Hi. The problem with the concept of "observation" in QM isn't due to ignorance. The real conceptual difficulty is that an "observation" isn't a fundamental act: within the context of quantum mechanics, all "observations" are really complex interactions between complex composite systems, so the concept is completely out of place in the postulates of QM. Replacing "observation" with "classical interaction" doesn't solve this: since the constituents of matter are all quantum particles, and there's no way of constructing a truly classical composite object out of constituent quantum particles, deciding you're going to ignore the underlying quantum nature of matter beyond some artificial scale basically tells you how to use quantum mechanics as a "black box" for generating predictions (which is what we already have anyway) as opposed to a coherent model of nature. For a brief tour of the criticisms of the Copenhagen interpretation of QM see: http://en.wikipedia.org/wiki/Copenhagen_interpretation#Criticisms, particularly the quote by Weinberg.
I do not find it a useful POV, but I agree that nothing can be known with certainty/ scientifically proven, even if one is "observing it." One's direct experiences are undeniable, but their cause is always only a postulate - a metaphysical problem, if you like. I.e. Even the existence of a physical world is only inferred from your direct experiences. Bishop Berkeley argued, with complete logical consistency that has survived many attacks for more than 300 years, that the physical world does not exist, and postulated that a very Christian like God gave him (only a "lesser spitit" of course since the physical world does not exist) his "direct experiences." It is also only by faith, but in contrast with the faith of the good Bishop, that I assume a physical world does exist and I include in that assumption that it exists whether or not I am looking at it. I admit I cannot prove the physical world exists; however if it does, to assume it only exists when I am looking at it seems extremely ego centric (worse than believing the Earth is the center of the universe). I cannot be sure the other human looking bodies I see are the same conscious creatures that I know myself to be. (The "other minds" problem.) I have no way to know that there is any "mind" other than mine in the entire universe. Likewise there is no way to be sure than any of the "physical laws" is true, especially if Bishop Berkeley's POV is correct. He BTW had a very clever reason why his perceived world did follow physical laws (most of the time when God was not making a miracle). The world of our dreams, frequently violates the physical laws, so if no physical world exists, then it is strange / a problem/ why the physical world, inferred from our experiences, is so regularly governed, normally. Bishop Berkeley inferred that God was making his experience regular, as if there were a physical world, so that God could occasionally make miracles. (By definition, "miracles" are exceptions to the physical laws. - If the world did not seem to be rule governed, then God could not make miracles.) SUMMARY: By assumption (and there are many equally un-provable alternatives) I believe the physical world exists and did so prior to any life form existing. Also the many times confirmed laws of physics are very likely to accurately predict the results of experiments if the world is governed by natural laws, but one cannot be sure, especially when they are applied in areas which have had few or no confirming tests. Consistent with this POV, old electron tracks in glass-plate photograph films developed 100 year ago do exist (or not) even if no one has ever looked at them. This is a consequence of my basic assumption that the physical world does exist even if no life form does and always does follow regular laws (i.e. that miracles do not occur). Part of the "well confirmed laws" is that objects with thousands of atoms (or more) are classical objects. I.e. they have well defined locations, movements, masses, energies, etc. but very tiny objects, with little mass also exist and follow different quantum laws. These quantum laws permit these quantum objects to be in mixed states, which transform into pure states when they interact classically with a classical object. Even when they have transformed into a pure eigenstates, they do not have simultaneously well defined values for certain pairs of properties (The pairs whose quantum operators do not "commute under the Hamiltonian" - if you know any quantum physics.) Two common examples of these pairs are: (1) the energy and when it had that energy and (2) the momentum and where it was when it had that momentum. BTW, energy and momentum do commute under the Hamiltonian so both can be precisely known at the same time. Many who are ignorant of QM think that measuring one variable makes it imposible to know any other. That is not true in principle, but may be in current technical practice. Thus it is no additional assumption or metaphysical postulate to say all cats, living or dead, observed or not, are classical objects. Likewise nothing more is assumed (other than the world exists and follows regular laws) to state that developed photographic films have or do not have electron tracks in them which were made 100 years before any one looked (assuming they have been properly stored). I admit to a basics "world does exist, even prior to life forms" metaphysical POV (in contrast to Bishop Berkeley's POV that it does not) and admit that there are several different formulations of the physical laws (even of mathematic procedures) which can predict the same results, with no fundamental or real reason to think one is better than the other. Thus, I think it an additional metaphysical assumption to assume that one of the equally predictive models, corresponds to "what is real" I.e. for me, Bohm's QM, the standard Copenhagen QM, the multi-universe QM (all results happen), etc are only prediction tools, not statements as to how things "really are." I make only one fundamental metaphysics assumption and all I believe follows from it. I.e. I postulate that the physical world is a real, closed system that follows regular rules (independent of the existence or not of life forms.)
