# Who/What counts as an "observer" in Quantum Mechanics? **URL:** \ **Category:** Factual Questions\ **Created:** [April 17, 2007, 1:19pm UTC](https://boards.straightdope.com/t/who-what-counts-as-an-observer-in-quantum-mechanics/400462 "2007-04-17T13:19:27Z")\ **Posts on this page:** 20\ **Page:** 3
**Author:** ![CJJ](https://avatars.discourse-cdn.com/v4/letter/c/ecc23a/32.png) [@CJJ](https://boards.straightdope.com/u/CJJ)\ **Post date:** [April 18, 2007, 8:17pm UTC](https://boards.straightdope.com/t/who-what-counts-as-an-observer-in-quantum-mechanics/400462/41 "2007-04-18T20:17:08Z")
[QUOTE=Stranger On A Train] Here’s the crux; you don’t know _anything_ about the state of the system before you’ve observed it (and it’s worth noting again that the act of observing means that you’ve interacted with the system, 'cause you can’t just stand back and look at it), and by observing it, you cause it to collapse. The oxidation reaction mentioned above is, like all other potential states, in superposition until you interact with the system. [/QUOTE] This made me think of a recent interview in NPR by Paul Davies, author of numerous pop-physics books, including his most recent _Cosmic Jackpot_. One of several ideas he floated in the interview (perhaps also included in his book) is this idea of the observer collapsing the wavefunction as a method of establishing events in the past. After all, upon observation of Schroedinger’s cat, which causes the wavefunction state of the cat to collapse, we establish something that happened in the past. He wonders, then, if this idea could be magnified to very large systems, such as the entire universe itself: Could the act of observing the universe today, and observing the detailed evidence of its earliest moments after the Big Bang, actually itself be the cause of the universe? In short, has physics allowed us to collapse the ultimate wave function that reaches back to the big-bang itself? He posited the idea as a possible way out of the Cosmological Argument for the existence of God, which is why I don’t think this needs to be pursued any further in GQ. I mention it here because I thought it was intriguing–not because I want to defend or debate it. In any event, if you’re interested, you can buy the book at [Amazon](http://www.amazon.com/Cosmic-Jackpot-Universe-Just-Right/dp/0618592261). ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [April 18, 2007, 8:20pm UTC](https://boards.straightdope.com/t/who-what-counts-as-an-observer-in-quantum-mechanics/400462/42 "2007-04-18T20:20:55Z")
[QUOTE=CJJ\*] One of several ideas he floated in the interview (perhaps also included in his book) is this idea of the observer collapsing the wavefunction as a method of establishing events in the past. After all, upon observation of Schroedinger’s cat, which causes the wavefunction state of the cat to collapse, we establish something that happened in the past. He wonders, then, if this idea could be magnified to very large systems, such as the entire universe itself: Could the act of observing the universe today, and observing the detailed evidence of its earliest moments after the Big Bang, actually itself be the cause of the universe? In short, has physics allowed us to collapse the ultimate wave function that reaches back to the big-bang itself? [/QUOTE] Revisionist solipsism makes me almost as nervous as naked singularities. It’s all just physics porn. Stranger ---
**Author:** ![Ludovic](https://avatars.discourse-cdn.com/v4/letter/l/7ab992/32.png) [@Ludovic](https://boards.straightdope.com/u/Ludovic)\ **Post date:** [April 18, 2007, 8:59pm UTC](https://boards.straightdope.com/t/who-what-counts-as-an-observer-in-quantum-mechanics/400462/43 "2007-04-18T20:59:17Z")
[QUOTE=Stranger On A Train] **There are no real world boundaries between quantum systems** (save for–presumably–event horizons like those found around a “black hole”, and even that’s questionable) and thus no way to establish where probability ends and reality begins, other than that we know when we interact with a particle we’re seeing a discrete state, not a superposition of waveforms. [/QUOTE] Hmmm–something I’ve been wondering for quite awhile but have never been able to get ahold of information online. What’s the furthest distance at which distinctly unresolved-wave function quantum-mechanical effects have been observed (e.g. wavefronts interfering with themselves.) Because if the distance is not so great, is it not possible that people will find that waveformations get collapsed after a certain distance, corresponding to a finite-distance “leading wave” hidden variable interpretation of QM? ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [April 18, 2007, 9:22pm UTC](https://boards.straightdope.com/t/who-what-counts-as-an-observer-in-quantum-mechanics/400462/44 "2007-04-18T21:22:52Z")
