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Jim Baggott on Where Physics Meets Philosophy

Communicating physics is difficult, partly because the underlying ideas can be hard to grasp, even for experts. Popular science writer, Jim Baggott, talks us through some of his favourite physics books.

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Jim Baggott

Jim Baggott is an award-winning popular science writer and author. His latest book is Mass: The Quest to Understand Matter from Greek Atoms to Quantum Fields.

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Jim Baggott

Jim Baggott is an award-winning popular science writer and author. His latest book is Mass: The Quest to Understand Matter from Greek Atoms to Quantum Fields.

Save for later
 

As a non-physicist, I find physics really hard to understand compared to most other subjects. I tried some of Brian Greene’s books, for example, which are for a general audience. Even those, I struggled with. I find this really frustrating because physics is so important—it’s telling us what’s around us and what’s going on in the universe. And yet, somehow, my brain can’t grasp it. Why?

There is a challenge that anyone faces trying to present some of the ideas of contemporary physics—to explain what are really quite deep and somewhat convoluted ideas in ways that are accessible. In all of the work that I’ve done, I feel I get a little better at it each time. But I still tend to produce books that are a struggle for anyone coming at this without any background.

The other thing that you learn from this is that there is a sense in which, in a curious way, there never was any real guarantee that nature would, ultimately, be understandable in a simple way. That was maybe a little bit of a mistaken view—brought about by the fact that some aspects of the classical ways of looking at things, like the mechanics of Newton, were easier to get our heads around.

That’s actually quite an important message. If you struggle with the concepts, it’s because nature is pretty complicated—at least as far as we currently understand it.

“Nobody, frankly, has got a decent grasp of the full picture. It really is that challenging”

And it’s always contingent. We never quite know when the next theoretical breakthrough or new piece of experimental data will turn our current ideas on their heads.

I think the concepts are graspable in a very general sense, that even people without the right kind of background can make some sense out of what’s going on. But it requires some effort, I have to say.

From reading your book about the discovery of the Higgs boson, it seems like you do find physics easy to understand?

No—I struggle with it. I’ve always had an ambition to write books where I’m stretching my own understanding and using it as a vehicle to learn. So I’m learning as I go along. And, then, you face the struggle of communicating that—to write about it in a way that’s hopefully accessible to as many people as possible.

But don’t be fooled. Some of the guys who seem very authoritative—who write best-selling popular science books—by and large they’re also on the edge of their own understanding. Nobody, frankly, has got a decent grasp of the full picture. It really is that challenging.

Yes, there is a level of deep mathematical complexity. But that’s a little bit of a red herring. That’s not the reason everyone struggles to come to terms with what the theories are saying. Irrespective of the mathematics, it’s the concepts that you end up wrestling with. They are actually quite baffling.

“There never was any real guarantee that nature would, ultimately, be understandable in a simple way. That was maybe a little bit of a mistaken view”

Richard Feynman—a very, very charismatic, American, Nobel prize-winning physicist—once said, ‘I think I can safely say that nobody understands quantum mechanics.’ Given that he won his Nobel Prize for developing a structure called quantum electrodynamics, you’d think that at least he would have the authority to say, ‘I fully understand that.’ But no.

I think anyone is kidding themselves if they say they understand these things. There’s an ability to work with these concepts, where you learn how to calculate things. If you can set aside any concerns for what the hell it might mean, then you get on and you can make some progress.

But the minute you start to ponder what it might actually all mean is the minute you start to tie yourself in conceptual knots. And that’s the way it is.

How many physics books have you written now?

I’ve written ten books. My first was published back in 1992, in the dark ages, and was called The Meaning of Quantum Theory. My most recent book, Origins, was a much more ambitious attempt to try and explain the scientific story of the whole of creation from the Big Bang to human consciousness. But mostly I’ve tended to write about things like particle physics and quantum mechanics. My latest book, called Mass: The Quest to Understand Matter from Greek Atoms to Quantum Fields, is firmly back in this territory.

In the title of your book about the discovery of Higgs boson you refer to it as the ‘God particle.’ Has your philosophical view of the world been affected by studying physics?

