It is an interesting approach to physics and good luck to them. But the video isn't promising. The reason a physicist models a thing as a random variable is because they don't know of a way to distinguish the thing from a random variable.
Dr. Deutsch spent far too much time talking about the fact that at a high level there are a lot of things we are certain about. That is very weak evidence of what is happening at the quantum level. The important part isn't conceiving of something as deterministic. That is easy to do. Proving it experimentally will be the hard part.
There is nothing to report until there is an experiment that people can hold up saying "see! we found it! This part is deterministic not probabilistic!".
> There is nothing to report until there is an experiment that people can hold up saying "see! we found it! This part is deterministic not probabilistic!".
To add a bit more on top of my earlier comment: I believe Deutsch would point out that all experiments that have ever been done do corroborate the determinism of quantum phenomena.
Experimental tests are only ever understood in terms of theory, and quantum theory, which Deutsch identifies with the many worlds "interpretation", says that the world evolves according to Schrodinger's equation. Other "interpretations" of quantum theory are actually rival theories that fall at the first hurdle of being worse theories. To Deutsch, a bad theory is one that is easy to vary -- in this case, for example, the "Copenhagen interpretation" says that QM -- i.e. Schrodinger's equation -- is true, except when you measure something -- and then it says that you're not allowed to ask what that means. Why not? You're just not, OK?
This may sound like sophistry, but it isn't. Consider a closely analogous case:
Denying that experimental tests of QM have corroborated that theory -- which is a deterministic theory -- is like saying that dinosaur bones are not evidence of dinosaurs because none of the experimental tests distinguish the theory that dinosaurs really existed from the one that says that God put the bones there: true, but that theory is ruled out because it's a bad explanation (easy to vary: why God, for example?).
From memory of listening to this a few times some time ago (caveat: I certainly didn't study the content of this video carefully, but I do understand some significant context of his work as he sees it reasonably well I think):
Deutsch here isn't trying to modify quantum mechanics, he's trying to "interpret" it. He wouldn't use the term "interpret" of course, for excellent and fascinating reasons that I can't quickly cram into an HN post, but you can find them in his book The Beginning of Infinity (I was convinced about this area of what he says in the book, not about everything else he says there -- there's a LOT of stuff in there!).
By the way, I don't know whether or not you meant to imply that Deutsch is not a physicist, but he is -- and well known for his work on the fundamentals of quantum physics.
> Dr. Deutsch spent far too much time talking about the fact that at a high level there are a lot of things we are certain about. That is very weak evidence of what is happening at the quantum level.
Especially given that sum of billion random variables is determined and pretty precise value.
This is what the video talks about. I don't like this video much. It's tedious and lengthly.
Probably no reasonable human being would assume that Quantum Mechanic as we know it is the "holy grail" of physics. We came up with it within 100 years. Can we explain everything? Of course not.
To me, the fact that we have the uncertainty principle and schroedingers cat already prove that we basically built our understanding of physics on the premise that we can never understand it. We were basically throwing the towel and saying "yeah this is it". Advances are made through measurement and verification. How do you understand something that you can't measure, because the measurement changes the system?
It was pretty obvious to me when I studied physics that this is 100% not how the world works. It's a model, like everything else. In the model of quantum mechanics, which undoubtedly is one of the most impressive human achievements nonetheless, we have essentially complete uncertainty on the quantum scale. We can not peek beyond it and it doesn't give us any insights into how to peek beyond it. It is, in a way, the end of the line.
And like any end of the line in science, it needs a radically different thought or model, to overcome. I always found it amusing how physicists, who really should know better, actually believe that quantum mechanics is how the world works and that this is it. I always was with Einstein in rejecting Quantum Theory. It's a nice model. But that's really all it is. A model. This is not how the world works and we have come to see its limitations. We need something better if we ever want to leave our solar system and colonize space. Even Einstein fell into the trap of thinking that Quantum Mechanics is more than a model. "God does not throw a dice". Probably he does not, but it's the best approximation we could come up with. He should have refuted it and looked for something better instead. Who knows where we would be now.
