[HN Gopher] A Century of Quantum Mechanics
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A Century of Quantum Mechanics
Author : bookofjoe
Score : 98 points
Date : 2025-07-10 10:41 UTC (4 days ago)
(HTM) web link (home.cern)
(TXT) w3m dump (home.cern)
| beckthompson wrote:
| haha I remember taking my quantum mechanics class. I thought I
| finally had "finished" old physics and was finally doing "newer"
| stuff.
|
| In the library there were some old physics books, looked at one
| that was like 70 years old and it was covering the stuff we
| learned that quarter... Guess I have a LONG way to go until I
| learn "new" things xD
| sampo wrote:
| There is no new foundational physics. The standard model of
| particle physics is from the 1970s, and the lambda-cmd model of
| cosmology is from late 1990s.
|
| Of course there is lots of new speculative ideas being
| produced, but it's really difficult to get anything confirmed.
| GoblinSlayer wrote:
| Is standard model confirmed? Then what is dark matter?
| thyristan wrote:
| In physics, there is never confirmation. At best there is
| "measurement agrees with the model as exactly as it is
| currently possible to measure". The standard model is
| confirmed in that sense.
|
| Dark matter is a problem from cosmology and astronomy, that
| maybe has a solution in an extension to the standard model.
| Maybe it hasn't and that solution will come from elsewhere,
| maybe there is a totally cosmological explanation after
| all. In all cases, the dark matter problem is not a
| contradiction to the standard model in our current
| experiments. If there were a particle-physics explanation
| to dark matter, it would be a sufficiently small alteration
| to the standard model that our current experiments couldn't
| tell the difference, to within experimental error. That's
| how confirmation and new models in physics work.
| ks1723 wrote:
| One of the major problems with dark matter and dark energy
| is, that the standard model has been experimentally
| confirmed to such high precision. All possible extensions
| proposed so far which tried to explain dark matter /dark
| energy have been basically falsified by the experiments.
|
| The standard model is so descriptive and accurate, there is
| just no room for extensions which predict new physics but
| are still consistent with existing data.
| dave333 wrote:
| So likely dark matter is a different flavor of something
| already in the model. Dr. Mills' Hydrino theory presents
| hydrogen with the electron in a lower orbit that does not
| radiate as a candidate for dark matter. These states are
| stable like the ground state. Transition into or between
| hydrino states emit light in the UV or soft X-ray
| wavelengths that is not seen in optical telescopes.
|
| https://brilliantlightpower.com/atomic-theory/
| jojobas wrote:
| Obligatory
|
| https://xkcd.com/2035/
| griffzhowl wrote:
| I don't believe all possible extensions have been ruled
| out: e.g. right-handed neutrinos are still a viable dark
| matter candidate as far as I know, and these are in fact
| motivated by the standard model, because every other
| fermion has both right and left chiral forms.
|
| https://en.wikipedia.org/wiki/Sterile_neutrino
| GoblinSlayer wrote:
| Intuitively speaking, if dark matter interacts only with
| gravitational field, then it's not affected by most
| standard model symmetries. A field bubble, so to say.
| Tachyons are somehow thought of as possible, meaning
| standard model doesn't say much about them?
| DebtDeflation wrote:
| >what is dark matter?
|
| I suspect in the end it will turn out to neither be exotic
| new particles nor modifications to gravity, but rather that
| there is something fundamental about large scale structure
| formation in the universe that we just do not understand at
| the present.
| mr_mitm wrote:
| How can insights into large scale structure formation
| help explaining galaxy ration curves, lensing
| observations or barionic acoustic oscillations?
| pantalaimon wrote:
| IIRC there has been no confirmation yet that dark matter
| actually exists - it might as well be true that our model
| of cosmology is wrong.
| vadansky wrote:
| Dark matter is the worst model, except for all those other
| models that have been tried from time to time.
| adastra22 wrote:
| Quantum mechanics is not the standard model. Quantum
| mechanics is the stuff developed in the 20's and 30's. It is
| really useful for solving real world problems, and for that
| reason is what is taught to undergraduates in a "modern
| physics" class. It is not a correct or complete description
| of reality, however, and is about 50ish years out of date.
| andrepd wrote:
| What do you mean? It's not "out of date", as Kepler's laws
| or the ideal gas law or whatever is not out of date. It's
| just incomplete.
|
| Also, "modern physics" is a term of art, vs "classical
| physics".
| thyristan wrote:
| Every physical description of reality is correct to within
| some error bars. Quantum mechanics is still useful and
| correct, there are just more precise theories that provide
| refinement. And in that sense are the "current" theories if
| they are the most precise ones currently known.
| IAmBroom wrote:
| Not true at all. Blackbody radiation goes to infinity
| with Wien's distribution; error bars aren't going to get
| you there.
