Hello 2ndreconmarine! Thank you so much for your thoughtful, beautiful post/essay. Sorry to be so tardy replying; but you’ve given me a lot to think about. Before I answer, may I mention here that I noticed on Alamo-Girl’s thread that you raised the issue of semantics? And that I think that was a “good spot?” The above italics suggest to me that we are involved in semantic tangles respecting the meaning of the word “observer.” You have invoked the meaning that Heisenberg gives it: it’s a kind of useful abstraction or “construct” used to properly qualify the application of HUP to given experimental conditions (if I’m following you here) for “scientific qualification” purposes.
And thus your essay, in effect, is a “classical” description of QM – classical because it effectively excludes the operations of the human mind from having a role. In general, classical theory assumes a direct one-to-one correspondence between every element of the physical theory and the physical reality it describes. Therefore it assumes such relations set up with or without a human observer on the scene to take note of them. The Universe is like a “clockwork” because it does not require a human observer to be what it is. It works as it does simply because matter follows laws. We can go make observations if we want to. But the clockwork will be what it is whether we do so or not.
But as Profs. Robert Nadeau and Menas Kafatos point out, this is the very expectation that quantum physics completely undermines: “Quantum physics profoundly disturbed physicists from its very inception because quantum mechanical experiments yield results that are clearly dependent on observation and measurement. And this resulted in a situation where a one-to-one correspondence between every element of the physical theory and the physical reality cannot be confirmed in the classical sense…. For this reason physicists have been obliged to appeal to Bohr’s CI in dealing with the epistemological situation in quantum physics.” [The Non-local Universe, p. 86f]
FWIW, I think Niels Bohr’s interpretation of the “observer” is both more subtle than Heisenberg’s or Schroedinger’s, and more penetrating into substantive issues of science that are frequently overlooked. This interpretation is not one of mere “semantics,” but of a profound insight into issues of epistemology. That is, the human mind ineluctably has a bearing on what can be observed and how it is observed, just as the measurement devices used may themselves have a “distorting” effect on outcomes observed -- in both cases because each is a part of the total system being observed.
To start with a generalization, as Clifford A. Hooker writes, “Bohr often emphasizes that our descriptive apparatus is dominated by the character of our visual experience and that the breakdown in the classical description of reality observed in relativistic and quantum phenomena occurs precisely because we are in these two regions moving out of the range of normal visualizable experience.” [“The Nature of Quantum Mechanical Reality,” p. 137]
The “central pillar” of Bohr’s Copenhagen Interpretation is complementarity – a term that applies to “‘apparently’ incompatible constructs like wave and particle, or variables, such as position and momentum”:
“And since one of the paired constructs or variables cannot define the situation in the quantum world in the absence of the other, both are required for a complete view of the actual physical situation. Thus a description of nature in the ‘special’ case requires that the paired constructs or variables be viewed as complementary, meaning that both constitute a complete view of the situation while only one can be applied in a given situation…. [C]omplementarity assumes that entities in the quantum world, like electrons or photons, do not have definite properties apart from our observation of them.” [Itals added]
This sort of “observer” is hardly what Heisenberg had in mind:
“The notion from classical physics that the observer and the observed system are separate and distinct is also, Bohr suggested, undermined by relativity theory before it was undermined in a slightly different way by quantum physics. Just as one cannot, in relativity theory, view the observer as outside the observed system because one must assign that observer particular space-time coordinates relative to the entire system, so one must view the observer in quantum physics as an integral part of the observed system. There is in both cases no outside perspective. [ibid., p. 92; emphasis added]
The thought occurs that the constructs involved in Lorentz transformations are essentially the same thing viewed in different frames of reference. The choice of referential frame can only be the observer’s. And as Kafatos points out, “Although we have in quantum mechanics complementary constructs that describe the actual situation, the experimental situation precludes simultaneous application of complementary aspects of the complete description. The choice of which is applied is inevitably part of the results we get.”
For Bohr, because the “quantum of action” is everywhere implicit in the phenomena of the macroworld that classical physics deals with, quantum mechanics is the complete description, and classical mechanics a subset or “special case,” “an approximation that has a limited domain of validity.” Thus Bohr argued that, in this situation, “a final renunciation of the classical ideal of causality and a radical revision of our attitude toward the problem of physical reality” are urgently needed.
Bohr points out that issues of complementarity apply to classical physics in yet another sense: “[R]adiation in free space as well as isolated material particles are abstractions, their properties being definable and observable only through their interactions with other systems.” In other words, as Kafatos puts it, “When we use classical terms to describe the state of the quantum system, we simply cannot assume that the system possesses properties that are independent of the act of observation. We can make that assumption only in the absence of observation.” [emphasis added]
Must close, so let’s give Bohr the last word on this, then I get to make one teensy comment, and say how much I hope you will share your thoughts with me further, 2ndreconmarine:
The notion of complementarity does in no way involve a departure from our position as objective observers of nature, but must be regarded as the logical extension of our situation as regards objective description of our field of experience. The recognition of the interaction between the measuring tools and the physical systems under investigation has not only revealed an unsuspected limitation of the mechanical conception of nature, as characterized by attribution of separate properties to physical systems, but has forced us, in ordering our experience, to pay proper attention to the conditions of observation [ibid., p. 94, quoting Bohr, Atomic Physics and Human Knowledge, p. 74]
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The article at the top of this thread argues that the “Cartesian split” is utterly false, and should be gotten rid of once and for all. IOW, the “philosophy side” of the Cartesian divide has something to say to science; and it seems to me that the magisterial epistemology (which indubitably is a discipline of philosophy) developed by the great physicist Niels Bohr, in his CI, provides evidence that “its author” is right about this. :^)
Thank you ever so much for your excellent post, 2ndreconmarine!
