Physicist: We’re definitely missing something, but we’re always missing something. One of the most famous quotes about quantum physics, often used in lieu of a shrug, is due to St. Feynman: “If you think you understand quantum mechanics, you don’t understand quantum mechanics.” Which is fair, but it applies equally well to bicycle mechanics. Or paper airplane design. Not even cake science has a hope of ever being completely understood.
The classical world (the world we experience) has one set of rules and the quantum world has another set of rules. But of course, they’re describing the same, one-and-only universe. The “correspondence principle” says that the quantum laws should, on a large and noisy enough scale, reproduce the classical laws. So far that seems to be exactly the case; as weird as they are, the laws of quantum mechanics are always compatible with the world we see around us. In other words, the very particular laws we consider “normal” are a special case of quantum laws. How that works is unfortunately a case-by-case thing. There’s no clean “quantum-to-classical translation technique”. The reason a thrown rock follows a particular path has a very different explanation than the cause of rainbows. Even the distinction itself, between classical and quantum, is often impossible to nail down.
Quantum mechanical laws are rules for the universe, and in that sense they’re no weirder than gravity or anything that Newton did. And we explore them in the same way: follow clues, come up with models, test them out, find out that practically all of them are wrong, etc. When it comes to the actual doing-of-the-math and the exploration-of-the-physics, there’s nothing unusual about quantum physics. After all, it wasn’t obvious that “for a set of isolated objects, the sum of their masses times the derivative of their positions with respect to time is invariant.” The math and experiments took a while to develop, but then we gave it a name and teach it to kids as “conservation of momentum” (an object in motion stays in motion…).
When you get into the nuts and bolts of physics (the math), no subject is terribly intuitive. If you study classical mechanics (how stuff moves) you run headfirst into Lagrangians and principles of least time or action, and suddenly conversations about balls bouncing and spinning tops become… abstract. Honestly, the big difference isn’t in the difficulty of the physics, it’s in the implications. If you learn about how to predict orbital trajectories, you’ll walk away with the sense that orbits are complicated. If you learn about how to predict quantum tunneling, you’ll walk away with the distinct sense that either the universe is messing with you or that someone, somewhere made a huge mistake and nobody’s bothered to double check their work. The difficulty is comparable, the unease is not.
So why is quantum mechanics so unintuitive? Because we’re not used to it. It would be difficult to get used to moving around in the world if you were a tiny insect, and drops of water stood up like boulders, or if you were a bird, and the air had a “landscape” of movement. We think of the world we live in as intuitive because we not only grew up and live in it, but evolved for it over millions of generations. Quantum effects seem strange to our minds because our brains have never had to deal with them before.
Everything lives in the “normal world”, but can disagree wildly on what “normal” is. For most of these critters you’d have to carefully explain basic stuff like “what goes up must come down”, “the sky is blue”, “fire is hot”, “water is wet”, etc. It’s no coincidence that minds are great at handling the environment they find themselves in, and remarkable that we can handle more.
On the other hand (literally), our bodies have had to deal with quantum effects since before they were bodies. While a human mind is really good at maneuvering a human body through the world, dealing with moving objects, weather, other humans, and making up dirty limericks, there hasn’t been much call (over evolutionary timescales) for us to worry about quantum effects. But on the scale of biochemistry, quantum effects are incredibly pervasive, and the tiny chemical mechanisms in every one of our cells take advantage of them all the time. On a chemical level, life has been dealing with quantum phenomena since it began, and (even though we don’t have to think about it) it’s gotten really good at it. For example, photosynthesis involves maintaining the coherence of incoming light (it acts like a wave, not a particle) until it can be directed to a set of molecules that can actually use the energy to make food. If plants didn’t take advantage of superposition and coherence (inherently quantum things), they’d need light-as-a-particle to bullseye the tiny receptors; a huge waste of the vast majority of photons that would be off-target.
At a basic level, every chemical process is inherently quantum mechanical. Chemistry and biochemistry are just applied quantum physics, so if you want to see some ridiculously fancy quantum physics at work, go no farther than your mirror. Or your dinner for that matter.
That said, your conscious mind isn’t there to understand every detail of how your body works down to the atoms, it’s there to react to information from your senses and direct your physical body in such a way that you live through the day (also fall in love and explore and appreciate beauty or whatever). So we’re good at that and we’re used to it. Atoms and quantum mechanics, although not inherently more weird than the “classical world”, take some getting used to.
