It’s time to admit quantum theory has reached a dead end
nautil.us
nautil.us
This article also misses what is likely the leading interpretation of quantum mechanics by actual quantum physicists, namely that the measurment problem is solved by decoherence (the quantitative theory of how classical states emerge from quantum states):
https://en.wikipedia.org/wiki/Measurement_problem#The_role_o...
https://royalsocietypublishing.org/doi/10.1098/rsta.2011.049...
Hawking espoused this idea he called “model dependent realism”. The idea is that every human understanding of reality is model-dependent, that is, it is not “reality” that we truly understand (we can’t) but rather in every case we have some model of reality that is useful in particular situations. For instance, we know that Newtonian physics are not “real” but they are perfectly accurate in certain situations. So they are not “wrong” when they are used in those situations, in fact, they are right.
The author of the article writes, “While Einstein won a Nobel Prize for proving that light is composed of particles that we call photons, Schrödinger’s equation characterizes light and indeed everything else as wave-like radiation. Can light and matter be both particle and wave? Or neither? We don’t know.”
In model dependent realism, we can ignore this apparent contradiction. In some situations the model of light as a particle is the most useful, and in others, the model where it is a wave is the most useful. We have to accept that it is not “really” either of these models, but that no matter what we do, any model we come up with for it will still just be a model.
"The Copenhagen Interpretation is sometimes called "model agnosticism" and holds that any grid we use to organize our experience of the world is a model of the world and should not be confused with the world itself. Alfred Korzybski, the semanticist, tried to popularize this outside physics with the slogan, "The map is not the territory." Alan Watts, a talented exegete of Oriental philosophy, restated it more vividly as "The menu is not the meal."
quite a good read if you liked his previous works.
Yes, we can only describe with models what can be observed. But it is a bad excuse for ignoring contradictions in (or between) models.
I don’t think anyone is saying that, but in pondering this issue, I remembered how in Spanish there are two verbs for “to know”, “saber” and “conocer”. That latter verb is often explained in English as “to be familiar with”. The usage makes the point best: you can “conocer” a person but cannot “saber” them. That is, you can be acquainted with someone but you cannot truly “know” them, no matter how close you are to them.
Think about it: how well do you know yourself? You live in your own head and yet you are probably surprised by some of your own reactions, or dismayed by your actions, or fearful of certain emotions. If you do not fully understand yourself then what does understanding nature even mean? I cannot inhabit the mind of my wife, let alone inhabit a photon.
But we know! The answer is neither.
Light and matter are weird things that is impossible to describe with usual language, but they can be described very precisely with math language. The problem is that the equations are too complicated and difficult to use.
They have been tested thoroughly, for example in particle accelerators but in experiments with very few things moving around. It's very difficult to use them when the experiment gets bigger.
In some cases, you can make some approximations and get almost the same result if instead of the full correct equations you use the wave equation. It's just an approximation. Light and matter are never waves, but in some case they can be approximated as waves.
In other cases, you can make some approximations and get almost the same result if instead of the full correct equations you use the particle equation. It's just an approximation. Light and matter are never particles, but in some case they can be approximated as particles.
And in other weird cases, bot approximations get very inaccurate predictions.
So has GR. Yet the two theories seem to be utterly incompatible.
There are whole textbooks written on the limit in which General Relativity and Quantum Mechanics work well together, with Birrell & Davies 1984 https://books.google.co.uk/books?id=SEnaUnrqzrUC being the most widely used by graduate students (and as a reference book for researchers).
Indeed, such textbooks go into where GR & QM make incompatible predictions, and almost all of those are in the limit of strong gravity, which in turn is almost certainly always deep within an event horizon, or isolated in the very very very early universe.
Semi-classical gravity (SCG) works well as an "effective field theory", and simply marries a classical curved spacetime (General-Relativity style) with a relativistic quantum field theory (standard-model-of-particle-physics style). In particular, with minor caveats, on the cusp of strong gravity SCG is successful enough in the astrophysical study of stellar remnants that it is reasonably believed to be good everywhere outside black hole horizons and after the very early universe. https://en.wikipedia.org/wiki/Semiclassical_gravity -- one of the caveats is noted there, namely given a sizeable mass (> kilograms) brought into a superposition of space, it is not clear at all what SCG predicts a cavendish apparatus or other gravimeter will point to. This is a possible incompatibility of SCG's two more-fundamental theories in the weak gravitational field, low-energy matter, and low-speeds-compared-to-c limit, and is a puzzle that hopefully will be informed by clear experimental data some day.
Since we can't get information back from inside a black hole horizon; can't see anything in the very very early universe (electromagnetism hadn't "frozen out" of the GUT yet for instance); direct detectors of very early universe gravitational radiation are implausibly hard engineering tasks; and a bowling ball sized mass will be extremely hard to keep in a coherent state for reasonably long periods of time; these are really academic problems rather than practical ones.
Maybe you meant to say "formerly paid to be a quantum physicist"? :-)
By disentangling himself with quantum physics. He was a quantum physicist, so I assume he knows how to do it.
I think "solved" is too strong. The Wallace paper you reference, for example, does not claim that decoherence solves the measurement problem. His claim is only the more modest one that understanding decoherence helps to clarify what the measurement problem actually is.
To be a bit more specific as to how _decoherence_ solves this, one way to see it is that classicality (i.e. observables having specific values) is an emergent property in the limit of near-infinite degrees of freedom in the same way that e.g. thermodynamic properties (temperature etc.) are emergent properties of classical systems in the limit of near-infinite degrees of freedom.
Putting it on the edge, claiming that quantum theory is at a dead end is like claiming statistical physics is at a dead end.
One of my personal favorites for how to formalize this is the work on "pointer states" by Wojciech H. Zurek. There is a freely available Physics Today articls [0], and you can find surveys of further work e.g. in the introduction of [1].
[0]: https://arxiv.org/abs/quant-ph/0306072 Zurek, Decoherence and the transition from quantum to classical -- REVISITED [1]: https://arxiv.org/abs/1508.04101 Brasil, Understanding the Pointer States
But could we then please stop teaching the collapse nonsense to first year students?