Quantum mechanics is a deterministic theory. It does not have "complete uncertainty at the quantum scale". The probabilistic aspect only comes into play when you cast a quantum state down to a classical observable quantity like position or momentum.
You may have missed the subtle but important aspect of the uncertainty principle. It is not the case that there is a true underlying value of position and momentum for which the error bars are limited by quirk of theory. It is more like you expect to be able to observe 2 bytes of position information and 2 bytes of momentum information but the underlying quantum state is defined by 2 bytes in total. The full 4 bytes cannot fit inside 2 bytes. You can have a state which encodes the 2 bytes of position information but no momentum information, a state which encodes 1 byte of each, a state which encodes 2 bytes of momentum information but no position information, and everything in between. The uncertainty principle is actually a non-existence principle. When the position information exists the momentum information isn't uncertain, it just outright doesn't exist.
People have already replied to a lot of you wrote here, so I just want to add that Einstein emphatically did not reject quantum theory. Indeed he is probably one of the people who could fairly be called the creator of quantum theory.
What Einstein was rejecting with that quote is what we call the "Copenhagen Interpretation" of quantum theory. In my opinion he was quite right to do so, I do not know anyone in the quantum foundations community that takes Copenhagen very seriously any more. Einstein's qualms about Copenhagen lead the way to us understanding its flaws, and to people like John Bell putting us on a path to fixing some of those flaws.
Einstein spent a lot of time looking for "something better" than Copenhagen, sadly he did not find it, but people who came later than him did (Everett, Bohm, the quantum Bayesianists etc).
I'm going to slightly repeat what others have said here and talk about your issue with the uncertainty principle. Think about a wave travelling on the surface of an otherwise smooth swimming pool. The wave is an extended object, it is spread out. When we model the wave the fact that we don't assign it a perfectly precise "position" is a feature, not a bug of our model. Similarly I would argue that the uncertainty principle is not some barrier "blocking" us from seeing the true values of observables as we would like. It is a statement telling us that our mental model of things having a precise position and momentum at the same time is wrong, as wrong as trying to locate the wave at a precise position on the pool would be.
You're treading down a well worn path here, Einstein was down this road as well as you note and got stuck there for the rest of his life.
Everybody in the field would WELCOME something we can measure but can't explain with QM. But there isn't, and not due to lack of trying. Cosmology aside (difficult to measure) all the measurements of femtoscale interactions and condensed matter "constants" and their corresponding QM/QFT calculations that match to like 13-15 decimal places.. there are just incredibly massive chunks of evidence in favor of QM. It's just not a "first approximation" of reality that can be thrown out easily.
Theorists and experimentalists in the field come up with new tests every year (they are my favorite papers to read!), so it's absolutely not like there is some inherent scare of not daring to contest it. It's just that you need experiments to contest well-established and working theories, you can't just go out and say "well, but I don't like it"..
By the way as I'm sure you know if you studied this kind of physics, the "it doesn't give us any insights into how to peek beyond it" isn't really true, there are falsifiable assumptions that are tested and peeked at all the time - I'm thinking on the hidden variable theorems and validations. The theorems don't assume any specific theory (QM or a new one would do). That road is a nice one to casually drive down.
>> I always found it amusing how physicists, who really should know better, actually believe that quantum mechanics is how the world works and that this is it.
Is this a reasonable stance to adopt? "All experts in a field disagree with me - how amusing". Amusing or not it suggests that perhaps you are missing something that those experts are aware of.
>> We need something better if we ever want to leave our solar system and colonize space.
The way I understand it -I am, myself, no expert in the matter- we could be colonising space right now, the challenges are primarily engineering and economic (it would cost too much to develop the necessary technology) but we are not really lacking fundamental knowledge of how to do it, e.g. generation ships could work for that purpose, in principle, but nobody is mad enough to build one, let alone ride it if one was built.
The uncertainty is not exclusive to QM and is a property of any ‘wavy’ system, it seems. It is inherent. Here is the example: https://m.youtube.com/watch?v=MBnnXbOM5S4 — if you want to defeat QM, attack its wave-part.