[QUOTE=Ludovic] Hmmm–something I’ve been wondering for quite awhile but have never been able to get ahold of information online. What’s the furthest distance at which distinctly unresolved-wave function quantum-mechanical effects have been observed (e.g. wavefronts interfering with themselves.) [/QUOTE] I know this is complicated, mind-bending stuff that’s hard even for people who spend years at school to wrap their heads around, but I feel like I’m completely failing to convey the fundamental notion here. There is no observing “unresolved-wave function quantum-mechanical effects”; it is resolved (or appears as a discrete state, or whatever fits your favored interpretation) as you observe it. There are no waves in a “real”, material sense to observe; the treatment of it as a wavefunction that collapses is a mathamatical formalism, a model, which gives an assignable starting point for an accurate result of what happens. As far as we can observer, the wavefunction is just an equation, period. What actually happens–whether the universe is “nonreal” and merely resolved locally for interactions, or is “real” but exists as an infinite number of possibilities, or is a simultaneous superposition of possiblities for all involved particles, or really does exist but for which the state is described by hidden parameters that connect everything to everything else like some hideously convoluted plumbing nightmare–is completely unknown, and indeed, seemingly impossible via any known implementation of QM, to investigate. There are some very bright people trying to figure out a way to distinguish some interpretations from others, and thus find loopholes around apparent limitations in communicating or controlling information, but this is all highly speculative; currently, we have no reason to believe that any of these interpretations are right, and moreover, no reason to especially care, since the theory of QM lays out a mechanic that gives an accurate prediciton of the result of an interaction. Stranger ---
**Author:** ![Ludovic](https://avatars.discourse-cdn.com/v4/letter/l/7ab992/32.png) [@Ludovic](https://boards.straightdope.com/u/Ludovic)\ **Post date:** [April 18, 2007, 9:39pm UTC](https://boards.straightdope.com/t/who-what-counts-as-an-observer-in-quantum-mechanics/400462/45 "2007-04-18T21:39:26Z")
> [@](#): > > There is no observing “unresolved-wave function quantum-mechanical effects”; it is resolved (or appears as a discrete state, or whatever fits your favored interpretation) as you observe it. But at what distance and time? Can observations of photons from the Sun not be explained using the corpuscular theory, or at least, assuming that the waveforms is relatively resolved prior to the “particles” arriving near the observer? ---
**Author:** ![Liberal](https://avatars.discourse-cdn.com/v4/letter/l/848f3c/32.png) [@Liberal](https://boards.straightdope.com/u/Liberal)\ **Post date:** [April 18, 2007, 10:04pm UTC](https://boards.straightdope.com/t/who-what-counts-as-an-observer-in-quantum-mechanics/400462/46 "2007-04-18T22:04:14Z")
[QUOTE=David Simmons] Of course nobody knows what is behind gravity either, so that’s also mysticism. And let’s not get started on what underlies electricity. [/QUOTE] Okay, but what about magnetism? ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [April 18, 2007, 10:14pm UTC](https://boards.straightdope.com/t/who-what-counts-as-an-observer-in-quantum-mechanics/400462/47 "2007-04-18T22:14:39Z")
[QUOTE=Liberal] Okay, but what about magnetism? [/QUOTE] It’s even worse than electricity. (Pulls covers up over head.) ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [April 18, 2007, 10:16pm UTC](https://boards.straightdope.com/t/who-what-counts-as-an-observer-in-quantum-mechanics/400462/48 "2007-04-18T22:16:31Z")
[QUOTE=Ludovic] But at what distance and time? Can observations of photons from the Sun not be explained using the corpuscular theory, or at least, assuming that the waveforms is relatively resolved prior to the “particles” arriving near the observer? [/QUOTE] These questions don’t make sense in the context of quantum mechanics. Quantum mechanics is a “corpsucular theory” (albeit not one that Sir Isaac would recognize); that it’s also a wave theory indicates that there’s something going on underneath that is not like waves or particles that we normally think of. There is no distance and time at which the waves become particles, or anything like; and since we can’t see the photons before we see the photons (“How can he see he’s got flies in his eyes if he’s got flies in his eyes?”) so we can’t assume anything about the wavefronts before we observe (interact) with them, and when we interact (observe) them they “collapse” into a single discrete state which is only predictable as a probability. This whole waveform collapse thing isn’t (as far as we can examine) a real event, it’s just a way of denoting t[sub]0[/sub] for doing calculations. Stranger ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [April 18, 2007, 10:18pm UTC](https://boards.straightdope.com/t/who-what-counts-as-an-observer-in-quantum-mechanics/400462/49 "2007-04-18T22:18:19Z")
[QUOTE=Liberal] Okay, but what about magnetism? [/QUOTE] That’s all done by Little Red Men who are always at odds with the Little Green Men of Electricity. Stranger ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [April 18, 2007, 10:48pm UTC](https://boards.straightdope.com/t/who-what-counts-as-an-observer-in-quantum-mechanics/400462/50 "2007-04-18T22:48:27Z")
