Maybe It’s All Jelly

From The New York Times:

It would be one thing to concede that science may never be able to explain, say, the subjective experiences of the human mind. But the standard take on quantum mechanics suggests something far more surprising: that a complete understanding of even the objective, physical world is beyond science’s reach, since it’s impossible to translate into words how the theory’s math relates to the world we live in.

[Angelo] Bassi, a 47-year-old theoretical physicist at the University of Trieste, in northeastern Italy, is prominent among a tiny minority of rebels in the discipline who reject this conclusion. “I strongly believe that physics is words, in a sense,” he said across the picnic table. [He makes] a case for what a vast majority of his colleagues consider a highly implausible idea: that the theory upon which nearly all of modern physics rests must have something wrong with it — precisely because it can’t be put into words.

Of course, much about quantum mechanics can be said with words. Like the fact that a particle’s future whereabouts can’t be specified by the theory, only predicted with probabilities. And that those probabilities derive from each particle’s “wave function,” a set of numbers that varies over time, as per an equation devised by Erwin Schrödinger in 1925. But because the wave function’s numbers have no obvious meaning, the theory only predicts what scientists may see at the instant of observation — when all the wave function’s latent possibilities appear to collapse to one definitive outcome — and provides no narrative at all for what particles actually do before or after that, or even how much the word “particle” is apropos to the unobserved world. The theory, in fact, suggests that particles, while they’re not being observed, behave more like waves — a fact called “wave-particle duality” that’s related to how all those latent possibilities seem to indicate that an unobserved particle can exist in several places at once….

Bassi’s research is focused on a possible alternative to quantum mechanics, a class of theories called “objective collapse models”…. And [he is] now leading the most ambitious experiment to date that could show that objective collapse actually happens….

The hard part [was making sure the new theory didn’t] contradict any of quantum mechanics’ many unerring predictions. The trick, it turned out, was to endow fundamental particles with some funky new properties.

“You should remove the word ‘particle’ from your vocabulary,” Bassi explains. “It’s all about gelatin. An electron can be here and there and that’s it.”

In this theory, particles are replaced by a sort of hybrid between particles and waves: gelatinous blobs that can spread out in space, split and recombine. And, crucially, the blobs have a kind of built-in bashfulness that explains wave-particle duality in a way that is independent of human observation: When one blob encounters a crowd of others, it reacts by quickly shrinking to a point.

“It’s like an octopus that when you touch them: Whoop!” Bassi says, collapsing his fingertips to a tight bunch to evoke tentacles doing the same.

If objective collapse were to be confirmed, … the way the world works will once again be expressible in words. “Jelly that reacts like an octopus” will be the new “particles subject to forces.” New, exotic phenomena will be identified that could spawn currently inconceivable technologies. Schrödinger’s cat will live or die regardless of who looks or who doesn’t. Even the unpredictability of the subatomic world could turn out to be illusory, a false impression given by our ignorance of octopoid innards.

“Devs” Is an Excellent Series, Except…

Devs is a science fiction series that’s streaming on the Hulu service. You have to pay for Hulu, but they usually have a free trial for new subscribers. If you have the right kind of Spotify account, Hulu is free.

The people who made Devs have done a brilliant job. The scripts are intelligent, the actors are talented. One thing that sets it apart is that it’s visually stunning. It’s a TV show that looks better than most big-budget movies. One reason it’s so good is that it’s written and directed by Alex Garland, the filmmaker hugely responsible for 28 Days Later, Ex Machina and Annihilation.

Another thing that sets Devs apart is that it concerns the nature of reality. Is the universe deterministic? What is the correct interpretation of quantum mechanics? Are there multiple worlds? Do you and I have free will? Should we be held morally responsible for our decisions if we couldn’t have chosen otherwise?

I haven’t finished the series yet. Maybe when it’s over, my opinion will have changed. I think Aristotle said we should judge a work of art as a whole.

What motivated me to write this post, however, was that one of the characters, Lily Chan, is now faced with what might turn out to be a truly momentous decision, possibly the biggest decision anyone has ever made. (A determinist would say I had no choice — the history of the universe made me start writing.) It isn’t giving much away about the show to say that Lily has been told she will be at a certain place later tonight and, assuming she is, things are going to go terribly wrong. She and her friend both think it’s crazy to think anybody could reliably predict such a thing, but at the same time she wants to make sure the prediction doesn’t come true. How should she make sure of that?

Here are two options:

(a) She and her friend, who are in the beautiful city of San Francisco, should get some cash, turn off their phones and start driving. They should drive as far away as possible from the place she’s predicted to be later tonight. They should definitely not stay in San Francisco, since it’s only a few miles from where the big, bad event is supposed to happen. Come on, Lily! Run away!

