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I think quantum mechanics is well-understood, the mathematics behind it provide us with excellent predictions. I think because at its core it is a probabilisti

I think quantum mechanics is well-understood, the mathematics behind it provide us with excellent predictions. I think because at its core it is a probabilistic (or perhaps there are many worlds, but the implications are identical) theory--there is some inherent uncertainty in the predictions. This uncertainty builds up over time if left unmeasured, due to the chaotic nature of the system. We won't be able to result this uncertainty until we have more precise and accurate measurement devices. I was thinking, the only real way for us to progress was to get the results out of CERN we were expecting--either smaller particles or some detection method which allows us to peer even deeper into the atom. I think certain physicists are tired of the search for a unifying theory since it probably won't help us make better predictions. We need to get out there and get new empircal data.

tempguy9999 7y ago
I've no idea about nuffink, but > We need to get out there and get new empircal data. To do this it's necessary to formulate the right questions first, as gathered data (which are in effect, answers) provide no information alone. Edit: "provide no information alone" is a bit too strong. What I'm trying to say is more precise questions tend to produce more precise answers in normal discourse, I'm generalising that.
jdc 7y ago
Would higher precision of measurements help here?
- analog31 7y ago
  Certainly. Effects can show up as qualitatively new things such as a new kind of particle, but also as tiny discrepancies between theory and experiment. There might be interesting new physics in every digit that gets added to the fundamental constants, for instance.
chr1 7y ago
Quantum computers working (or not working) would be another important test for quantum mechanics. Because quantum computer with n qubits to work requires amplitudes to behave the way quantum mechanical equations predict to the precision of 1/2^n which for 256 bits is much larger than the precision amplitudes can be measured in principle (e.g. for a spin ~1/planck length)
beloch 7y ago
I did my M.Sc. in quantum physics, and I'll be the first to admit I don't understand it. Yes, the equations do seem to predict what we observe in experiments very well. Shockingly well, given how strange some of the predictions made by them are! However, we lack an intuitive understanding of why the equations work. Matter and energy behave very differently on the quantum scale than they do on the macroscopic scales we're used to observing. If you're trying to model a pendulum, your intuition about how objects behave in the real world can be of immense help when performing sanity checks on your equations. Your intuition is worse than useless when it comes to quantum systems. It's not just flat-out wrong much of the time, it can lead you to ignore things that should not be ignored. Quantum physics has all sorts of English language, short-hand descriptions for mathematical functions like "tunnelling", "non-local", "spooky action at a distance" or, as is pertinent to this article "observation". You may think you understand what these mean, but you're probably at least partly wrong if you're thinking about them in terms of human language, natural human intuition, or even the very specific short-hand terminology of physicists. We are continually teasing out nuances in the math that language simply does not capture. If we lack the language to adequately describe reality, can we really understand it? Feynman was very correct to observe that people who think they understand quantum physics on a deep, intuitive level, probably do not. Doing quantum physics with a human brain evolved for bashing stones together is like trying to breathe in outer space. It's possible with considerable effort and the right tools (e.g. a space-suit), but if you ever forget that it's a deeply unnatural thing to be doing you're probably going to get yourself into trouble.
- jshaqaw 7y ago
  I ask you because I definitely do not have an M. Sc. In quantum mechanics - at the lowest level of any system isn’t it inevitable that there is no deeper understanding. At a certain point you have hit the base level and things just “are.” Correct me if this is erroneous!
  - platz 7y ago
    This is a bigger question than physics can answer. The project of hard science is essentially reductionist and based on predicting events based on hypothesis. Your question is more logical or philosophical. Logic may have something to say about open or closed systems, but mapping that onto the real world will always be a following question.
platz 7y ago
quantum mechanics is well-understood if you don't question the axioms and blindly calculate probabilistic outcomes. That doesn't mean we understand why those calculations work in the first place, what their limits are, what they represent, etc... ptolemy might object, 'but we can calculate the answer with arbitrary precision!!' but his 'model' didn't capture reality in a meaningful way dispite the accuracy. The same could be said of quantum mechanics
- MiroF 7y ago
  Ultimately you have to accept axioms of how the universe functions... we didn't question the non-probabilistic newtonian outcome metaphysically when it was presented, why is QM now being held to that standard?
  - platz 7y ago
    We questioned non-probabilistic newtonian physics when we asked harder questions than it could answer or it gave wrong answers when pushed to a higher regime. Something similar is going on now in QM. And do you really think we have discovered the "axioms of the universe" already? That is quite haughty. No we don't have those. We have models that perform well in certain regimes. Push those regimes, and the models break, then we find new and better models.. rinse and repeat. That is science. https://youtu.be/ka9KGqr5Wtw https://youtu.be/ka9KGqr5Wtw * We have 'axioms' (I would not call them that. I would say models) that work in a limited regime e.g. quantum field theory or Maxwell's equations, but we don't know if they are truly fundamental - in that sense they are not axioms , which in math have a precise meaning.
    - earenndil 7y ago
      > And do you really think we have discovered the "axioms of the universe" already? That is quite haughty. No we don't have those. That is also haughty. It is possible--probable, even--that our current models of physics are incorrect. We should certainly continue to probe them and look for something better. I would bet money that before my lifetime is out, some part of QM or relativity are overturned just like newtonian physics. However, you cannot just assume that that is the case. It is no certainty. We do not have certainty. The universe is sticky; it very well may be that we can never reduce it to something as simple as rule 30. It may be that our current theorems are axiomatic--at least, as far as the universe can be said to have axioms. (Or, as I think is more likely in the universe where we never discover any more physics, the difference between our laws and 'truth' is smaller than is possible to detect. That is, any instrument we use to measure will inherently produce too much noise to produce a statistically significantly different result.)
username90 7y ago
> quantum mechanics is well-understood No it is not, we don't even understand what causes quantum waves to collapse. We call it "observation" but we don't know what that is. So you can't say we understand quantum mechanics until we have a theory which can accurately predict when wavefunctions will collapse. When two quantum systems interact their wave functions either gets entangled with each other or they cause each other to collapse, it seems like the first happens in small systems and the second happens in large systems, we don't know much more than that.
- internet_user 7y ago
  From what it seems, we don't actually even know if "collapse" as such is a thing, nevermind what causes it. We are one experiment away from placing serious doubts even on counterfactual definiteness.
- ssijak 7y ago
  Observation = interaction
  - AstralStorm 7y ago
    But what kind of interaction? Is it a tensor field? Change of spacetime? Particle mediated? Wavelike? Nonlocal string or brane vibrations? Does it interact with other known fields and particles and in what way? What is its range and speed? Does it work same in very low or very high energies? Does temperature affect it? Does it change at relativistic speeds? Etc. The tool we have to probe it is currently only entanglement and secondarily tunneling. Maybe some calorimetry and charge detection.
    - atq2119 7y ago
      None of that is a problem if you accept MWI. The mental benefit of MWI is that instead of worrying about both entanglement and observation/wave function collapse, you only need to worry about entanglement because what Copenhagen describes as collapse is really just entanglement of the observed system with the observer.
internet_user 7y ago
> I was thinking, the only real way for us to progress was to get the results out of CERN we were expecting--either smaller particles or some detection method which allows us to peer even deeper into the atom. This cannot be more wrong. Science advances with one unexpected experimental hypothesis failure at a time.
mathgenius 7y ago
> excellent predictions Sometimes QM provides us with no prediction whatsoever as to what will happen next (eg. photon splitting experiment.) I would not call this "excellent." > chaotic nature Chaos theory is something else. > results out of CERN Particle physics is also not particularly relevant to this discussion. Fundamental particles is a separate issue to interpretations (foundations) of QM.