It helps to understand where that term came from. An American particle physicist called Leon Lederman published a book in 1993 called The God Particle. He explains, in the foreword to the book, that he actually wanted to call it The Goddamn Particle, but his publisher wouldn’t let him.

The search for the Higgs in the early 90s was causing unbelievable anguish. At the time, American theorists were pitching for building something called the Superconducting Supercollider which was going to cost I don’t know how many billions of dollars. Eventually, in 1993, Congress cancelled it.

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Although the name ‘the God particle’ brings a lot of baggage with it, there is a sense in which it is quite important. It’s a particle that physicists had been wanting to find for a very long time.

The way that modern quantum field theory works is that you have a field, which has values everywhere throughout space and time. Particles are therefore considered to be fundamental disturbances or fluctuations of the quantum field. They kind of pop out, they undergo collisions, and we make measurements on them.

The Higgs boson is the fundamental quantum particle of the Higgs field. And it’s the Higgs field that actually gives you the ‘woo’ effect and starts to lead you to become somewhat metaphysical or even theological because the existence of this field means that particles in the universe have mass. There’s absolutely no doubt that, according to current theories of physics, if the Higgs field did not exist then nothing would exist—at least, nothing with mass. Everything in the universe would be a bit like light—it would just zip around at the speed of light and nothing would ever happen.

That was one of the reasons that Lederman felt compelled to say there’s a sense in which we’re at the book of Genesis here. Whether you accept his arguments or not is neither here nor there, but it was a name that struck a chord in the popular imagination and it’s a name that tended to stick. I have no bones about using it in the subtitle of my book, which was published just a few short weeks after the discovery of the Higgs was announced.

“If you can set aside any concerns for what the hell it might mean, then you get on and you can make some progress”

When I talked to Peter Higgs about it, and asked, ‘Do you have a problem with that?’ he actually didn’t. He’s been on the record as saying he hates the name, but he didn’t seem to mind. It’s one of those things. As a writer and as a communicator, you have to find a way to hold people’s interest.

Ok, you are straying along the edges of science and theology maybe a little bit. There was never any sense in which ‘the God particle’ was suggesting, in any way, the existence of a creator but, at the same time, it stimulates discussion and gets people interested. If they pick up an article or a book or watch a documentary because of a trigger like that then, hopefully, what they’re going to learn is going to be useful. It is an important particle.

I notice from your book that a lot of these particles are either named after people or something like ‘quark’ which was, again, a bit like ‘Goddamn’ wasn’t it?

The origin of ‘quark’ is Finnegans Wake. There’s another American theorist called Murray Gell-Mann who was a bit mischievous. He thought the whole naming business was quite ridiculous. So he happily named these things and perhaps even surprised himself when it turned out that this was actually a correct way of describing elementary particles.

“He explains, in the foreword to the book, that he actually wanted to call it The Goddamn Particle, but his publisher wouldn’t let him”

We have things like up and down quarks, strange quarks, charm quarks, top quarks, bottom quarks—all of these different names represent what are known as quark ‘flavours’. Quarks also have ‘colour’. Not, literally, a colour in the sense that we would understand it; they have properties that come in triplets and, in an attempt to keep things in order, physicists chose to call them colours: red, green, and blue. So, you can have a red up quark, and a green down quark, and a blue strange quark, and so on. These are all aspects of things that we’ve learnt about some of these elementary particles. But in a moment of non-seriousness, yes, they can get named sometimes rather strangely.

And ‘boson’ was named after an Indian physicist.

Satyendra Nath Bose. His work came to the attention of Einstein. There’s a branch of development in physics called Bose-Einstein statistics. All of the particles that make up atoms and molecules, that make us up and the universe that we know, the elementary particles that sit at the root of all of those—very much in the nature of Greek ‘atoms’—are all particles with a characteristic spin that means that they’re classed as something called fermions. It doesn’t matter what spin is and it doesn’t matter what properties fermions have, but they are very different from the kinds of particles like photons which carry forces between the matter particles. They have a different spin, of a type that classifies them as bosons. And if you want to know what the fundamental difference is then, in a sense, if it’s a matter particle, such as a quark or an electron, then it’s also a fermion. If it’s a particle that transmits forces between matter particles, then it’s a boson. That’s a simple rule of thumb but that’s how nature is.