The logical inconsistencies of the collapse interpretation are an insult to their intellect.
Can you explain or express this in a simpler way? Is it almost like saying macroscopic?
In essence the Copenhagen interpretation is still correct as a simplification that can still be OK in most cases. This is reflected by the fact that practising solid state physicists have successfully used this 20's style of QM for 100 years now.
There has been roughly a century worth of experiments since the quantum theory came into being. Those experiments have scythed through myriad attempts to explain the mechanism by which quantum theory apparently describes reality.
Physicists can choose between interpretations of quantum mechanics according to "taste" precisely because there are no observable ways to differentiate between them. As soon as those ways become available to us, "taste" will give way to experimental tests.
There is still ample room for cleverness. Experimentalists are pushing forward where we can, but another observation like Bell's might be sufficient to allow, pardon the pun, a quantum leap.
Hasn't yet made useful predictions though.
https://en.wikipedia.org/wiki/A_New_Kind_of_Science
https://en.wikipedia.org/wiki/Chaos:_Making_a_New_ScienceGranted, I'm not mathematically fluent enough to know if they represent a deviation from variational calculus!
We might already have a modern day Copernicus. Could be string theory, could be something else. The problem is that we don't really have any experimental data that can't be explained by the Standard Model. What we really need is a modern day Galileo that can perform some sort of observations, like finding Jupiter's moons, that don't fit in with the existing conventional physics.
Feels very epicycle-ish and ripe for a major shift.
not very observable
We have a model and weer have observations. The two don't match, so there is a problem with at least one (model or observations). MOND posits the problem is with the model and proposes refined models. These are refutable and indeed, counterevidence is often found.
Dark matter posits the problem is worth observations. Its solution is to propose a tiny particle that is basically invisible. For every situation, you then can invent an amount and a distribution of these tiny, invisible, undetectable particles to match observations and thereby substantiate your theory.
It's not really surprising that so far, folks have succeeded in inventing a distribution of undetectable clouds of particles, clouds weighing in at multiples of the solar system's combined mass.
What was the evidence Copernicus saw that epicycles didn't explain? (Honest question.)
It wasn’t until Kepler that a geocentric model involving ellipses actually was more predictive.
Might be worth returning to the Pythagorean interpretation (which Bohr discussed): All is number. The world is made of math, not stuff.
You mean heliocentric?
IMO, some of the smartest people that have ever lived, live right now. Mainly because we have more humans alive than ever before. The amount of brain power working to find these simpler models is breath taking, yet we aren't seeing the elegant simple solutions fall out like we once did. I don't think that's a problem with the ingenuity, I think that's a problem with the problem.
It is a hard balance to strike because on the one hand you want to be constantly challenged by your fellow scientists but on the other hand also just take the foolish liberty to fully develop your (most likely flawed) intuition.
So even if I'm highly sceptical of Wolfram he gets my full respect and also Hugh Everett [0] who wrote a letter to Einstein as a 12-year old with Einstein answering: Dear Hugh: There is no such thing like an irresistible force and immovable body. But there seems to be a very stubborn boy who has forced his way victoriously through strange difficulties created by himself for this purpose. Sincerely yours, A. Einstein And later in life courageously confronted Nils Bohr with the [...] idea that the universe is describable, in theory, by an objectively existing universal wave function (which does not "collapse") i.e. Many-Worlds-Interpretation.
There are lots of nifty ideas that are explored until insurmountable holes are found in them. The two main nonstandard lines of thought that have had any real progress are decoherence, which I'd call a success, and string theory, which I'll avoid rating because I have string-theorist friends but am not a liar. There are plenty of others, and maybe one will bear fruit, but honestly when the next big break comes it'll probably be really obvious.
If one wanted to cast doubt upon, if not "debunk", his idea from the science of the times, it would not have been difficult to do so (see: Tycho Brahe). And that was on an issue that was likely some orders of magnitude less complex than the one we may be facing today. The implication of that being that the "right" answer may initially seem to have more holes than swiss cheese. I think it's very safe to say that relativity, undoubtedly the monolith to which all scientists aspire, was an exception and not the rule in the march of discovery, in its reception/clarity.
We wouldn't need a Copernicus to solve this problem, we would need a Copernicus, then a Kepler, (ellipses & non-uniform speed) then a Newton, (gravity causes ellipses and non-uniform speed) and then an Einstein. (gravity is warping of space-time)
If quantum field theory is as wrong as Ptolemy's geocentric model was, we're hopeless. Because QFT very well predicts the observations; our observations have no ellipses in them that invalidate circular orbits, our observations have no anomalous Mercury precession that invalidates Newtonian gravity, no speed of light being consistent in all directions to invalidate luminiferous aether. To say that we simply need a smarter theoretical physicist is simply wrong -- our current theories do not contradict the things we are able to observe.
We know that general relativity and quantum mechanics do not play nice at small scales and high local gravity. But we cannot observe this conflict. And that's nothing to go on.
We would need an observation which shows that general relativity or QFT is wrong about something before we could conceivably make foundational progress on making new or different theories. And every few months there's a new article about "Einstein is proven right again" or "LHC experiment shows all readings are nominal".
This thing that keeps galaxies bound that we cannot see but can only observe the effects… I think the hunt for it will push us into new territory.
That being said, as you say there has been nothing yet found that violates GR/QFT.
If that's true we're hosed. There would be no insights, no way to theory ourselves out of it. Only nerds wailing futilely about dark matter on the internet. And sadness. And we wouldn't know it's because all our theories are correct, but we don't have the complete picture of the extra-Standard Model dark matter particles, or if it's because some variation of MOND is true, (although it's extremely unlikely to be a MOND variation) or if we're as wrong as epicycles vs curved fabric of spacetime.
Arbitrarily advanced is pretty strong in a world where some people think dyson sphere scale stuff could be real.
The history of QM that I learned in school a long time ago, is that a few physicists endorsed adopting a purely mathematical formalism with no preferred interpretation in order to be free of preconceptions that might prevent them from making progress. They were still free to debate interpretation, but considered it to be separate from the problem of forming an experimentally testable theory.
