STORY WATER

When Reality is Real: An Interview with Antony Valentini

by Jill Neimark

Note: Since this interview took place, Antony Valentini and Guido Bacciagaluppi have completed a new book, Quantum Theory at the Crossroads: Reconsidering the 1927 Solvay Conference, to be published in 2007 by Cambridge University Press. A complete draft of the book is available online at www.arxiv.org/abs/quant-ph/0609184

I first met theoretical physicist Antony Valentini at a conference honoring John Wheeler last spring (funded in part by the Templeton Foundation and featured on Metanexus as well). I was walking up the stairs with cosmologist Lee Smolin, telling him that he made me nervous because he was so smart. As a friend once said of Lee, ‘He pours new ideas on his cereal for breakfast.’

We paused at the top of the stairwell and a man with curly dark hair smiled at us, and Lee said, “This man makes me nervous.”

I figured this fellow had to be eating some really far-out cereal for his breakfast. In fact, Lee has supported Antony’s work, and invited him twice to Canada’s new Perimeter Institute for extended visits (where Antony will work as of next September; he is currently at Imperial College in London). Even so, at the conference Mr. Valentini was clearly an outsider, an interested audience member, but not one whose ideas were about to have their day in the sun. Not that month, anyway. Not long after the conference, New Scientist got wind of Antony’s theory, and ran a cover story on him (see God Doesn’t Play Dice: Certainty Beneath the Quantum World, New Scientist, June 29, 2002).

What is so unusual about Antony Valentini? Just this: he’s resurrected a theory that undoes the central tenet of quantum mechanics, and gives relativity theory a good punt to left field as well. The theory follows quantum math, but at the same time allows for new possibilities beyond conventional quantum mechanics..

It’s a theory that says there is indeed an objective reality behind the things we observe—that quantum uncertainty is not fundamental. And that somewhere, somehow, time is universal—not relative. Goodbye, ghostly probabilities, with their strange propensity for collapsing into real things while apparently sort of holding back and remaining always a bit coy and ghostly…hello, hidden variables that are objective. And Antony’s particular twist on the theory suggests a new explanation for the uniformity of the early universe—where, he suggests, quantum law might not have applied, where stuff could interact faster than the speed of light—and where those interactions were actually visible.

There’s no proof, of course—at least not yet. But it’s fun to think about. The actual physics is a bit tough, so I only wiggled my toes in it—read on, there’s nothing to be nervous about. This is the fourth in a series of conversations with deep thinkers on life, the universe and cosmology. The first three were with Lee Smolin, Stuart Kauffman, and Sherrilyn Roush.

Q: You’ve spent the last twelve years working on the pilot-wave theory, which was originally formulated by French physicist Louis de Broglie in the 1920’s, and then developed by American physicist David Bohm in the 1950s. The mathematics of the de Broglie-Bohm theory is similar to that of quantum mechanics, but the interpretation of what’s going on is quite different. Why don’t we start with the famous double-slit experiment, which is the one everybody refers to when trying to explain quantum weirdness. What does quantum mechanics say is going on, and what do you think is really going on?

A: The basic idea of the two slit experiment is that electrons are fired one at a time through a screen with two holes and land on a solid wall. After firing thousands of particles you see a distribution of points where they landed, and this has a wavy structure. But if you block either one of the slits, the points where the electrons land tend to be concentrated behind the open slit. Naïve logic suggests that if you take the pattern that occurs when slit “a” is open, and the pattern that occurs when slit “b” is open, and add them together, you should get the same pattern as when both slits are open.

Q: But that’s not the case, right? You get a wavy pattern when both holes are open.

A: That’s what the experiment shows. And to explain this, quantum mechanics says that somehow the electron does two things at the same time. In this ill-defined sense, when both holes are open, the electron supposedly goes through both holes at once.

Q: It’s both a wave and a particle. I’ve never really understood that, or the idea that these ghostly probabilities are real but not real, and collapse into actual, observed things at the moment we observe them. But apparently I’m in good company. I was re-reading Richard Feynman’s wonderful little book, QED: The Strange Theory of Light and Matter, recently. It’s a set of four lectures. He says right at the beginning, “Will you understand what I’m gong to tell you?...No, you’re not going to be able to understand it…You see, my physics students don’t understand it either. That is because I don’t understand it. Nobody does.” But he also points out that quantum theory is incredibly successful.

