Main Question or Discussion Point
I'm studying quantum mechanics and I can't seem to understand what qualifies as an observer. Does the "observer" need to be a conscious one? Yes or no and why? Thanks in advance :)
No. Observation in quantum mechanics means interaction/measurement with e.g. an instrument in general.I'm studying quantum mechanics and I can't seem to understand what qualifies as an observer. Does the "observer" need to be a conscious one? Yes or no and why? Thanks in advance :)
Hmm. Let's try this: You have many small (biological) photodetectors in your eyes, which enables you to detect light. But we can build a lot of other kinds of photodetectors, which obviously are not conscious.[...] why?
Here you defined observation as interaction/measurement, which can sometimes leave people with the wrong impression, that interaction alone is enough to collapse the probability wave, which it absolutely isn't. Only measurement collapses the probability wave, and then only for the property for which the state of the particle is thus known. Thus in the double slit experiment you could interact with, and measure the particle, until the cows come home, you could knock the heck out of it, but if none of those measurements gives you which path information, then the interference pattern isn't going anywhere. The probability wave ain't gonna collapse for just any old measurement, it's gotta be specific. The particle somehow seems to know what you're measuring, but not only that, it also seems to know what you may indirectly learn from that measurement. So while the observer may not need to be a conscious one there appears to be more going on here than merely, I measure it, it collapses.No. Observation in quantum mechanics means interaction/measurement with e.g. an instrument in general.
While it's true that we can easily build a photodetector to "see" the particle in question, in what way is this evidence that such a detector could collapse the probability wave? The last time that I checked, every biological photodetector is connected to a biological brain, and who's to say that it's not the latter that actually collapses the probability wave? Is there indisputable evidence that detection alone collapses the probability wave?Hmm. Let's try this: You have many small (biological) photodetectors in your eyes, which enables you to detect light. But we can build a lot of other kinds of photodetectors, which obviously are not conscious.
I'm not surprised. I guess that's why there are 17+ interpretations of quantum mechanics .I don't really mean to imply that a conscious observer is absolutely necessry to collapse the probability wave, but I do have a couple of problems with your answer.
The notion of wave function collapse originates from the Copenhagen interpretation, and there is no scientific consensus which interpretation is most satisfactory. Yes, there are issues to consider; Measurement in quantum mechanics and Measurement problem.[...] So while the observer may not need to be a conscious one there appears to be more going on here than merely, I measure it, it collapses.
I take the scientific method very seriously, and just like Carl Sagan I say "extraordinary claims require extraordinary evidence".It does seem logical that there is no need for a conscious observer, but is there evidence?
Well, quantum mechanics is science. Some interpretations of quantum mechanics are, how shall I put it, science with a twist. I personally try to stay away from them .After all, this is science, right?
I know that my previous post gave the impression that I believe that a conscious observer is necessary to collapse the probability wave, but that is actually not the case. My own personal opinion, (and that's all that it is) is that a conscious observer is not necessary to collapse the probability wave. Indeed my view is much in line with what bhobba proposed, that "An observation is anything capable of leaving a mark here in the common sense macro world." I believe that so long as the information about which state a particle is in exists anywhere, then the particle will absolutely be in that state. Simply put, if the information exists, then the state exists.Does that mean that the particle hitting a photo detector does not collapse until 20 years later when the data is checked by a human?
I have no problem whatsoever with this . And I did not get the impression you believed in e.g. "consciousness causes the collapse".I know that my previous post gave the impression that I believe that a conscious observer is necessary to collapse the probability wave, but that is actually not the case. My own personal opinion, (and that's all that it is) is that a conscious observer is not necessary to collapse the probability. Indeed my view is [...]
Yes. I was short in post #2, but I think I was honest. There is no notion of consciousness in formal quantum mechanics. And - as a sidenote - consciousness is as far as I know a very slippery term. How should it be defined with pure physics - can it be defined with pure physics? I guess the consciousness question is a question mainly for biologists and possibly chemists.The OP was looking for a yes or no answer. But there isn't a yes or no answer. To claim otherwise wouldn't be completely honest. And we all want to be completely honest, right?
There is a definite no answer is the sense QM requires a conscious observer - it doesn't. There is a definite yes answer in the sense you cant prove consciousness doesn't cause collapse. But consciousness causes collapse does lead to a very weird view of the world - so weird I think anyone that understands its full implications, such as what happens if you replace the conscious observer with a computer (think about it) will reject it.The OP was looking for a yes or no answer. But there isn't a yes or no answer. To claim otherwise wouldn't be completely honest. And we all want to be completely honest, right?
It's good that we're somewhat in agreement as to the necessity of a conscious observer, but I don't believe that I'm as steadfastly against the idea as others may be. It would help if I had a clearer understanding of what exactly constitutes an observer.There is a definite no answer is the sense QM requires a conscious observer - it doesn't.
