6 ms·

Purifying Physics: The quest to explain why the “quantum” exists

37 points by aethertap 11y ago

dschiptsov 11y ago
After couple of thousands of years LHC would be viewed the same way we consider Egyptian Pyramids today. Back then Egyptians were sure that everything they do makes a perfect sense - the height and shape of structures are in accordance with the opinion of the most knowledgable and authoritative experts, writings on the walls are perfectly correct and verified many times, etc.
- bitwize 11y ago
  I think the LHC would rather be recognized as the precursor to the tabletop hadron colliders that smart kids get as birthday presents. Beaides which, the pyramids are pretty remarkable from a scientific and mathematical standpoint.
  - noir_lord 11y ago
    Indeed and despite our greater understanding of the world, We can still appreciate the magnitude of what they did in context. When I look at the (often) over engineered (by modern standards) Victorian bridges and such I don't scoff because they didn't understand the tensile strength of the materials like we do now I appreciate the mastery they had at the time.
  - dschiptsov 11y ago
    The point was about a set of current beliefs which determined the direction which big social events would take. GHC project, like pyramids, is a way to get living for so many people and organizations in the first place. There is still no consensus among philosophers and, of course, no empirical evidence of existence of time as a phenomena of the Universe, apart from mental concept which could be derived from this or that physical processes using mathematical modeling. But for math models being proven does not imply existence. There are phenomena we call "mass", and hence phenomena we call forces, there is notion of distance, succession, rate of change, but there is no phenomena of time apart from some physical process observable by a mind. The famous clocks being accelerated is mere a mental construct. How come that we are so convinced that time exist? Well, suppose you have arrived to some big Tibetan Monastery in Lhasa or Shigatse at the beginning of the last century. You will be overwhelmed by the architecture, paintings, buzzing activities, which all seemingly makes perfect sense for those who performs them. All the rituals, offerings, recitation of scriptures, daily duties, strict hierarchy, etc. Much like MIT nowadays.) Unless you are questioning everything, trying to reduce everything back to first principles, being skeptical and aware of socially constructed dogmas, you will be convinced very quickly that there are various buddhas and other deities which appear and disappear upon their will, that they hide some scriptures in the past, to be revealed when humanity will be ready for the knowledge. You will study cosmology, reasoning, philosophy of emptiness, as a refinement of crude ancient Indian philosophy (which is the only real marvel Tibetan culture produced) and so on. If you are good student you will become very good rimpoche, expert in all the subtle details of the teachings. I am seasonal guide in Tibet, so I know what I am talking about.) What do we call notions held firmly by society but which cannot be empirically proven? We call it beliefs. How do we call organized beliefs, supported by social institutions? We call it a religion. Modern quantum physics is nothing but a bunch of religious sects. BTW, traditional Indian philosophy, which goes back to Upanishads, put the human mind in the center, so it could observe itself, how easily and readily it produces chimeras and dogmas. The two almost unbreakable of these is "myself" and "time". Upanishads were the very first systematic discourses which attempted to prove logically non-existence of these mental concepts. Still, no one managed to refute Upanishads. "A priori" established by Kant is related to that mind - an observer, not to the observed Universe.
    - evanb 11y ago
      I feel like you don't appreciate the way science works. If we found out tomorrow that the universe were, at its bottom, made of string cheese, that would not invalidate Newtonian Mechanics. Newtonian / Classical Mechanics is an effective theory in the technical sense[0], which means that it is independent (up to some unspecified constants) of the finer underlying details. Yes, we may be wrong about how we see the world. But wrong is relative. No amount of science or new discovery will make us see the Earth as flat. [1] [0] https://en.wikipedia.org/wiki/Effective_theory [1] http://chem.tufts.edu/AnswersInScience/RelativityofWrong.htm
    - AnimalMuppet 11y ago
      > There are phenomena we call "mass", and hence phenomena we call forces, there is notion of distance, succession, rate of change, but there is no phenomena of time apart from some physical process observable by a mind. The famous clocks being accelerated is mere a mental construct. Well, you list "rate of change" among your phenomena, but deny time as part of the phenomena. But how can rate of change be a "real" phenomena without time also being "real" in the same sense? "Rate of change" is really "rate of change with respect to time", after all.
      - dschiptsov 11y ago
        There are slow rivers and quick ones. Even same river has spots with different rates of flow. But there is still no time.)
  - sageikosa 11y ago
    The pyramids are interesting from an engineering and human organization standpoint. You don't need elaborate maths to place stones on the ground in a square-like shape; just a piece of cord as long as the radius, and something smaller and vaguely orthogonal enough to help check the cardinality of the points.
- cbd1984 11y ago