[QUOTE=Belrix] OK. So - try this. I take a ball and pitch it into a dark room. I watch the ball go away until it enters the darkness. At the point where I can no longer see it, is it now a wave function and not collapsed? Has it moved from the realm of “reality” to “probability”? What happens when I hear it strike the back wall? [/QUOTE] According to my source, Dr. Howard Wilcox former proffesor of Physics at UC Berkeley, any interaction with a quantum particle is an observation of that particle. So in solids, liquids and gasses, particles are always interacting and so their particles always exist as collapsed waveforms, or particles. It seems to me that requiring that a measurement be made in order for a particle to be observed is too strict a standard. Quantum mechanics don’t apply to macroscopic entities. For them either classical, Newtonian, mechanics, or relativistic mechanics apply. The ball disappears from your view but it remains a physical ball. ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [April 18, 2007, 11:15pm UTC](https://boards.straightdope.com/t/who-what-counts-as-an-observer-in-quantum-mechanics/400462/51 "2007-04-18T23:15:16Z")
[QUOTE=David Simmons] Quantum mechanics don’t apply to macroscopic entities. For them either classical, Newtonian, mechanics, or relativistic mechanics apply. The ball disappears from your view but it remains a physical ball. [/QUOTE] This is called [decoherence](http://en.wikipedia.org/wiki/Quantum_decoherence), where all the waveforms/smeared out probability distributions/wavy particles/whatever glom together into a blob where the composite waveform is much, much smaller than the actual system itself, and on objects large enough that you can actually see them the probability potential is so small that it actually can’t reasonably be resolved beyond the visible boundaries of the overall system, and so big things act in a classical fashion, which is good because on objects large enough that gravity is the dominant force quantum field theory doesn’t currently say anything coherent. There are a [few](http://en.wikipedia.org/wiki/Bose-Einstein_condensate) [types](http://en.wikipedia.org/wiki/Fermionic_condensate) of macroscopic entities that do behave in a quantitized fashion (not cats in boxes though) but they don’t exist in nature, or at least not under any conditions we’re likely to observe. Stranger ---
**Author:** ![scotandrsn](https://avatars.discourse-cdn.com/v4/letter/s/a4c791/32.png) [@scotandrsn](https://boards.straightdope.com/u/scotandrsn)\ **Post date:** [April 18, 2007, 11:38pm UTC](https://boards.straightdope.com/t/who-what-counts-as-an-observer-in-quantum-mechanics/400462/52 "2007-04-18T23:38:30Z")
QM is a bitch. The best understanding I ever had of it was given to a bunch of science teachers by Raymond Hall of Fermilab. He gave a great thought to start with, that helps you get away from thinking about things at this scale in terms of the physical reality you are familiar with: > [@](#): > > Stuff is made of atoms. Therefore, atoms can’t be made of stuff. ---
**Author:** ![Liberal](https://avatars.discourse-cdn.com/v4/letter/l/848f3c/32.png) [@Liberal](https://boards.straightdope.com/u/Liberal)\ **Post date:** [April 19, 2007, 12:14am UTC](https://boards.straightdope.com/t/who-what-counts-as-an-observer-in-quantum-mechanics/400462/53 "2007-04-19T00:14:05Z")
Great quote! Added to my collection. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [April 19, 2007, 12:25am UTC](https://boards.straightdope.com/t/who-what-counts-as-an-observer-in-quantum-mechanics/400462/54 "2007-04-19T00:25:54Z")
> [@](#): > > Quantum mechanics don’t apply to macroscopic entities. For them either classical, Newtonian, mechanics, or relativistic mechanics apply. The ball disappears from your view but it remains a physical ball. Not exactly. Quantum mechanics applies to everything (except for maybe gravity, but we’re not sure about that, and we’re working on it). It’s just that, for systems with very large action or angular momentum, the differences between classical and quantum theories are very, very small. ---
**Author:** ![scm1001](https://avatars.discourse-cdn.com/v4/letter/s/c4cdca/32.png) [@scm1001](https://boards.straightdope.com/u/scm1001)\ **Post date:** [April 19, 2007, 12:49am UTC](https://boards.straightdope.com/t/who-what-counts-as-an-observer-in-quantum-mechanics/400462/55 "2007-04-19T00:49:03Z")
[QUOTE=David Simmons] According to my source, Dr. Howard Wilcox former proffesor of Physics at UC Berkeley, any interaction with a quantum particle is an observation of that particle. So in solids, liquids and gasses, particles are always interacting and so their particles always exist as collapsed waveforms, or particles. It seems to me that requiring that a measurement be made in order for a particle to be observed is too strict a standard. [/QUOTE] that is not my understanding (though IANA physicist but a humble chemist). Any interaction between two quantum states will just produce new quantum states according to the theory. Now in the case of say a collection of gases