I like the picture you have in your book, of Margaret Thatcher entering a room, as a way of illustrating the Higgs boson. Do you think more illustrations, more being able to visualise things, would help people?

I don’t know. To a certain extent, it depends what it is you’re trying to convey. If you look at the background to that story, there was a competition. High-energy physicists were bidding for more money to contribute to CERN. William Waldegrave was, at one time, the Science Minister—not in Thatcher’s government but in the successor government after Thatcher was deposed, in John Major’s government.

“It’s a bit like smashing two watches together and then trying to work out how watches work by looking at all the springs and the other bits and pieces that come out from the mess that results.”

Waldegrave demanded to know what the hell this Higgs boson was and why it was important, so he initiated a competition. The prize was a bottle of vintage champagne, for any physicist who could actually explain what the hell was going on. And one winning entry used the analogy of Thatcher entering a room full of acolytes and attracting attention and drawing a crowd around her as one way of understanding how a massless particle interacts with the Higgs field and slows down, in effect, and becomes stuck. As a consequence, we interpret that slowing down and getting stuck as the particle gaining mass.

And that was to give funding to CERN?

Yes, that was the basis for the UK’s contribution to CERN–they were asking for more money or it may well be that they were just asking for the contribution to continue. I forget the details. There had been a new science policy announced that was wanting to make UK science more supportive of the national interest, for UK PLC. There was some consternation that funding for things that were a bit more esoteric—that weren’t directly linked to the idea of driving economic growth for the country—might get sacrificed in the interests of other priorities. But it turned out that the UK continued to contribute and, of course, eventually all those years later, the Higgs boson was, indeed, discovered.

The LHC is in Geneva. Are there other things like it? You mentioned the one in Texas that didn’t go ahead. Is it unique?

No. CERN is unique only in the sense that it’s the largest particle collider in the world, currently. The corresponding American collider is called Fermilab. It’s just outside of Chicago. Fermilab has made a lot of particle discoveries over the years.

The idea is that you want to blow particles like protons around at speeds really quite close to the speed of light and then engineer it so that they smash into each other. And when they smash into each other, all hell breaks loose. But what happens then is dependent on the energy of the collision, the joint energy of motion of the two particles. And then whole sprays of debris and other things are released. The experiment is done by examining what comes out.

It’s a bit like smashing two watches together and then trying to work out how watches work by looking at all the springs and the other bits and pieces that come out from the mess that results.

Fermilab was never going to have the collision energy to find the Higgs, that was clear. As I said, the physicists in the early eighties pitched to the US government for funding to build the Superconducting Supercollider but the cost of that escalated so much that in the end it got canned.

“There was another American theorist called Murray Gell-Mann who was a bit mischievous. He thought the whole naming business was quite ridiculous”

At around about the time that was happening, decisions were already being made to build the next generation of particle collider at CERN—there were predecessors—and this was called the Large Hadron Collider. Protons are hadrons. Effectively, we could call it the Large Proton Collider if we wanted to. It was always going to be designed to have collision energies that gave it the potential to find the Higgs.

So, it has been a bit of a one-horse race. But I should point out that there are many US physicists that contribute to the work at CERN. It is very much an international collaboration, it’s not a purely European collaboration any longer.

The first book on your list is Asimov’s Guide to Science. I know him as a science fiction writer, so I’m intrigued that he’s got this guide to science.

Asimov was one of the first real prolific science popularisers, in my opinion—though there were others, like Carl Sagan. Asimov is probably most well-known for his science fiction stories and I’ve got many of them. I used to browse quite a lot of bookstores in those days, because you didn’t have the internet.