  The things the Egyptians actually verified hold true today. The rising of Sirius would correlate with the flooding of the Nile if not for the Aswan dams, for example. Things don't stop being true just because our opinions about them change: If something made a correct prediction, it will keep making those correct predictions within its realm of applicability. I won't bore you with an exegesis of how accurate the current Standard Model is when it comes to making predictions about lepton and hadron behavior. I'll simply emphasize that the behavior it's good for won't change tomorrow even if all our opinions change. That means any new theory will have to make all the same predictions about all the same behavior, just like Special Relativity has to agree with Newtonian mechanics in the low-speed realm. I'll close with an apposite link: "The Relativity of Wrong" by Asimov http://chem.tufts.edu/answersinscience/relativityofwrong.htm http://chem.tufts.edu/answersinscience/relativityofwrong.htm > [W]hen people thought the earth was flat, they were wrong. When people thought the earth was spherical, they were wrong. But if you think that thinking the earth is spherical is just as wrong as thinking the earth is flat, then your view is wronger than both of them put together.
stared 11y ago
Please... what is "embarrassing" about quantum mechanics? (As an (ex) quantum physicist I consider the desire to "metaphysically understand" anything a mental trap.)
- tim333 11y ago
  I guess embarrassment might be the wrong term but it's still an interesting question why quantum mechanics is like it is. And my personal feeling is it's something like people in the past wondering why the sun shines or how life got here - it wasn't that it was a mental trap to ask but just that they hadn't figured out fusion and evolution yet.
- jostylr 11y ago
  As often presented, QM asserts that the system collapses under measurement. But for a fundamental theory, measurement as an external thing doesn't make sense. Thus, when does collapse happen? This is that cat thing. One can shrug and say, we know what we need for computations. But a fairly fundamental theory should be cleaner. Of course, there is a perfectly simple theory (Bohm's) involving Schrodinger's equation and a guiding equation for particles that has all of this quantum formalism derivable from its dynamics. A paper by Bell that goes into this point more clearly than I can articulate: http://www.tau.ac.il/~vaidman/IQM/BellAM.pdf http://www.tau.ac.il/~vaidman/IQM/BellAM.pdf
  - stared 11y ago
    Decoherence-based interpretations (Everett, Żurek, Fuchs...) do not have measurement as anything separate - it's an emergent phenomenon based on the (already present) rules of unitary evolution. So for me its a clear argument why some of the interpretations make more sense that the others.
    - cygx 11y ago
      Decoherence alone doesn't solve the collapse problem.
fengwick3 11y ago
Paper on the 5 axioms: http://physics.aps.org/featured-article-pdf/10.1103/PhysRevA.84.012311 http://physics.aps.org/featured-article-pdf/10.1103/PhysRevA... It looks familiar actually; it could be posted on HN or had generated an initial pop science hype wave when it was first published.
- musgravepeter 11y ago
  Thanks for the link. That is a pretty long paper!
sandworm101 11y ago
>>Quantum mechanics ... allows us to describe elementary particles and fundamental forces, to understand chemical reactions, and to construct lasers, transistors, and computers. What? So much for purifying the discussion. I know a little about the history of electronics and do not remember any discussion of quantum mechanics by those building the first computers, lasers or transistors. These were rather practical inventions based on easily observable experimentation. The field of quantum physics certainly allows us to better understand how and why these devices work, and to improve them, but it is not responsible for their existence.
- swehner 11y ago
  One explains semiconductors using quantum mechanics. Computers are constructed with semiconductors.
  - sandworm101 11y ago
    That was my point. The OP states that quantum mechanics "allows us to construct", not only describe.
    - typon 11y ago
      Incorrect. Lets say I grant you that Shockley and Bardeen didn't know anything about quantum mechanics and constructed the first transistor purely due to "observable experimentation" (whatever that means), that idea is completely false today. I use and write atomistic simulators and semi-classical (finite-element analysis based) simulators to simulate modern FET devices every day as part of my research. I literally use quantum mechanics to write the algorithms behind the simulator (DFT, NEGF in my case). Moreover, if you look at the manual for Synopsys Sentaurus (which is the semi-classical simulator), they have hundreds of pages describing the derivation of their mobility models and structural models from basic quantum theory. In summary, modern transistors are most definitely constructed taking quantum mechanics into account because without it you wouldn't have transistors functioning at 90nm much less at 14nm. You wouldn't take into account gate-leakage, tunneling, stress, bandstructures, and a host of other properties of modern transistors.
pjdorrell 11y ago
From my limited understanding of QM, it would appear that their assertion, that all "mixed" states are really part of a "pure" state, is just a restatement of the Many Worlds hypothesis. In the MW hypothesis, reality is described by the wavefunction of the whole universe, which is a single "pure" vector in Hilbert space whose operators are observables on the whole universe.

