creates always different possibilities some place.GZ: How about string theory then. Does it fit your two requirements for an explanation?
LS: I think that string theory provides us with a space of enormous possibilities. By involving so many mechanisms put together in various combinations the number of possible universe is 10500or something. We don’t what the number is, but it’s vast. The other thing we need is something like Linde’s and Lincoln’s theory of eternal inflation, where inflation takes place constantly and spins off different environments. Their ideas seem to me to be very, very reasonable, that the universe expands to something enormously big and it creates patches of all different kinds of what Alan Guth calls “pocket-universes”.GZ: Could we ever find if that is true?
LS: For the moment it looks impossible because of the horizon problem. Our world has a horizon that we can not see beyond. Presumably these other worlds are behind this horizon. One of the things we’ve learnt from thinking about black holes in the context of string theory, is that at quantum level the horizon is not really a barrier to knowledge. What goes on outside the horizon is also equally well described by the Hawking radiation of the black hole. I suspect that cosmic horizons are scrambled in complicated ways. Cosmic microwave background, which is light Hawking radiation, has this information in it. Can anybody ever extracted it? Certainly not with experimental tools currently available. But as I said never say never. We don’t know what the limits of imagination, or the limits of intelligence, are and that’s something for the future to do. Young smart physicists want to be explorers. They want to explore those things which everybody else says are impossible.GZ: The LHC is underway and will soon start experiments for the Higgs particle . Will they find it?
LS: I think so. I don’t see any other good alternative.

GZ: So the LHC is money worth spent!
LS: Well, yes, whether we find the Higg’s particle or not. If we find it’s there, that’s wonderful and confirms everything we knew. If it’s not there, it’s even more radical and money will have been even better spent. It will mean that we have been thinking wrong about physics for thirty years now.

GZ: Is time is an illusion?
LS:Space is an illusion. You are an illusion.

GZ:This sounds very Buddhist to me.
LS:Well, physicists don’t think that way because it’s not a useful way to think. We can measure time, just like as we can measure space, just like we can measure electrons. So why pick on time as being an illusion? Everything is an illusion in that view. But it’s not a useful view for a physicist. If you can measure it, if you can describe it, then we regard it as real.

GZ: Let me press this point of illusion a little further. Quantum mechanics introduces the observer into the very fabric in reality. Somehow if you take observers out, if you take consciousness out, “reality” ceases to exist. Does the universe exist when we do not observe it?
LS: I’m not a philosopher and I’m trying not to be philosophical. I’m trying to be more practical. Let’s see…Ask me the question again.

GZ: Is there something that we can call extended reality, a reality outside our perception? Or are we constantly creating reality through our measurements or our observations?
LS: We don’t really know how to understand the world of quantum mechanics. We know how to understand one special set of circumstances, where you can clearly separate the world in observer and system.
But the real world is not like that. We the observers are always part of the system. In the context of the laboratory we can usually make some separations. We cannot make that separation about cosmology of the universe. We are part of it. We influence it. So we do not really understand how to think about a system when we are a part of it, because of quantum mechanics. A very good friend goes so far as to say that he doesn’t think that quantum mechanics is complete because of this. And he thinks underlying the quantum mechanics is something much more deterministic. Most physicists think it’s a screwy idea. My answer is I don’t know.

GZ: When we talk about physics, when we talk about reality, we usually talk about energy, talk about matter, interactions between particles and fields etc. Let me for a moment suggest to you that the universe is not like that at all, the universe is made out of bits and information. Wolfram wrote a book about cellular automata which made quite of sensation. Could you believe in Matrix world? Could the universe be made out of bits, at an elementary level?
LS: Yes I think that it is made out of bits. It is nothing but information .

GZ: Could this notion change our physics?
LS: No, it can explain our physics. With respect to Wolfram, I’ m a physicist who thinks Wolfram’s ideas are interesting. But keep in mind that Wolfram’s ideas have no place for quantum mechanics. And the world is quantum mechanical. Wolfram believes that the world is cellular automata. But he knows that cellular automata are not quantum mechanical. Quantum mechanics has to come from somewhere. Where does it come from I don’t know. So I would say, until you can understand why the world is quantum mechanical, to say that it’s made of cellular automata is servicing a point. No quantum mechanics no cigar.