(b) Lily and her friend should stay in her apartment in San Francisco, but not go outside. That should be good enough.

If you were in her situation and you wanted to prove the prediction wrong, which option would you choose? Would you choose (a) or (b) to make sure the very, very bad thing didn’t happen?

This is a TV show. Which option does she choose?

I think we all know the answers to these questions.

Einstein’s Unfinished Revolution: The Search for What Lies Beyond the Quantum by Lee Smolin

Lee Smolin is a theoretical physicist who is dissatisfied with the state of theoretical physics. He is not alone in being dissatisfied. Physicists have two wonderful theories —  quantum mechanics (which deals with the very small) and general relativity (which deals with the very large) — that don’t fit together. Some of them have been trying for decades to reconcile the two theories. In addition, there is a lot about quantum mechanics that seems crazy or at least paradoxical. It’s been argued, therefore, that the theory is incomplete.

Smolin believes that there is a fundamental reality separate from our perceptions that underlies both quantum mechanics and general relativity. He would like to figure out what that reality is. He says this makes him a “realist”.

The first part of the book discusses what Smolin calls “anti-realist” views, primarily the so-called Copenhagen interpretation of quantum mechanics (sometimes referred to as the “shut up and calculate” view). He then outlines some competing views, such as Einstein’s, according to which quantum mechanics is incomplete.

In the final chapters, he offers the beginnings of his own theory. I won’t try to explain it, but he begins with an idea proposed by the brilliant German philosopher Gottfried Willhelm Leibniz (who died 300 years ago). Leibniz suggested that the universe is composed of an infinite number of simple substances called”monads”. The Wikipedia article on Leibniz says “each monad is like a little mirror of the universe”, i.e. a mirror reflecting all the other monads.

Near the end of the book, Smolin offers a one-sentence summary of his theory:

The universe consists of nothing but views of itself, each [view being from the perspective of] an event in [the universe’s] history, and the [universe’s] laws act to make these views as diverse as possible [271].

For Smolin, time is a fundamental feature of the universe. Space isn’t. Space emerges from events. Furthermore, the fact that space isn’t fundamental helps explain how two particles that are millions of miles away from each other can be “entangled”, so that an effect on one can immediately affect the other. That’s the idea of “non-locality” that Einstein called “spooky action at a distance”.

Smolin is sure that he doesn’t have all the answers, but he believes it’s worth trying to find them. If you’d like to know more, you’ll have to read the book or find someone else to explain it. There are diagrams and no math!

Where Does the Weirdness Go? (Why Quantum Mechanics Is Strange, But Not As Strange As You Think) by David Lindley

If you want an introduction to quantum mechanics, this is a very good book to read. I didn’t get some of it, but I don’t blame the author, who does an excellent job. He was a theoretical astrophysicist before he began editing science magazines. Since the book was published in 1996, some of it may be out of date, but not enough to make a difference to the general reader.

The title “Where Does the Weirdness Go?” refers to a puzzle. Since events at the quantum level are weird, why doesn’t that weirdness show up at the level of our ordinary experience? Reality looks fairly well-defined to us. We don’t see the things around us as probabilities. The chair you’re sitting on is right there under you; it’s not possibly there and possibly not there. Electrons and photons may be in an indeterminate state, possibly here and possibly there, but that probabilistic weirdness disappears when it comes to higher-level stuff.

I think the book’s subtitle (“Not As Strange As You Think”) refers to the puzzle’s answer. Lindley explains that, roughly speaking, quantum weirdness disappears when something called “quantum coherence” turns into “quantum decoherence”. When a quantum state is “coherent”, its properties are mere probabilities. But that can only be the case if the quantum system is isolated from other quantum systems. Here’s how Wikipedia puts it:

… when a quantum system is not perfectly isolated, but in contact with its surroundings, coherence decays with time, a process called quantum decoherence. As a result of this process, the relevant quantum behaviour is lost.

The quantum behavior referred to here is the weirdness (things like “is it a particle or is it a wave?” and “spooky action at a distance”). Since quantum systems (photons, electrons, paired particles) are rarely, if ever, appropriately isolated inside objects like chairs, clouds and chickens, those types of things don’t behave weirdly.  The constant atomic and sub-atomic turmoil inside everyday objects means that their properties are defined or definite, not probabilistic. The stuff we see around us doesn’t display any quantum weirdness because there are trillions upon trillions of quantum-level interactions occurring at every moment.