Fortunately for us, we seem to be pretty adaptable. For example, the Earth intuitively seems to be flat, motionless, and not a brief exception to an infinite nothingness, when in fact it’s round, spinning, unimaginably old, and hurtling through the void at 30 km/s. And yet, most people don’t seem to mind. The nature of the planet we’re on is totally unintuitive, but it’s something you get used to with experience.
The classical world is already incredibly complex and weird and, as “intuitive” as it seems, it still takes a lot of work to understand it (as much as anyone can). But we get used to it. Quantum mechanics is weird too and involves plenty of ideas that seem totally bizarre to our squishy hominid brains. But we get used to it.
Bertrand Russell described ‘common sense’ as the metaphysics of the Stone Age. This was in response to claims that theories such as special relativity must be wrong because they defy common sense.
Wow ! That was one of the nicest and cleverest explanations I have ever read. It pretty much sizes of Reality itself, and makes not understanding that Reality, understandable. I’m definitely saving this one.
All those usual words that our world is so different from the world of particles and that’s why quantum mechanic is so counterintuitive.
But the world of atoms and molecules is also very different from the world where we live – so why is chemistry not counterintuitive at all? We don’t live inside bacteria or eucaryotic cells and we never observe DNA or proteins molecules in our world, but why biochemistry and genetics are not counterintuitive?
We never see electric current, but why the physics of electricity is so logical and understandable?
Why chemistry, genetics etc. can be easily understood by normal reason and logic whilst quantum mechanics cannot?
It seem that the true reason is in the quantum mechanics itself and not in the world it describes. Every scientific theory comes to make things clear to human mind. This is the primarial aim of science. Quantum mechanics is the worst of all theories with regards to clearness. Which means quantum mechanics is not a great theory.
Another aim of scientific theories is to predict. Indeed in predicting quantum mechanics is as good as electricity, chemistry or genetics. But as for clearness and understandability for the human mind – no.
I hope some day will come another theory which will replace quantum mechanics, will give same accuracy in predictions, but will be logical, reasonable and will give understanding of the world of particles for the human brain.
I understand your frustration, but being a theory about the essence of Reality, in this case, only the matter and energy side of it, being understandable by the Human Mind probably means that it is always going to be incomplete in some way. The Human mind has limitations and to try and insist that nature be reasonable to those limitations is nothing more than whining.
You write very well, Physicist, very well indeed. I am principally a Product Research Engineer, but I am also an author of novels and non-fiction books, so I know of what I speak. To answer the primary questions you were addressing, i.e., “Why are the laws of quantum mechanics so strange? Does it mean that we’re missing something?” I can answer what’s missing with three words, The Atemporal Particle. I’ve study the question, and now the answer, for over 30 years. Scientists will not be able to fully understand quantum mechanics, nor vision, consciousness, autism, savant abilities, cellular control and certainly not cancer, until scientists look beyond the corporeal aspect of life. We already think in terms of massless particles, why not massless, atemporal particles in control of all cellular functions, storing all memory and cooperating in the very ununderstood phenomenon of consciousness.
I only can add to these astute comments by saying the world is so much easier to comprehend when realizing that everything we perceive emanates from the nonphysical world. We, as humans, are mostly stuck in our little physical bubble, and can only look out in wonder at it all. That being said, we are capable of astonishing leaps into that unknown.
This a very dishonest article. Most physicists admit that our picture of what’s going on in QM is unavoidably incomplete. And something certainly is going on. In the 22nd century we’ll know an enormous amount more about what’s going on. We’ve made rapid progress already this century, especially in decoherence, which has been confirmed in the lab. The article says:
There’s no clean “quantum-to-classical translation technique”. Not true, decoherence has shown some clues about how it works. We can calculate the RATE of decoherence nowadays, and larger objects go through collapse quicker than smaller ones. They do that by interacting with the matter around them, for some reason. We’re finding out as we go, but we don’t have the main picture yet. We’ll get to it.
But some physicists just won’t admit that they don’t know it all. Good physicists do though – that’s where they start. Einstein and Newton started by admitting what we don’t know, that’s healthy, it allows progress. People who refuse to admit we’re on a journey hold up progress with the journey.
The difference between fiction and reality is that fiction has to make sense.
Reality is. No-one ever held the universe to account and told it that it had to make intuitive sense to the instincts of a bunch of primates. Our instincts developed to be good at understanding how to find ripe fruit, avoid snakes, throw pointy sticks at tasty-looking animals, run away from lions, set things on fire and other such early human activities.
