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 Since the book was published in 1996, some of it may be out of date, but not enough to make a difference to the general reader.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]

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Other Minds: The Octopus, the Sea and the Deep Origins of Consciousness by Peter Godfrey-Smith

Peter Godfrey-Smith is an Australian professor of philosophy who has spent many hours scuba-diving in order to observe the behavior of octopuses and cuttlefish. The book is an attempt to trace the evolution of mental activity from its earliest beginnings hundreds of millions of years ago, when bacteria began reacting to their surroundings. The author believes that mind and consciousness didn’t suddenly spring into existence; they developed gradually through millions of years. But he admits that nobody knows for sure.

Neither do we know what it’s like to be an octopus. We don’t even know for certain that it’s like anything at all. Maybe octopuses go about their business without feelings or anything like consciousness. Godfrey-Smith, however, argues that it’s reasonable to believe that creatures of many sorts feel pain when they are injured. But where to draw the lines (if there are any lines) between bacteria that simply react, animals that feel pain and creatures like us who are self-conscious is a mystery.

Octopuses are especially interesting because our common ancestors lived about 500 million years ago. Octopuses developed complex nervous systems, arranged differently than ours, independently from most other animals, including us. That means, in Godfrey-Smith’s words, “meeting an octopus is, in many ways, the closest we’re likely to get to meeting an intelligent alien”. It’s really too bad that they can’t tell us what it’s like to be them.

I wish the book ended with a summation of the author’s conclusions. I do remember the idea that nervous systems first evolved in order to respond to a living thing’s surroundings, and then to monitor its internal states and control its movements. And I remember a lot about the interesting behavior of octopuses and their close relations, cuttlefish. But I can’t say I came to any solid conclusions about the deep origins of consciousness. If the author reached any conclusions, he should have reminded his readers what they were.

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.

Time Travel: A History by James Gleick

There are two principal topics in this book: time travel and time. Since time travel is fiction, the history of time travel presented in the book is the history of ideas about time travel, mostly ideas expressed in novels like H. G. Wells’s The Time Machine, short stories like Robert Heinlein’s “By His Bootstraps” and movies like The Terminator. Time travel can be fun to think about, and ideas about time travel are suggestive of what people have thought about time, but I quickly lost interest in the topic. So I ended up skimming those sections of the book.

On the other hand, Gleick’s discussion of time itself was worth reading. He covers both physics and philosophy, and does an excellent job explaining complex, competing ideas about time. For example:

You can say Einstein discovered that the universe is a four-dimensional space-time continuum. But it’s better to say, more modestly, Einstein discovered that we can describe the universe as a four-dimensional space-time continuum and that such a model enables physicists to calculate almost everything, with astounding exactitude, in certain limited domains. Call it space-time for the convenience of reasoning….

You can say the equations of physics make no distinction between past and future, between forward and backward in time. But if you do, you are averting your gaze from the phenomena dearest to our hearts. You leave for another day or another department the puzzles of evolution, memory, consciousness, life itself. Elementary processes may be reversible; complex processes are not. In the world of things, time’s arrow is always flying.

It’s an interesting question whether the calculations of the physicists are so accurate because the universe really is a four-dimensional space-time continuum. And is the passage of time some kind of illusion, like many physicists believe? Gleick leans toward time being quite real and physicists taking their models a bit too seriously. I think this would have been a better book if he spent more time on the physics and philosophy and less time on the fiction.

Time Reborn: From the Crisis in Physics to the Future of the Universe by Lee Smolin

The theoretical physicist Lee Smolin has written 4 books. I’ve read 3 1/2 of them.

His first book, The Life of the Cosmos, applied the theory of evolution to cosmology. Smolin suggested that our universe might be a good home for life because universes breed new universes, which differ somewhat from their parents. Over time, a universe with lots of black holes will generate a number of new universes with lots of black holes, and universes with lots of black holes tend to be hospitable for life, since their fundamental constants (like the strength of their subatomic forces) have values that permit life to evolve.

His next book, Three Roads to Quantum Gravity, was too technical for me, but I did finish his 3rd book, The Trouble With Physics. In that one, he argued that string theory is much too popular among physicists, since it isn’t a proper scientific theory. It’s too speculative and might never generate testable predictions.

Now there is Time Reborn. This is a kind of sequel to Smolin’s earlier books. He still subscribes to the evolutionary views presented in The Life of the Cosmos, but his principal thesis now is that time is real. In fact, time is more real than space. This contradicts the common view among physicists and philosophers that space and time are the four dimensions that make up “spacetime”. The standard view among physicists is that all events, whether past, present or future, are equally real. There is nothing special about the present moment. In fact, our perception that time passes is an illusion.