When I was studying for my degree in chemistry at the University of Manchester, I came across Asimov’s Guide to Science. There was something about becoming a student, a science student, you get to that stage in your development—you’ve done ‘A’ Levels, you cover a wide range of subjects (I’d done Maths, Physics, and Chemistry) but when you get to university you really are then starting to specialise. It’s almost like putting your head above the parapet. You start to get very deep into a particular subject.

“It’s very much written for the layman”

There was part of me that, in an odd way, didn’t want to lose a connection with physics and biology. There was never going to be time to drill deep into these subjects in a research sense, or even in a degree sense, but I wanted to stay in contact with them. I wanted to stay in touch with them and I wanted to be familiar with them. Asimov’s Guide to Science was a great way of doing that. He was a great writer.

Does he start at the beginning?

No. His book is more a compendium. The first volume is the physical sciences. He’s got sections on what is science, the universe, the earth, the atmosphere, the elements, particles, waves, machines, the reactor and nuclear physics. He’s got different topics but effectively it’s an exploration of all of the different aspects of science that touch on that. The second volume is the life sciences—biology, evolution, microbiology and so on.

Is it easy to understand for a non-physicist, would you say?

Yes, it is. It’s very much written for the layman. You have to bear in mind that’s it outdated. It was first published back in 1972. I know, however, that it’s been republished. I’ve seen it recently on bookshelves in bookstores. For me, it’s still well worth having a look at. If you just want a broad introduction—on the understanding that the world of science has moved on quite a bit since those days—then it’s a really good place to start.

I noticed one commentator saying that it’s ‘probably the best general science book ever written.’

I would agree with that.

Let’s talk about your next book. This is Subtle Is the Lord: The Science and the Life of Albert Einstein.

The five books that I’ve given you are really books that have been important to me. They’re not books that I think are the best introduction to the Higgs, or the best guide to particle physics. They are books that have been personal. And this book is very personal. I picked it up after I graduated. I moved from Manchester to Oxford to study for a PhD.

Again, you’re now drilling very deeply into a particular subject—in my case, chemical physics—and you become conscious that you’re almost putting the blinkers on and have become a little bit blind to other things that are interesting. I didn’t want that to happen.

“What I find quite extraordinary is that some of the bizarre stuff that we’re having to deal with now—stuff that makes us all a little bit uncomfortable, some of the madder aspects of quantum mechanics—was very much anticipated by Einstein”

Einstein, of course, is a pivotal individual in 20th century physics. I must have spotted the book in the mid-eighties, not long after it was first published in 1982, and picked up a copy. I read it in some detail and I didn’t understand it all—not by any stretch of the imagination. It’s a scientific biography, not a biography necessarily about Einstein the person, although there’s a lot of personal stuff in it. It is about his work on the special and general theories of relativity, and quantum theory.

You mentioned in your email that you regularly pull this book down, even though it’s more than 30 years old.

I do. I learn something from it every time that I look at it. What I find quite extraordinary is that some of the bizarre stuff that we’re having to deal with now—stuff that makes us all a little bit uncomfortable, some of the madder aspects of quantum mechanics—was very much anticipated by Einstein.

He had this famous debate with Niels Bohr. Although Einstein was instrumental in adopting the idea of the quantum, the truth was that he didn’t like what the theory was then saying about the nature of probability and causality in the physical world. You know—his famous ‘God does not play dice’ argument. It’s easily one of the best debates in the whole of the history of science, in my opinion.

Again, from Abraham Pais’s biography, you get some sense of Einstein’s thinking. And it’s extraordinary how deeply he thought about some of these things. There’s a real strong element of philosophy in Einstein’s thinking, which is, to a certain extent, inevitable when you’re at that level—at the frontier of physics, talking about your understanding of space and time and matter and radiation. It is really a very good book.

We’re still following in the footsteps of Einstein these days, are we? Is he a bit like Darwin for evolutionary biology?

In some aspects, yes, but Einstein’s resistance to quantum ideas eventually meant that in his scientific career, certainly in the later years, towards the end of his life, he wasn’t part of the process driving physics forward. He was overtaken by events. There was the discovery of all sorts of weird particles that couldn’t really be understood. There was the development of something called ‘quantum field theory’ which he didn’t really participate in. And so he went off a little bit at a tangent and became a bit of a sorry figure, not really adding anything further.