GZ: Einstein once said that the most inexplicable thing about this universe is that we can explain it. Are we now reaching the limits of our cognitive abilities? Do you believe that there are cognitive limitations to the human mind?
LS: Sure there are limitations. The human mind can not have more bits of information than the whole universe has. There are limitations to the human abilities in general. I would have bet anything on that no human being can play six musical instruments at the same time. I would have bet very much that nobody can jump as high as Michael Jordan. It turns out that the ranges of people have in the very, very far parts of the distribution are so amazing that nobody would have guess that they were possible. When people say such things as we’re reaching the limits, what they really mean is that I ´m reaching my limit. When they say they can’t conceive of anybody solving a certain problem what they really mean is that they can conceive of themselves solving this problem. The limits are probably way beyond what we imagine. They always are. The danger in trying to predict the limits of human abilities is always going in the wrong direction. It’s much more likely to underestimate than to overestimate. As long as it’s physically possible, as long as it doesn’t violate the laws of nature, it means there’s a possibility that human beings can do it. Forget individuals. Collectively human beings have such a diversity of different kinds or ways of thinking, they have the flexibility to be able to bend their own way of thinking about new things. We simply don’t know, but I would guess that when we try to estimate these things we ‘re in much more danger of underestimating to what people can do than overestimate it.

GZ: As we expand our knowledge of the cosmos through our physics, if we ever reach points that we don’t really understand and we can not possibly falsify, then are we in a danger that science, physics can regresses to religion?
LS: There is such a danger. So, on one hand there is such a danger and in the other hand I also say that you are also in danger of underestimating what people will be able to do in the future. Will they be able to do experiments that now seem to be so completely out of this world that they seem totally impossible? I‘ll give you two examples. The first is the inflationary theory of the universe. Everybody who saw that the first time said “well, that’s very nice Alan Guth, but your own admission of the inflation of the universe wipes out any evidence of itself. Nobody will ever be able to make science out of it”. That’s what everybody said, including Alan. Nobody expected that within twenty-five years people would figure out how to confirm observationally that the inflation theory was right. But it happened. I’ll give you another example. I can easily imagine people telling Darwin “nice theory Charles, but the only way to confirm it will be to go back a billion years and see what’s going on, and that’s simply impossible”. Well, it took a hundred years to make science out of evolutionary theory. It took a hundred years for people to get enough knowledge about biochemistry and genetics, to watch microorganisms evolve. It took a hundred years but it happened. And as I said the two dangers are, falling into a trap of t faith-based physics, but also giving up because it looks too hard.

GZ: Apart from technological development making life more comfortable what is the role of science in the 21st century? With regards to politics, society and perhaps ideologically. Does science play a role in modern world of religious conflict, fanaticism and lack of rationality?
LS: To a certain extent I think physicists have been the keepers of the truth. A case of point would be the Soviet Union during the dark days when the keepers of the truth were physicists, people like Zakharof and Orlof. They were people who simply believed in the concept of the truth. You know what’s happened to the concept of the truth in American society? It’s been replaced by advertising! All kinds of things which tend to make irrelevant to what’s true and what’s not true. Scientists in general are people who recognize what it means for something to be true. They are people who will question when something it’s not true. And their whole mental make up, their whole ideological basis, has to do with finding the truth. That’s necessary for preserving society.

GZ: So you are not a postmodernist?