|
| Likewise, our 1/r^2 understanding of forces goes to
| infinity as distance goes to zero, but we currently can't
| resolve that problem with error bars for the nucleus of
| an atom, where Heisenberg tells us any two protons can
| sometimes appear closer to each other than the "radius"
| of the nucleus.
|
| You can't make Schottky diodes using Maxwell and error
| bars.
|
| That is the entire problem: the classical models weren't
| merely inaccurate; they predicted completely absurd (and
| provably wrong) results at extreme scales.
| GoblinSlayer wrote:
| Infinite error bars.
| chermi wrote:
| What? What are the more precise theories that aren't
| fundamentally QM?
| GoblinSlayer wrote:
| Quantum field theory and string theory. Fundamentally
| they are QM, but not formally.
| pessimist wrote:
| The standard model is 100% quantum mechanics. It's just QM
| as applied to fields. While undergrads start with single or
| few particle quantum mechanics.
|
| There is a lot of hard math and fundamental physical ideas
| that pop out when we apply quantum mechanics to fields, but
| it's still QM.
|
| The work of Heisenberg, Schrodinger, Dirac, Pauli from
| 1925-28 or so is absolutely not our date.
| adastra22 wrote:
| We are getting into definitions and common usage debates,
| which is the most uninteresting debate to have. I will
| simply state that "quantum mechanics" unqualified
| typically refers to the description of reality developed
| on Copenhagen in the 1920's. When people are referring to
| quantum field theory, they are usually explicit in doing
| so.
| volemo wrote:
| I think "new foundational [science]" is a bit of an oxymoron:
| theories need time to become established as foundational.
| There may well be ideas (currently hypotheses) that will
| someday be considered foundational, but we lack the hindsight
| and experimental validation to claim that status now.
|
| And if you try to present your theory as foundational from
| the outset -- like S. Wolfram does -- you'll be laughed at,
| much like he is.
| griffzhowl wrote:
| Hmm, I don't think so. General relativity and quantum
| mechanics were acknowledged as fundamental (relative to
| previous theories) more or less immediately, because they
| provided a coherent theoretical scheme that accounted for
| the observations which were problems for previous theories,
| and they also made many new predictions which were
| experimentally confirmed within a few years.
|
| The problem for theoretical physics now is that all
| experiments from the LHC and so on are consistent with the
| standard model. So there are no recalcitrant observations
| that can guide new theory formation. The regime where we
| might get new physics, where gravity and QM are both
| significant, is so far experimentally inaccessible, though
| see here for a nice talk by Carlo Rovelli on one such
| experiment that might be plausible in the coming years:
| https://www.youtube.com/watch?v=tgieRctZ4dE
|
| The problem with Wolfram/Gorrard's model is that it doesn't
| relate to any experiments. As far as I know the most that
| can be said for it is that Gorrard showed that in some
| limit the model is able to replicate some features of GR
| and QM, so that by definition doesn't go beyond the
| predictions of GR nor QM.
| volemo wrote:
| Fair point. Thanks for the link!
| GoblinSlayer wrote:
| >The problem with Wolfram/Gorrard's model is that it
| doesn't relate to any experiments
|
| That's because quantum gravity regime is so far
| experimentally inaccessible?
| griffzhowl wrote:
| No, I don't think it's to do with quantum gravity. Their
| model makes no experimental predictions at all.
| pantalaimon wrote:
| the late 1990s is actually fairly recent
| HPsquared wrote:
| I remember thinking calculus was this modern high-tech thing in
| high school.
| dang wrote:
| [stub for offtopicness]
| zkmon wrote:
| This is probably the slowest branch of the sciences, not able
| to get out of labs even after a century. The fundamental
| problem appears to be that we are trying to control
| probabilistic nature using concrete real world things. I
| suspect this is not allowed, at least at an industrial scale.
| At some point humanity might need to stick what they need
| instead of what they can.
| mr_mitm wrote:
| What do you mean? We have been profiting massively from the
| fruits of QM for the last five decades easily. Transistors,
| LEDs, Lasers, MRT imaging, solar panels, CCD cameras, etc.
| have arguably changed the world and would not have been
| possible without QM. It came out of the lab a long time ago.
| colechristensen wrote:
| Not to mention the entire science of chemistry and
| everything made from it.
|
| Quantum mechanics started with the description of electron
| orbitals around an atom; how they work is the foundation of
| chemistry.
| kqr wrote:
| I think GP was thinking of quantum computers, maybe?
| colechristensen wrote:
| I think they made a very uninformed comment, that's all.
| novaomnidev wrote:
| That's engineering not science
| isolli wrote:
| Engineering is how science gets out of the lab...
| jeffwass wrote:
| I think you just wrote that 'off the cuff' but it's
| really a brilliant quote that succinctly clarifies
| science vs engineering.
| ekunazanu wrote:
| How else does science get 'out of the lab'?
