What is Copenhagen interpretation: Definition and 45 Discussions

The Copenhagen interpretation is a collection of views about the meaning of quantum mechanics principally attributed to Niels Bohr and Werner Heisenberg. It is one of the oldest of numerous proposed interpretations of quantum mechanics, as features of it date to the development of quantum mechanics during 1925–1927, and it remains one of the most commonly taught.There is no definitive historical statement of what is the Copenhagen interpretation. There are some fundamental agreements and disagreements between the views of Bohr and Heisenberg. For example, Heisenberg emphasized a sharp "cut" between the observer (or the instrument) and the system being observed, while Bohr offered an interpretation that is independent of a subjective observer or measurement or collapse, which relies on an "irreversible" or effectively irreversible process, which could take place within the quantum system.Hans Primas describes nine theses or principles of the Copenhagen interpretation: quantum physics applies to individual objects, not only ensembles of objects; their description is probabilistic; their description is the result of experiments described in terms of classical (non-quantum) physics; the "frontier" that separates the classical from the quantum can be chosen arbitrarily; the act of "observation" or "measurement" is irreversible; the act of "observation" or "measurement" involves an action upon the object measured and reduces the wave packet; complementary properties cannot be observed simultaneously; no truth can be attributed to an object except according to the results of its measurement; and that quantum descriptions are objective, in that they are independent of physicists' mental arbitrariness.Over the years, there have been many objections to aspects of the Copenhagen interpretation, including the discontinuous and stochastic nature of the "observation" or "measurement" process, the apparent subjectivity of requiring an observer, the difficulty of defining what might count as a measuring device, and the seeming reliance upon classical physics in describing such devices.

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  1. Jacob Peters

    B Copenhagen Interpretation - Superposition - confirmed?

    Hi, From what I read here, they did a double slit experiment test with neutrons that seemed to confirm superposition that the particle was in both places at once. Thoughts?
  2. entropy1

    B Copenhagen Interpretation and collapse moment

    Is it still true that under the Copenhagen Interpretation the standard theory of QM tells us that a measurement apparatus gets into superposition of possible measurement outcomes and does not tell us how and when we get a single decisive outcome? (The so-called "Measurement problem")
  3. sergiokapone

    A Quantum superposition: Is a problem of space-time worldview?

    One of the paradoxical principles in Quantum Physics is the principle of quantum superposition, since in quantum theory we are not really talking about the superposition of waves or oscillations, but about the superposition of states. A classic example demonstrating the phenomenon of quantum...
  4. D

    I What is the Copenhagen interpretation according to its originator(s)?

    I feel that contemporary authors' statements about the copenhagen interpretation don't really match with what the founders of quantum mechanics said. Also, different authors give seemingly contradictory statements about it is. What do the members here think about this? What is the copenhagen...
  5. entropy1

    I Probability in MWI and the Copenhagen interpretation

    Suppose we have an operator with three eigenvectors/eigenvalues ##e_1##, ##e_2## and ##e_3##. The operator measures wavefunction ##\psi##. Could we say that we find outcome ##e_x## with probability ##P(\psi,e_x)##, and could we extend this to an infinite dimensional operator as a spectrum of...
  6. johnconner

    I Copenhagen interpretation & Delayed-choice quantum eraser

    For explaining Delayed-choice quantum eraser experiment, what if I change the Copenhagen interpretation a little. When the experiment is concluded, we observe one detector (the first detector with the shortest path) has detected the pattern long before the wavefunction is collapsed (before the...
  7. LCSphysicist

    I What are current Physicists' general positions on the Copenhagen Interpretation?

    Actually, is not a doubt as a question, in which there is wrong or right. I just want to update myself with respect to the current physicists opinion about the Copenhagen interpretation of Bohr and Heisenberg. Summarizing, there is a consensus among the majority? In another words, there is still...
  8. Lynch101

    I For and Against the Copenhagen Interpretation

    Given the various different interpretations of quantum mechanics, I am interested in getting a general overview of most/all of them. I think it would be interesting to hear what people list as the positives of each interpretation as well as issues they perceive with each. I was thinking that, if...
  9. Quantum Alchemy

    I A question about Many Worlds and my Remote Control

    I get so many different answers to this question so maybe here someone can pin this down. When I get up in the morning and I turn on my TV, I have over 3,000 channels so is there a universe with a version of me going to each channel? If not, how do I go to one channel over the other? Can my...
  10. Quantum Alchemy

    I Why can't there be a Universal Interpretation of Quantum Mechanics?

    Why can't there be a Universal Interpretation of Quantum Mechanics? If you unite Copenhagen and Many Worlds than all other interpretations will fall under the umbrella of a Universal Interpretation of Quantum Mechanics. The main problem with interpretations seems to be the role of the observer...
  11. DarMM

    Quantum Interpretations of QM in different countries

    More a sociological question. I was talking to a former Japanese colleague by email recently and he mentioned that the Copenhagen interpretation is almost universally accepted there. I already knew Huzihiro Araki and many other researchers from Japan in mathematical field theory take a fairly...
  12. M

    I Qbism vs Copenhagen: What is the Difference?