But I would argue that he’d already done more than any other individual in the history of physics to clear some of the mists of understanding.

It’s amazing that he did all this while he was working as a patent clerk.

He wrote a series of five fundamentally important papers that were published in 1905. Out of those papers came the idea of the light quantum—the very beginnings of quantum theory, five years after Planck in 1900. There’s a paper on Brownian motion. You have to bear in mind that, in those days, people were very sceptical of the idea of atoms and molecules—of bits of matter. Many argued that matter was continuous and came all in one structure. You’ve got special relativity and you’ve got a paper with an equation related to the famous ‘e=mc squared’ in it.

“There’s a real strong element of philosophy in Einstein’s thinking”

So, that’s in 1905 when he was a ‘technical expert, third-class.’ Then he had an insight, I think in 1907 or 1908, that would lead him, ultimately, some years later, to the general theory of relativity which explains how gravity works. By then, he had been promoted to ‘technical expert, second-class.’ I just love that.

Shall we talk about book number three? This is Alastair Rae’s Quantum Physics: Illusion or Reality.

Again, bear in mind what I’ve just said, that when you start to embark on a career as a scientist it’s about digging a hole for yourself. You effectively want to create a reputation, you want to create a name for yourself, publish papers, and that means devoting all your energy and time to becoming an expert in the area in which you’re doing research.

I did my first degree, I did a PhD at Oxford, I’d done a couple of years of postdoctoral research, and then I became a university lecturer at the University of Reading. So, I’m teaching as well as doing research and trying to write research papers. Your time really is squeezed. But there was still that bit of me that didn’t want to let go.

I happened to pick up a book when I was doing some work at the University of Madison, Wisconsin in 1987, and it gave me an introduction to something that I had completely missed and that is the famous Einstein–Podolsky–Rosen experiment.

“When you start to embark on a career as a scientist it’s about digging a hole for yourself”

So, in the culmination of Einstein’s big debate with Bohr in 1935, he devised this devious, what he called ‘gedankenexperiment’ or thought experiment—that arguably undermined Bohr’s defensive position. It’s a bit like a game of chess between these two grandmasters.

Bohr’s response was quite weak, in many ways, but also opened the door to a really quite bizarre interpretation of quantum mechanics which says that nothing is anything until it’s seen or measured. This kind of thing gives rise to all of those great questions like, ‘If a tree falls in the forest, and there’s no one around to hear, does it still make a sound?’ ‘Is the moon there when nobody looks?’ You’re kind of in that bizarre mode of thinking.

But what had happened was that, having been nothing other than a thought experiment, by the time you got to the 1970s and early 1980s, there were guys doing experiments to find out whether this thought experiment actually did open up quantum mechanics to the cry that it was somehow incomplete or inconsistent.

“Alastair Rae’s little volume is a wonderful introduction”

These experiments proved very clearly that quantum mechanics is complete for all practical purposes, it is consistent—it’s just mad. Understanding the nature of these experiments, understanding the nature of the Einstein–Podolsky–Rosen challenge, became a mission.

I learned about it, I bought some other books, but Alastair Rae’s little volume is a wonderful introduction. There’s a little bit of maths in it, for the initiated who are comfortable with a bit of algebra. But there’s nothing particularly difficult about what Alistair Rae says. I just felt that this made it all clear. I finally understood what the hell was going on with this challenge and the nature of the experiments that were being performed.

At the beginning, you were talking about whether nature is simple or not. Is the conclusion that nature is not simple?

Nature is what nature is. It’s us that then looks it at and says ‘Oh, that’s really difficult’ or ‘That doesn’t make any sense.’ What these experiments and quantum theory are telling us is that objects like electrons don’t exist in the way that we understand them—with mass, with spin, with charge—until we look. That sounds like a piece of childish, kindergarten philosophy. But it’s true. It’s amazing to me, I’ve called these experiments ‘experimental philosophy.’