It's certainly fine to believe in an objective physical world that exists whether observed or not (though this would be the primary, though not only, metaphysical assumption that I was thinking of). The notion is intuitively appealing (to you and to the vast majority of people who have ever lived, I suspect). The curiosity is that the facts you cite regarding classical objects in the real world would be equally well "confirmed" from our point of view—with confirmation based on observations—under a variety of settled interpretations of quantum mechanics, not all of which agree that the macro world is necessarily objectively real, not all of which leave the unobserved cat or moon as clearly a classical object in all circumstances and not all of which agree that electrons can exist in superpositions. (From a purely logical perspective, of course, even assuming the unobserved world in general is objectively real does not necessarily mean that cats are...so there is a second assumption that cats possess whatever class of properties that makes the macro world real, whereas individual atoms do not. We could have a universe where the Moon is objectively real, but all cats are of the Cheshire variety. Again, though, the assumption that there is "nothing relevant that is special about unobserved cats which differentiates or separates them from the world as a whole" is an intuitive one to make.) The notion of the superposition itself is an interpretation base don the way the people interpreted the math, but it is not necessarily an accurate physical description of reality. The same goes for the randomness of quantum mechanics...it pops up in the math and there it looks fundamental, and yet the Bohm formulation of quantum mechanics can be set forth as an entirely deterministic one (and yet just as consistent with all experimental results), albeit with hidden variables. There is a lot of metaphysical interpretation of the math that gets passed along in an effort to help people develop an intuition about QM, that has never been strictly proven. One of those things is the notion that sizable objects are (usually) classical objects. It makes sense and it does provide a practical intuitive insight, but there is no reason to accept it as scientific fact. At the very least, given that there are interpretations of QM where, if true, that hypothesis would be incorrect, and given that those interpretations are every bit as consistent with observed reality (and we have no data on reality "unobserved" from which to form conclusions), we certainly should respect others' beliefs based on those interpretations, even if contrary to our own. There's no way to discern the people who are "correct" from those who are not. We might as well the objective merits of Big- and Little-endianess, whether it is "best" to crack open hard boiled eggs starting at the hard end or the small end. Perhaps someday new insights will enable us to say whether cats are always purely classical objects with a degree of scientific certainty, but at the moment our current understanding makes the question entirely moot, even though intuition leads us to thing the answer is obvious. It is a western, scientific koan, and educated people who live and work with QM are all over the place on it for that reason.
The photographic slides which have not been looked at will be the same as those that have been looked at. Take my word for it.