37 points by aethertap 11y ago

After couple of thousands of years LHC would be viewed the same way we consider Egyptian Pyramids today. Back then Egyptians were sure that everything they do makes a perfect sense - the height and shape of structures are in accordance with the opinion of the most knowledgable and authoritative experts, writings on the walls are perfectly correct and verified many times, etc.

bitwize 11y ago
I think the LHC would rather be recognized as the precursor to the tabletop hadron colliders that smart kids get as birthday presents. Beaides which, the pyramids are pretty remarkable from a scientific and mathematical standpoint.
- noir_lord 11y ago
  Indeed and despite our greater understanding of the world, We can still appreciate the magnitude of what they did in context. When I look at the (often) over engineered (by modern standards) Victorian bridges and such I don't scoff because they didn't understand the tensile strength of the materials like we do now I appreciate the mastery they had at the time.
- dschiptsov 11y ago
  The point was about a set of current beliefs which determined the direction which big social events would take. GHC project, like pyramids, is a way to get living for so many people and organizations in the first place. There is still no consensus among philosophers and, of course, no empirical evidence of existence of time as a phenomena of the Universe, apart from mental concept which could be derived from this or that physical processes using mathematical modeling. But for math models being proven does not imply existence. There are phenomena we call "mass", and hence phenomena we call forces, there is notion of distance, succession, rate of change, but there is no phenomena of time apart from some physical process observable by a mind. The famous clocks being accelerated is mere a mental construct. How come that we are so convinced that time exist? Well, suppose you have arrived to some big Tibetan Monastery in Lhasa or Shigatse at the beginning of the last century. You will be overwhelmed by the architecture, paintings, buzzing activities, which all seemingly makes perfect sense for those who performs them. All the rituals, offerings, recitation of scriptures, daily duties, strict hierarchy, etc. Much like MIT nowadays.) Unless you are questioning everything, trying to reduce everything back to first principles, being skeptical and aware of socially constructed dogmas, you will be convinced very quickly that there are various buddhas and other deities which appear and disappear upon their will, that they hide some scriptures in the past, to be revealed when humanity will be ready for the knowledge. You will study cosmology, reasoning, philosophy of emptiness, as a refinement of crude ancient Indian philosophy (which is the only real marvel Tibetan culture produced) and so on. If you are good student you will become very good rimpoche, expert in all the subtle details of the teachings. I am seasonal guide in Tibet, so I know what I am talking about.) What do we call notions held firmly by society but which cannot be empirically proven? We call it beliefs. How do we call organized beliefs, supported by social institutions? We call it a religion. Modern quantum physics is nothing but a bunch of religious sects. BTW, traditional Indian philosophy, which goes back to Upanishads, put the human mind in the center, so it could observe itself, how easily and readily it produces chimeras and dogmas. The two almost unbreakable of these is "myself" and "time". Upanishads were the very first systematic discourses which attempted to prove logically non-existence of these mental concepts. Still, no one managed to refute Upanishads. "A priori" established by Kant is related to that mind - an observer, not to the observed Universe.
  - evanb 11y ago
    I feel like you don't appreciate the way science works. If we found out tomorrow that the universe were, at its bottom, made of string cheese, that would not invalidate Newtonian Mechanics. Newtonian / Classical Mechanics is an effective theory in the technical sense[0], which means that it is independent (up to some unspecified constants) of the finer underlying details. Yes, we may be wrong about how we see the world. But wrong is relative. No amount of science or new discovery will make us see the Earth as flat. [1] [0] https://en.wikipedia.org/wiki/Effective_theory [1] http://chem.tufts.edu/AnswersInScience/RelativityofWrong.htm
  - AnimalMuppet 11y ago
    > There are phenomena we call "mass", and hence phenomena we call forces, there is notion of distance, succession, rate of change, but there is no phenomena of time apart from some physical process observable by a mind. The famous clocks being accelerated is mere a mental construct. Well, you list "rate of change" among your phenomena, but deny time as part of the phenomena. But how can rate of change be a "real" phenomena without time also being "real" in the same sense? "Rate of change" is really "rate of change with respect to time", after all.
    - dschiptsov 11y ago
      There are slow rivers and quick ones. Even same river has spots with different rates of flow. But there is still no time.)
- sageikosa 11y ago
  The pyramids are interesting from an engineering and human organization standpoint. You don't need elaborate maths to place stones on the ground in a square-like shape; just a piece of cord as long as the radius, and something smaller and vaguely orthogonal enough to help check the cardinality of the points.
cbd1984 11y ago
The things the Egyptians actually verified hold true today. The rising of Sirius would correlate with the flooding of the Nile if not for the Aswan dams, for example. Things don't stop being true just because our opinions about them change: If something made a correct prediction, it will keep making those correct predictions within its realm of applicability. I won't bore you with an exegesis of how accurate the current Standard Model is when it comes to making predictions about lepton and hadron behavior. I'll simply emphasize that the behavior it's good for won't change tomorrow even if all our opinions change. That means any new theory will have to make all the same predictions about all the same behavior, just like Special Relativity has to agree with Newtonian mechanics in the low-speed realm. I'll close with an apposite link: "The Relativity of Wrong" by Asimov http://chem.tufts.edu/answersinscience/relativityofwrong.htm http://chem.tufts.edu/answersinscience/relativityofwrong.htm > [W]hen people thought the earth was flat, they were wrong. When people thought the earth was spherical, they were wrong. But if you think that thinking the earth is spherical is just as wrong as thinking the earth is flat, then your view is wronger than both of them put together.