You have to go back to Immanuel Kant. What you take as the things-in-themselves, reality-in-itself, we can have no knowledge of that reality because, by definition, we only know of the things that we look at: the things that we measure. So what we see is not the thing-in-themselves but only the things as they appear.

“These experiments proved very clearly that quantum mechanics is complete for all practical purposes, it is consistent—it’s just mad”

But there is nature. I am a realist so I believe that the universe really does exist when nobody looks. What quantum theory is telling you is that everything that you understand about the nature of that reality depends on you looking. And don’t be surprised when what you get when you look is not necessarily entirely representative of what the thing is in-itself.

Are you saying that, in the example you gave of the tree falling in the forest, the answer is that it does not make a sound if no one is listening?

Yes.

That’s good to know.

Arguably, what you have is the sense that sound is a relational thing. You have to have something with an auditory sensory apparatus or, at least, a recording instrument of some description. You have to have something; you have to have a measurement. Without a measurement, there is a sense in which it makes no sound at all. Now, does it produce an acoustic disturbance in the air? For sure, I would argue. But you can’t call that a sound unless you’ve got something on the other end to detect it.

The next book on your list is The Philosophy of Quantum Mechanics. You’ve already mentioned that philosophy is important.

By this time, I’m snowballing a little bit. I’m still trying to earn a crust as a university lecturer and researcher. I co-wrote a research paper that won a prize—nothing grand by today’s standards—but enough for me to afford what was an expensive book then. It’s by Max Jammer and it’s called The Philosophy of Quantum Mechanics. This really appealed to me.

This is a proper textbook. It’s detailed, it’s not for the layman. There’s bits of it that I still don’t understand. Again, this is somewhat outdated and the world has moved on. I was challenged so much by grappling with these ideas, that I felt that I really did need to get a better grip on them and understand them better. Not because that would aid my abilities as a researcher doing what I was doing, or, in fact, aid my abilities as a teacher because I was teaching a completely different subject. This was certainly off-piste, as far as anything to do with my research or teaching career was concerned.

But I was just deeply disturbed. I needed to know, I needed to understand a bit better. And Max Jammer’s book allowed me to do that, enough to give me confidence that I could actually make sense of this, to the point where I could begin to write about it myself. I actually wrote a short article that was published in, I think, the Journal of Chemical Education, and, eventually, I wrote a book called The Meaning of Quantum Theory which was published by Oxford University Press back in 1992. But, in order to do all of that, I had to make the decision to quit. I left academia at the end of 1988. I finally got to write about this but, in order to do that, I had to stop working in a university.

Is there anything we can say about The Philosophy of Quantum Mechanics? You’ve mentioned that it opened the floodgates to general problems in philosophy, like the nature of reality and the philosophy of science.

Yes, which I’ve always been interested in. There had been the odd flirtation where I’d buy an introduction to philosophy, but there’s a lot of stuff in there about metaphysics and moral philosophy. That is interesting—don’t get me wrong—but what I was really interested in was the place where philosophy meets physics.

And this is one of those places. You can’t have a conversation, really, about quantum theory without introducing some arguments and points that are really philosophical in nature.

“there was a time when some well-known, Nobel Prize winning physicists were quite derogatory about philosophy”

It also helped me understand a little bit about what science is trying to do. What has happened in contemporary physics is the rise of string theory, these guys who argue in favour of the multiverse theory. I felt anger at the capabilities of scientists, seeking their own self-promotion, who really ought to know better, advertising what string theory can achieve.

That actually encouraged me to write a book called Farewell to Reality, which was published in 2013. This argued that all of this is rather metaphysical in nature; there is no experimental evidence for any of it. There is not a leg for string theory to stand on. Now, is it a valid theoretical structure that’s worth pursuing? Probably, yes. But people really shouldn’t be saying that string theory is the answer, because we don’t know that.

So modern physicists should move in the direction of philosophy?

It’s interesting because there was a time when some well-known, Nobel Prize winning physicists were quite derogatory about philosophy. Some argued that philosophers put a nice historic gloss on science but can add nothing to how we think about problems that we face today.

