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.
I must however continue to protest your tendency to bury Einstein.
Physical causality under general relativity is not rigorously established nor are the causality issues fully explored in extra dimensional theories (particularly extra temporal dimensions) - thus it is premature to consider causality with reference to non-locality and superposition (including randomness in quantum field theory) settled.
It would be very interesting to hear Einstein's views of locality and realism in light of current string theory and higher dimensional dynamics.
YIKES!!! Me too, 2ndreconmarine!!! It’s like Dorothy said to Toto: “I don’t think we’re in Kansas anymore.” :^)
Thank you so much for your excellent, elegant presentation of the two-slit experiment. Thank you also for the book recommendation: Timothy Ferris’ The Whole Shebang. I’m looking forward to reading it!
May I return the favor and make a book recommendation? That would be Heinz Pagels’ The Cosmic Code: Quantum Physics as the Language of Nature (Simon & Schuster, 1982). His Chapter 13, “The Reality Marketplace,” is especially relevant to the present issues, since it deals with the various interpretations and constructions of what quantum physics is and what it “means.” It’s also hilariously funny in places. Just a sampler/teaser:
Pagels opens: “We are coming to the end of our road to quantum reality. The road may well go on far into the future of physics, and new insights into the quantum theory may be found. Perhaps quantum theory is experimentally wrong or incomplete, something that is not logically impossible. No doubt there are incredible things yet to be discovered on the road to quantum reality. But in the absence of a new interpretation or the experimental failure of the quantum theory, for us the road has come to a resting place. What we find here is a kind of marketplace – a reality marketplace.
“The reality marketplace has lots of shops, each with a merchant who wants to sell us his version of physical reality. The way the market is set up, we have only enough cash to buy one reality, so it is a very competitive market. We are rather sophisticated buyers now, having learned about the two-[slit] experiment, the EPR and Bell’s experiment, the work on quantum logic and Schrodinger’s cat. The merchants in the shops know about these, too, and nobody disagrees with the actual experiments. It is the interpretation of these experiments in terms of physical reality that is being sold. The interpretation of experiment is, however, not decided by experiment. To distinguish realities as buyers, we must invoke other criteria, such as paucity of assumptions, potential empirical content, and taste. There are many shops, but we need only look in a few shops with the finest merchandise. We go into these to listen to the sales pitch.”
I just want to give the names of the shops here, and also give one key statement for each:
(1) “Many Universes for Sale”: “Reality is the infinity of all those universes existing in a ‘superspace’ that includes them all.”
(2) “Quantum Logic Shop”: “The lesson of quantum theory can be interpreted to imply that the logic of the physical world is non-Boolian. Logic, usually thought to be prior to any experience, becomes empirical – depending on our experience – just like geometry.”
(3) “Objective Reality Shop”: “The basis of physics … indeed the whole of science is predicated on the existence of objective reality – a world of objects that exists independently of our knowing it.”
(4) “Local Reality Shop”: “…true randomness is unbeatable, which … means it will always defeat you if you try to detect real nonlocal influences. There’s no randomness like quantum randomness.”
By this point in the narrative “our hero,” the reality-buyer, notices that he hasn’t seen anything he really wants to buy, and his head is totally spinning. Then a rabble collects, and a riotous scene ensues, yelling and screaming that the CI is “subjective.”
And so our hero decides to exit the scene and “find a cool park, and there, on a bench smoking a pipe, sits an old man” [who speaks “in a thick Danish accent”]…. And our hero asks him, “Have you bought a reality yet?”
And the old man replies, “No, not yet, and I’m doubtful I will…. I have thought about the problem for a long time and have come to some conclusions in discussions with Einstein.”
So our hero asks, “Where is Einstein now?”
To which the reply: “Einstein left the reality marketplace a long time ago, leaving his cash to me. He would have none of it and took to wandering farther down the road, like the wanderer he was in his youth….
“What I am certain of is that quantum reality is not classical reality – there is no way you can fit it into classical reality. Quantum theory does not predict individual events and classical reality would; the two theories are logically distinct. But even in our attempt to characterize what quantum theory is not, we appeal to classical concepts such as objectivity and local causality. We have no choice in doing this, because we are macroscopic beings and live in a classical, visualizable world to which those concepts apply…. [W]ithin the framework of material possibilities your reality is a matter of choice. Once your mind accepts this, the world will never be the same again. The material world actually imposed this way of thinking on us. I cannot stop wondering about that…. That we may not always know reality is not because it is so far from us but because we are so close to it.”
There’s more; but I can’t spill the beans more than I already have. Anyhoot I thought this was a great chapter in a great book. The topics it raises seem like great grist for the mill of public discussion….
I, too, “am having a great deal of fun with this -- it brings back memories of the intellectual adventure I had when in college.” I remember such days myself. In that spirit, can I tell you what is the single most monstrously bizarre statement that I have ever come across? That would be this conjecture:
There is only one single photon in all of the Universe, “instantiated” in some 1080 simultaneous (i.e., superluminal) occurrences at any given frame (ultimately denominated in terms of the Planck constant and Planck time) of 4D spacetime. Talk about “quantum entanglement,” or “quantum non-locality” here! If such a beastie were to exist, then my question would be: How could a denizen of 4D spacetime like me distinguish such an “omnipotent,” singular photon from a universal field?
That’s probably a “crazy question.” But then, the “single photon” conjecture seems pretty nuts to begin with. Still, I think about it anyway. Actually, other people have already been wondering about the incredible natural “sympathy” that seems to obtain between what are regarded as “separate” (i.e., nonlocal) photons, and various hypotheses have been advanced to account for this. To me, the “single photon theory” might actually have explanatory power. But if it did, I wouldn’t quite know what to do next. :^)
Which just tells me, I need to take a rest! For now, anyway.
Thank you, 2ndreconmarine, for your excellent conversation and your perceptive insights.
p.s.: Truly I’m glad my last tiny screed met with your approval. I thought your more “classical” presentation was elegant on its own merits, and duly note that what you espoused therein has been the foundation of extraordinary scientific achievements in recent times.