I would not even start to go down that path without a proper definition of conscious observer. So, what is your definition of a "conscious observer"?It may well be that an environment is capable of causing the collapse only when that environment contains a conscious observer.
I don't agree. I do not think it's reasonable that quantum mechanics on the far side of the Moon (or Mars etc - choose any place you like in the Universe) would work differently than quantum mechanics on Earth.Until then it is perfectly reasonable to argue that a conscious observer is indeed necessary, at least indirectly.
Possible - well, with a considerable grain of salt. But is it probable? Well, that's certainly up for debate. Extraordinary claims require extraordinary evidence. I also personally like to apply the tools in Carl Sagan's so-called Baloney Detection Kit;Until you rule it out, even the outrageous is possible.
Baloney Detection Kit said:Among the tools:
- Wherever possible there must be independent confirmation of the "facts".
- Encourage substantive debate on the evidence by knowledgeable proponents of all points of view.
- Arguments from authority carry little weight -- "authorities" have made mistakes in the past. They will do so again in the future. Perhaps a better way to say it is that in science there are no authorities; at most, there are experts.
- Spin more than one hypothesis. If there's something to be explained, think of all the different ways in which it could be explained. Then think of tests by which you might systematically disprove each of the alternatives. What survives, the hypothesis that resists disproof in this Darwinian selection among "multiple working hypotheses," has a much better chance of being the right answer than if you had simply run with the first idea that caught your fancy.
- Try not to get overly attached to a hypothesis just because it's yours. It's only a way station in the pursuit of knowledge. Ask yourself why you like the idea. Compare it fairly with the alternatives. See if you can find reasons for rejecting it. If you don't, others will.
- Quantify. If whatever it is you're explaining has some measure, some numerical quantity attached to it, you'll be much better able to discriminate among competing hypotheses. What is vague and qualitative is open to many explanations. Of course there are the truths to be sought in the many qualitative issues we are obliged to confront, but finding them is more challenging.
- If there's a chain of argument, every link in the chain must work (including the premise) -- not just most of them.
- Occam's Razor. This convenient rule-of-thumb urges us when faced with two hypotheses that explain the data equally well to choose the simpler.
- Always ask whether the hypothesis can be, at least in principle, falsified. Propositions that are untestable, unfalsifiable are not worth much. Consider the grand idea that our Universe and everything in it is just an elementary particle -- an electron, say -- in a much bigger Cosmos. But if we can never acquire information from outside our Universe, is not the idea incapable of disproof? You must be able to check assertions out. Inveterate skeptics must be given the chance to follow your reasoning, to duplicate your experiments and see if they get the same result.
Well, it could also be the case that Fred in Pittsburg actually monitors all quantum interactions and decides which ones collapse.Could be the case.
No - it goes away ie regardless of if it is connected to a storage device or not the interference pattern disappears. An observer, detector or whatever you want to call it, is anything capable of leaving a mark here in the macro world. If its a particle detector it will click or flash. The storage thing is just to bring out what kind of a weird view you are led to if you think its consciousness that causes collapse. In modern parlance the detector becomes entangled with the particle and its position becomes localized through one slit or the other so it can no longer interfere.if we put a detector at the slits, such that it measures which slit the particle went through, but we don't attach this detector to any type of data storage device, then the interference pattern will remain.
Make no mistake - its a valid explanation - but the world view you are led to if you accept it is very very bizarre and totally unnecessary.Until you rule it out, even the outrageous is possible.
That's a perfectly valid interpretation, just in the light of decoherence overkill because once decoherence occurs all observers agree. Its examined in the link I gave before (see section 3.2.3):My personal view is that collapse is a relative view (relational) and that things are as defined as they need to be (relative to other things) to properly correlate. I haven't gotten to decoherence in the susskind lectures yet, so maybe that will change my mind.
Its provable to be on time scales that even with modern equipment you cant detect. It has been possible to rig it so it occurs slower to actually observe it - and that has been done - ie decoherence has been observed - but that is a very special experimentally designed setup for that purpose - it never occurs in practice.That doesn't say anything about what could be significant lengths of time during which observers
Yes, the issue is controversial and having been involved in a few discussions about it know no definite answer will be reached.I personally subscribe to the consciousness 'causes collapse' view, and agree that decoherence is nowhere near to solving the measurement problem.
Yes, I think so too.Best I think to point to good literature on it an get people to make up their own mind.
I must politely disagree with this statement. Although the way that you have phrased it does make it technically correct, but it is not the situation that I was attempting to describe. Specifically, in the highlighted sentence you essentially described turning the environment into a storage device. A particle detector that clicks or flashes, obviously has the potential to leak information into the environment. Making the environment the storage device. But if our detector does not leak information into the environment, then it will of its own accord be unable to introduce decoherence.No - it goes away ie regardless of if it is connected to a storage device or not the interference pattern disappears. An observer, detector or whatever you want to call it, is anything capable of leaving a mark here in the macro world. If its a particle detector it will click or flash.