Quantum mechanics

"The general notions about human understanding ... which are illustrated by discoveries in atomic physics are not in the nature of things wholly unfamiliar, wholly unheard of, or new. Even in our own culture, they have a history, and in Buddhist and Hindu thought a more considerable and central place. What we shall find is an exemplification, an encouragement, and a refinement of old wisdom."

"I argue that what breathes fire into the QM equations is field-theoretic what-it's-likeness: "microqualia" to use a philosopher's term of art. The different values of the solutions to the ultimate physical equations exhaustively yield the abundance of different values of subjectivity. There is no room for dualism; "nomological danglers"; causally inert epiphenomena; classical, porridge-like lumps of otherwise insentient but magically mind-secreting matter, etc. There is no "explanatory gap" because there aren't any material objects - not even brains or nerve cells as commonly (mis)perceived. Instead, over millions of years, non-equilibrium thermodynamics and universal, (neo-)Darwinian principles of natural selection have contrived to organise a minimal and self-intimating subjective sludge of microqualia into complex functional living units. Initially, these units have taken the form of self-replicating, information-bearing biomolecular patterns. Eventually, selection-pressure has given rise to complex minds as well, albeit as just one part of the throwaway host vehicles by which our genes leave copies of themselves. Conscious mind, on this proposal, is a triumph of organisation: our egocentric virtual worlds are warm and gappy QM-coherent states of consciousness. Contra materialist metaphysics, sentience of any kind is not the daily re-enactment of an ontological miracle. Moreover the idea that what-it's-like-ness is the fire in the equations is (at least) consistent with orthodox relativistic quantum field theory - because the theorists' key notions (e.g. that of a field, string, brane, etc) are defined purely mathematically. In other cases, they readily lend themselves to such a reconstruction. Using the word "physical" doesn't add anything of substance."

"I should begin by expressing my general attitude to present-day quantum theory, by which I mean standard non-relativistic quantum mechanics. The theory has, indeed, two powerful bodies of fact in its favour, and only one thing against it. First, in its favour are all the marvellous agreements that the theory has had with every experimental result to date. Second, and to me almost as important, it is a theory of astonishing and profound mathematical beauty. The one thing that can be said against it is that it makes absolutely no sense!"

"I also knew the formula that expresses the energy distribution in the normal spectrum. A theoretical interpretation therefore had to be found at any cost, no matter how high. It was clear to me that classical physics could offer no solution to this problem, and would have meant that all energy would eventually transfer from matter to radiation. ...This approach was opened to me by maintaining the two . The two laws, it seems to me, must be upheld under all circumstances. For the rest, I was ready to sacrifice every one of my previous convictions about physical laws. ...[One] finds that the continuous loss of energy into radiation can be prevented by assuming that energy is forced at the outset to remain together in certain quanta. This was purely a formal assumption and I really did not give it much thought except that no matter what the cost, I must bring about a positive result."

"Planck ...devised his quanta theory, according to which the exchange of energy between the matter and the ether—or rather between ordinary matter and the small resonators whose vibrations furnish the light of incandescent matter—can take place only intermittently. A resonator can not gain energy or lose it in a continuous manner. It can not gain a fraction of a quantum; it must acquire a whole quantum or none at all."

"Ask anyone today working on foundational questions in quantum theory and you are likely to hear that there is still no consensus on many of these questions—all the while, of course, everybody seems to be in perfect agreement on how to apply the quantum formalism when it comes to making experimental predictions."

"For Mendeleev the rare earths were a complete nightmare because he didn't know where to put them. He couldn't fit them in the table..! Five of them had been found by the time he was building the table, and so he... stuck them in somewhere where things went 3+, and then went "Uh?" and... left it at that. ...[T]his was a real problem, because no one knew where these building blocks went into the periodic table. ...[I]t wasn't ...until Moseley had established what was, that things began to fit together... and suddenly they realized that there couldn't be more than 14... [T]hen as the quantum mechanics rules came through it became clear... that... you'd found the hole. There was the gap... in , and so that became a target."

"If we really want to understand quantum mechanics, the goal should be more about letting go of our biases and embracing what the Universe tells us about itself. Instead, Carroll regressively campaigns for the opposite in teasing his upcoming new book. Unsurprisingly, most physicists are underwhelmed."

"Quantum mechanics is science’s equivalent of political polarization.Voters either take sides and argue with each other endlessly, or stay home and accept politics as it is. Physicists either just accept quantum mechanics and do their calculations, or take sides in the never-ending debate over what quantum mechanics is actually saying about reality."

"The rules of quantum mechanics work, but only if all natural phenomena in the world of the small are subjected to the same rules. This includes viruses, bacteria, even people. However, the bigger and heavier an object is, the harder it becomes to observed the quantum mechanical deviations from the ordinary, 'classical' laws of movement."

"The inner mysteries of quantum mechanics require a willingness to extend one’s mental processes into a strange world of phantom possibilities, endlessly branching into more and more abstruse chains of coupled logical networks, endlessly extending themselves forward and even backwards in time."