I just find that incredible and absurd because, by its very nature, if your interest is in the fundamental nature of things, then you are in the realm of philosophy.

It’s a game that scientists play rather well, particularly the theoreticians. In a sense, what you do is that you’ve got a problem, there’s something you can’t explain, there’s no data out there that says why it’s wrong or where it’s wrong. So, you speculate. Maybe nature looks like this—and you develop a structure. And the idea is that you torture that structure such that it eventually spits out a prediction of some kind. You twist it, you torture it.

“If you interest is in the fundamental nature of things, then you are in the realm of philosophy”

And then you say, ‘Well, if this is true then we should see this.’ So, what you do is you play a game. You wander into metaphysics because there is absolutely no evidence, by definition, for your speculation. That’s why it’s a speculation. I would prefer to call it a hypothesis, not a theory—but that’s semantics.

The challenge you have, because science is about data and it’s about empirical facts, is to find a way of connecting your speculation—your piece of metaphysics—back with the real world, with the empirical world that we live in.

And the string theorists spectacularly fail to do that and have spectacularly failed for forty years. Arguably, string theory isn’t actually even a theory. It’s a hypothesis that has no foundation in empirical data. There is no evidence for it. It’s a nice way of looking at how elementary particles might be structured but it’s telling us nothing that we don’t already know.

For a time, it seemed that publishers didn’t want to do anything other than publish reams of bestselling books about the elegant universe and the fabric of reality and the hidden universe—whatever it is. All I would say is, ‘For heaven’s sake, don’t get me started on the multiverse because that would really have me going off on one.’

“Arguably, string theory isn’t actually even a theory. It’s a hypothesis that has no foundation in empiral data”

I actually watched a BBC Horizon documentary, I think in January 2011, called “What is Reality?” It started off really quite nicely. There was a lovely introduction to particle physics, the discovery of something called the ‘top quark’ at Fermilab. Then there was a little sequence on the more weird results of quantum theory. And then, we were off into the realms of fantasy with string theory, the multiverse, the mathematical universe hypothesis—all of this stuff. And I got really quite nervous. Horizon has got an incredible reputation in the UK and I just sat there worrying, after half an hour, that people were actually taking this seriously. Were they really thinking that this is what scientists agree reality looks like? That encouraged me to write a book about it.

Your final book is Heisenberg’s War: The Secret History of the German Bomb. This is about Werner Heisenberg, the German theoretical physicist.

As a science student, you grow up with these names. These guys have their fingerprints all over quantum theory and relativity: Einstein, Bohr, Schrödinger, Heisenberg, Oppenheimer. You’ve got all of these people making tremendous contributions to the structure of physics. Although it’s moved on since their day, we owe them a tremendous vote of thanks for the work that they did in getting us to where we are today.

It always struck me as quite extraordinary that these same people then found themselves embroiled in a project to build the most horrendous weapons that mankind has ever seen.

I had read some books about the development of the atomic bomb—the Manhattan Project—and had some understanding of a parallel project that Heisenberg led in Germany during the war to build, it turned out, not a bomb—they were trying to build a nuclear reactor. They didn’t succeed.

Thomas Powers’s book, Heisenberg’s War, is a somewhat flagrant…I was going to say misinterpretation of the historical record, but I don’t think that’s wholly fair. Powers argues that Heisenberg’s motive for a lot of what he did, working on that project, was to delay it, so that they would never be in a position where they’d have weapons that Hitler could use.

“if you were to look at it in the cold hard light of day and declare it as a work of fiction, you’d be criticised for not making it realistic. But it happened.”

I don’t agree with that thesis. I don’t think that that’s true. But reading the book really got me interested in the parallels between these different projects. And the story. With the book that I eventually wrote, what I tried to do was almost to tell it like a work of fiction, to try and keep it dramatic and pacey.

It starts with the discovery of nuclear fission at the end of 1938—look at that timing, war broke out in September 1939—all the way through to the Soviet Union detonating its first atomic bomb in August 1949. So it’s effectively ten years.