We know a great deal about the quantum world. The last 100 years of the history of the science of quantum mechanics has had turning points where divisions arose and out of those divisions came a form of consensus. The consensus is formed around the uncertainty principle and the wave function. This thread and the views brought out are evidence to me that the consensus is the current best thinking but no one is completely comfortable that this thinking is the final version. There is a need for more to be said by quantum mechanics about reality before the nature of reality can be put to rest. Reality is a broad subject so I will qualify it by saying that physical reality at the quantum level cannot be determined for certain. However, there is a mathematical approach that works satisfactorily to enable the science to describe particle interactions using the wave function, i.e. all possible locations of the presence of that "point" that would represent a particle location. What I get from that is we can live with not knowing exactly where that focus point is at all times as long as we can describe mathematically all of the possibilities. Some say there is no focus point at all until an observation occurs. Observation can take all of the forms mentioned including visual, instrument, particle interactions, or mathematical calculations. Others say that there doesn't have to be any observation to convince them that an object has reality in the form of a physical presence. Some say that a physical presence requires some minimum mass. None of us are smart enough to know what quantum reality really is. All of us who take a position on it based on our own individual thought process and our degree of understanding of the science will have a different physical picture. Each of our individual physical pictures will require a thousand words (thousands of words if it is a discussion) to convey our thinking. Few of us in a forum like this have a detailed visualization of the physical picture of our own version of quantum reality and at the same time are willing to discuss why one is right and one is wrong. There is really no way to determine if anyone is right and we all have our reasons for why we think we are right and others are not. Here is my thinking in a nutshell (<400 words): At the quantum level even the fundamental particles of the standard particle model have a hidden quantum nature. Hidden in that nature is the cause of mass and gravity. Mass and gravity exist independently from electromagnetic fields, charges and forces associated with the standard particle model. Anything, particle or group of particles with mass has a physical presence that is a mix of both waves and particles at the same time. The waves included in that mix overlap to cause particle points (high density spots), and the particle points form and burst into waves. Each wave/particle is either a wave or a particle at any given instant but as long as they are within a given mass they are always in the process of changing from a wave to a particle or from a particle to a wave. Each wave/particle represents a quantum of energy and mass is composed of energy in quantum increments. A single quantum of energy will have mass during the "high density spot" phase and that spot will change to reveal its energy content and wave nature as the spot bursts into spherical expansion. The spherical waves are expanding waves of energy that overlap with each other as they travel through the mass. In the overlap, the energy from the overlapping waves is the sum of the energy of the individual waves in that overlap space. When the overlap accumulates a quantum of energy then quantum collapse occurs and that quantum of energy collapses into a high density spot. I accept quantum collapse as a natural phenomenon for which I have another thousand words Please Register or Log in to view the hidden image!. The collapse of the high density spot creates a potential void in space since the spot occupies less space than the overlap from which it formed. Gravity is caused by that collapse as the surrounding energy quanta are pulled into the potential void in space. This thousand words touches on my view of the cause of mass and gravity and I am the first to admit that none of it can be proven because we just don't have the ability to observe at this level of quantum mechanics. Some will compare it to speculating about wild creatures at the far reaches of the galaxy, some will dismiss it due to its lack of proper jargon or mathematics, and some will think about it and then dismiss it politely. Some will have something in mind from it that is worth discussing and I am willing to discuss any of it on their thread or mine. I would understand if the originator of this thread wanted this post moved and if so, please move it to a new thread in the Cosmology forum where I have been discussing these ideas as part of Quantum Wave Cosmology.
I think any idea about what is real in nature should start by explaining why relativity phenomena is real.
Vern, the pages this quote comes from on Photontheory.com are very interesting. You base the view of reality on electromagnetic forces. All particles are constructed from photons where one wave length curls around and appears as a particle, I think. Every particle is its own electromagnetic construct if I understand it. And in contrast, my view is that mass and gravity are independent of electromagnetic forces and that there is a quantum level at which quantum action takes place. That level is common to all particles with mass. All of the particles of the standard particle model would be composed of energy and force that cause the presence of mass to occur, and that at the same time cause quantum waves of gravity to emanate from them. Mass *has* gravity so to speak. I see how photontheory characterized mass but I am wondering how gravity is explained. Are you employing general relativity and the warping of spacetime by mass? Or is there an explanation of gravity that coincides with Photontheory?
Yes; I suspect gravity results from the fact that photons exist as saturated points of electric and magnetic amplitude driven by fields of electromagnetic force. Since the fields of other photons contribute to the saturation of the points the points must migrate toward increasing field strength.