A: It is, it has given us lasers and superconductors and all kinds of things.

Q: So what’s wrong with it?

A: It doesn’t give a clear explanation of what’s happening. People say the two slit experiment proves that a deeper explanation is impossible. But that argument is wrong, because it assumes that opening or closing a hole doesn’t affect the motion of the electron. In the pilot wave theory it can. The electron, or any particle, is actually being guided by a wave in space. So in this theory the motion of the electron is definite and has a trajectory. There’s no blurring of reality. But the particle is traveling in a wave that guides it along.

Q: So what is that wave made of?

A: It’s not like ordinary matter.

Q: Okay then, is it an abstraction?

A: No, it’s more like a new kind of physical entity. Think of the 19^th century when we discovered electric and magnetic fields. For a long time people said, what are these things made of? What is light made of? What are electromagnetic waves made of? And they tried to build models, and eventually they realized these fields were not like ordinary matter. I’m saying this is similarly a new kind of physical entity.

Q: How will we figure out what this wave is, then?

A: It already exists in quantum mechanics. They call it the wave function, but they view it as a probability. It’s essentially a mathematical object that tells you the chance of finding the electron at any point in space. That chance is proportional to the square of the amplitude of the wave at that point in space.

Q: So quantum theory has a wave function that is purely mathematical, where the pilot wave theory treats the wave as physical and real?

A: Right. That means that in the double slit experiment, when the wave hits the screen it’s like a water wave hitting a barrier with two holes. Two waves will emerge and they’ll spread out and eventually move into each other and when they overlap they’ll form a complicated pattern. And the electron coming out of one of the holes will be influenced by both waves as well. So where the electron lands is very much affected by the whether one or both holes are open. There’s no reason why the pattern with both holes open should equal the sum of the patterns with one hole closed.

Q: That brings me back to QED again, because in talking about light and how it goes through glass, he notes that for every 100 photons, about 96 will pass through the glass, and about 4 will be reflected back. But if you put two layers of glass near each other, depending on the thickness of the glass, you’ll either get almost no photons reflected back, or you’ll get twice as many reflected back. Could a physical wave account for this?

A: Certainly. The waves passing through or bouncing off the slabs of glass can either interfere with each other and cancel each other out, or they can amplify each other.

Q: All right. Any philosophical thoughts about why quantum theory is so popular—when it puts uncertainty at the heart of everything?

A: I think there was a philosophical fashion in the 1920s where people were moving away from 19^th century materialism and the clockwork universe. In Germany there was a strong movement against British and French enlightenment philosophy. This really began with the rise of romanticism at the end of the 18^th century, following the work of Kant, who supposedly said it was impossible for us to ever know the so-called “ding an sich.” Many people interpreted Kant as saying you can’t really know the world as it is. I think quantum mechanics was influenced by the fallout from this idea—that it’s philosophically naïve to assume your picture of the world is literally how the world is. This sent people down the slippery slope of subjectivism and by the early 20^th century physicists in Germany had this idea that you shouldn’t speculate about what might be hidden behind appearances. You can see that in the late 19^th century argument over the existence of atoms. Many people said the idea of atoms was just metaphysics and you should simply deal with what you can observe in the lab.

Q: Quantum mechanics is definitely weird and strange. Still, you’re criticizing the most successful theory that ever was. I guess a lot of physicists figure quantum mechanics works, and works so well, that it’s okay if the interpretation seems counter-intuitive and even absurd.

A: Quantum mechanics ignores the electron and just looks at the waves. If you’re only interested in the pattern against the wall, and not in each individual electron, you can forget about trajectories and work with the wave as a mathematical formula. The problem comes when you ask what is actually happening, and then you get into paradoxes.

Q: What got you interested in the pilot wave theory in the first place?

A: I came across it as an undergraduate at Cambridge, but at that time the papers I looked at were not very convincing. Then I came around to it again when I was a PhD student in Trieste and read a wonderful book by John Bell at CERN in Geneva. It was called, Speakable and Unspeakable in Quantum Mechanics.

Q: What was his basic point?