LS: Postmodernism has some truth but it has been carried too far. It is true that the way humans think about the laws of nature, the words that we use to explain things, are dependent on culture and so forth. When new scientific ideas come into the front a lot of the argument about them tends to be dominated about the language that we should use to describe them. But, eventually, through some filter, what comes out of the other end is pretty much independent of the specific mentalities of the people who discovered it. And so yes, I believe there is real truth in the bottom of all of it, and it’s also true that the language we use to describe things depends on culture. So, that was a good idea, it was an important idea but it got carried too far when it said that there’s no such thing as objective truth.
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Interview with Jean-Marie Lehn, Nobel Laureate in Chemisty (in Greek)

Jean Marie Lehn

Jean Marie Lehn

This is an edited transcript of an Interview of Jean-Marie Lehn taken by George Zarkadakis in Athens on 3/05/2006)

Ο Jean-Marie Lehn γεννήθηκε στη μεσαιωνική πόλη Rosheim της Γαλλίας το 1938 και στα νεανικά του χρόνια αμφιταλαντεύτηκε να επιλέξει ανάμεσα σε πανεπιστημιακές σπουδές στη φιλοσοφία ή στη χημεία. Τελικά επέλεξε τη δεύτερη και το 1987 κέρδισε το Βραβείο Νόμπελ Χημείας για την έρευνά του στη μοριακή αναγνώριση, δηλαδή τον τρόπο που ένα μόριο-δέκτης εκλεκτικά αναγνωρίζει και προσδένεται σε ένα υπόστρωμα. Σήμερα ο Jean Mari-Lehn είναι Διευθυντής του Εργαστηρίου Υπερμοριακής Χημείας, στο Ινστιτούτο Επιστημών και Υπερμοριακής Μηχανικής του Στρασβούργου (ISIS).

ΓΖ: Τι είναι η ζωή;
L: Δεν υπάρχει μεμονωμένη χημική ουσία που να μπορεί να θεωρηθεί έμβιο ον. Το ζήτημα είναι ποια, ποιο είναι το όριο πέρα από το οποίο ξεκινά αυτό που λέμε ζωή. Η απάντηση είναι οι ιοί. Οι ιοί είναι σαν ένα σακούλι γεμάτο πρωτείνες, το οποίο ωστόσο διαθέτει γονιδίωμα. Όταν ο ιός είναι απομονωμένος θεωρείται νεκρός γιατί πολύ απλά δεν μπορεί να πολλαπλασιαστεί από μόνος του. Όταν όμως προσβάλει κάποιο κύτταρο παίρνει από αυτό τα ένζυμα που είναι απαραίτητα για τον πολλαπλασιασμό και αναπαράγει τον εαυτό του. Τότε θεωρείται ως μορφή ζωής. Μόλις όμως αναπαραχθεί και βγει από το κύτταρο, αυτόματα χάνει την ικανότητα αναπαραγωγής και θεωρείται απλά ως ένα σύνολο μορίων.

ΓΖ: Η ζωή είναι πληροφορία;
L: Το γονιδίωμα είναι η πληροφορία. Ο ιός έχει μια δεδομένη δομή. Για να αναπαραχθεί αυτή η δομή, δηλαδή για να «ξαναφτιαχτεί» ο ιός, χρειάζεται η πληροφορία του γονιδιώματος. Στο DNA, για παράδειγμα, η πληροφορία είναι αποθηκευμένη με τη μορφή τεσσάρων γραμμάτων. Η ακολουθία και οι αλληλεπιδράσεις μεταξύ των γραμμάτων είναι αυτό που λέμε γονιδίωμα.

ΓΖ: Η εξέλιξη είναι μονόδρομος;
L: Όχι, πολλές διαδρομές. Οι προβιοτικοί χημικοί πιθανολογούν ότι η ζωή προχώρησε παράλληλα σε πολλές διαδρομές. Αυτό που συνέβη όμως ήταν το εξής: όταν μια μορφή ζωής ήταν επιτυχημένη συνέχιζε να εξελίσσεται Αντίθετα οι υπόλοιπες σταδιακά εξαφανίστηκαν. Αν η ζωή βρεθεί σε εξελικτικό αδιέξοδο δεν μπορεί να γυρίσει προς τα πίσω, προς το σημείο εκκίνησης, και να διαλέξει άλλο δρόμο εξέλιξης. Έτσι μπορούμε να πούμε η ζωή ήταν ένας συνδυασμός άτακτης και αυτοβελτιούμενης εξέλιξης.