So it won't be like in Back to the Future where an image on a photo just materialises out of nowhere when looked at? Please Register or Log in to view the hidden image!
Is there a directional bias to the field strength? Gravity ignores any directional bias in electromagnatic field strength and responds only as a result of the mass and motion of the objects.
I don't understand your question. If electromagnetic fields exist in a spacial area apart from the points of saturation they would diminish in amplitude as the inverse square of distance away from the points. I'm not sure if current QM theory even accepts the existence of the fields; mostly we just hear about the wave function with no way to visualize it.
I have no problem with that, as a statement of belief, but whether what those slides will show regarding the quantum interactions that they captured so long ago is objectively set in stone right now, or subject to a superposition, if not known. Again, Einstein and others debated whether the Moon exists when it is not being observed, and some people took the position that it might not. It's understandable that most people believe the unobsevred Moon exists in an objective sense, but that intiutive belief is an issue presently not provable by science. An indivudual's belief one way or another, arises from the assumptions that person prefers. Given the general preference for objective theories, I am not sure why objectivist interpretations of quantum mechanics, like many worlds, are not more popular. I suppose it's just historical accident, in that the Copenhagen school dominated for so long.
If, as seems to be the case, you are claiming that large scale objects like cats and glass photograph plates remain in mixed quantum states until some life form looks at them, be honest enough to clearly affirm this. I think that an extremely foolish POV. For one reason: That POV would prevent the first life form from ever evolving - I.e. it could not "look" before it existed and prior to a life form looking, it would be in a mixed state. Or in other words, the universe could not have any, (Not even one) classical objects in it even today.
I hate the many worlds theory. IMO it is as ludicrous as believeing that the moon doesn't exist until observed
Not exactly, I am saying that unobserved cats, the Moon and photographic plates *may* remain in mixed quantum states until observed. In some interpretations of SM, they do. In others the do not. (In some others, nothing is ever in such a mixed state.) There is no was to objectively determine which, if any of the generally well known interpretations of QM is correct, so any attempt to answer the question of unobserved cats in mixed quantum states will be based on one's subjective preference for a given interpretation. We all have such preferences, and that's fine, but selecting one over the other is a question of philosophy, not science, at this stage. It depends. First, "observation" in the thought experiment is a shorthand and not well defined. In the decoherence approach that I do tend to favor, the cat is in a superposition, it's just that the wavefunction *appears* to collapse from my perspective, yet it does not actually collapse. In the decoherence model, a human being is not required and "observation" is used to mean, in a sense "interaction with the environment in a way that causes a thermodynamically irreversible change." According to decoherence (and several other interpretations) not only is the cat in a superposition, so is the whole of the universe By way of the universal wave function. In some interpretations, of course, living things (or even "sentient beings") and the tools they build are thought of as the measure of "observation" and it is from the Copenhagen interpretation especially that "observation" came to be the term we use when describing that cat. That a living observer is needed is not necessarily fatal based on evolution though, because it cannot be assumed that objects in superpositions are static or unreal. Whatever the nature of an "observation" is under these views, there is nothing that strictly prohibits an observer from observing itself. Atoms and subatomic particles cannot observe themselves, of course, but all that is to say is that they are not "observers." Under this view, the cat may be able to observe itself. Even if one assumes that observers cannot observe themselves, there are other ways out. Perhaps deities observed the process, for example. (We have already left the realm of science, so there is no need to avoid invoking theology.) Again, people have spent a lot of time thinking through the varying interpretations of quantum mechanics, and several of them have withstood the analysis. If there is a way to disprove those more robust ones, I think a grad student could make a reasonable name for himself or herself in publishing that paper. Although I gravitate to decoherence myself, I can see the point of the other ones, and have no myself seen any glaring flaws in them, once I set aside my own biases. In you view of things, I'm curious, what distinguishes quantum objects from classical ones? One atom still has quantum mechanical features, once you have a 10,000, what "switches off" the quantum rules? How do you avoid the same sort of evolutionary problem? The universe starts out as a sea an individual particles, too hot to be bound together, and all in their own superpositions. Maybe the atoms start to accumulate into "classical objects", but to do that, the existing superpositions have to go away, don't they? Assuming there is a threshold separating quantum and classical objects, what collapses the wave functions in a hot primordial universe sufficiently for subatomic particles to generate classical objects?