But in terms of finding a philosophically satisfactory interpretation, we don't know what to look for. No science has ever attempted to dig deeper than the level of analogies that are easy to grasp. And it seems reasonable that the interpretation should depend on the science. Otherwise we risk embracing an interpretation that becomes a barrier to progress, or that is overturned by new experimental evidence.
I think the biggest problem with fundamental physics today, is that it's hard. As in, hard enough that it's not yielding answers at the rate that it was 100 years ago, and we don't know when it will: 10 years, 100, 1000? The big problem -- reconciling quantum mechanics and gravity -- won't be solved until we solve it. A theory that solves this problem will require one of those two things to be "wrong" in some sense, in which case its interpretation will have to be revised.
> Deutsch, too, seemed impatient with my dissatisfaction over our understanding of the nature of reality. “Someone might equally well say: We may know what dogs look like and how they behave, but we don’t know what a dog ‘actually is’,”
What was the cliche? All theories are wrong, some theories are useful. It needs to be rephrased from vector codes into massively parallel codes but people can work with that.
Quantum theory isn't. It's not a single, cohesive, consistent theory.[1] There is no recipe you can apply, it's just a bunch of guessworks and heuristics that happen to produce the numerically correct equations if you keep trying long enough. This isn't secret or some sort of external criticism, you'll find this front-and-centre in the foreword of many a QM text!
Schrödinger famously arrived at his equation basically through numerical methods. He just tried things until it "fit" the desired output.
Now, there's nothing wrong with this, per-se. It's a perfectly viable approach for getting going, for getting something and using it as a starting point. But it isn't the endpoint, because approaches like this often have virtually no explanatory power.
A similar example is collecting insects, categorising them, giving them Latin names, and putting them up for display in a museum. You can learn a lot, amass enormous amounts of information, but without a theory of genetics and natural selection you will always be blind to the underlying truth of it all.
QM is just like bug collecting. We're collecting numerical equations that work, but we have essentially no clear understanding why. We've built a tree of life, and nobody has had the lightbulb moment that explains why it's a tree.
[1] There was a paper published a few years back where a bunch of working quantum physicists were asked some simple multiple-choice questions about the fundamentals of the theory. There was no consensus opinion on anything! PS: You'll get similar results if you ask priests of a random Christian sects about the basics of religion. Conversely, you will get nearly zero disagreement if asking Chemists about the basics of their science.
Also, physicists disagreeing on interpretational issues related to quantum foundations is not the same thing as disagreeing about the fundamentals of the theory.
Also chemists have the luxury of agreeing because the fundamentals of their work (not the day to day act of doing chemistry) gets to assume the presence of physics i.e. it's stampkeeping (depending on who you ask).
Note that protein structure prediction finally fell to machine learning and it was "mostly stamp collecting" (IE, the accurate predictions come from subtle analysis of rich protein sequence alignments, not from understanding the fundamental principles of protein folding).
The simplified protein folding problem states that proteins fold to their energy minimum, and a succesful heuristic can find the "correct" fold by finding the structure argmin(energy). Although this is a real simplification that doesn't represent actual proteins, even that is not something you'd solve with matrices; combinatorial math.
More importantly, "protein folding" is the biophysical process that proteins experience; what DeepMind did was solve "structure prediction", which is another simpler problem, and they didn't do it by energy minimization, they did it by exploiting sequence similarity to provide structural constraints that massively reduced the search space.
might be true, but it's computationally intractable and even if you did find a way around it you'd just learn that your force field was inaccurate, or that proteins don't actually fold to their energy minimum.
Not just hard, but NP-hard. In fact, the "protein folding problem is NP hard" is misleading; in fact, the "static protein structure problem" is NP hard, and protein folding is "harder" than that (it's a superproblem of static structure prediction).
The way to describe angles for a protein is this: you use degrees or radians to describe the torsion angles of the backbone (2 torsions per amino acid, 360 possible positions per torsion, times the number of backbone atoms in the protein). Treat side chains with rotamers, that's already a solved problem. However, you can't compute self-collisions in angle space you need to embed the protein structure in cartesian coordinates, which is how they are normally represented (as a graph representing the bond topology, and an N*3 array of positions).
> it's as solved as it can really be as far as human understanding is concerned
You handwave away several interesting parts of the problem without providing real justification for why that would be necessary or acceptable.
It's like saying "politicians are made up of atoms, and since we know how atoms interact, our understanding of politics is reasonably complete".
What DeepMind solved was a far simpler problem: reproduce the structures that get produced by some experimental method. That's a well posed problem but ultimately a less interesting one, even if it's immediately "useful".
the famous feynman have produced a response to this train of thought - usually from the laymen - where they demand an "explanatory theory". The answer is usually "don't know"; why gravity work the way it does? - don't know, but we can calculate orbits to great precision; why does photons or electrons travel the way it does? - don't know, but we can make very precise predictions via Quantum Electrodynamics theory.
The laymen demands an explanatory theory, because there's an underlying assumption they don't even verbalize - that such an explanatory theory can be understood _without the maths_, that the principles of the laws of physics operate on basic, understandable lego pieces. What is somewhat unconceivable is that the explanation _is_ the maths. To whit, we don't even have an explanation for the idea of inertia! We just observe it, and measure it (as mass). There's no explanatory theory.
"Honey did you take the garbage out?"
"When you say garbage, have you considered if garbage can even really exist?"Still, it's fun to play with this idea via figures who are a little more philosophically rarified as it were:
https://www.tiktok.com/@davecolumbo/video/706085573209017886...
Do school names determine how good a school will be? Of course not. However, schools have names which tend to be reused: cultural icons, scientists, etc.. And schools in low performing areas are going to have a different distribution of chosen names than schools in high performing areas. So you can create a model that will not only demonstrate this but also offer legitimate observational predictability that a school's name will, on average, determine how well it will do.
The only way you could really refute this hypothesis is by understanding the true confounding variable, or by running some huge scale multiple decades long experiment where you changed the names of new schools and measured the performance difference. That experiment is clearly not really practicable, so all you're left with is understanding.