It would be nice to have much better (deterministic, measurable) physics, but some properties just emerge from a fundamental level and you can’t do much about it (monster group etc). Nature and maths don’t care about our confusion and convenience.
>should have refuted it and looked for something better instead
Afaik, the time when theories were driven by ideas is over. Today it’s petabytes of data that you can’t really argue with over a mailbox, only discuss. (I’m just a layman physicist with deep interest, but shallow understanding, so please don’t quote me on any of this)
Honestly, seeing the high-level requirements for what constructor theory defines as Possible / Impossible, I mostly expect that it will have to conclude that many of the transformations that happen in QM are Impossible (a constructor can't be conceived that could achieve those tasks with arbitrary precision and reliability).
Related to your observations, I believe you are absolutely right in that it's likely we've sort of reached the end of the road in exploring beyond the quantum scale with the current approach. I do believe there are some dangling threads that can be pulled to help guide some other directions - such as the measurement problem and the no-communication theorem.
I also have some hope that computer theory may be able to shed some light - at the moment, we have a clear distinction between quantum algorithms and classical algorithms, but we don't know if they are fundamentally different or not. A discovery of how to efficiently compute quantum algorithms on classical computers (i.e. BQP = P or at least BQP = NP) would likely be a major insight into QM itself. Conversely, proof that quantum computers are fundamentally different from classical computers would also hopefully show WHY/HOW they are different and help in this area. Alternatively, if it turns out that quantum computers are in fact not physically realizable or require exponential memory or energy would essentially prove that physical reality does not obey some of the properties that make quantum computers (apparently) more powerful than classical computers.
> Probably no reasonable human being would assume that Quantum Mechanic as we know it is the "holy grail" of physics.
Fully agreed. This, however, rests on the assumption that there is a 'holy grail' in physics (aka a theory of everything). It's a matter of taste, but I don't like that idea that there is a theory of everything because it doesn't seem reasonable that every last bit of our universe is explainable by a single theory. Why would that be? Seems like a conspiracy, if this was the case. To me, it's rather quite comforting to assume that there is something (be it the position and momentum of an electron) which we won't ever be able to understand because it just seams realistic. If this wasn't the case and we could show that there is a theory of everything I would immediately start my quest to find Morpheus to ask him to give me the right pill to wake up.
Strong assertions.. I think that you'd better study the EPR paradox (E as in Einstein), Bell's inequality https://en.wikipedia.org/wiki/Bell%27s_theorem and the Alan Aspect (and other) experiments.
To summarize: reality isn't "local" even though we cannot send information faster than light..
Shrodinger cat is not a physical thing. It just comes from interpretation which has no mathematics behind it. There are many equivalent interpretations. And they are equivalent because none of them postulates any additional math to observe.
I think they're begging the question a bit when it comes to thermodynamics. In their video on http://constructortheory.org/what-is-constructor-theory/ they simply claim that no constructor exists that can turn a cooked egg into a raw egg and that allows their theory to reason about thermodynamics. Now presumably this is meant to be about entropy and not merely the amount of energy. However given the exact right amount of energy it is possible for a constructor to 'uncook' an egg, it's just that this constructor will work only for exactly that egg at exactly that time.
The resolution is that you're extremely unlikely to pick the right constructor but then we're back to probability again. In fact anything the recovers the laws of thermodynamics simply ends up recovering probability theory as the laws of thermodynamics are inherently probabilistic.
Their definition of "constructor" is as something that will perform a task reliably (whose meaning they define as including repeatably) for any choice of input with the specified attribute. If you can't come up with some reliable repeatable way of turning any cooked egg into a raw egg, then you don't have the thing they call a "constructor" for turning cooked eggs into raw eggs.
Knowing a bit of maths, I'm having trouble understanding how this isn't just categorical logic. They say that the laws of physics should be expressible in terms of statements about which physical transformations are possible or impossible, and why. In categorical logic, laws are expressible in terms of statements about which morphisms exist or would be contradictory/absurd to exist, and include proofs. What's the difference?
I read through a couple of their preprints but didn't find much concrete material, just a lot of complaints about existing theoretical physics traditions.
Watched 30 minutes and pretty much didn't get what he wanted to express, which is pretty fine because I'm not well versed in the art of Physics.