    I read a few articles about Qbism, but feel like I don't understand the difference from Copenhagen. One author claims the difference is that each observer has his own view of the world (and own probabilities in qbism). I thought that was also the case in Copenhagen. E.g. the old Wigner's...
  13. mollwollfumble

    A Bohr's contribution to the Copenhagen interpretation

    I wish to learn about Bohr's contribution to the Copenhagen interpretation by reading his original papers on QM, preferably in English. Which papers are most important?
  14. A

    A Has the 2-stage Stern-Gerlach experiment been performed?

    In http://www.feynmanlectures.caltech.edu/III_05.html#Ch5-S1, Feynman mentions that the 2-stage Stern-Gerlach experiment, which proves the electron spin states to be in a superposition, has never been actually done! I have also not seen any paper reporting such an experiment. My question is, has...
  15. P

    Stargazing What is the best Dobsonian telescope with a goto feature?

    My interests include; Large telescopes & Astrophotography Sub-atomic particles The Copenhagen Interpretation Black Holes Bubble universes and the Multiverse Many Worlds Theory The Holographic Proposal Quantum entanglement Causality, determinism and free will
  16. MichPod

    I What has changed since the Copenhagen interpretation?

    If to look at the foundations of QM and if to ignore various not much verifiable alternative interpretations of QM which emerged since the Copenhagen, starting with Bohm and Everett, what are the commonly accepted and recognized changes to the original views of the QM creators? There are planty...
  17. LarryS

    I How can laser photons have the same precise energy?

    The photons generated by a conventional quantum laser are all in the same quantum state. Doesn't that mean that they all have the same exact energy? Yet, because of energy-time uncertainty, the exact energy of any particle can never be measured. Also, the Copenhagen Interpretation says that...
  18. durant35

    I Can entropy drop in the Copenhagen interpretation?

    I've been reading some speculative articles about the possible quantum arrow of time which emerges through collapse and irreversibility. My question is: does collapse in the Copenhagen interpretation (or perhaps in a objective-collapse model) allow the spontaneous decrease of entropy where an...
  19. N

    I Is there a psi ontic Copenhagen interpretation?

    Is there a psi ontic version of the Copenhagen interpretation ( where the wave function is regarded real)? Can the wave function be real in Copenhagen interpretation?
  20. hsdrop

    Does the Copenhagen interpretation require consciousness for the same outcome?

    does it matter if a person or a computer looks at the result I guess I'm asking if something needs consciousness to have the same outcome in the case that I'm not making any sense please ask and I will try to seaplane in more detail and thank you for anyone that respons
  21. D

    Copenhagen interpretation and entropy confusion?

    I don't see how the Copenhagen interpretation and the second law of thermodynamics can be compatible. In the Copenhagen interpretation, upon losing coherence the system chooses a single definite state and all other possible states are eradicated. This seems to be losing entropy to me, as it's...
  22. A

    Can decoherence validate the Copenhagen interpretation?

    Hi, I am an amateur enthusiast and this is a direct question (not a proposal, I'm not nearly qualified to offer a proposal). I would like to throw to experts and people who are more qualified, because it's got me a bit stumped. Could I ask for an answer which is as simple as I am please, lols -...
  23. S

    Is Copenhagen interpretation a collapse theory?

    I have been learning about the different interpretations of QM, and I am trying to build a taxonomy of them in my mind (I find that trying to build taxonomies is a good way of learning about things). I have read about collapse theories and non-collapse theories. If I have got this right, the...
  24. 1977ub

    Copenhagen Interpretation of Sleep / Unseen brain?

    What is the accepted interpretation of these two similar related issues: 1) When I am sleeping do my brain and body revert to un-collapsed wave state until and unless seen by a different observer? 2) I *never* have "seen" my brain - have the wave functions of the atoms and cells collapsed?
  25. N

    Question about copenhagen interpretation

    Does the Copenhagen interpretation allow for particles(electrons) to be in more than once place at the same time. I am not talking about quantum superposition here. I'm asking if it allows for electrons to be in many places at once like the many worlds interpretation does.
  26. J

    Living Opponents of the Copenhagen Interpretation

    I was wondering if anyone could tell me who are considered the leading opponents of the Copenhagen Interpretation who are alive today?--and even what would be the best way to get myself some formal physics education under such individuals? I would love to learn more about physics, although I...
  27. P

    A question regarding the Copenhagen interpretation.

    hi guys, i just have a quick question concerning the Copenhagen interpretation of things. say there is a star, very far away (perhaps 1 billion light-years from Earth) that for the sake of this idea, has never been observed, by any intelligent being, anywhere. we happen to turn our telescope...
  28. A

    Copenhagen Interpretation vs Instrumentalism

    For 2 years now I have been reading posts at my university student forums about how the Copenhagen Interpretation is redundant because ensemble physics is the equivalence of CI and it is ensemble that is used in day to day physics. While I sympathize with applied physics and engineering I just...
  29. T