They did not develop to be good at understanding how subatomic particles interact with each other, that was not something that our ancestors ever needed to directly deal with.
That Quantum Mechanics doesn’t make intuitive sense isn’t surprising; it would be more surprising if it -did-. That we can, through extensive study, experimentation and so-forth, figure it out anyway is a testament to just how remarkable intelligence is as an attribute that living creatures can develop.
Thank you ! Your comment, is one of the most Intelligent I have read about this subject and the article. I started life as a Physics major and completed the undergrad work. Then, because of some very difficult experiences in the Military, I switched over to Psychology…first experimental, then Brain correlates of learning. I ended up being a Clinician, which I am happy to say I am retired from at this stage of my long life. Your last paragraph is especially sequiter as it is truly remarkable that we can, as mammals, who have been through a remarkable journey toward both Consciousness and finally Consciousness with Intelligence, which I like to say is Sensitivity to Order, can in fact discern how the Universe operates. Thank you, for your clear thoughts. RHP.
You are implying, as the article implies, that QM is irreducible beyond what we already have for it. You say that it just ‘is’, but what you mean is, we can’t find out any more about what’s going on. Explaining something means greatly reducing the conceptual description.
Throughout history there have been people who have said “Science has gone as far as it can go”. They thought that at the end of the 19th century.
Physics is about finding patterns in nature. We’ve found that nature has very universal patterns in it. And everything that they thought was irreducible has so far always turned out to be reducible further – which means that there is a deeper explanation underneath what we have at present.
The only reason some people decide we’ve finished the job is that it gives them a feeling of security – ‘we know all there is to know’.
But study decoherence, and you’ll soon see that we don’t. Matter interacts with the matter around it, and in doing so it becomes more clearly defined. Most good physicists think that has an explanation. 50 or 100 years from now we’ll know a lot more, and people who said there’s nothing more to be discovered will look like Lord Kelvin did at the end of the 19th century, when he said science had nothing more to discover. It’s a smug, self-satisfied position to take.
Forgive me David, but I’m not seeing that the Physicist who answered the question, or anyone else here said that we were all done. I also don’t see any smug, self-satisfied positions in any of these responses. The commenters are suggesting that what ever is going on at the Quantum level is, by it’s very nature going to seem strange to our minds that spend 24/7 living in the larger aspect…actually, somewhere in the middle…of the overall Reality. No one here has suggested that we have “finished the Job”, as you put it. You may want to re-read and re-think the Scientists answer to the question. You are directing us, to study Decoherence…..Decoherence does NOT solve the Measurement Problem. You are making unfounded statements about Decoherence, and giving us your opinion on how matter interacts with itself. This is not science and your comprehension, I suggest, is a bit faulty. I suggest you study the Measurement Problem, with depth.
In decoherence we find that interactions are causing the so called collapse of the wave function. This comes from the original quantum theory, and it has been confirmed by experiment. It happens without a measurement, so people started to suspect that the interaction required for the measurement, when we do make a measurement, is also what’s doing it there. It totally removes the measurement problem, but only if we can explain what interactions do. We can’t yet, but we will one day.
That’s why it’s a taboo, and why you haven’t heard much about it. People are terrified of things they don’t understand, same as the people on this thread. But people like Einstein was not afraid of things he couldn’t understand. While one lot of people were papering over the cracks, like in the article here, people like Einstein would be found staring into them.
I understand your point that what the world contains doesn’t necessarily have to make intuitive sense to us – I agree on that. But with QM it’s clear enough that there’s more to be found out. The new clues are only a few years old, we’ve got much better at experiments, and there’s a range of new experimental evidence. Weak measurements, quantum eraser experiments, these are only a few decades old at most. Of course we’re going to find out more.
I agree, that we have a lot more to learn from nature, and we will eventually move beyond the Standard Model. Our minds are designed to keep our bodies alive and discern data coming in from the outside environment to turn it into the kind of information we can use to keep breathing. The realms of Mathematics and Physics, take our awareness of Reality way beyond the confines of mere perception. QM, is one of the hallmarks of the Human Intellect….and as you have been promulgating here….we have far to go. I do not believe that our reach will exceed our grasp. Thank you, for your input.
