QM says no observer, no existence

[Les Sleeth]

So the "observer" is just the screen. And personifying the observer is unjustified- period. ??

I have the same problem trying to figure out why consciousness is being given any status in the observation. It's like if we want to see what a gust of wind looks like, so we invent two machines, one which can freeze the wind, and the other which provides a senstive material the wind can imprint so we can see the effect of its movement into the material. When we use one machine it tells us wind is a clump of atmosphere, and when we use the other machine it tells us the wind is spread out.

So isn't it the particular device used for observation that's giving us our results, and not actually consciousness itself?

 

[El Hombre Invisible]

So the "observer" is just the screen. And personifying the observer is unjustified- period. ??

I mean, I see the role of speculation. But when someone invokes, what- the most successful physical theory ever? and never mentions they are speculating, it bothers me. I don't mean that everyone does it purposefully.

Well, to your first point, as I understand it the human observer is not essential - if in principal the event may be observed then it is the same as if it were observed, regardless of it is or not. In the case of the two-slit experiment with electrons, if in principal the slit through which the electron traveled could be known, you know you will NOT get interference. If even in principal it cannot be known, you know you WILL get interference. And you may set this experiment up again and again and be sure each time whether or not you will get interference. So as to your second point, I don't see what you consider to be speculative.

 

[vanesch]

Okay, I'm confused again. Can someone give an example of an observation in QM? I guess I'm familiar with the double-slit experiment. When does the observation occur there? When an electron (or whatever) interacts with the screen?

This is often said, but it is (unfortunately) not true. When an electron interacts with the screen (supposed to be a detector), then you can, in principle, work out the interacting hamiltonian electron-screen and you will just find out that the detector is now in a superposed state (has no definite "click" or "no-click" result!). That's simply a result of the fact that ALL interaction is described by a hamiltonian (and thus also a UNITARY time evolution operator).

Imagine a photon hits a beam splitter, and can be transmitted or reflected.
Imagine now that you have a photodetector behind it. You might think that the detector "observes" the photon, and clicks, or doesn't click. But that's not what QM tells you, if you analyse the physics of the detector.

Before the BS, you had: |photon-in>
After the BS, you had the photon state: 1/sqrt(2) ( |T> + |R> )

When the detector is hit (in the T beamline), you then simply have:

1/sqrt(2) ( |T> |click> + |R> |noclick> ).

The detector didn't "observe" anything. It just interacted with the photon state, and now finds itself into a superposition of "click" and "no click".

Quantum theory NEVER indicates a special process (electron interacting with light, electron hitting screen etc...) that can be labeled "observation". If we look in enough detail, it is all just interaction, and that means, it is all described by a unitary operator. And such an operator, being linear, cannot "undo" any quantum superposition.

cheers,
Patrick.

 

[Burnsys]

Is this true? i was reading and when i came to this part i was really surprised.. but i don't know if they really did all this or not:

---------------------------------------------------
http://www.bottomlayer.com/bottom/reality/chap2.html

We would like to think that the particle detectors at the slits are affecting the passage of the electron -- perhaps deflecting it, or modifying it's path, or in some other way influencing the experiment. We could accept such an explanation. But that does not seem to be the case. A series of experiments have been conducted to test just such a hypothesis, and the results are uniformly negative. I will quickly run through some of the more ingenious attempts to isolate and remove any possible influence stemming from the detectors located at the slits.[1]

1. Turn off the electron detectors at the slits. Suppose we take our modified double slit set up -- with electron detectors at the slits -- and leave everything intact. But, we will conduct the experiment with the electron detectors at the slits turned off, so that we will not actually detect any electrons at the slits.

The result upon analysis: an interference pattern at the back wall. So it seems that mere passage through the electron detectors at the slits does not affect the electron, so long as those electron detectors are not functioning.

2. Leave the electron detectors on, but don't gather the information. Suppose we take our modified double slit set up -- with electron detectors at the slits -- and still leave everything intact. And we will keep the electron detectors at the slits turned on, so that they will be doing whatever they do to detect electrons at the slits. But, we will not actually look at the count of electrons at the slits, nor will we record the count at the slits in any way, so that we will not be able to obtain any results from these fully-functioning electron detectors.