tempguy9999 7y ago

I've no idea about nuffink, but > We need to get out there and get new empircal data. To do this it's necessary to formulate the right questions first, as gathered data (which are in effect, answers) provide no information alone. Edit: "provide no information alone" is a bit too strong. What I'm trying to say is more precise questions tend to produce more precise answers in normal discourse, I'm generalising that.

jdc 7y ago

Would higher precision of measurements help here?

analog31 7y ago
Certainly. Effects can show up as qualitatively new things such as a new kind of particle, but also as tiny discrepancies between theory and experiment. There might be interesting new physics in every digit that gets added to the fundamental constants, for instance.

chr1 7y ago

Quantum computers working (or not working) would be another important test for quantum mechanics. Because quantum computer with n qubits to work requires amplitudes to behave the way quantum mechanical equations predict to the precision of 1/2^n which for 256 bits is much larger than the precision amplitudes can be measured in principle (e.g. for a spin ~1/planck length)

beloch 7y ago

I did my M.Sc. in quantum physics, and I'll be the first to admit I don't understand it. Yes, the equations do seem to predict what we observe in experiments very well. Shockingly well, given how strange some of the predictions made by them are! However, we lack an intuitive understanding of why the equations work. Matter and energy behave very differently on the quantum scale than they do on the macroscopic scales we're used to observing. If you're trying to model a pendulum, your intuition about how objects behave in the real world can be of immense help when performing sanity checks on your equations. Your intuition is worse than useless when it comes to quantum systems. It's not just flat-out wrong much of the time, it can lead you to ignore things that should not be ignored. Quantum physics has all sorts of English language, short-hand descriptions for mathematical functions like "tunnelling", "non-local", "spooky action at a distance" or, as is pertinent to this article "observation". You may think you understand what these mean, but you're probably at least partly wrong if you're thinking about them in terms of human language, natural human intuition, or even the very specific short-hand terminology of physicists. We are continually teasing out nuances in the math that language simply does not capture. If we lack the language to adequately describe reality, can we really understand it? Feynman was very correct to observe that people who think they understand quantum physics on a deep, intuitive level, probably do not. Doing quantum physics with a human brain evolved for bashing stones together is like trying to breathe in outer space. It's possible with considerable effort and the right tools (e.g. a space-suit), but if you ever forget that it's a deeply unnatural thing to be doing you're probably going to get yourself into trouble.