Smolin argues that this consensus view of the universe as a “block universe”, in which all moments are the same, is a mistake. He agrees that the laws of physics and the equations that express them can run forwards or backwards, but only on scales smaller than the universe as a whole. The planets could revolve the other way around the sun, just like clocks can run in reverse. But the universe as a whole has a history that is real and a future that isn’t determined. Smolin thinks that treating time as real might help resolve certain issues in physics, such as the “arrow of time”, i.e., the fact that certain processes always go in one direction (entropy tends to increase in isolated systems).

Professor Smolin tries to explain how his view of time fits with Einstein’s special theory of relativity (in which temporal properties are relative to an observer) and how something can act like a particle and a wave at the same time (as shown by the famous “double-slit” experiment). I don’t know if those explanations or some of his other technical explanations make sense. But it was reassuring to read a book by a reputable physicist who believes that time is real, physicists have overemphasized the importance of mathematics in understanding the universe, and there is a reality beyond what we can observe. Smolin also believes that there are probably more fundamental, deterministic laws that underlie quantum mechanics. I believe that’s what Einstein thought too.

Time Reborn veers into philosophy at times. There is much discussion of the Principles of Sufficient Reason and the Identity of Indiscernibles. The book concludes with some comments on subjects that aren’t physics, like the nature of consciousness. Smolin’s philosophical remarks are relatively unsophisticated. I assume his physics is better.

Even if he’s wrong about the reality of time, however, I enjoyed the book. For one thing, I can now see how two particles at opposite ends of the universe could be “entangled”, such that a change to one would automatically result in an immediate change to the other. Space might have more dimensions than we recognize. In another spatial dimension, the two entangled particles might be very close neighbors, making what Einstein called “spooky action at a distance” (“spukhafte Fernwirkung“) less mysterious. That makes me feel a lot better.

The Scientific Revolution by Steven Shapin

Historians refer to the changes brought about by such luminaries as Galileo, Descartes, Bacon, Boyle and Newton in the 16th and 17th centuries as the “Scientific Revolution”. The science of the Greeks and Scholastics was replaced by something that looks like science as it’s practiced today.

The theme of this book is that the “Scientific Revolution” wasn’t as clear-cut as historians and philosophers often imply. The scientists of the time disagreed about how science should be conducted. For example, some questioned the value of experimentation. If an experiment contradicted received opinion, many concluded that the experiment was performed incorrectly. Robert Boyle thought that scientists should perform many experiments and describe them in great detail. He never expressed “Boyle’s Law” (pV = k) in mathematical terms. Isaac Newton thought that a single experiment was good enough to allow the mathematical formulation of a law of nature. 

Science was also generally considered to be the “handmaiden of religion”. Showing that nature operated like a vast machine was thought to be evidence of God’s supernatural powers and wisdom. We had to wait for Darwin to show how “mere chance” could write a chapter in the Book of Nature.  (2/9/12)

Why Does E=mc2? (And Why Should We Care?) by Brian Cox and Jeff Forshaw

Two English physicists try to explain Einstein’s famous equation and much more, including relativity and quantum mechanics. I didn’t understand quite a bit and didn’t try to do the math (which is relatively limited), but found their explanations reasonably helpful. For example, they explain that the speed of light is an upper limit because photons have no mass. It isn’t anything to do with light per se. Any particle with no mass travels at the speed of light and no faster. Gluons don’t have mass and, if they exist, neither do gravitons. So we might just as well call it “the speed of particles with no mass”. 

They also explain that mass and energy are constantly being exchanged in accordance with Einstein’s equation. Atomic weapons are just the most spectacular example of a process that is universal to nature, and occurs, for example, every time heat is generated or there is some other chemical reaction.

I’m still confused by the Twin Paradox. Why would someone in a spaceship moving close to the speed of light age more slowly than someone staying on Earth, if all motion is relative? Why not say that the person moving near the speed of light is standing still and the person who stayed at home is moving near the speed of light? The answer is that the person in the spaceship is accelerating and decelerating, and that’s why we can properly say that he or she is moving faster than the person on Earth and why he or she ages more slowly. There are formulas that explain this, but it still sounds fishy. 

I’m also bothered by the idea that the Big Bang had no location. If the universe is expanding in all directions, why can’t we say where the Big Bang occurred? And maybe put a monument there with a gift shop?  (9/8/11)