Just one thing about probability. My theory is that we use probability because we don't really understand the true "why" of things, or we don't know them. For example, we use probabiliy to guide us when playing poker, but that's because we don't know the cards. Whence we know the cards there is no need for probability.
But again, he is probably not speaking about the same "level" of things. I wish I knew more Physics.
I'm with you, we use probability to wave away effects we don't understand or cannot measure. There's a flat rate probability that each of us has cancer right now, when perfect knowledge of our bodies could answer the question precisely. Each doctor exam we have reduces or increases that probability until we subjectively understand it's time to sample a point of the body and know for certain.
The local sample is related to the larger system, and the hidden variable (cancer or not). The local sample at the time of capture has a probability of being malignant. We measure directly and back propagate the results to the system.
But, unintuitively, there's been some famous results that seemingly preclude a deterministic explanation of quantum mechanics. See:
[+] [-] roenxi|5 years ago|reply
Dr. Deutsch spent far too much time talking about the fact that at a high level there are a lot of things we are certain about. That is very weak evidence of what is happening at the quantum level. The important part isn't conceiving of something as deterministic. That is easy to do. Proving it experimentally will be the hard part.
There is nothing to report until there is an experiment that people can hold up saying "see! we found it! This part is deterministic not probabilistic!".
[+] [-] thingification|5 years ago|reply
To add a bit more on top of my earlier comment: I believe Deutsch would point out that all experiments that have ever been done do corroborate the determinism of quantum phenomena. Experimental tests are only ever understood in terms of theory, and quantum theory, which Deutsch identifies with the many worlds "interpretation", says that the world evolves according to Schrodinger's equation. Other "interpretations" of quantum theory are actually rival theories that fall at the first hurdle of being worse theories. To Deutsch, a bad theory is one that is easy to vary -- in this case, for example, the "Copenhagen interpretation" says that QM -- i.e. Schrodinger's equation -- is true, except when you measure something -- and then it says that you're not allowed to ask what that means. Why not? You're just not, OK?
This may sound like sophistry, but it isn't. Consider a closely analogous case:
Denying that experimental tests of QM have corroborated that theory -- which is a deterministic theory -- is like saying that dinosaur bones are not evidence of dinosaurs because none of the experimental tests distinguish the theory that dinosaurs really existed from the one that says that God put the bones there: true, but that theory is ruled out because it's a bad explanation (easy to vary: why God, for example?).
[+] [-] thingification|5 years ago|reply
Deutsch here isn't trying to modify quantum mechanics, he's trying to "interpret" it. He wouldn't use the term "interpret" of course, for excellent and fascinating reasons that I can't quickly cram into an HN post, but you can find them in his book The Beginning of Infinity (I was convinced about this area of what he says in the book, not about everything else he says there -- there's a LOT of stuff in there!).
By the way, I don't know whether or not you meant to imply that Deutsch is not a physicist, but he is -- and well known for his work on the fundamentals of quantum physics.
[+] [-] scotty79|5 years ago|reply
Especially given that sum of billion random variables is determined and pretty precise value.
[+] [-] marta_morena_9|5 years ago|reply
This is what the video talks about. I don't like this video much. It's tedious and lengthly.
Probably no reasonable human being would assume that Quantum Mechanic as we know it is the "holy grail" of physics. We came up with it within 100 years. Can we explain everything? Of course not.
To me, the fact that we have the uncertainty principle and schroedingers cat already prove that we basically built our understanding of physics on the premise that we can never understand it. We were basically throwing the towel and saying "yeah this is it". Advances are made through measurement and verification. How do you understand something that you can't measure, because the measurement changes the system?
It was pretty obvious to me when I studied physics that this is 100% not how the world works. It's a model, like everything else. In the model of quantum mechanics, which undoubtedly is one of the most impressive human achievements nonetheless, we have essentially complete uncertainty on the quantum scale. We can not peek beyond it and it doesn't give us any insights into how to peek beyond it. It is, in a way, the end of the line.
