There's been two big problems with attempts to fathom the meaning of quantum mechanics (the commonly used term by scientists in that field, rather than quantum physics).
New Age types, along with other mystically-inclined fans of quantum mechanics, make too much of what quantum mechanics means -- spouting indefensible notions of how we create our own reality, consciousness pervades the cosmos, and such.
Physicists, along with others who work with the applications of quantum mechanics, typically make too little of what quantum mechanics means -- proclaiming that all that counts is the astoundingly precise mathematics underlying this field, often encapsulated as "shut up and calculate."
People like me fall into an in-between realm. We're fascinated by quantum mechanics and devour attempts to make sense of quantum phenomena, but have minimal comprehension of the mathematics needed to truly understand quantum mechanics.
So I was excited when I learned about Heinrich Pas' book The One: How An Ancient Idea Holds the Future of Physics. Pas is a professor of theoretical physics at a German university and has conducted research visits at CERN and Fermilab, which makes him well qualified to explore the meaning of quantum mechanics.
His first paragraph in the chapter following an introduction does a good job of outlining what his book is about.
Quantum mechanics is the science behind nuclear explosions, smart phones, and particle collisions. But it is more than that. It sketches a hidden reality beyond what we experience in our daily routines and holds within it the power to transform our notion of what is real -- provided that it is taken seriously as a theory about nature. And therein lies the debate that begins our journey: How can we know that there exists something hidden that we can't experience directly? Doubts about this question launched the debate that ultimately returned the notion that "all is One" to the science most concerned with the separate identities and behaviors of the universe's most finicky bits and pieces.
Because quantum mechanics can be so complex, Pas makes use of metaphors to help us non-physicists grasp the central issues. Here's a key metaphor which I'm going to share by quoting from the first chapter, "The Hidden One," since if I tried to summarize the metaphor, I'm worried that I'd leave out something important.
We can obtain an even better understanding by comparing cosmic history with an old Hollywood movie. When we watch a film like Bringing Up Baby, the 1938 American screwball comedy starring Katherine Hepburn and Cary Grant, we experience a hilarious plot about a paleontologist trying to assemble the skeleton of a huge dinosaur, a project disrupted when he meets the crazy but beautiful Susan, who owns a tame leopard, and Susan's dog steals the last missing bone and buries it somewhere.
But the story we experience in the theater is not really stored on the roll of film. Instead, a traditional movie projector displays the information on the film, one picture after another, flashed so quickly that the viewer has the impression of an unfolding story line. Again, the story is not really on tape; it is created by the viewer's perspective onto the projected film.
The story is created by us watching it, while the original source of information remains unswayed, mounted on the projector. In the same way, cosmic history may be understood as what we experience, created by our perspective onto a fundamental "quantum reality."
The "Hollywood movie plot interpretation of cosmic history" offers an astonishingly accurate picture of how quantum mechanics works, highlighting the most important question quantum mechanics forces us to ask: What is reality? Is it the light bulb and the collection of pictures stored on the film roll inside the projector, or is it the story experienced on-screen?
Even today, there are two camps of physicists and philosophers arguing fervently about exactly this question.
The orthodox "Copenhagen" interpretation of quantum mechanics, advocated by Niels Bohr, Werner Heisenberg, and the overwhelming majority of physicists, insists that the movie plot constitutes reality. For many decades only a small number of outcasts, including (at least for some time) Erwin Schrödinger, Wheeler's student Hugh Everett, and the German physicist H. Dieter Zeh, populated the "projector camp."
This renegade view, however, is getting increasingly popular. It is part of a controversy that originated in the 1920s, as physicists fought out the question of how strange reality really is.
As you can probably guess, Pas is in the renegade projector camp. Otherwise his book would be a rather boring rendition of the traditional Copenhagen "shut up, calculate, and don't worry about the meaning of quantum mechanics" camp.
I'll be writing more about this book. For now, I'll end with the final paragraph in "The Hidden One" chapter, just to bookend how Pas begins and ends the chapter. Well, actually I need to include the next to final paragraph also. I'll break the paragraphs up to make them easier to read.
In a different place, though, Wheeler provided some clues: "The point is that the universe is a grand synthesis, putting itself together all the time as a whole... It is a totality." He also speculated whether "a comprehensive view of the physical world [would] come not from the bottom up -- from an endless tower of turtles standing one on the other --but from a grand pattern linking all of its parts."
The Hollywood movie plot interpretation can help to illustrate this point: Onscreen, Susan, the paleontologist, and the leopard appear as distinct, individual characters. On the film roll, though, they are all mere features of a single camera shot.
Quantum mechanics goes even further. In quantum mechanics, so-called entangled systems get so completely and entirely merged that it is not possible to say anything at all about the properties of their constituents anymore. In quantum mechanics, all individual objects and all their properties result from the perspective of the observer -- as, at least potentially, do matter, time and space: they don't really exist on the film but are part of the story experienced as unfolding on-screen.
In fact, this view again is strikingly similar to Plato's philosophy, which assumed that hidden on the most fundamental level there exists only one single object in the universe: the universe itself. Or, in the words of Plato, "The One."