A: He said there is a theory which reproduces quantum mechanics completely and not just for special cases and it also offers a definite reality of a particle’s trajectory. So I went back and read the original papers and I realized he was right.

But what really excited me about the whole thing was that according to this theory, you get quantum mechanics only if you assume that initially the particles have a certain distribution. Well if you take the pilot wave theory seriously, there could be circumstances where particles did not have this distribution. Such as the early universe.

In the early universe space was expanding so fast that particles in each region couldn’t interact with particles in distant regions, if those interactions were limited by the speed of light. In the pilot wave theory, however, particles can interact faster than light. In fact, they can inteact instantaneously. In this theory two particles really form a single system in a six-dimensional “configuration space,” and the pilot wave guiding the system exists in this higher dimensional space.

Now If, in the early universe, the distribution of particles violated quantum mechanics, then these faster than light influences would have been visible. And that could help explain why the early universe is so uniform in its density of matter and temperature. Non-uniformities could have been smoothed out over large distances by these instantaneous interactions.

Q: Let me see if I understand. You’re saying that when we view the early universe, we see a mysterious uniformity. And that uniformity wouldn’t be possible without faster-than-light interactions. If we didn’t have quantum mechanical distribution back then, the faster-than-light interactions would have been visible. But right now, we do have quantum mechanics, and right now, in our universe today, if such interactions are going on, those interactions are invisible.

A: Yes. And we have quantum mechanics today only because, soon after the big bang, the distribution of particles became equal to the quantum distribution. So what I’m saying is that quantum mechanics works now, but it’s not a fundamental theory. It didn’t always work, and the faster than light influences were not always hidden.

Q: How are you going to convince anybody of this?

A: We need to find a violation of quantum mechanics in the early universe. We need to find a non-quantum distribution of particles. There may be particles floating around in space now which were left over from that very early time. People are looking for particles of dark matter left over from the early universe, and some of these may be good candidates. Another possibility is relic gravitons, particles associated with gravity that are believed to have stopped interacting with other particles at a very early time. Perhaps these relic gravitons from the early universe don’t obey quantum mechanics.

Q: You’ve told me in previous conversations that you feel Bohm’s original work on this theory has been misinterpreted. Can you mention that here?

A: Bohm had an interesting trajectory. There are really three Bohms. There’s the very early Bohm who was interested in Niels Bohr’s ideas about complementarity. Then there’s the Bohm of the 1950s who worked on the pilot wave theory of hidden variables. Then in the 1960s he changed again. He met Krishnamurti and got very interested in Indian philosophy and started trying to tag some mystical ideas onto the pilot-wave theory. If you look at the yoga sutras of Patanjali you can see this idea that material objects are somehow illusions and projections from something deeper, that things emerge from this deeper level and disappear into this deeper level again. So Bohm tried to adopt an interpretation of the wave as a manifestation of a deeper level, perhaps associated with consciousness. He called the wave an implicate order and the particle an explicate order.

Q: What do you think?

A: I find these ideas intriguing, but I don’t think Bohm managed to connect them seriously with physics. And unfortunately he confused people about the de Broglie-Bohm theory. It actually tended to put people off, and it hasn’t led to anything really solid and interesting.

Q: How does the pilot wave theory view time and space?

A: It goes against relativity theory, because it has faster-than-light processes, and in relativity nothing is supposed to go faster than light. So it seems to me that we may have to revise relativity theory and end up with a notion of universal time. In relativity, different observers at different speeds have their own time and there is no absolute time. But in this theory, distant observers can communicate instantaneously if they have control at this fundamental level of non-quantum particles. So they would be able to synchronize their clocks instantaneously even if they were millions of light years apart. Of course, some people don’t like the idea, and that’s a problem.

Q: What do you see happening with this theory? Is there a future in it?

A: Right now, there’s no career in it. There’s no funding for it and no place where young people can go to work on it. I myself couldn’t resist it, and spent years working alone, supporting myself with private tuition. I always thought it was the way to go and I’ve never regretted my decision. But we need more than just a handful of people working on it.

Q: How do you keep yourself inspired?

A: I look at the history of physics and I see how we’ve been in similar situations before. I listen to Mozart. And I’ve become a realist. I believe there is a real world, and we need to find out about it.