"(\left|x\right\rang \left|y\right\rang- \left|y\right\rang \left|x\right\rang) ... was my first lesson in quantum mechanics, and in a very real sense my last, since the rest is mere technique, which can be learnt from books."

"Respectable scientists like de Broglie himself accept wave mechanics because it confers coherence and unity upon the experimental findings of contemporary science, and in spite of the astonishing changes it implies in connection with ideas of causality, time, and space, but it is because of these changes that it wins favor with the public. The great popular success of Einstein was the same thing. The public drinks in and swallows eagerly everything that tends to dispossess the intelligence in favor of some technique; it can hardly wait to abdicate from intelligence and reason and from everything that makes man responsible for his destiny."

"This theoretical failure to find a plausible alternative to quantum mechanics, even more than the precise experimental verification of linearity, suggests to me that quantum mechanics is the way it is because any small change in quantum mechanics would lead to logical absurdities. If this is true, quantum mechanics may be a permanent part of physics. Indeed, quantum mechanics may survive not merely as an approximation to a deeper truth, in the way that Newton's theory of gravitation survives as an approximation to Einstein's general theory of relativity, but as a precisely valid feature of the final theory."

"It is truly surprising how little difference all this makes. Most physicists use quantum mechanics every day in their working lives without needing to worry about the fundamental problem of its interpretation. Being sensible people with very little time to follow up all the ideas and data in their own specialties and not having to worry about this fundamental problem, they do not worry about it. A year or so ago, while Philip Candelas (of the physics department at Texas) and I were waiting for an elevator, our conversation turned to a young theorist who had been quite promising as a graduate student and who had then dropped out of sight. I asked Phil what had interfered with the ex-student’s research. Phil shook his head sadly and said, “He tried to understand quantum mechanics.” So irrelevant is the philosophy of quantum mechanics to its use, that one begins to suspect that all the deep questions about the meaning of measurement are really empty, forced on us by our language, a language that evolved in a world governed very nearly by classical physics. But I admit to some discomfort in working all my life in a theoretical framework that no one fully understands. And we really do need to understand quantum mechanics better in quantum cosmology, the application of quantum mechanics to the whole universe, where no outside observer is even imaginable. The universe is much too large now for quantum mechanics to make much difference, but according to the big-bang theory there was a time in the past when the particles were so close together that quantum effects must have been important. No one today knows even the rules for applying quantum mechanics in this context."

"My own conclusion is that today there is no interpretation of quantum mechanics that does not have serious flaws. This view is not universally shared. Indeed, many physicists are satisfied with their own interpretation of quantum mechanics. But different physicists are satisfied with different interpretations. In my view, we ought to take seriously the possibility of finding some more satisfactory other theory, to which quantum mechanics is only a good approximation."

"Quantum theory does not trouble me at all. It is just the way the world works. What eats me, gets me, drives me, pushes me, is to understand how it got that way. What is the deeper foundation underneath it? Where does it come from? So that we won’t see it as something that is unwelcome by friends that we admire—John Bell and many others—it will be something that will make you say, ‘It couldn’t have been otherwise.’ We haven’t gotten to that stage yet, and until we do, we have not met the challenge that is right there. I continue to say that the quantum is the crack in the armor that covers the secret of existence. To me it’s a marvelous stimulus, hope, and driving force. And yet I am afraid that just the word—‘hope’—is what does not eat, or possess, or drive so many of our colleagues in the field. They’re content to take the theory for granted, rather than to find out where it comes from. But you would hardly feel the drive to find out where from if you don’t feel that the theory is utterly right. I have been brought up from ‘childhood’ to feel that it is utterly right. Here I was, reading that book of Weyl’s at the age of eighteen and just crazy about it."

"I had the feeling that the stuff was beautiful. I learned it from Weyl, and Weyl had the art of putting things in a lovely perspective. More so than anybody else I have ever read. That book was just a treat. So the feeling of ‘rotten’ would be the absolutely last feeling I would ever have about it. ‘Beautiful’ is what I would call it. To me it’s the magic way to do it. I think that having started early and having used it in lots of different contexts, all the way from my doctor’s thesis on the dispersion and absorption of light in a helium atom, to nuclear physics, to the decay of elementary particles, I feel absolutely at home with it. But John Bell’s question I certainly sympathize with. An ‘irreversible act of amplification’? As Eugene Wigner always says, ‘What means it "irreversible"?’ [...] I think it is just wonderful to have puzzles like that staring us in the face. You’d be amused. Every day I try to write down something in my notebook, although I don’t always succeed, pushing things ahead just a little bit. I only got in two or three sentences this morning. ‘Nada. The photon doesn’t exist in the atom. It doesn’t exist in the photodetector after the act of emission, and you have no right to talk of what it’s doing in between. Nada—it’s nothing.’ Then there’s the irreversible act of amplification where you’ve got a whole lot of things. It’s nada to nada."

"For a zeroth slogan about quantum mechanics, I’ve chosenWhat’s hard to understand is classical mechanics, not quantum mechanics."

"The world is not as real as we think.… My personal opinion is that the world is even weirder than what quantum physics tells us."