An interview with Manuel Lozano Leyva

This post is also available in: Spanish

Physics assumes there’s an external reality.

That’s the eternal dilemma between materialism and idealism. In Physics, at the quantum level, it has been shown that measurements alter reality, what we’re measuring, and out of purely physical reasons, not philosophical ones, so there’s still no reason to say we’ve solved that problem. An electron may be there or may just be generated by the interaction with our measurement. That’s the eternal question: is the moon there if we’re not looking at it? We can’t be sure. But the answer is yes, it’s there. But, at the quantum level, at the atomic scale, things start to get complex. So Physics cannot elucidate between Platonism and materialism; whether there’s an external reality or not. That belongs to the realm of each person’s philosophical attitude.

Doubts about existence would disappear if there was a God who was always perceiving.

The God problem is something Physics has a clear view on, especially since the seventies. Even though now Hawking has brought it to light and become even more famous, I think mainly out of commercial reasons, because Physics-wise there’s no novelty. This has been clear since we found out about vacuum fluctuations. They became well known in the seventies. What are they? Spontaneous generation of energy, and thus of energy and matter, as an uncaused phenomenon. There are many of those in physics. Radioactivity, for instance, doesn’t need cause: it appears spontaneously. From the moment we discover vacuum fluctuations, we can see the idea of God is superfluous or, at least, unnecessary. Something which, with intuition, has been thought for long. The person to best phrase it was Laplace, who was a minister for Napoleon, even though he was shortly kicked out because he wasn’t so good a minister. Laplace showed Napoleon a paper where he had mathematically described the whole solar system. Napoleon didn’t understand a thing and said to Laplace: “I can’t see God anywhere”. And Laplace answered: “Sire, I never had need to make use of such hypothesis.” Vacuum fluctuations show not only that Physics does not need to make use of the God hypothesis but that the greatest thing that is attributed to God, the spontaneous generation of something, the Universe, can be achieved without a cause. And now all we have to do is discuss the fact that a vacuum fluctuation has little energy but the Universe has a lot but, what do “little” and “a lot” mean? That is a purely relative question. I think Hawking is right, even though it’s something we’ve know for long, so his bringing it up obeys mainly commercial reasons.

How is the notion of causality affected by Quantum Mechanics?

If is affected by the indeterminacy principle. Sometimes it’s called the uncertainty principle, but that’s ill formulated; it is ideologically loaded. Uncertainty is different from indeterminacy. The correct formulation of Heisenberg’s principle is indeterminacy. You have, for example, an indeterminacy in the particle’s position: it’s not a point anymore, like with Laplace or Newton, but is somewhat diffuse. The spacial extension of the particle depends on many things, that’s what we call indeterminacy. If that particle reaches a pace at a time where you’re not sure of where it is, it may cross some barrier by tunnel effect. That’s an effect which is used for building TV’s; actually, almost all the electronic devices we have are somehow based on it. In fact, the particle may cross the barrier before it even gets to it! Why? Because of the spacial indeterminacy those particles have. Always in a relative way, the principle of causality can be questioned by the Quantum point of view. Bear in mind, though, that only on a subatomic scale.

General Relativity has a different conception of space from Quantum Mechanics. And then we have Quantum Loop Theory, where space is but an emergent property resulting from the loops’ interaction. We also have Supersting theory, which seems to be able to create space from nothing. What’s the state of matters regarding space?