And like any end of the line in science, it needs a radically different thought or model, to overcome. I always found it amusing how physicists, who really should know better, actually believe that quantum mechanics is how the world works and that this is it. I always was with Einstein in rejecting Quantum Theory. It's a nice model. But that's really all it is. A model. This is not how the world works and we have come to see its limitations. We need something better if we ever want to leave our solar system and colonize space. Even Einstein fell into the trap of thinking that Quantum Mechanics is more than a model. "God does not throw a dice". Probably he does not, but it's the best approximation we could come up with. He should have refuted it and looked for something better instead. Who knows where we would be now.
[+] [-] IIAOPSW|5 years ago|reply
You may have missed the subtle but important aspect of the uncertainty principle. It is not the case that there is a true underlying value of position and momentum for which the error bars are limited by quirk of theory. It is more like you expect to be able to observe 2 bytes of position information and 2 bytes of momentum information but the underlying quantum state is defined by 2 bytes in total. The full 4 bytes cannot fit inside 2 bytes. You can have a state which encodes the 2 bytes of position information but no momentum information, a state which encodes 1 byte of each, a state which encodes 2 bytes of momentum information but no position information, and everything in between. The uncertainty principle is actually a non-existence principle. When the position information exists the momentum information isn't uncertain, it just outright doesn't exist.
[+] [-] eigenket|5 years ago|reply
What Einstein was rejecting with that quote is what we call the "Copenhagen Interpretation" of quantum theory. In my opinion he was quite right to do so, I do not know anyone in the quantum foundations community that takes Copenhagen very seriously any more. Einstein's qualms about Copenhagen lead the way to us understanding its flaws, and to people like John Bell putting us on a path to fixing some of those flaws.
Einstein spent a lot of time looking for "something better" than Copenhagen, sadly he did not find it, but people who came later than him did (Everett, Bohm, the quantum Bayesianists etc).
I'm going to slightly repeat what others have said here and talk about your issue with the uncertainty principle. Think about a wave travelling on the surface of an otherwise smooth swimming pool. The wave is an extended object, it is spread out. When we model the wave the fact that we don't assign it a perfectly precise "position" is a feature, not a bug of our model. Similarly I would argue that the uncertainty principle is not some barrier "blocking" us from seeing the true values of observables as we would like. It is a statement telling us that our mental model of things having a precise position and momentum at the same time is wrong, as wrong as trying to locate the wave at a precise position on the pool would be.
[+] [-] l33tman|5 years ago|reply
Everybody in the field would WELCOME something we can measure but can't explain with QM. But there isn't, and not due to lack of trying. Cosmology aside (difficult to measure) all the measurements of femtoscale interactions and condensed matter "constants" and their corresponding QM/QFT calculations that match to like 13-15 decimal places.. there are just incredibly massive chunks of evidence in favor of QM. It's just not a "first approximation" of reality that can be thrown out easily.
Theorists and experimentalists in the field come up with new tests every year (they are my favorite papers to read!), so it's absolutely not like there is some inherent scare of not daring to contest it. It's just that you need experiments to contest well-established and working theories, you can't just go out and say "well, but I don't like it"..
By the way as I'm sure you know if you studied this kind of physics, the "it doesn't give us any insights into how to peek beyond it" isn't really true, there are falsifiable assumptions that are tested and peeked at all the time - I'm thinking on the hidden variable theorems and validations. The theorems don't assume any specific theory (QM or a new one would do). That road is a nice one to casually drive down.
[+] [-] aeternum|5 years ago|reply
[+] [-] YeGoblynQueenne|5 years ago|reply
Is this a reasonable stance to adopt? "All experts in a field disagree with me - how amusing". Amusing or not it suggests that perhaps you are missing something that those experts are aware of.
>> We need something better if we ever want to leave our solar system and colonize space.
The way I understand it -I am, myself, no expert in the matter- we could be colonising space right now, the challenges are primarily engineering and economic (it would cost too much to develop the necessary technology) but we are not really lacking fundamental knowledge of how to do it, e.g. generation ships could work for that purpose, in principle, but nobody is mad enough to build one, let alone ride it if one was built.