particles, the collective quantum behavior looks like what we expect a gas to behave like due to the averaging behavior. The difficult case comes where there appears to be a critical point and the quantum states, instead of just “averaging out” form two (or more) separate states (e.g. with radioactive decay). QT will give each possibility (decay, no decay) a probability. Interact that with the poor Shroedinger’s cat and all QT says there are now two new states (decay, dead cat and no decay, live cat). We appear to see only one of these states. Why this is the rub. The problem is that there is no obvious boundary between the quantum world and our experienced world and no obvious point at which the wave potential collapses. There are a set of possible explanations which have been detailed above, but possibly no way of ever telling between them. ---
**Author:** ![scm1001](https://avatars.discourse-cdn.com/v4/letter/s/c4cdca/32.png) [@scm1001](https://boards.straightdope.com/u/scm1001)\ **Post date:** [April 19, 2007, 1:40am UTC](https://boards.straightdope.com/t/who-what-counts-as-an-observer-in-quantum-mechanics/400462/56 "2007-04-19T01:40:15Z")
I should also add that diffraction has been observed in C60 molecules [http://www.quantum.univie.ac.at/research/matterwave/c60/](http://www.quantum.univie.ac.at/research/matterwave/c60/) . So if something that big can show quantum behaviour, where indeed is the boundary? ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [April 19, 2007, 1:59am UTC](https://boards.straightdope.com/t/who-what-counts-as-an-observer-in-quantum-mechanics/400462/57 "2007-04-19T01:59:40Z")
This sort of begins to resemble how many angels can dance on the head of a pin. I can’t see that anything is lost by adopting Dr. Wilcox’s point of view. Every time we look in enough light that ball is there reflecting light. If it is dark we can hear the ball parting the air if we have good ears, Macroscopic objects get wet in the rain and hot in the sun whether or not anyone is observing them. They also run into other objects in the dark. The operations of QT that result in effects on the world external to the quantum object are pretty well defined and follow definite rules. Speculation about what the quantum objects are when they aren’t interacting with something else is like a fascinating parlor game, but , I think, just a game. 🙂 ---
**Author:** ![Keeve](https://avatars.discourse-cdn.com/v4/letter/k/f07891/32.png) [@Keeve](https://boards.straightdope.com/u/Keeve)\ **Post date:** [April 19, 2007, 12:17pm UTC](https://boards.straightdope.com/t/who-what-counts-as-an-observer-in-quantum-mechanics/400462/58 "2007-04-19T12:17:18Z")
[QUOTE=David Simmons] Macroscopic objects get wet in the rain and hot in the sun whether or not anyone is observing them. … The operations of QT that result in effects on the world external to the quantum object are pretty well defined and follow definite rules. [/QUOTE] But those rules all invoke probability, right? That simply means that a macroscopic object which is sitting in the rain will **probably** get wet. But every once in an extremely long time (like a coupla gazillion googleplex years, which is not the same as infinity), the quantum forces inside the raindrops will all align to provide a dry area in the middle of the rainstorm. The far ends of a bell curve approach zero, but they don’t actually reach it. Given enough time, those monkeys **will** type whatever you want. ---
**Author:** ![Ludovic](https://avatars.discourse-cdn.com/v4/letter/l/7ab992/32.png) [@Ludovic](https://boards.straightdope.com/u/Ludovic)\ **Post date:** [April 19, 2007, 12:54pm UTC](https://boards.straightdope.com/t/who-what-counts-as-an-observer-in-quantum-mechanics/400462/59 "2007-04-19T12:54:02Z")
[QUOTE=Stranger On A Train] These questions don’t make sense in the context of quantum mechanics. [/QUOTE] Of course they don’t, not according to current theory, and specifically the CI. But my central question still was not answered. Does any one here know the largest distance across which experiments (such as the two-slit experiment, or Bell’s Inequality experiments,) have been run that firmly support QM and specifically the CI? Because, while at this point I will be jumped upon by people who say that I should not even _consider_ a “leading wave” as it is firmly “disproven” by Occam’s Razor, I am just throwing out a possibility and wondering how firmly out of the range of probabilities it is. Which it could be. Wildly. Which is why I am asking. ---
**Author:** ![Liberal](https://avatars.discourse-cdn.com/v4/letter/l/848f3c/32.png) [@Liberal](https://boards.straightdope.com/u/Liberal)\ **Post date:** [April 19, 2007, 1:34pm UTC](https://boards.straightdope.com/t/who-what-counts-as-an-observer-in-quantum-mechanics/400462/60 "2007-04-19T13:34:38Z")
Ockham’s Razor doesn’t prove or disprove anything. Parsimony is a principle, not a law. [Previous page](https://boards.straightdope.com/t/who-what-counts-as-an-observer-in-quantum-mechanics/400462.md?page=2) [Next page](https://boards.straightdope.com/t/who-what-counts-as-an-observer-in-quantum-mechanics/400462.md?page=4)