Today superstrings and branes are outdated. It’s the age of M theories. They’re the unification of all those kinds of theories, which try to unify, as you said before, the concept of the macroscopic, the Universe as a whole, that is, that which is governed by the force of gravity. On one hand we have Einstein’s theory of gravitation. It’s perfectly well described. On the other hand we have Quantum Mechanics, which describes perfectly, up to an astonoshing detail, the microcosmical world, that is , atoms, nuclei and the particles that come out of it. At that level we have three forces: the electromagnetic force, the weak nuclear force and the strong nuclear force. Those are unified reasonably well. And the other force -and that’s all with forces- is gravitation. Theoretical Physics tries to unify all of them, because that’s what we’ve always done. The history of Physics is a history of unifications, of trying to generate as much as we can from a unified point of view. And, furthermore, to express it mathematically. Well, we’re having a lot of problems with this last unification. We have conjectures. First we started with strings, then with superstring. Now we need 11-dimensional spaces, instead of the four we used to have. And, in order to show these extra dimensions, we need energies at a range we’re unable to achieve. And now the Physics community is trying, with every means available, to find some experimental confirmation of these theories, the M ones in particular. And that cannot be done with current technology. Therefore: are M theories Physics? Because, if there’s no experiment, if there’s no checking to be done in the same conditions, that’s not science. What Galileo taught us, where science’s greatness lies, is that we need experiments. That, if I publish some results and I say how I got them, anyone else -with the same means- can obtain the same results. That’s science. And if that cannot be done with M theories, we can discuss if what they’re doing is science or some new kind of philosophy, expressed mathematically.

Smolin, who defends Quantum Loop Theory, says his theory does make falsifiable predictions.

But those predictions, right now, are out of experimental reach.

Also those ones?

I think so. Except for the ones which were thoroughly confirmed at CERN. Those are the ones I was talking about before, which started with vacuum fluctuations. From that moment, that’s still one of the greatest mysteries in Physics. Dark energy. Maybe gravitations has some component we don’t know about, because the Universe -if there was only the gravitational force we know today- should be slowing down its expansion and it’s doing exactly the opposite. There’s a lot of uncertainty, many things which are still open. Luckily; otherwise, we’d lose our jobs. I do not agree with those people who say that Physics, and Science in general, is coming to an end, I think that’s nonsense.

What’s the role of time in current Physics?

Time has always been a parameter in Physics. Physics, in general, is the description of material systems in space and time. In Newton and also in Aristotle, who’s the first to call for our attention on space and time as the sight for natural phenomena. What Einstein’s Special Relativity does is considering time as just another dimension. Until then, we had three space dimensions and a temporal one: what Einstein did was placing them in the same footing. And in his General Relativity what he does is give them some majestic properties, relating the content of space-time with its geometry. Space time has properties which only depend on its content: the matter of galaxies and stars, etc. And that, the geometrical explanation of the Universe, is what we call General Relativity. We can do that with only four dimensions. If we want to unify the microcosm, they jump to eleven. Since the beginning, Mathematics and Physics students have used that as an exercise: we can put the number of dimensions we feel like in problems. But one thing is working with dimensions as some abstract entity and a very different one is to seriously consider them as real. Many things I compare that to a river: the river flows in a certain way and always in the same direction, which is what happens with time. But then there’s a series of movements, those of the water molecules and atoms which, indeed, follow the river’s movement, but the set of internal movements of those atoms and molecules has nothing to do with the general movement of the river. When we talk about eleven dimensions, about dual spaces or M theories it’s like when we’re talking abut those intimacies at a much smaller scale than the flow of this the spacial and temporal current. That is unconfirmed.

What is the effect of preserving the status of time in General Relativity on Quantum Theories?

It raises the number of dimensions from four to eleven. And exploring that requires an energy we cannot reach. For now. The effort we’re making now is to try to find some consequences of these theories we can actually check. But, for now, we’ve got nothing. We’re hopeful, though. We’ve got to possibilities: one is the LHC, the particle accelerator, which can produce a great amount of energies and, thus, can probe space at very small distances. Space, energy and matter can be conceived as the same thing. At least, they’re intimately related to each other, in such a way that if we probe one we can draw conclusions about the others. Because of what I said before: matter and space geometry are intimately related since Einstein and all that. With the LHC we hope to find something, even though we don’t expect too much. But we have more realistic hopes with high energy cosmic rays, even though they’re far more incontrollable. With those cosmic rays, which have an energy which is much higher than what we can generate in CERN, we could study some phenomenons which may confirm those theories. But, at the moment, we are still clueless.

What is the Universe made of?