And this is really where the risk is. If we ever begin to build upon something that is unsound then it risks everything from that point onward being also invalid. At best everything collapses and you realize you must have made a mistake. At worse, you simply end up adding endless epicycles until at some point everything starts to completely stall out muddled in its own invalid fundamentals and irreconcilable complexity.
"The laymen demands an explanatory theory" -- and so do scientists! Why do you assume scientists are somehow "above" explanations, and are content in ignorance?
"explanation _is_ the maths." -- People had good rules of thumb for evolution (such as dog breeding practices), and Gregor Mendel could have come up with his mathematical rules for selection before Darwin published his explanatory theory of natural selection. That doesn't mean that it's worthless to try to aim for an explanatory theory of QM instead of a purely numerical / observational one.
That's literally what goes on at CERN. They run effectively trillions of experiments, collect millions of them (after some filter), and then they draw histograms.
Unless you know nothing about mathematics, you know that histograms are inherently statistical beasts. It's meaningless to talk about the histograms of one experiment.
Could you learn to play, say, tennis by drawing histograms of player movements? Ball bounce locations? No? Why not!? It's tons and tons of data! Accurate, scientific data!
Quantum physicists would argue that only statistics exists. I like to point to the fact that one hydrogen atom can exist, and it can have on electron. Or zero electrons. In nice countable, integral quantities. You can place a single gold atom on a crystal lattice with an AFM or even draw cute pictures with them: https://cen.acs.org/analytical-chemistry/imaging/30-years-mo...
Just because some people think only collecting bugs is what biology is all about, doesn't mean that there isn't more to it...
I expect as we see quantum computers increase in scale it will become more apparent and accepted that there is no such thing as "collapse": that is just the approximation for a large system including the observer becoming entangled with a smaller quantum system under consideration.
I think even the disillusioned author here would have to take that as progress.
To me it's quite simple. We haven't detected what is causing the waves that the particle of light is riding on. The particle of light is like a surf board, riding a wave and will always hit the shore in the interference pattern. Einstein and Bohr were both right.
What has been the wrong assumption over the years is that the light is generating the waves. It seems obvious to me that something else outside of the light (that we haven't detected yet) is generating the waves.
My amateur physicist guess is the waves are generated by the clock cycles of the computer simulation we are in. All computers require a clock to function. Why would our universe be any different?
We just like to make metaphors to put this thing in a box that we can't understand. But perhaps at its most fundamental level it will defy comprehension or even definition.
[0] In the philosophical sense; https://en.wikipedia.org/wiki/Mechanism_(philosophy)
[1] https://syncedreview.com/2020/04/17/stephen-wolfram-the-path...
Because information is fundamental.
Computers just so happen to be our best tools in the information domain.
Being a hologram is something I see as a significantly different type of comment. That's about how a sphere of space is mathematically equivalent to a flat 2d shell using equivalent but warped physics. It doesn't change anything about the nature of the universe except sort of the number of dimensions. And it's orthogonal to those ideas.
I'm not sure how to categorize the graph thing but it's not widespread at all.
Clocks are not required at all, even for digital computers. They only make designing computers a lot simpler.
If even a single bit gets hung up in a straightforward clockless design, everything else waits for it.
None of that is really visible to something inside the computer, though. The OP is describing calculation steps, not clock cycles.
Or perhaphs if we do have one big global clock, your distance from it warps/distorts other parts of the reality at each point in space? Maybe there is a limit to how far this heartbeat travels (edge of the universe)?
You can also then ask, at what speed or clock cycle is reality "rendering" and is it the same speed everywhere? It would seem each point renders itself and there would be no big global processor doing the rendering.
Then finally if you really want to dig deep, ask why is it being rendered to begin with. Might need some psychedelics for this one instead of math.
What if there are no clocks nor any points, what if matter is just a condensate of frequencies/sound/harmonics - that is, there is a "great piano player" and the "sound" it emits is the universe, just a side effect. If it stops playing, the universe disappears/collapses into nothingness.
note: A point here referring to a point in a massive 3d grid of points.
This is exactly Bohm's Pilot Wave theory that the article talks about. It has been debunked to some extent but I believe the debunking is still somewhat controversial for proponents. There are neat macro-level simulations of it called "Walking Droplets" if you search for them.
However, whenever I read the comments on any subject I happen to know something about, like physics, they are always completely nonsense from people who clearly have absolutely not even the smallest amount of experience in the area they are talking about. The worst part is, all these comments sound extremely authoritative, if I didn't know any better I would have believed they were experts.
This makes me very worried about the Gell-Mann Amnesia affect. I'm very worried that all the comments I've been reading on here about tech and computer topics are also just from larpers who are pretending to be experts but actually don't know anything.
https://hn.algolia.com/?sort=byDate&type=comment&dateRange=a...
And you stay polite and interactive?!
Are you sure you are human?
I wish I could do more actually - especially right now because the war is putting a lot of pressure on the container here.
I only know a tiny bit of modern physics, and in a sort of backdoor fashion through electrical engineering, and even I can spot the occasional "this guy learned quantum physics via Star Trek" post.
I also know a little about Covid (having a minor in molecular and cell biology, and obsessively consuming resources like TWiV for a while), and the median amateur virologist comment here is just a howler. Occasionally you'll have people who really know what they're talking about comment, but it usually gets drowned out.
The key, then, as always, is to read everything critically. Then there's some real insight to be gained here.
That isn't to say that there aren't voices from experts in those fields that contribute to the discussion, but they are usually drowned out with "The sample size it too small" with an n=20000 or "they aren't letting different ideas into [insert scientific field here]" as they've mentioned further up in this thread.
- I wanted to work on nuclear fusion energy, for the future of humanity.
- I was told that if I had a PhD in physics, I could do just about anything - it's a way of keeping options open.
- I liked tinkering in the lab & learning new mind-expanding concepts in textbooks.
- I viewed it as a test of my intelligence. (Turns out, it's more about perseverance.)