jshaqaw 7y ago
I ask you because I definitely do not have an M. Sc. In quantum mechanics - at the lowest level of any system isn’t it inevitable that there is no deeper understanding. At a certain point you have hit the base level and things just “are.” Correct me if this is erroneous!
- platz 7y ago
  This is a bigger question than physics can answer. The project of hard science is essentially reductionist and based on predicting events based on hypothesis. Your question is more logical or philosophical. Logic may have something to say about open or closed systems, but mapping that onto the real world will always be a following question.

platz 7y ago

quantum mechanics is well-understood if you don't question the axioms and blindly calculate probabilistic outcomes. That doesn't mean we understand why those calculations work in the first place, what their limits are, what they represent, etc... ptolemy might object, 'but we can calculate the answer with arbitrary precision!!' but his 'model' didn't capture reality in a meaningful way dispite the accuracy. The same could be said of quantum mechanics

MiroF 7y ago
Ultimately you have to accept axioms of how the universe functions... we didn't question the non-probabilistic newtonian outcome metaphysically when it was presented, why is QM now being held to that standard?
- platz 7y ago
  We questioned non-probabilistic newtonian physics when we asked harder questions than it could answer or it gave wrong answers when pushed to a higher regime. Something similar is going on now in QM. And do you really think we have discovered the "axioms of the universe" already? That is quite haughty. No we don't have those. We have models that perform well in certain regimes. Push those regimes, and the models break, then we find new and better models.. rinse and repeat. That is science. https://youtu.be/ka9KGqr5Wtw https://youtu.be/ka9KGqr5Wtw * We have 'axioms' (I would not call them that. I would say models) that work in a limited regime e.g. quantum field theory or Maxwell's equations, but we don't know if they are truly fundamental - in that sense they are not axioms , which in math have a precise meaning.
  - earenndil 7y ago
    > And do you really think we have discovered the "axioms of the universe" already? That is quite haughty. No we don't have those. That is also haughty. It is possible--probable, even--that our current models of physics are incorrect. We should certainly continue to probe them and look for something better. I would bet money that before my lifetime is out, some part of QM or relativity are overturned just like newtonian physics. However, you cannot just assume that that is the case. It is no certainty. We do not have certainty. The universe is sticky; it very well may be that we can never reduce it to something as simple as rule 30. It may be that our current theorems are axiomatic--at least, as far as the universe can be said to have axioms. (Or, as I think is more likely in the universe where we never discover any more physics, the difference between our laws and 'truth' is smaller than is possible to detect. That is, any instrument we use to measure will inherently produce too much noise to produce a statistically significantly different result.)

username90 7y ago

> quantum mechanics is well-understood No it is not, we don't even understand what causes quantum waves to collapse. We call it "observation" but we don't know what that is. So you can't say we understand quantum mechanics until we have a theory which can accurately predict when wavefunctions will collapse. When two quantum systems interact their wave functions either gets entangled with each other or they cause each other to collapse, it seems like the first happens in small systems and the second happens in large systems, we don't know much more than that.

internet_user 7y ago
From what it seems, we don't actually even know if "collapse" as such is a thing, nevermind what causes it. We are one experiment away from placing serious doubts even on counterfactual definiteness.
ssijak 7y ago
Observation = interaction
- AstralStorm 7y ago
  But what kind of interaction? Is it a tensor field? Change of spacetime? Particle mediated? Wavelike? Nonlocal string or brane vibrations? Does it interact with other known fields and particles and in what way? What is its range and speed? Does it work same in very low or very high energies? Does temperature affect it? Does it change at relativistic speeds? Etc. The tool we have to probe it is currently only entanglement and secondarily tunneling. Maybe some calorimetry and charge detection.
  - atq2119 7y ago
    None of that is a problem if you accept MWI. The mental benefit of MWI is that instead of worrying about both entanglement and observation/wave function collapse, you only need to worry about entanglement because what Copenhagen describes as collapse is really just entanglement of the observed system with the observer.

internet_user 7y ago

> I was thinking, the only real way for us to progress was to get the results out of CERN we were expecting--either smaller particles or some detection method which allows us to peer even deeper into the atom. This cannot be more wrong. Science advances with one unexpected experimental hypothesis failure at a time.

mathgenius 7y ago

> excellent predictions Sometimes QM provides us with no prediction whatsoever as to what will happen next (eg. photon splitting experiment.) I would not call this "excellent." > chaotic nature Chaos theory is something else. > results out of CERN Particle physics is also not particularly relevant to this discussion. Fundamental particles is a separate issue to interpretations (foundations) of QM.