ΓΖ: Τι είναι η «υπερμοριακή χημεία»;
L: Η υπερομοριακή χημεία ασχολείται όχι με τα μόρια των χημικών ενώσεων, αλλά με τις αλληλεπιδράσεις μεταξύ των μορίων μέσα στις χημικές ενώσεις. Η υπερομοριακή χημεία είναι η χημεία που μελετά με ποιες διαδικασίες τα μόρια αναγνωρίζονται μεταξύ τους και γιατί δημιουργούν επιλεκτικούς χημικούς δεσμούς.

ΓΖ: Ποιες είναι οι μεγάλες προκλήσεις της χημείας τον 21ο αιώνα;
L: Αυτό που προσωπικά με ενδιαφέρει είναι η έρευνα γύρω από την οργάνωση της ύλης, η μετάβαση από ένα μεμονωμένο μόριο σε πολύπλοκες μορφές ύλης. Ένας άλλος ενδιαφέρων τομέας της χημείας είναι η κατάλυση, δηλαδή το πώς θα δημιουργήσουμε χημικές αντιδράσεις οι οποίες θα είναι πιο αποτελεσματικές και ταυτόχρονα θα απαιτούν λιγότερη ενέργεια. Επίσης η νανοτεχνολογία, η σύμπραξη χημείας και φυσικής, και η προσπάθεια να ελέγξουμε τις κινήσεις των μορίων ώστε να κατασκευάσουμε μικρομηχανές με μοριακό μέγεθος.

ΓΖ: Πολλοί άνθρωποι θεωρούν τη χημεία συνώνυμη με τη χημική ρύπανση…
L: Καταρχήν να ξεκαθαρίσουμε ότι παράγουμε χημικές ουσίες επειδή ο κόσμος τις χρειάζεται. Αν για παράδειγμα οι άνθρωποι δεν οδηγούσαν αυτοκίνητα δεν θα είχαμε τόση πολύ ρύπανση. Οπότε ας σταματήσουμε να χρησιμοποιούμε το αυτοκίνητό μας αλόγιστα. Αν δεν θέλουμε να το κάνουμε αυτό, τότε πρέπει να δεχτούμε τις συνέπειες των πράξεών μας, δηλαδή την ατμοσφαιρική ρύπανση. Επιπλέον η χημεία ενοχλεί επειδή μυρίζει. Πράγματι, οι άνθρωποι είμαστε ζώα και η αίσθηση της όσφρησης είναι πολύ σημαντική για τα ζώα. Για παράδειγμα, αν βλέπαμε ένα κατακόκκινο σύννεφο το οποίο δεν ξέραμε ότι ήταν τοξικό και δεν μπορούσαμε να το μυρίσουμε, τότε όχι μόνο δεν θα μας ενοχλούσε αλλά μάλλον θα μας γοήτευε κιόλας. Πάντως τα τελευταία 30 χρόνια έχει γίνει μεγάλη πρόοδος στον τομέα της ρύπανσης. Και μπορεί να γίνει ακόμα περισσότερη αρκεί να είμαστε πρόθυμοι να πληρώσουμε. Ένα εργοστάσιο που θα εγκαταστήσει φίλτρα και θα χρησιμοποιήσει αντιρρυπαντική τεχνολογία θα πρέπει να ξοδέψει πολλά χρήματα. Προφανώς το προϊόν που θα βγαίνει από τη γραμμή παραγωγής θα είναι ελαφρώς ακριβότερο και το κόστος αυτό θα μετακυληθεί στον πελάτη. Σε κάθε περίπτωση όμως πρέπει να ξεκαθαρίσουμε ότι με όρους τοξικότητας η φύση παράγει πολύ πιο τοξικές ουσίες απ’ ότι ο άνθρωπος. Για παράδειγμα, υπάρχουν φυτά που χρησιμοποιούμε, μετά από κατεργασία βέβαια, ως φάρμακα και τα οποία είναι τόσο τοξικά ώστε στη φύση είναι άκρως δηλητηριώδη.