I know at least one string theorist, and they seem to be motivated primarily by liking to mess around with abstruse mathematics. Some others seem to enjoy the 'nerd cred.' I think the ones whose sole motivation is 'getting to the bottom of the universe' probably burn out early, b/c there's so little of that to be had right now. (I've heard from several people who got their PhDs in particle physics who went on to do data science/programming, saying that the field is depressing and that's why they didn't pursue it further.) As for me, I found the 'shut-up-and-calculate' attitude a major turn-off to studying quantum physics. (Plasma physics uses little or no QM, so that worked out for me.)
Someone who is genuinely interested in understanding the way the world works ends up asking questions about what goes into the calculations - what's the Lagrangian, how many degrees of freedom (i.e. quantum fields) are there, what symmetries or constraints are satisfied by the laws of physics, how can we set up the math to avoid pathological situations where the results of our computations are infinite, and so on. Philosophically motivated interpretations of quantum mechanics shed exactly zero light on these questions.
Well.. there is a caveat. If quantum mechanics was somehow incorrect - that is, if unitary evolution of a state vector in a Hilbert space didn't actually describe reality at all - then all of the above would be wrong. But in that case, every single interpretation of quantum mechanics would be wrong as well. Quantum computers would just flat out not work.
This isn't the problem with Bohmian mechanics at all. Bohmian mechanics "solves" the EPR experiment by letting hidden variables jump around across spacelike separations. This cannot be disproven by Bell tests.
The problem with Bohmian mechanics (which I have always heard called "Bohmian mechanics", and not "pilot-wave theory") is that it isn't truly relativistic; it doesn't happen in Minkowski space and nobody has to my knowledge extended it to Minkowski space in a way that is widely considered acceptable. If the author likes Bohm's approach so much, he should learn about the ongoing developments:
http://en.wikipedia.org/wiki/de_Broglie-Bohm_theory#Relativi...
This is a bit too pessimistic. There's the possibility their experiment will confirm local realist retrocasuality (by finding a result different from what typical QM would suggest) - at which point we will have reduced the options considerably.
Whether it is QM, or Dark M/E, etc. A lot of these constructs feel strained to me at times.
But. having said that, I am guessing, that back when the cutting edge was Maxwell, and Lorentz, and along came a burst of genius, named in the article, Bohr, Einstein, Schrödinger, and Heisenberg, and I would include Pauli, Godel and probably a bunch of others.
My prediction is that there will be a burst of insight and innovation, these things tend to come in clumps, when a lot of people start "riffing" off of each other.
There is no way to predict when, but I only hope I am still breathing to witness it!
It is human nature to quit, most especially, when there is no foreseeable benefits.
But think about it this way, science is like the human body.
The head of science, are those scientists who make a new discovery by going through research articles of their predescessors, who were just 1 mm from digging up gold.
The necks are those scientists, who almost made a new discovery, but couldn't see the light at the end of the tunnel.
And the legs, are the early scientist like Galileo, who laid the ground work.
Anyways, wherever you find yourself, it is imperative you don't lose faith in the process.
Afterall, everybody mocked the Wright brothers, for building a plane. And most advanced scientist question, why they venture into this field called science, afterall it is a labor of love, and only the lucky few get glorified.
But I get your point through and through, it is better scientists pour in their brains in more linear science, like things we can see and computate, instead of pouring brain power in abstract concept that has no current benefit in the present society.
>>> But I’m still waiting for a straight answer as to what the structure of the atoms that make up my body is.
I find this to be the simplest explanation of light: E=htf where h is in joules per cycle, t is measurement time and f is cycles per second.
Every wavelength of light has the same energy, regardless of frequency. That energy is 6.26e-34 Joules.
Every “photon” is actually 1 seconds worth of light energy at some frequency f.
Once you see that the time variable was hard coded to one second in planck’s constant of action it starts to make sense. It’s not surprising that single photons cause diffraction patterns because photons aren’t real particles.
forgottenphysics.com
https://img1.wsimg.com/blobby/go/e266e5e7-739c-437c-89c3-eed...
Maybe we do need a Copernican revolution. But how many areas of physics and science can we say that? A lot.
I think for sure the idea of measurement as a passive activity revealing pre existing values is gone though. No matter what happens. How long was that a paradigm?
The guy who did the hard work was Kepler. Copernicus's model of the solar system was just idle speculation. Also widely off the mark (it had epicycles, lots of thyem, twice as many as the Ptolemaic model [1]). Kepler sifted through the mountains of astronomical observations made by Tycho Brahe over many decades, and used the latest cutting edge math tools available (logarithms) to come up with his 3 laws.
The true revolution is science was obviously Isaac Newton. But if he had some giants on whose shoulders to stand, they were Kepler and Brahe, not Galileo and Copernicus.
[1] http://tofspot.blogspot.com/2013/08/the-great-ptolemaic-smac...
A bar magnet is surrounded by magnetic flux lines. Apparently it takes no energy to maintain that magnetic field.
If I heat the bar in boiling water for long enough, it becomes demagnetized. On the macro level there's no visible/measureable change in the bar. We need a lot of magnification to see that the 'particles are no longer aligned'.
On the other hand, I move the bar magnet over a pile of iron filings, some of the filings will fly up against gravity to the bar, against the force of gravity. It takes energy to lift these filings. Where does that energy come from? (It never seems to be exhausted.)
When some force acts to remove those objects from the magnetic field, that energy is converted into potential in the magnet again.
Are you claiming that the alignment of the magnet will fade slowly over time when the field is interacted with, more quickly than it would if it were left on a proverbial shelf for millions of years?
This is true, it's just not why magnets can lift things.
That's potential energy. When you made the magnet, you created a potential between everything else and the magnet. When you unmake the magnet, you change the potential again in the other direction. Changing said potential consumes energy.
The potential can be exhausted as only so much mass/magnetic-potential can fit within the magnets field. To use the field with more stuff, you have to pull some stuff out of the field, which takes energy.
And why is there a magnetic field? Basically it's a consequence of the electric field plus relativity.
In this example the energy comes from whatever is holding the bar magnet itself up against gravity. If it's not doing any work (ie. it's not adding energy; say it's a rope or a spring) then it's not just the filings that move: the bar magnet and the filings move towards each other (with the filings moving the bulk of the distance) and the end result is that some of the gravitational energy in the bar magnet is transferred to the filings.