I do want to expand on the following from 2ndreconmarine’s post:
Moreover, a postulate of special relativity is that “there exist global spacetime frames [4 space/time coordinates, and covering all of space/time] with respect to which unaccelerated objects move in straight lines at constant velocity" whereas in general relativity, which allows for curved space/time, rather than a global inertial frame there is a weaker postulate of a local inertial frame.
That relativity [special or general] exists even when it is not being “observed” is moot. Statements concerning relativity are generally made as if the observer is on either worldline. Nevertheless, even if the observer were a third worldline, his observation would still be “in” space/time and therefore, relative per se.
Also, for the discussion, concerning locality and realism:
THE FIRST ENTANGLEMENT OF THREE PHOTONS has been experimentally demonstrated by researchers at the University of Innsbruck (contact Harald Weinfurter, harald.weinfurter@uibk.ac.at, 011-43-512-507-6316). Individually, an entangled particle has properties (such as momentum) that are indeterminate and undefined until the particle is measured or otherwise disturbed. Measuring one entangled particle, however, defines its properties and seems to influence the properties of its partner or partners instantaneously, even if they are light years apart. In the present experiment, sending individual photons through a special crystal sometimes converted a photon into two pairs of entangled photons. After detecting a "trigger" photon, and interfering two of the three others in a beamsplitter, it became impossible to determine which photon came from which entangled pair. As a result, the respective properties of the three remaining photons were indeterminate, which is one way of saying that they were entangled (the first such observation for three physically separated particles). The researchers deduced that this entangled state is the long-coveted GHZ state proposed by physicists Daniel Greenberger, Michael Horne, and Anton Zeilinger in the late 1980s. In addition to facilitating more advanced forms of quantum cryptography, the GHZ state will help provide a nonstatistical test of the foundations of quantum mechanics.
Albert Einstein, troubled by some implications of quantum science, believed that any rational description of nature is incomplete unless it is both a local and realistic theory: "realism" refers to the idea that a particle has properties that exist even before they are measured, and "locality" means that measuring one particle cannot affect the properties of another, physically separated particle faster than the speed of light. But quantum mechanics states that realism, locality--or both--must be violated. Previous experiments have provided highly convincing evidence against local realism, but these "Bell's inequalities" tests require the measurement of many pairs of entangled photons to build up a body of statistical evidence against the idea.
I agree with your qualification about the "observer." Having said that, I will offer some additional perspective that actually supports your original assertion about the observer (against my own thesis)). LOL.
Following the discussion of Neils Bohr, he also said: "If someone says that he can think about quantum physics without becoming dizzy, that shows only that he has not understood anything whatever about it." I confess that it took me three tries in college to learn quantum: the undergraduate course, the graduate course, and studying for the general exams. Fortunately, I had the same professor for both the undergraduate and graduate courses, so the ideas began to sink in (eventually). I remember a comment a friend made to me in the physics lounge in school, when we were stuggling with this: "To learn quantum, you just have to let go..."
I believe the most famous example of the effect of the observer is with electon interference waves. The best description I know is in Feynman's Lectures on Physics volume III, chapter 1. The significance is that electrons, which are particles are shot into a 2 slit diffraction grating. The result is that the electrons are detected in an interference pattern. In order to interfere, the electron must be a wave. More importantly, the electron must be a wave that goes through both slits (the experiment is done one lonely electron at a time). Well, how can an electron be in two places at once and go through 2 slits at the same time?? But it gets worse. If you now shine a light on the two slits, you see the individual electrons and they go through each slit or the other, but not both. But, if you shine a light on the slits, the diffraction pattern dissapears and you see the electrons as if they were particles. So, how can an electron be at two places at once and then not be at two places at once when you observe them??? Or, if the electron is at two places at once, (i.e. going through both slits at the same time), and you shine a light and see the electron at one slit, how does the rest of the electron, that part at the other slit, "know" not to be there anymore???
OK, I'm dizzy.
The answer appears to be that quantum is non local. Which means that quantum is everywhere at once. This is the basis for the "spooky action at a distance" or the quantum entanglement. This is just a result of mutliple Stern-Gerlach experiments. A nice lay explanation is provided in Timothy Ferris' book The Whole Shebang, chapter 11. (Absolutely great book!!). I found the formal quantum description in Merzbacher's Quantum Mechanics on pages 289-293. (It is in the section on spin).
However, for the purposes of these threads, Einsteins thesis of hidden variables, which was formulated also by DeBroglie, was made most formal by David Bohm. Bohm was a Marxist who believed in absolute control. There could be no randomness. There had to be hidden variables. (It's funny how politics is involved with so much, even science.) Subsequently Stewart Bell formulated the experiments to test the non-locality of quantum and these experiments were conducted in the 70s by Clauser and Freedman at Berkeley and at the University of Paris. The results are in: quantum is non-local and random. Bohm and Einstein were wrong.
As an aside. Feynman took the non-local aspect of quantum to its logical conclusion. That was the premise he used to develop Quantum Electro Dynamics (QED). QED calculates the probabilities of events and of movement by considering that everything could have ocurred everywhere. When you consider the path of a photon (and its likelihood for interference) you run the calculation by including every possible path for the photon. The direct line of sight and the path that goes from here to Venus and back. All are summed with appropriate weighting to get the correct answer.