ΓΖ: Βλέπετε να αλλάζει ο χάρτης της επιστήμης με την είσοδο νέων «παικτών», όπως η Κίνα ή η Ινδία;
L: Η επιστήμη είναι επιστήμη. Δεν έχει σημασία αν γίνεται στην Ανταρκτική, στην Αλάσκα ή στην Νότια Αμερική. Αυτό που ίσως αλλάξει είναι το επίκεντρο των επιστημονικών ανακαλύψεων. Η Κίνα και η Ινδία διαθέτουν λαμπρούς επιστήμονες και σίγουρα θα καταλάβουν δεσπόζουσα θέση στην παγκόσμια επιστημονική κοινότητα. Αναπόφευκτα η Ευρώπη θα περάσει σε δεύτερη μοίρα εκτός αν προσπαθήσουμε πολύ σκληρά. Αν δεν φτιάξουμε το σύστημα μας, θα μετατραπούμε απλά σε τουριστικό προορισμό και τίποτα παραπάνω. Επιπλέον πιστεύω ότι αν και στην Ευρώπη εδραιώθηκε ο ορθολογισμός, δεν έχουμε καταφέρει να τον περάσουμε στην κοινωνία. Για παράδειγμα πληροφορήθηκα ότι στην Ελλάδα δεν διδάσκεται η θεωρία της εξέλιξης των ειδών στα σχολεία. Αν αυτό ισχύει τότε υπάρχει πρόβλημα. Αντίστοιχα φοβάμαι την άνοδο του φονταμεταλισμού στην Ευρώπη. Η εντύπωση μου είναι ότι οι Κινέζοι εξαιτίας της κουλτούρας τους δεν έχουν ισχυρό θρησκευτικό φονταμεταλισμό, αντίθετα είναι πιο πρακτικοί.

ΓΖ: Πώς θα εξηγούσατε την αβεβαιότητα των επιστημονικών ανακαλύψεων σε ένα κοινό που αναζητά τη βεβαιότητα;
L: Οι άνθρωποι οδηγούν το αυτοκίνητό τους και πιστεύουν ότι σίγουρα θα φτάσουν στον προορισμό τους. Ξαφνικά όμως ένα δέντρο πέφτει στο δρόμο ή σκάει το λάστιχο και τότε… Η βεβαιότητα, το 100%, δεν υπάρχει πουθενά στη φύση γιατί λοιπόν να το απαιτούμε από την επιστήμη;

Interview with Christof Koch

Christof Koch

Christof Koch

(Christof Koch is one of the most eminent researchers in consciousness studies and a collaborator of the late Nobel laureate Francis Crick. This is an edited transcript of an interview of Christof Koch, taken by George Zarkadakis on April 2004, in Tucson, AZ)

GZ: How would you define the problem of consciousness?

CK: The problem is very difficult to define. We are conscious right now, when you ´re talking to me you are conscious, you can hear things, you can see things, you can remember things, that´ s what we mean by consciousness. It becomes very difficult to define it in more rigorous ways. There is an objective aspect, a feeling aspect, the feeling of being hungry, the feeling of seeing something, of seeing a bird, the feeling of remembering something, because of our conscious sensations. There are many things going in our body that don´ t involve consciousness. I can move my eyes, I can drive a car, I can climb, I can run, all those things bypass consciousness. Where’s the difference in between? To define it right now is not possible. However it is not necessary to define everything rigorously in order to advance. Historically, definitions only happen by hindsight. If you see the history of biology – genes for example – even today it’s not easy to define what’s a gene.GZ: I see parallels between the difficulty of defining life and consciousness. Is there another parallel between the two that we should be aware of.
CK: Depending on which philosophers you believe the problem of life was one of the big problems in early 20th century. People saw no way that chemistry and physics could allow the transmission of information from one generation to next. People said we know chemistry, we know physics, we know there’s no way that all the information that makes you up, your eye color, your height, can be just chemistry. What people didn’t realize was the ability of one dimensional change in macromolecules. They just didn’t know about this so they said well, we probably need new principles. So the lesson here is that we want to be cautious about what’s consciousness is. Many people say we need some fundamental new laws, but perhaps they are wrong, and consciousness can be explained when we discover the neural mechanism that evokes it.GZ:Why is consciousness necessary for life?
CK: It is very difficult to speculate its functions. I mean why do you have only two arms rather than four arms? You can suggest various reasons but it’s difficult to confirm. Human psychology seems to need consciousness. Say there is an earthquake or a fire, you know we have to do something we have never done before, we have to quickly get out, we have to leave the building etc. That’s an unplanned contingency, so that’s what I think we need consciousness for. However for most things that you typically do you do without consciousness.