Scientists will not be able to fully understand Quantum Mechanics, vision, consciousness, autism, savant abilities, nor cellular control, including DNA replication, mitosis, meiosis, and certainly not cancer, nor will they solve the Binding Problem until scientists look beyond the corporeal aspect of life. My new book, The Atemporal Particle Theory – New Supporting Evidence, suggests some answers to these questions. Things are not as they seem. The book should be available in about 6 weeks. It’s at the publisher now.
Can you prove that in the 22nd century the physics of particles will look same very strange to the human mind as it looks now to anybody who studies quantum mechanics? Maybe already in 30 years from now there will emerge a new theory that will make things much more intuitive? Who knows?
When the theory of Darwin just emerged, it was the most counterintuitive theory and many people could not believe in it and could not agree with it. But more and more facts supported the theory, similar to many facts supporting quantum mechanics.
However later when genetics developed and when microbiology developed, it became clear that Darwin’s theory is correct and indeed very intuitive.
Who knows, maybe at some time in the future an additional theory will emerge that will make quantum mechanics clear and intuitive which it is not now.
Perhaps the theory of strings or something else?
I dare to compare quantum mechanics with laws of Kepler. They were a clear math describing how the planets move and were making good predictions.
However laws of Kepler did not answer the question: Why? Later came Newton with his law of universal gravity which did explain why. And the math of Kepler laws became intuitive: the force decreases with square of the distance because the force is spread around a star and the area is proportional to the square of the radius.
Same for quantum mechanics. It is a great math. A particle can be in multiple states with different probabilities. It has a wave function. The wave function collapses once we make measurements.
But why is all that? Because. No explanation behind the math. And that’s why quantum mechanics is counterintuitive. Because it is a pure math without explanation.
But there must be some explanation. It has not just been discovered yet.
But it will be! I believe that every math can be explained with an adequate model. It has yet to come.
I agree. There’ll be some sort of explanation, certainly be more explanation than we have now. Experiment has recently connected with the quantum scale, and we’re finding a lot of new clues. That’s why I say that by the 22nd century we’ll know a lot more. I think it’ll be sooner, but I put it 80 years away to be on the safe side! And for those who are prepared to admit there’s more to be found out, it’s very exciting – that’s science, you’re always trying to find out more.
Things like evolution aren’t inherently intuitive, you were simply taught about them at a relatively young age and as such have gotten used to thinking about them, causing them to become intuitive to you: Humans, like all living creatures, are adaptable and can become used to almost anything under the right circumstances.
Even if nothing at all about our understanding of the subject changes, our descendants won’t find Quantum Mechanics to be as strange as we do simply because they will be taught about it from a young age. It is not intuitive to think that the planet is a sphere hurtling through empty space at incredible speeds around a ball of nuclear fire; instinctively we think that it is flat and stationary, because that is how it seems to be to our senses.
But because we are taught that is not true, why it is not true and how to prove that it is not true while we are young and still in our primary learning phase of growth, we adapt to what we are taught. In truth; an explanation isn’t even really necessary, religion demonstrates that it is entirely possible to teach people to believe things simply by telling them that they are true without any explanation at all. The important part isn’t whether the things make sense, the important part is the age at which you tell them the things.
Whatever you are regularly exposed to as a child is what you will grow up to consider normal as an adult, this works for literally anything and everything, from something as abstract as the mathematics behind the nature of reality to familiarity with using an iPhone.
So pointing out that other things make intuitive sense, but QM doesn’t, therefore QM must be special, is not seeing the forest for the trees. Those things only make intuitive sense to you because you have the benefit of a modern education where you were taught about those things; a human from ~5000 years ago without that education would find evolution and standard model particle physics to be just as confusingly magical as quantum mechanics, despite possessing exactly the same cognitive ability as a modern human.
As we find out the truth about what’s out there, step by step, we find out that some of it is intuitive and some of it isn’t. Therefore intuitiveness is no indicator of anything – perhaps we agree on that.
But so far we’ve found that more or less everything complicated we’ve ever encountered has a further layer of explanation underneath it. And with QM, new experimental techniques that came in since the ’80s that have given us a long list of new clues. Weak measurements, quantum eraser experiments, experiments confirming decoherence, and many others. And they all suggest that something we don’t yet understand is going on. And they suggest it in many different ways.
Now for some people that ‘doesn’t compute’: something we don’t yet understand, but we almost certainly will in the future. But a good scientist knows that such things exist.
You seem to say that our ability to understand doesn’t really exist. But if you want to do science, then you better believe that it does, as that’s a large part of what science is about – gaining an understanding of how the world works.
I freaking love this article and this entire website.