I think this only seems like a tricky question with an informal idea of what "energy" is. It doesn't have the same interpretation problem as what the linked article is about.
There's nothing actually holding atoms together, it's all electric fields. So why is a magnet different? (it's not).
People also don't ever ask this question about gravity itself.
Trying to teach yourself physics by reading wikipedia is like trying to learn how to program by reading the C++ standard. It's a fine resource, but not for that. You need an introductory physics textbook, not an encyclopedia. Griffith's Introduction to Electrodynamics is a classic choice.
> those iron filings are pulled by virtual photons created by the magnet
No. Virtual particles are part of a notational scheme for carrying out certain computations in quantum field theory. They're not particles, and they're definitely not involved in classical electromagnetism.
> I've concluded that magnetism is an unexplained phenomenon, just like gravity: we have accurate formulas, but nobody knows what those formulas describe.
The formulas, ultimately, describe the relationship between our observations. This is the only sense in which we ever explain anything, and a sense in which magnetism and gravity are both very well-explained.
> For intuitive understanding, I see a magnet as a well, except that this well can be moved around and has two poles.
You should not try to understand electromagnetism intuitively yet. You haven't built the right intuitions, and to do that you first need to tear down your wrong ones.
Don't get hung up on the "virtual" in the lingo about particles. All particles are more or less "virtual" depending on how you analyze the problem.
I'm sorry there is not a more intuitive explanation of this.. The underlying QFT building blocks are so far from classical physics. Even concepts like energy and momentum are in some sense emergent properties that lose most of their classical intuition "at the bottom", this is reflected by the Heisenberg uncertainty relationship for example.
There's no evolutionary reason why we would have: our brains only hold like 7 ~ 11 things in working memory, we're almost always thinking about either food, entertainment, sleep, or sex, we can't conceptualize infinities, we're stuck living in linear time at 1 second per second, our long term memory is so full of holes it's practically non-existent, etc.
Either we're unexpectedly capable at making the most of our wetware or the universe is unexpectedly simple to understand.
It's a subject of professional interest to me for decades, what impresses me is how much isn't known about how our built-in "computer" actually works. Above all neurons are extraordinarily intricate structures, and beyond that the contributions of non-neurons in the brain appear to be considerable. Given that the brain contains at least 100's of millions of participating neurons organized in a complex hierarchical network, no wonder it's still not possible to adequately account for many relatively simple phenomena let alone the emergence of towering genius.
Indeed our wetware is collectively both more capable (and more limited) than we generally appreciate. Definitely we can't predict where genius will arise, it always seems to surprise when it happens. To say it's a miracle may be naive, but perhaps that just expresses wonder and gratitude for a rare, random and highly fortuitous event.
I know that for every problem there is a solution that is simple, neat—and wrong. And above proposition is most probably the same. But still I'll be glad to read the answers.
(Disclaimer: I'm a novice)
> this energy (of wave nature obviously) passes through the slits
The question then is what type of object would possess this energy as it passes through the slits and hits the screen behind it. Since the screen is specifically set up to detect electrons, the simplest explanation is that it is really the electrons performing the interference.
(Footnote, just to be safe: Energy conservation can be broken on very very short timescales, but this is not relevant for the double-slit experiment.)
You walk up to the wall and press a button. A few feet away, a light flashes green. You press the button again. The same light flashes green. "Aha!" you think. "I have figured out what this button does: it causes that light to flash green." On a table to the side of the room is a notepad and a pencil. You jot down your discovery.
You walk back to the wall, and press a different button. Once again, the same light flashes green. You begin to wonder if all the buttons affect that one light. You press the original button to confirm your suspicions. The light flashes blue.
---
Months have passed. You have covered the three previously unadorned walls with notes, with diagrams, with layer upon layer of discarded theory. But you're so close! The machine you've designed perfectly matches everything you've observed. It's so vivid in your imagination that you can practically see it through the wall. There's just a single lever you're unsure about; you can't decide if it's part of a complex mechanical linkage, or if it simply closes an electrical circuit. It would all work either way. You draw both options and place a question mark between them.
You wander down the hall to an office, pop your head in and say to the person seated at the desk: "I think I've figured it out. Could you come take a look?"
---
THEM: "So you're not sure which one of these it is?"
YOU: "It could work either way, so I drew both. I couldn't find any way to determine the answer."
THEM: "Well, that's not very satisfying. Are you sure you tried everything? What about this button, how many times did you press it?"
YOU: "That one? Tens of thousands of times, cumulatively."
THEM: "Have you tried pressing it repeatedly? Over and over again, I mean, without anything in between."
YOU: "I have the notes over here... yes, one hundred times in a row to confirm my theory was correct."
THEM: "Only a hundred? What if it does something different after a thousand presses? You should try that; it might solve your dilemma."
YOU: "I... could, but that seems awfully time-consuming. None of the other buttons did anything different after more than a dozen presses."
THEM: "Yes, but couldn't this button be different?"
YOU: "Maybe, but there's a point where I have to assume I've got it right. After all, there's no way of knowing whether it does something different at ten thousand presses, or a million presses!"
THEM: "All the same, we would really like to know what's behind that wall. It's a bit disappointing to only know what will happen but not know what's really going on back there. Could you try it the thousand presses? Perhaps twiddle some other widgets at random, see if that creates any discrepancy?"
YOU: "But that might never end! If nothing comes up after a day of effort, you could ask me to do it for a week. If nothing comes up after a week, you could ask me to do it for a year. Can't you just accept that either option works?"
---
The moral of the story: there's a limit to knowledge gained by inference. The problem is even worse than the story described, because even if you resolve the dilemma of the lever:
-It's impossible to know that the 200 sextillionth press (and only the 200 sextillionth press) of that button does something slightly different. Your design is wrong, and you'll never discover the discrepancy.
-It's impossible to know that the first time you pressed the button (and only the first time), it lit up a yellow light in the corner that you didn't see. Your design is wrong, and the information needed to resolve it is lost to you forever.