[+] [-] warbaker|5 years ago|reply
[+] [-] wruza|5 years ago|reply
It would be nice to have much better (deterministic, measurable) physics, but some properties just emerge from a fundamental level and you can’t do much about it (monster group etc). Nature and maths don’t care about our confusion and convenience.
>should have refuted it and looked for something better instead
Afaik, the time when theories were driven by ideas is over. Today it’s petabytes of data that you can’t really argue with over a mailbox, only discuss. (I’m just a layman physicist with deep interest, but shallow understanding, so please don’t quote me on any of this)
[+] [-] simiones|5 years ago|reply
Related to your observations, I believe you are absolutely right in that it's likely we've sort of reached the end of the road in exploring beyond the quantum scale with the current approach. I do believe there are some dangling threads that can be pulled to help guide some other directions - such as the measurement problem and the no-communication theorem.
I also have some hope that computer theory may be able to shed some light - at the moment, we have a clear distinction between quantum algorithms and classical algorithms, but we don't know if they are fundamentally different or not. A discovery of how to efficiently compute quantum algorithms on classical computers (i.e. BQP = P or at least BQP = NP) would likely be a major insight into QM itself. Conversely, proof that quantum computers are fundamentally different from classical computers would also hopefully show WHY/HOW they are different and help in this area. Alternatively, if it turns out that quantum computers are in fact not physically realizable or require exponential memory or energy would essentially prove that physical reality does not obey some of the properties that make quantum computers (apparently) more powerful than classical computers.
[+] [-] edna314|5 years ago|reply
Fully agreed. This, however, rests on the assumption that there is a 'holy grail' in physics (aka a theory of everything). It's a matter of taste, but I don't like that idea that there is a theory of everything because it doesn't seem reasonable that every last bit of our universe is explainable by a single theory. Why would that be? Seems like a conspiracy, if this was the case. To me, it's rather quite comforting to assume that there is something (be it the position and momentum of an electron) which we won't ever be able to understand because it just seams realistic. If this wasn't the case and we could show that there is a theory of everything I would immediately start my quest to find Morpheus to ask him to give me the right pill to wake up.
[+] [-] renox|5 years ago|reply
To summarize: reality isn't "local" even though we cannot send information faster than light..
[+] [-] scotty79|5 years ago|reply
[+] [-] mrmonkeyman|5 years ago|reply
[deleted]
[+] [-] contravariant|5 years ago|reply
The resolution is that you're extremely unlikely to pick the right constructor but then we're back to probability again. In fact anything the recovers the laws of thermodynamics simply ends up recovering probability theory as the laws of thermodynamics are inherently probabilistic.
[+] [-] Chinjut|5 years ago|reply
[+] [-] quirky_mind|5 years ago|reply
[+] [-] myWindoonn|5 years ago|reply
I read through a couple of their preprints but didn't find much concrete material, just a lot of complaints about existing theoretical physics traditions.
[+] [-] lisper|5 years ago|reply
http://blog.rongarret.info/2019/07/the-trouble-with-many-wor...
[+] [-] markus_zhang|5 years ago|reply
Just one thing about probability. My theory is that we use probability because we don't really understand the true "why" of things, or we don't know them. For example, we use probabiliy to guide us when playing poker, but that's because we don't know the cards. Whence we know the cards there is no need for probability.
But again, he is probably not speaking about the same "level" of things. I wish I knew more Physics.
[+] [-] jvanderbot|5 years ago|reply
I'm with you, we use probability to wave away effects we don't understand or cannot measure. There's a flat rate probability that each of us has cancer right now, when perfect knowledge of our bodies could answer the question precisely. Each doctor exam we have reduces or increases that probability until we subjectively understand it's time to sample a point of the body and know for certain.
The local sample is related to the larger system, and the hidden variable (cancer or not). The local sample at the time of capture has a probability of being malignant. We measure directly and back propagate the results to the system.
But, unintuitively, there's been some famous results that seemingly preclude a deterministic explanation of quantum mechanics. See:
- https://en.wikipedia.org/wiki/Hidden-variable_theory
- https://en.wikipedia.org/wiki/Bell%27s_theorem
[+] [-] f430|5 years ago|reply