The Universe is radiation and matter. That is, energy, in the shape of radiation, and matter in the shape of elementary particles, which make up protons, neutrons and matter in general. What happens is that what I described is just the content we detect. There’s still some 90% which remains undetected. The fact that we haven’t detected it doesn’t mean detecting it will radically change our image of the Universe. That ninety something percent which hasn’t been detected is a dark matter component and another component, which makes up sixty something percent, is called dark energy. At first sight, one may ask why there’s some ninety percent of the Universe that we don’t know.

I usually don’t say we don’t know what it is -which is correct- but that it hasn’t been detected. Because, if it’s detected… imagine the neutrino, a kind of particle that’s constantly passing through our body by the millions, because all the stars are emitting it and, since it has no mass or energy it can go through a whole galaxy without even noticing, without even changing direction. If those particles had a mass, however small, we would explain dark matter by changing hardly anything. If there was an overabundance of some heavy elements, like brown dwarfs… anyway, there are plenty of candidates for dark matter. If it turned out to be one of these candidates, it would be a surprise, but it wouldn’t change our paradigm at all. As to dark energy, the remaining seventy percent that makes the Universe expand with an acceleration, against intuition, we could explain it by simply adding a repulsive term to gravitation at large distances, and that wouldn’t change much either. What happens is that our lack of certainty makes us expect some surprises, but in principle we’re pretty sure the Universe is made of matter and energy which, since Einstein’s famous equation e=mc2, where m is matter and e is energy, are known to be the same. They’re in a proportion of one thousand million photons for each material particle, so the Universe is mostly radiation, with very little matter (fortunately we’re a part of it). And, together with the two unknowns which are dark matter and dark energy, that’s the whole of the Universe. When we speak about matter and energy, we’re talking since Einstein, about the geometry of space-time, that is, about space and time. So, in a way, the Universe is simple.

Is there room for free will?

I don’t see free will can fit into the law of gravity. Science, and Physics in particular, is much more modest than Philosophy or Theology. We want to test things experimentally and that restricts us a lot, theoretically. Because if we don’t experiment that’s not Science, so it has nothing to do with me, free will or anything else. I can have my free will to do an experiment or not, but if I do, it means a great restriction. But when Science says something or concludes something, that’s forever. And I mean it: it’s forever. Many people say that Science reaches some conclusions and then, later, they change them. No. That’s denying the steam engine ever existed. And steam-powered trains existed and worked perfectly. What happens is that later more advanced ones came. But steam worked fine. Newton’s mechanical theory is exact, rigorous, perfect, what happens is it cannot be applied to atoms. If you apply it to atoms, it fails. Why? Because it’s applied where it shouldn’t. And that’s Physics. Free will doesn’t have a place in it, or in beliefs. So there’s a 99% of Philosophy, of the human constructions that doesn’t have a place in it. We are modest, what happens is later we place satellites in orbit and the GPS tells you exactly where you are. And GPS is based in Relativity. GPS devices have to be adjusted according to Einstein’s theory of General Relativity. And a plane flies, whatever your opinion is and however stubborn you may get.

But, in a world where all the particles’ movements are determined…

No, no. Not only does Quantum Mechanics question the causality principle, but it is also not fully deterministic. Precisely because of the indeterminacy principle. When classical mechanics is applied to the normal world, it is rigorously exact. What does “deterministic” mean to Physics? It means you have some particle at a given instant and, with the equations of movement, you can predict exactly where and when it’s going to be at a later time. And that is determined by Newton’s equations. However, when you apply that to a subatomic particle, using quantum equations, you cannot speak about positions at instants, but about probability. A probability distribution means you measure the position or the instant and you do not get certainty about whether the particle is there or not at that time. You get a probability of finding it there when you make a measurement. Probability is a concept which is not deterministic. I teach Quantum Mechanics and I always give my students the following example: imagine a map of Spain on December the 22nd, made like this: every lottery ticket (before the day of the results) on every person is a little red dot. The more money you bet that day, the brighter the dot is. If you only see the map like that, it looks pretty much like a normal road map, because of the population densities and so forth. When the result is finally made public, all the lights go off and only one remains shining in some remote little village. That’s what Quantum Mechanics does. It doesn’t predict where the prize is going to appear, only the possibility of its appearing at some place. And it does that in an exact and rigorous way. What it gives with precision is the probability. Not the exact determination of the position of an object, a system or whatever. Despite all that, the reality that both maps reflect -the one with lights and the geographical one- are very alike. But Quantum Mechanics doesn’t aspire to so much.