In the real world, maybe we'll get lucky and produce a theory that has only a single interpretation. Maybe there is a discrepancy that rules out all but one solution. (And maybe we'll get extra lucky and it will be easy to visualize.) But even then, we can never be sure. I feel as though the author of the article isn't clear enough about this. You can never know what's behind the wall.
Explanation 1: The universe is not random and doesn't have cause and effect. All scientific experiments appear to work because the whole universe is actually a movie playing out where each new frame has been edited to produce the results we see, but for some reason the author decided to never violate QM.
Explanation 2: Unlike what QM predicts (true randomness) there's a finite amount of randomness added at the beginning of the universe, enough that our experiments appear to follow QM, but eventually if we looked hard enough there would be a predictable result with finite entropy. So it's actually regular determinism.
A few people claim #2 is true and doesn't imply #1. Everyone else thinks they're the same and doesn't like it for philosophical reasons.
Quantum field theory is definitely not stuck in the 1920s. Modern physics has a lot more going on than 19th century mathematics. We understand quite a lot about the mathematical structure underpinning quantum field theories.
Quantisation is a nearly well understood process, it’s not simply heuristics and guesswork.
Unfortunately, it’s not like much smarter than anyone posting here haven’t considered lots of wild ideas, it’s just that a lot of them haven’t worked, and we have been funnelled into what we currently have. There are infinitely many more interesting mathematical objects and ideas possible than what is allowed.
Quantum mechanics, or say quantum field theory, has really good predictive power. What ever comes next needs to at least be consistent. Unfortunately I think things are going to get more complicated. Don’t use your intuition developed from grinding out web crap to try and reason about the forefront of human knowledge.
Have you tried front end web frameworks recently? String theory has nothing on them.
My friends a pretty decent physicist at Oxford and the hardest part of his research? Makefiles.
I wish qmake had won the makefiles generator war the same way I wish hg won over git
The layman’s explanation I received for this, perhaps incorrectly, is that you fill in variables for factors that you don’t understand or can’t measure with whatever value makes the rest of the theory / equation work. Is that at all correct?
You can rearrange some of the parameters so that they're not free, and redefine each of these in terms of some other related parameter — your choices here are pretty arbitrary; these values being chosen as the 'free' ones does not represent some fundamental truth.
We do not have some underling deeper theory that indicates why these numbers are the way they are. Why is the electron mass ~511 kEv while the up quark is 2.2 mEv? Why not 1.9 mEv? Why not 2.3 mEv? The Standard Model doesn't generally explain it, nor does it even really intend to explain it, just to describe it.
Imagine, if you will, benchmarking some unknown CPU, and determining that the fused multiply-add operation takes, idk, 17 times as long to execute as an increment operation. We might postulate that there other CPUs out there where it takes a different amount of time — arbitrary amounts of time! Alternatively, we might gain knowledge of the underlying CPU architecture and understand that fused multiply-add is implemented with a certain set of transistors, and that it's fundamentally more complex, though there's room for some variability based on the specific implementation. In such a world this "free parameter" is set as it is for a very specific reason: a transistor arrangement.
We have limited visibility into what's actually happening "underneath" our laws of physics. Some of the values we see could be truly arbitrary. Some of them might actually be controlled by some other field and change over time (though we haven't seen evidence of that so it seems less likely). Some of them could be a deeper artifact of the way the universe works.
If you look at things like string theory, which do try to describe in more detail and dial down the free parameters to just one ("length of the fundamental string" more or less) we are left with something that's frustratingly nonspecific until you locate a more-specific solution within the broader string-theory solution space and call it "the laws of physics." That specific location might indeed seem quite arbitrary; the question might then become, what relation does this hundreds-of-dimensional solution space have with our concepts of physical reality? And can other areas of that landscape be probed in any way meaningful to our experience of physics?
I'm not saying I'm not a little miffed there isn't yet a nice, lower-level theory that predicts all of QM, but man is it frustrating when people flip flop to and from pure empiricism at the drop of a hat, based on a layman's understanding of a mature, developed field.
Oh ... and if things are still a bit floppy, just fix the gauge and you are good.
Regularization techniques take effective field theories like the Standard Model, which are known to be inaccurate at high enough energies, and isolate their low-energy behavior.
For example: classical electrodynamics, interpreted naively, says that the total energy stored in an electron's electric field is infinite, since the field strength blows up to infinity at the position of the electron itself. As this isn't actually true, we know there must be physics going on very close to the electron that our theory doesn't account for. But even if our theory isn't the Final Truth, it's still capable of making perfectly good predictions far away from the electron, and we can't just sit around waiting for quantum mechanics to be discovered.
So we make the structure of the electron a parameter of our theory: it can't tell you what the force between two electrons is, but if you posit that the electron's charge is distributed like so, it can tell you what the force between two electrons would be.
We then use empirical data to reabsorb our new degree of freedom: this is renormalization. Instead of trying to predict the force between two electrons, we measure it, and then work backwards to figure out what the electron's charge distribution would have to look like to produce that force. In this particular case: the electron behaves as if it were a sphere about 10^-15 meters across. This is of course not the actual structure of the electron, but it reproduces the same low-energy classical physics.
Notably, in a less rigorous field, this process would be called "doing science to determine physical properties of things", which most people consider an acceptable pastime for physicists. As it turns out we can be pretty confident that the "experimental evidence" is bunk and there's something going on the theory can't account for, but it's funny that so many of the Monday morning quantum physicists think all this math stuff is just confusing the issue and pure, blind empiricism is the way to go.
The one that I remember foremost is tunneling to (dis)charge the floating gates on flash memory transistors, but that just scratches the surface.
"Flash memory chips found in USB drives use quantum tunneling to erase their memory cells."
https://en.m.wikipedia.org/wiki/Applications_of_quantum_mech...
This I did not know:
"It even exists in the simple light switch. The switch would not work if electrons could not quantum tunnel through the layer of oxidation on the metal contact surfaces."
https://www.scientificamerican.com/article/when-it-comes-to-...
Ironic that plastid-based life is so much more advanced than us, but we are the ones that ended up with (super)intelligence.