stared 11y ago

Please... what is "embarrassing" about quantum mechanics? (As an (ex) quantum physicist I consider the desire to "metaphysically understand" anything a mental trap.)

tim333 11y ago
I guess embarrassment might be the wrong term but it's still an interesting question why quantum mechanics is like it is. And my personal feeling is it's something like people in the past wondering why the sun shines or how life got here - it wasn't that it was a mental trap to ask but just that they hadn't figured out fusion and evolution yet.
jostylr 11y ago
As often presented, QM asserts that the system collapses under measurement. But for a fundamental theory, measurement as an external thing doesn't make sense. Thus, when does collapse happen? This is that cat thing. One can shrug and say, we know what we need for computations. But a fairly fundamental theory should be cleaner. Of course, there is a perfectly simple theory (Bohm's) involving Schrodinger's equation and a guiding equation for particles that has all of this quantum formalism derivable from its dynamics. A paper by Bell that goes into this point more clearly than I can articulate: http://www.tau.ac.il/~vaidman/IQM/BellAM.pdf http://www.tau.ac.il/~vaidman/IQM/BellAM.pdf
- stared 11y ago
  Decoherence-based interpretations (Everett, Żurek, Fuchs...) do not have measurement as anything separate - it's an emergent phenomenon based on the (already present) rules of unitary evolution. So for me its a clear argument why some of the interpretations make more sense that the others.
  - cygx 11y ago
    Decoherence alone doesn't solve the collapse problem.

fengwick3 11y ago

Paper on the 5 axioms: http://physics.aps.org/featured-article-pdf/10.1103/PhysRevA.84.012311 http://physics.aps.org/featured-article-pdf/10.1103/PhysRevA... It looks familiar actually; it could be posted on HN or had generated an initial pop science hype wave when it was first published.

musgravepeter 11y ago
Thanks for the link. That is a pretty long paper!

sandworm101 11y ago

>>Quantum mechanics ... allows us to describe elementary particles and fundamental forces, to understand chemical reactions, and to construct lasers, transistors, and computers. What? So much for purifying the discussion. I know a little about the history of electronics and do not remember any discussion of quantum mechanics by those building the first computers, lasers or transistors. These were rather practical inventions based on easily observable experimentation. The field of quantum physics certainly allows us to better understand how and why these devices work, and to improve them, but it is not responsible for their existence.

swehner 11y ago
One explains semiconductors using quantum mechanics. Computers are constructed with semiconductors.
- sandworm101 11y ago
  That was my point. The OP states that quantum mechanics "allows us to construct", not only describe.
  - typon 11y ago
    Incorrect. Lets say I grant you that Shockley and Bardeen didn't know anything about quantum mechanics and constructed the first transistor purely due to "observable experimentation" (whatever that means), that idea is completely false today. I use and write atomistic simulators and semi-classical (finite-element analysis based) simulators to simulate modern FET devices every day as part of my research. I literally use quantum mechanics to write the algorithms behind the simulator (DFT, NEGF in my case). Moreover, if you look at the manual for Synopsys Sentaurus (which is the semi-classical simulator), they have hundreds of pages describing the derivation of their mobility models and structural models from basic quantum theory. In summary, modern transistors are most definitely constructed taking quantum mechanics into account because without it you wouldn't have transistors functioning at 90nm much less at 14nm. You wouldn't take into account gate-leakage, tunneling, stress, bandstructures, and a host of other properties of modern transistors.

pjdorrell 11y ago

From my limited understanding of QM, it would appear that their assertion, that all "mixed" states are really part of a "pure" state, is just a restatement of the Many Worlds hypothesis. In the MW hypothesis, reality is described by the wavefunction of the whole universe, which is a single "pure" vector in Hilbert space whose operators are observables on the whole universe.