Maybe this randomness gives us room for choice. But to what extent does a die have free will?

Einstein’s doubts when he said God doesn’t play dice were profound. Einstein didn’t get Quantum Mechanics much, though. After discovering the photoelectric effect and much more he helped build the pillars of the discipline, but he never believed it and ended his days still not understanding it. He said, and he was partially right, that the sentence “God doesn’t play dice” mean the following: Quantum Mechanics says that, if the die is perfect, you throw it and you have one in six chances for any of the faces coming up, and that’s exact. That’s the prediction from Quantum Mechanics. Einstein said that cannot be so, the world cannot be described in terms of probabilities. What happens is that if I knew the die’s mass, its irregularities and the weight of the number six face relative to the number one face, the angle between my hand and the table, friction, etc., it would be deterministic. And I would know exactly which face I’m going to get if I throw it a certain way. The problem is that, since it’s impossible to control all that, there’s a huge amount of what we call “hidden variables”. These hidden variables, which we cannot reach, make up the indeterminacy. Quantum Mechanics is a tremendous restriction and it uses probabilities because it can’t do anything else. But that’s all false. There are no hidden variables. That’s simply an objection Einstein raised. Just look at our technology: it is calculated that nowadays 90% or our technology, including trucks, is based on Quantum Mechanics. Quantum Mechanics works perfectly with these probability distributions. Is there anything hidden we’re not using? No. What happens is Science is still not finished, there’s no unification, there are lots of things we still we don’ know. Every time someone thinks Science, with unified theories, M theories, has practically reached its limit, it reminds me of a dialog between Schroedinger and some other guy, at the end of the XIXth century: Science is almost over, Physics especially, they said, it’s reached its limit, electricity and magnetism is are perfectly formulated. We’re talking about the end of the XIXth century. So, this physicist wrote to Schroedinger saying he was sad about getting to the end of his life and seeing Physics was over: “except for some details, we’ve done our job.” Then, Schroedinger answered with a funny letter, almost completely blank. He had drawn a frame and, inside, a crude drawing with just some lines. And he said below: “except for some details, I paint like Titian.” Every time someone tells me M theories unify everything and we’re only left with details, I think about that.

Schroedinger has a book about life.

Yes, “What is life?” It’s fantastic, because… Schroedinger was a serial lover. A sex fanatic. He was a guy who wasn’t even very attractive, but he performed all kinds of sexual deeds. He left Germany when the Nazis got there, even though he was an aristocrat, from a good family who had nothing to do with the Jews. He left because he felt the Nazis were quite distasteful. He went to Dublin, where they made an institute for him. And it was a scandal, because the president gave him the institute and he would go there with his wife and his lover. The three of them lived together. It was fantastic. In that society, doing that was really hardcore. Schroedinger was basically a philosopher. Is actual area of expertise was Greek and Latin philosophy, but then he got interested in Physics. He had very wide interests. He also didn’t fully believe in Quantum Mechanics, even though he was one of its founders. Schroedinger’s cat is a bit like the “God doesn’t play dice”, an objection to Quantum Mechanics. So, he had a wide range of interests, he gave conferences in Spanish, defended the Republic publicly, and amongst all that he wrote that little work called “What is life?” And it’s fantastic because it already suggests the existence of genes. And we’re talking about many years before they were detected. Of course, a gene, in a way, is a Quantum expression of life. Lots of genetics professors I know greatly admire that book and some of them have told me that, if Schroedinger hadn’t got the Nobel prize in Physics and had kept working on biology, he would probably have gotten the one in Medicine. He presented the Quantum outlook on life.

Does life have a meaning?