    Can Quantum Mechanics be studied without the Copenhagen interpretation

    Hello everyone, I'm a doctoral student of particle physics in ETH Zurich, and have a question in fundamental QM. I remember a friend telling me that the professor that taught him Quantum Mechanics in ETH Zurich did not believe in the Copenhagen interpretation, and thus taught the class...
  30. G

    Understanding the Copenhagen Interpretation

    This is from Wikipedia regarding the first point of the Copenhagen Interpretation: What does it mean to make a measurement? Is this something that only living beings do or can a dead particle make a measurement? Why does measurement collapse the wave function.
  31. A

    Copenhagen interpretation of Big Bang

    How old was the universe when the first wave function collapsed? Just wondering. I've checked all the FAQs on this, and the one hit in Google doesn't really cover it from a cosmological angle. I see there is a "Participatory Anthropic Principle" but my question is really more about, well, how...
  32. R

    Arrow of time in copenhagen interpretation.

    Most physicists don't draw a distinction between past, present and future.. this is called the arrow of time. Physicists such as Sean caroll, Paul Davies e.t.c But if all events exist in some sense then the future is <not> open. If the future is not open then determinism is true.. thus...
  33. S

    Understanding the copenhagen interpretation

    This is an extract from the lecture notes I took for the 'Foundations of QM' third year course. Copenhagen QM - classical-quantum division State: wavefunction ψ(x); (ψ,\varphi) = \int d^{3}r ψ^{*}(r)\varphi(r) Evolution: TDSE Observables (\hat{x},\hat{p},\hat{H}): A = A-dagger...
  34. A

    MWI vs Copenhagen Interpretation

    I recently read an article entitled, "The Interpretation of Quantum Mechanics: Many Worlds or Many Words?" authored by Max Tegmark and it raised many questions on the matter as well as curiosity. In the article, Tegmark provides two tenable but diametrically opposite paradigms regarding physical...
  35. C

    What are the differences between the old and current Copenhagen Interpretation?

    Hi all, I have read in several places about an "old Copenhagen Interpretation" and I wonder what are the differences between the old one and the current one. I read several times Wikipedia article about CI but had no success finding any references about the old one. I guess that the old...
  36. Demystifier

    There is no Copenhagen interpretation of QM

    Many physicists say that they prefer the "Copenhagen" interpretation of QM, but it does not mean that all these physicists prefer the same (or even a very similar) interpretation. There are at least 4 very different interpretations that are sometimes referred to as "Copenhagen": 1. Shut up...
  37. jambaugh

    Measurements and The Copenhagen Interpretation

    I started this thread to continue the following discussion from the thread: https://www.physicsforums.com/showthread.php?p=2203566#post2203566" But you and Weinberg are both making a mistake in assuming ontological status to both the collapse of the wave function and to entanglement...
  38. E

    Basis of the Copenhagen Interpretation

    Bohr believed that the observer effected the outcome of an experiment at the subatomic level, and it wasn't necessarily the photons used to measure the particle like in Hesienberg's Uncertainty Principle that effected the outcome. What was the basis of this idea if the only way to measure...
  39. jal

    Copenhagen interpretation QGsquared

    The Copenhagen interpretation, (the wavefunction collapse) is not what caught the interest and imagination of the scientific community. It was the Schrödinger's Cat. Is the cat alive or dead? “QGsquared” will not catch the imagination of the 10’s of thousands of interested people by saying...
  40. H

    Delayed choice in the Copenhagen interpretation

    Could someone explain to me how the delayed choice experiment is described within the framework of the Copenhagen interpretation? (Double slit experiment with two slits open but a late decission to measure the path of the particle). I do not understand how the deterministic evolution of the...
  41. B

    Questions on the Copenhagen Interpretation

    Just had four quick questions on the Copenhagen Interpretation (CI). 1. Where is the boundary between realm (classical) space and quantum space. I understand that there is no solid definition for this boundary, but where would we begin to see quantum events occur and see classical events...
  42. P

    Is the Copenhagen Interpretation a Consequence of the Uncertainty Principle?

    Hi, Can we know the Copenhagen interpretation, a result of uncertainty principle? If you don't agree with that, mention your reasons to see taht will conclude a safe answer or not. Thanks. ------------------------ Formulate realities.
  43. I

    Hidden variable and the copenhagen interpretation.

    Hi, I just had this argument with this person on another forum and the gist of it was that he was saying collapse is predictable to within a negligible precision if you average out the results a huge number of identical wave-particles that had already collapsed. My contention was that...
  44. Q

    Copenhagen interpretation of Quantum Theory

    I found a website that says: "The still-dominant "Copenhagen interpretation" of Quantum Theory developed by Niels Bohr, Werner Heisenberg, Wolfgang Pauli, and others says two basic things: 1. Reality is identical with the totality of observed phenomena (which means reality does not exist...
  45. D

    Anyone know a logical expression of Copenhagen Interpretation

    hiya! Does anyone know of any logical expressions of the Copenhagen Interpretation. I've read about it, I can summarize it, but I've never really seen anything other than discussions of it in pop-science books. I'd really like to break it down if I could.
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