One thing the book makes clear is that there’s nothing special about quantum states being measured. Nor does human consciousness have any special role in quantum mechanics. In fact, measurement is an example of decoherence. When a physicist measures an electron, it is no longer isolated. In order to be measured, the electron has to interact with something else at the quantum level. That results in the electron’s possible position or momentum becoming real, not probabilistic. So when we hear about the importance of measurement in quantum mechanics, it only means that something at the quantum level is interacting with something else at that level. Most such interactions have nothing at all to do with us humans. 

Something (among many) I don’t understand: Once an electron has lost its probabilistic nature by interacting with some other quantum-level thing, do any of its properties ever become probabilistic again? If not, it would seem like every electron or photon in the universe would eventually have well-defined properties. 

I’ll say one more thing about the book. The author subscribes to what’s known as the “Copenhagen interpretation” of quantum mechanics. Apparently, most physicists do. The Copenhagen interpretation is a response to questions like “what’s really going on at the quantum level?” and “is it possible to explain why quantum events are so weird?” The answer given by the Copenhagen interpretation is: “Don’t bother trying to understand what’s happening. We can’t explain what’s happening and there is no sense in trying, because there is no definite reality to be explained at that level until measurement (or quantum-level interaction) occurs. This is just the way the world is.”

The author concludes by asking “will we ever understand quantum mechanics?” Here’s his answer:

But we do [understand it], don’t we? As an intellectual apparatus that allows us to figure out what will happen in all conceivable kinds of situations, quantum mechanics works just fine, and tells us whatever … we need to know….

[But] quantum mechanics clearly does not fit into any picture that we can obtain from everyday experience of how the world works… It throws us off balance… Physics, and the rest of science, grew up with the belief in objective reality, that the universe is really out there and that we are measuring it…. And the longer the belief was retained, the more it came to seem as it must be an essential part of the foundation of physics….

Then quantum mechanics came along and destroyed that notion of reality. Experiment backs up the axioms of quantum mechanics. Nothing is real until you measure it [or it comes into contact with something else!], and if you try to infer from disparate sets of measurements what reality really is, you run into contradictions….

A true believer might conclude that objective reality must still be there somewhere, beneath quantum mechanics. That’s what Einstein believed….[But] if quantum mechanics does not embody an objective view of reality, then evidently an objective view of reality is not essential to the conduct of physics…

[But] quantum mechanics, despite its lack of an objective reality, nevertheless gives rise to a macroscopic world that acts, most of the time, as if it were objectively real… And so, almost paradoxically, we can believe in an objective reality most of the time, because quantum mechanics predicts that the world should behave that way. But it’s because the world behaves that way that we have acquired such a profound belief in objective reality — and that’s what makes quantum mechanics so hard to understand [222-224]

Reality Is Not What It Seems: The Journey to Quantum Gravity by Carlo Rovelli

Carlo Rovelli is an Italian theoretical physicist whose previous book, Seven Brief Lessons on Physics, was a bestseller. In this one, he tells a familiar story: the history of physics from ancient Greece to the present day. But he tells it in such a charming and enlightening way that the story feels new.

One of the lessons from the book that will stick with me is that, according to current physics, the universe isn’t infinitely divisible. At some point, you’ll get to the bottom where the quanta (or tiniest pieces) are. The surprising part of that idea is that these quanta apparently include the quanta or tiny pieces of spacetime. But these tiniest pieces of spacetime aren’t in space or time. They compose space and time. Here’s how he sums it up at the end of the book:

 

The world is more extraordinary and profound than any of the fables told by our forefathers…. It is a world that does not exist in space and does not develop in time. A world made up solely of interacting quantum fields, the swarming of which generates — through a dense network of reciprocal interactions — space, time, particles, waves and light….

 

 

A world without infinity, where the infinitely small does not exist, because there is a minimum scale to this teeming, beneath which there is nothing. Quanta of space mingle with the foam of spacetime, and the structure of things is born from reciprocal information that weaves the correlations among the regions of the world. A world that we know how to describe with a set of equations. Perhaps to be corrected.

 

The biggest puzzle Rovelli and his colleagues are working on is how to reconcile the small-scale physics of quantum mechanics and the large-scale physics of general relativity. They aren’t consistent. Currently, the most popular way to resolve the inconsistency is string theory, but Rovelli’s preferred solution is loop quantum gravity. Unfortunately, his explanation of loop quantum gravity was the part of the book where he lost me. Maybe a second or third or fifteenth reading of that section would clear things up.

The other idea that will stick with me is from quantum field theory: among the fields that make up reality, such as the electron field and the Higgs boson field, is the gravitational field. But the gravitational field is just another name for spacetime. Spacetime is the gravitational field and vice versa. That’s what Rovelli claims anyway, although he ends the book by pointing out that all scientific conclusions are open to revision given new evidence and insights.