GZ:You are studying vision. Why so? Why not the hearing system or some other body system?
CK: It’s a tactical decision. I´ m a vision scientist, it’s my own personal interest. Also in vision we’ve learned to do things that are very difficult to do with any other body system, to manipulate the relationship between physical world and its subjective interpretation in a very precise way. We can use these techniques to manipulate the relationship between subjective person and physical stimulus, in order to track the footprints of consciousness in the brain.

GZ:The Holy Grail for neuroscientists is to identify the neural correlate of consciousness. What exactly is that?
CK: It is the minimal set of neural mechanisms that are sufficient for consciousness in a person. Once we have the neural correlate of consciousness we can track what happens in diseases like schizophrenia and autism that intervene with consciousness, what happens in a newborn baby, how do we know that a newborn baby is conscious, or what happens in patients in a coma. Once we have the neural correlate we can begin to tackle these questions in a rigorous way.

GZ: Do you think that the so called “hard problem” will fade away?
CK: Practically speaking, methologically speaking, conceptually speaking, intellectually speaking, it may turn out to be an easy problem. Because of the really difficult problem is that the brain is by far the most complex system in the known universe. We are missing many basic aspects. We don’t understand how very complicated networks of tens of thousands of millions neurons interact with each other. Once you understand this network, you say “oh that’s how it happened!”

GZ: Roger Penrose is suggesting what he calls “platonic realism” and says that consciousness is somehow a fundamental property of the universe and that through quantum effects it is being picked up from the brains and therefore we have qualia. What is your opinion?
CK: Even if you assume quantum gravity to be relevant to the brain it doesn’t really make answer why quantum gravity should solve the hard problem. By involving yet another physical law, not just electromagnetism or chemistry, you introduce just another set of physical laws that do little to solve the mystery. Once you understand the brain as a classical device, then from the energies and the time scales involved, there’ s no evidence of any short of quantum superposition. I will stick with studying the brain as a classical rather than as a quantum system.GZ:Why so many scientists are having a hard time accepting the fact that the brain can be explained?
CK: It depends who you talk to. Biologists, physicists which are not much involved are generally skeptical, but not the neuroscientists that deal with the problem of consciousness. Anyway, I think there are many people on the planet who don’ t want to hear about this kind of research because they are afraid of the picture of humans that may emerge.

GZ: What is like working with Francis Crick?
CK: I continue to work with him. It’s very intense. He’s 87 years old and he’s never seized to stop wondering, he’s never lost his curiosity and he is a person who, more than anybody else, questions every assumption, even his own assumptions.GZ: You do rock climbing. How do you combine consciousness and rock climbing?
CK: Rock climbing is very intense and you have to focus when you do it. So it’s a bit like science, if you do it you are totally absorbed into it, because you cannot afford to do anything else.GZ: Are you an optimist?
CK: Of course I am an optimist.GZ: You think is possible for science to enlighten people or is it a luxury only for an elite?
CK: In the long term science is going to make people healthier, safer and happier, living longer lives, no question about that. This has been happening for the last 2.000 years and I see no reason why shouldn’t continue in the future.

GZ: So why most people read their horoscopes?
CK: You got to ask them if they really believe in the horoscopes. Also many people believe in superstitions, but I don’t think that these things affect dramatically the way we generally think, which is, basically, rational.