There are two currents with respect to that. One says that every parameter in the Universe, be it the speed of light, Planck’s constant, the electron’s charge, etc. up to a great precision, have to be like this because, if they hadn’t, life would never have evolved. Then there’s the question that life, in a Universe as large as the one we inhabit, could have developed in many places. That is, Giordano Bruno. One of the reasons why they tortured him for eight years, and they burn him with his tongue nailed to a post, so that he couldn’t talk, was that he said: “there are innumerable suns, innumerable worlds spin around them, there’s life in them.” When you think that in our Galaxy has hundreds of thousands of stars like the sun and that the number of galaxies has a similar figure; on top of that, now we’re discovering exoplanets which, until 10 years ago, were like Jupiter, but now we’re finding more and more planets the size of the Earth. So, even though the Universe has its constants adjusted for life, that is compatible with our whole galaxy brimming with life. And in the other galaxies, of course. Which kind of life? Who knows! From some nasty mold to more evolved beings than us, which will have evolved towards mysticism or technology, or maybe they’ll just be herbivores or bacteria. We don’t know, but that physical constants in the Universe could be adjusted or, on the contrary, that life is just a consequence of those constants, which seems to be the case, does not make us necessarily the only living things in the Universe, even though that could also be the case. In conclusion: we have no idea but, from Science’s point of view, both things are compatible.

What are the possible explanations for the fine-tuning of the constants?

Maybe they just ended up like that. We don’t need a hand to adjust them. The fact that the constants are fine-tuned means that, if they weren’t constant but one of them could vary, let’s say, the fine structure constant or any other in Physics, then atoms would be unstable, matter would collapse and we would not be here. There’s no mystics involved. The electron’s charge, the fine structure constant, Planck’s constant, the mass of this and that, if any of those values was a little different, the Universe would be different. In fact, the theory that Hawking defends no in his book -which wasn’t written by him- the multiverse theory, says that there are multiple universes where the constants would have different values. However, they are not causally connected to ours, that is, we could never communicate with them. But, really, the fact that if we altered these values the Universe would collapse and we wouldn’t be here is like some hand has adjusted a TV with 28 buttons in such a way that, if you touched anything, you’d lose the image. In that case, you could say someone adjusted it, but maybe the Universe, in its evolution, just ended up having those values, so they haven’t necessarily been caused.

I was thinking about the anthropic principle.

There are two of those: the weak and the strong one.

The weak one.

Again, we are in the same page: experimental checking. And, if there’s no experiment, we’re not talking about Physics. We’re talking about Philosophy, which is all right to me, but we should know where we are.

Some people defend multiverse theory does make different predictions to the Copenhagen interpretation.

Unfortunately, I have to insist on the same: if there’s no experiment, we’re not talking about Physics. I mean, it’s pretty cheap to do research on these things, so OK, let’s investigate, but it shouldn’t have further consequences. I don’t think it’s a good idea to have a lot of doctoral thesis on that. When there are social and economic consequences I get a bit defensive with these matters. Because, if there’s no experiment, we’re talking about a different job and we’re not paid for that. Let’s pay the philosophers to do that. I can actually tolerate it, I have many friends who do research on that, in the Universidad Autónoma de Madrid or in the Universidad de Barcelona. It’s OK for a group of people to work on that, but bearing in mind we’re at the limits of Physics. And I’m a total physicist: either there’s an experiment or not.

Do you see any candidate to unification which seems more promising than the others?

Yes. M theories. M theories put together in a more unified and even more pedagogic way in one same body of knowledge all the other theories we’ve been working on until now: superstrings, branes, dual spaces, etc. When you finally formulate a unified theory in a more compact and clear way, more people have access to it. Right now they’re already working on some experimental confirmation at an energy scale which is compatible with current technology. And they’re hopeful. Some friends of mine tell me they’re about to come out with an experiment to prove all that. That would be great, but they still haven’t given us one.

See this author’s biography.


Share and Enjoy:
  • Digg
  • del.icio.us
  • Facebook
  • Yahoo! Buzz
  • Twitter
  • Google Bookmarks
  • Bitacoras.com
  • Google Buzz
  • Meneame
  • Reddit
  • RSS

Leave a Reply

You can use these HTML tags

<a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>