"Breaking bad" covered this with an etch-a-sketch. Sometimes chemistry can be surprising.
Quantum computing is an elective at every half-decent University.
To think that programmers have zero understanding beyond high school math is just ignorant.
Now compare that with AI/ML or large scale data processing over the last 20 years. I don’t think you should assume that the smartest people were those that didn’t see this coming and wanted to spend their life on interpretations of double slit experiments and string theory.
If you know more than others, that's great—the best thing is to share some of what you know, so the rest of us can learn. Just please do it without swipes and putdowns.
https://hn.algolia.com/?dateRange=all&page=0&prefix=true&sor...
All the evidence suggests the "particle" interpretation of QM is simply wrong, that light or energy really is just a self propagating wave, which explains the double slit experiment cleanly, and is not incompatible with energy levels or quantization if formulated correctly.
Experiments that claim to show light consists of particles need to be reassessed wearing a philosopher's hat.
https://en.m.wikipedia.org/wiki/Interpretations_of_quantum_m...
The idea of their being both a wave and particle based description of photons that don't mix well is basically physics as known in the 1920s. The modern theoretical framework of light is quantum field theory (special relativity + quantum mechanics, but actually not quite that for [insert qft textbook] reasons...), which doesn't fit into either of those old ideals particularly well because they are basically shadows of an underlying model projected at different angles.
Edit (further detail): The way physics is taught in British secondary schools is a tragedy - ignoring that you don't even learn the fundamentals properly (no calculus!) - you aren't given a non-mathematical outline of these modern theories. In their eyes quantum mechanics has not really advanced beyond the photoelectric effect, which is where unhelpful weirdness like you'll see in this thread comes from.
i dont think that's true. A lot of people would assume that this "mathematical game" is like theories with air pressure. The statistical methods used for computing heat and pressure can be "explained" as little particles of atoms moving about due to their vibrations, and the ultimate observed behaviour is just that - a lot of particles pushing and shoving dependent on the temperature of these particles. this simple explanation can be understood without the maths - after all, the maths is only there to tackle the large numbers and statistical inferences needed. The statistical methods "isn't the theory".
However, such views restricts the mind imho. To seek a simple, understandable explanation that is not mathematical is probably a wrong goal. A lot of people have tried to explain laws such as gravity using such simple rules - a particle that moves and hits in all directions, but bigger bodies will block certain direction (thus resulting in a net force from the opposite side - aka, gravity).
https://www.youtube.com/watch?v=nRSBaq3vAeY
Apologies if its considered off topic - I see double slit experiment and I always think of this. It blew my mind.
I would expect that to decouple the experimenter to the experiment and should result in no change to the output.
As far as I understand it is because light can only be emitted by atoms with discrete energy levels, but (IMHO again) light is emitted by atoms with discrete energy levels because it is emitted when electrons jumps from one energy level to another and that the possible trajectory of electrons around the atoms aren't continuous, I don't see how this is related to the nature of light..
I think that with an [undulator](https://en.wikipedia.org/wiki/Undulator) you can tune "continuously" the energy of the light emitted: in the webpage it is written "the emitted radiation is coherent with a wavelength determined by the period length and the beam energy", but as the precise relationship between the beam energy and the wavelength produced isn't specified I'm not 100% sure..
It's one of Einstein's key insights, one of the foundations of quantum theory.
In Quantum Field Theory you have quantum fields. There are no 'waves' and no 'particles', there's only a 3D probability density field which defines the probability of particle-like events at specific locations. It's the probability field that is 'wave-like', and particles are considered excitations of the field.
So you know you're quite likely to see an electron-like or photon-like event in one location, and not at all likely in another.
Calling this a 'particle' is just an analogy. All you can really say is that a particle-like measurement is likely and/or did happen in one region.
What this really means - whether it's an observer artefact, or an exchange of information, or the output of some kind of computational and/or causal substrate, or something else entirely - is still a mystery.
So as a programmer's example you might have an idea that to simulate a QFT you could have an array of floats over space to describe your "electron field", and you draw in values to reflect a probability distribution and you'll write some update rules to describe how this evolves in time. But this won't work, because it's not how nature works.
What you need is that electron field array (and a photon field array to make any kind of non-trivial observations), but in 4D (space + time), and you need to iterate over all possible values in all array bins for all fields, calculate a magic number for each configuration, and weigh all these magic numbers together to figure out the actual probabilities for any configuration.
Even for a 16x16x16x16 array, that is 65536 bins, even with only 2 levels in each bin this is 2^65536 combinations.
All of practical QFT (theoretical, perturbative or non-perturbative lattice methods) is about doing this calculation with (obviously radical) simplifications.
That we can do these enormous simplifications and still get usable results, can be a very good sign that the underlying reality is in fact simpler than what QFT implies but nobody has figured this out yet.
So how do they produce an inference pattern in the double slit experiment? I know you don't have an answer to that, but that's rather the point - neither does QM. Probability density does not explain an interference pattern. Only one thing does - that light is in fact a wave.
I feel like I've seen experts say that yes, the fields are real, and particles are approximate descriptions.
But if it means anything, it's math.
The real problem is we don't have an analogy for what actually happens, because - by everyday expectations - the traditional interpretations are beyond weird. And the more recent interpretations are even weirder than that.
It's likely - after Bell - that there's something non-local happening. And after this paper it's likely that whatever it is may not even be compatible with a stable identity for the observer.
https://www.nature.com/articles/s42005-021-00589-1
Which seems to be arguing that instead of many worlds, there are many observers - not just simultaneously, but sequentially.
In other words, it's our belief in a consistent self with stable memories that may be wrong.
Not USA, but I know some really highly talented physicists who now work as rather badly paid software developers. Lesson: outstanding skills in and passion for physics not necessarily tranfer into high pay in the corporate job market.
It is rather the politicization and lack of perspective in academia that makes these people leave academia: doing your PhD/doctorial degree in physics already bears a high opportunity cost, so you really do that because you have a deep passion for physics and not because you expect a high pay.
1) understand why science avoids these 'what, really, is X' questions in favor of 'how does X work'
2) circumvent this existential crisis