You’ve got spies like Klaus Fuchs. There was an American spy called Theodore Hall also working at the heart of the Manhattan Project. Again, I was interested not only in the relationship with the German project but also with the Soviet project that followed. And I was always fascinated to ask myself the question, ‘Whatever happened to all the espionage materials that were gathered by Klaus Fuchs that were transmitted to Moscow?’

With the fall of the Berlin Wall, at the end of the 1980s, it started to become possible to get access to Soviet historical archives. And the Soviet spies themselves were quite keen to tell the story of their own role in helping to build Soviet atomic weapons.

And, obviously, then you had the beginnings of the arms race that certainly clouded my childhood when I was growing up. The Cuban Missile Crisis was in ’63.

So my book is (a) about physics which is obviously a passion, but (b) it’s about these people that had their sticky fingers all over quantum physics and particle physics also getting involved in building this weapon.

I was just fascinated by the nature of the story. You’ve got commando raids on the heavy water plant, you’ve got all sorts of Boy’s Own stories to tell. What I wanted to do, really, was to put them together. I honestly think I was able to do that. I got some quite nice reviews. And, certainly, if you were to look at it in the cold hard light of day and declare it as a work of fiction, you’d be criticised for not making it realistic. But it happened.

So Heisenberg was a leading figure in the German atomic effort. Germany was the birthplace of modern physics, but a lot of those physicists were Jewish. Do you think that if Hitler had not gone after the Jews, he could have won World War II because he would have been the one to get the atomic bomb first?

Hitler’s views on the Jews was probably an immovable object. A lot of the Jewish physicists—Einstein, for example—went to America in 1933 and never went back. A lot of the physicists that found themselves working on the Manhattan Project were Jews that had emigrated from Germany at the time of Hitler’s rise, when he became chancellor, five or six years before he declared war. So, to a certain extent, yes.

But there were still plenty of smart cookies left in Germany. What I learned from Thomas Powers’s book was how quickly the idea of nuclear power and nuclear weapons were brought to the attention of Germany army ordnance, and to Hitler himself, right at the beginning of the war. This was a project that wasn’t an afterthought.

I was just fascinated by Heisenberg’s role and the role of other German physicists who were involved in the Uranverein or ‘Uranium Club’. All of the physicists like Heisenberg who were still in Germany—Heisenberg was no Nazi but he was very much sympathetic to the idea of being German and wanting to do the best for Germany—saw the whole project as an opportunity to do physics. You can have an interesting debate about the naivety of that view, given the nature of Hitler and what he was capable of, with hindsight. Perhaps, it was not quite so obvious in 1939/1940.

What was not known to me was that towards the end of the war, as Germany was capitulating, there was an Allied project called Alsos, involving a Dutch physicist called Samuel Goudsmit. He went into Germany with a team to round up the theoretical physicists that had been involved in Germany’s project. They were all arrested and brought to England and interned in a place called Farm Hall in Cambridgeshire. They were treated very well—they had food and access to music but no access to news.

The whole house was wired—it was bugged—so that the MI6 could listen in to the physicists’ conversations. The one piece of news they were allowed to listen to was reports of the atomic bombing of Hiroshima by the Allies in August 1945.

Their reactions! They had already dismissed the idea that a bomb was possible in the timescale of World War II. They had failed to build a nuclear reactor. It turns out that, in the Manhattan Project, it was necessary to build a nuclear reactor in order to make plutonium that was an ingredient of the bomb that was dropped on Nagasaki.

These were just fascinating events. You look around at some of the physicists today, can you imagine them going through experiences like that? I just find it extraordinary. After the war, eventually they got back to Germany and they got on with their academic careers.

And what were their reactions when they heard about Hiroshima?

They couldn’t believe it. And then there was a scramble to try and understand how the Allies had done it. What had they missed? Where had they gone wrong? How had they failed? And, what’s really interesting is that out of those conversations was born what is known, in this particular instance, as the ‘Lesart’. Effectively, it’s the argument that, ‘actually, we were smart enough, we could have done this, but we didn’t want to.’

And that’s not true?

I don’t believe so.

Interview by Sophie Roell

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