You answered this final question for me: "interaction with the environment in a way that causes a thermodynamically irreversible change." I.e. when a collection of particles that have only kinetic energy (and their rest mass energy) forms a collection of atoms (or a star) then that kinetic energy is converted to heat. ("a thermodynamically irreversible change") --------- I am curious about the timing of the collapse of the moon from its postulated superposition state when no one is looking. Consider a cloudy sky covering the night side of Earth. (No one can see the moon so in POV you support it is not the classical object I believe it always is.) But to be clearer let’s have the clouds cover the sunlit side of the Earth and recall that it takes light about 8.5 minutes to travel from the sun to the Earth. Case"A": Now assume a tiny "hole in the clouds" very briefly opens up and one guy looks at the sun during this time, which I will call T= 0. When (at what time) does the sun collapse into the classical object? Please answer in the form: "Sun becomes classical at T = ?" Case "B": Same as case "A" but the hole remains open and the guy has dark glasses on so he continues to stare at the sun. Same question. Case "C": Same as case "B" but the hole remains open for only four minutes and then closes again and the guy with dark glasses stares at the sun for the full four minutes. Same question (When does the sun become classical?) Plus for how long is the sun in a classical state? I.e. can the sun be classical even if no one is looking at it? If I look at stars in the night sky, am I forcing zillions of objects to "go classical." (Assume only Earth has life forms and only I am looking at the night sky, to answer.) Case "D": An alien astronomer, 10,000 light years away looked at the sun (via his telescope) 10,000 years plus 10 minutes ago and five minutes later ceased to view the sun. During these five minutes, I think your POV has the sun a classical object, even though the sunlit side of Earth is fully cloud covered. Now also during these five minutes an Earth satellite is viewing* the sun and making a video recording which starts 2 minutes before and continues 2 minutes after the 5 minutes that alien astronomer forced the sun to be classical. (Video record of solar image has 5m of classical and 4m of quantum mixed state sun recorded.) This video record is down loaded to a ground station and hour later and viewed by a human. Same question almost: I.e. when is the sun classical and when a quantum object? (Before the human views the video record or only when he does?) Is the video recording itself in some mixed state until viewed? What does it mean to state that a strip of plastic tape, with magnetic particles on it is in a "mixed state"?** I cannot see any way for a consistent set of answers can be made for these questions, unless it is to say that there is no observable (IN PRINCIPLE) difference between the sun in a classical and quantum mixed state. Do you hold this same POV? For me, when IN PRINCIPLE there is no observable difference between states "A" & "B," then they are the same state. Application of this rule to this discussion implies that looking at the sun cannot change its state. (From quantum mixed to classical object.) Do you hold this same POV? ---------------- *I.e. sunlight photons are being absorbed in the inanimate matter of the camera's detector. Likewise they are being absorbed in the inanimate clouds. What is the difference? (As far as ability of inanimate absorption to force the sun from mixed quantum state to a classical object?) **Note that magnetic domains are self stabalizing structures the orienent in ONLY ONE DIRECTION. They are stable against the thermal effects that tend to disorganize the alinment of the individual atomic magnet moments, up to the Curry temp, where this order disappears / is destroyed by thermal agitation. They can not be simultaneously pointing in two different directions as that is not an energetically lower energy state than all moments aligned in one direction. (The extra energy required for pointing in two different directions at the same time, far exceeds the uncertainity principle limits. I.e. that mixed sate can not even exist, by quantum theory itself.) A lot of questions here - answer what you think will explain your POV.