| kgwgk wrote:
| >not able to get out of labs even after a century
|
| It got out of labs in a quite spectacular way in the summer
| of 1945, eighty years ago.
| isolli wrote:
| Thought experiment: did we really need quantum mechanics to
| build an atom bomb? Couldn't we have built one with a model
| of the atom based on classical particles (with protons
| leading to a chain reaction)? Is either the quantized or
| the uncertainty aspect of QM necessary for this?
| adastra22 wrote:
| The very idea of matter and energy being quantized into
| particles and photons is the starting point of "quantum"
| mechanics.
| bookofjoe wrote:
| >Planck discovers the quantum nature of energy in 1900
|
| https://www.pbs.org/wgbh/aso/databank/entries/dp00qu.html
| adastra22 wrote:
| It wasn't developed into a mechanics until the 1920's.
| GoblinSlayer wrote:
| Nucleon orbitals rely a little on Pauli exclusion
| principle, which you need to add as an ad hoc hypothesis
| every time in classical physics.
| perihelions wrote:
| Most of the science going into the Manhattan Project was
| experimental measurements and phenomenological models,
| not fundamental physics at the QM level. There were no
| usable quantum-mechanical models of nuclear physics at
| that point.
|
| No; they didn't really need it.
| kgwgk wrote:
| It's just a coincidence that they employed so many
| experts in quantum mechanics to do those nothing-to-do-
| with-quantum-mechanics experimental measurements.
| GoblinSlayer wrote:
| Coincidence. If you wanted to do something with
| elementary particles, you couldn't possibly ignore
| quantum physics.
| colechristensen wrote:
| >did we really need quantum mechanics to build an atom
| bomb?
|
| Yes. Nuclear reactions require understanding and modeling
| of the strong force, you can't understand or even see
| what protons and neutrons are without understanding the
| strong force. The mixture of positively charged and
| neutral particles being stuck together with enormous
| force which essentially does not exist at all outside of
| the nucleus of an atom. (there is more than _three
| pounds_ of force between every pair of protons inside
| every nucleus with the strong force counteracting the
| electrostatic force)
|
| You couldn't design a bomb without being able to model
| the strong force and you couldn't get to that point of
| investigating the atom without coming up with QM.
|
| You couldn't get the idea of isotopes and enriching U-235
| to U-238 or transmuting uranium to plutonium without
| understanding QM.
|
| Or the circumstances that would lead someone to blindly
| creating a controlled nuclear reaction without coming up
| with QM in the process would be pretty absurd.
|
| The idea for the bomb came from the understanding of the
| strong force. Step one: notice that there's a crazy
| powerful force keeping positively charged particles stuck
| together in the nucleus. Step two: the eureka moment of
| realizing you can "release" that force by causing a chain
| reaction of fission in heavy elements.
| andrepd wrote:
| What has physics ever done for us? Apart from computers,
| satellites, planes, communications, sensors, and health...
| What has physics ever done for _us_?
|
| The roads?
|
| Well obviously the roads go without saying!
| the-mitr wrote:
| Nature _is_ probabilistic. And we know how to calculate those
| probabilities, that is one of the core ideas of quantum
| mechanics. Why is it "not allowed"? By whom? Since you are
| commenting on HN, you are already are using the very mature
| applications of QM out of laboratory. The proverbial cat (is
| it Schroedinger's?) is out of the bag!
| GoblinSlayer wrote:
| Theory is probabilistic, nature isn't.
| nathan_compton wrote:
| I don't know dog, that is a pretty bold statement given
| everything we can presently firmly say about the
| universe.
|
| Like we can _imagine_ some kind of purely deterministic
| thing going on but when the rubber meets the road the
| best ways of working stuff out seem to very strongly
| imply some fundamental indeterminism. No one likes it,
| but thats the way it is.
| GoblinSlayer wrote:
| When the rubber meets the road the best ways of working
| stuff out is to shut up and calculate, you don't figure
| out anything by assuming unobservable fundamental
| indeterminism.
| nathan_compton wrote:
| No one assume it.
| IAmBroom wrote:
| Nature doesn't obey your opinions.
| GoblinSlayer wrote:
| That's an argument against solipsism at best, not much
| else.
| chermi wrote:
| What a take. All of modern technology, materials, solid
| state, semiconductors, transistors... And uhhh did you forget
| chemistry itself?
| zkmon wrote:
| Just came back from work to see all the battering and
| downvoting. Clam down. I meant Quantum computing using
| qubits. Apologies for not being specific. Quantum computing
| itself is also a century old (almost)? Where are we with
| this?
|
| Jeez - HN is brutal. Even a bot could have understood the
| context I meant.
| kgwgk wrote:
| If this is the definition of offtopic then 90% of HN comments
| are offtopic. https://en.wikipedia.org/wiki/Sturgeon%27s_law at
| work!
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