The result upon analysis: an interference pattern at the back wall. So it seems that the electron detectors located at the slits do not themselves affect the electron, even when the equipment is fully functioning and detecting (in a mechanical sense) the electrons, so long as we don't obtain the results of these measurements.

3. Record the measurements at the slits, but then erase it before analyzing the results at the back wall
. Suppose we take our modified double slit set up -- with electron detectors at the slits -- and still leave everything intact. And we will still keep the electron detectors at the slits turned on, so that they will be doing whatever they do to detect electrons at the slits. And we will record the count at the slits, so that we will be able to obtain the results. But, we will erase the data obtained from the electron detectors at the slits before we analyze the data from the back wall.

The result upon analysis: an interference pattern at the back wall. Notice that, in this variation, the double slit experiment with detectors at the slits is completed in every respect by the time we choose to erase the recorded data. Up to that point, there is no difference in our procedure here and in our initial procedure ([pp. 15-17]), which yielded the puzzling clumping pattern. Yet, it seems that if we, in a sense, retroactively remove the electron detectors at the slits (not by going back in time to physically remove them, but only by removing the information they have gathered so that it is not available from the time of the erasure going forward into the future), we can "change" the results of what we presume is a mechanically complete experiment, so far as those results are determined by a later analysis, to produce an interference pattern instead of a clumping pattern. This is mind-boggling.

4. Arrange the experiment so that we can make an arbitrary choice at some later time, after the experiment is "complete," whether or not to use the information gathered by the electron detectors at the slits.
Suppose we take our modified double slit set up -- with electron detectors at the slits -- and still leave everything intact. And we will still keep the electron detectors at the slits turned on, so that they will be doing whatever they do to detect electrons at the slits. And we will record the count at the slits, so that we will be able to obtain the results. But (this gets a little complicated), we will
(1) mix the data from the slits with additional, irrelevant garbage data, and record the combined (and incomprehensible) data;
(2) design a program to analyze data coming from the slits in one of two ways, either
(a) filtering out the garbage data so that we will be able to obtain clean results of electrons going through the slits, or
(b) analyzing the mixed-up data so that we will not be able to obtain the results of electrons going through the slits; and
(3) leave it up to a visiting politician which way we actually analyze the data from the slits.

The result upon final analysis by method (2)(a): a particle clumping pattern appears from the data.
The result upon final analysis by method (2)(b): an interference pattern appears from the data.

 

[honestrosewater]

Okay, I think I've gotten all I can out of this for the moment. Thanks to everyone for the help.

I don't see what you consider to be speculative.

Just reasoning on insufficient evidence or going beyond the evidence.

 

[Q_Goest]

Burnsys

The link you're referring to is an interesting one. I think the conclusions given in that link are largely based on a number of experiments, but probably none more than this one: Delayed Choice Quantum Eraser

The original paper and a discussion of it can be found on Physics Forums here: Physics Forums Discussion

One possible interpretation of the experiment is given by the website you reference - that a conscious observer is needed to 'collapse the wave function' (so to speak). On the other hand, I see from the discussion on Physics Forums that there are those who would simply suggest the interpretation is nothing more than a calculable result.

From reviewing both the paper and discussion it seems people still can't agree on the physical interpretation of QM. At two ends of the spectrum are the "shut up and calculate" group and the MWI believers, with other interpretations sprinkled throughout. Unfortunately, without a reason to distingquish between the various interpretations, no single interpretation has become accepted.

 

[gptejms]

Vanesch,you(or all MWI adherents) seem to reserve the word measurement till the point a conscious creature comes in.Upto the point it's a detector interacting with the particle,it's all linear superposition, but when the observer comes in, linear superposition(via unitary evolution) still continues but the world splits and the unobserved branch goes into some mysterious other world.How does the particle being observed or the system of particle + 'observer' come to know that the observer is conscious,so I must now split up?

Also coming to the cat paradox--say the cat observes itself to be alive--now the human observer comes in after some time---how do you explain from theory that he should necessarily find the cat to be alive and not dead(apart from common sense)?

 

[Tournesol]

There might be somehing about the physics of conscious observers that explains this, but there might be something about the physics of macroscopic measuring instruments.

 

[gptejms]

decide which one it is-----the physics of conscious observers or the physics of macroscopic measuring instruments?

 

[Canute]

I have a related question. Suppose for a moment we assume that the 'wave' does 'collapse' on being 'observed' and that this collapse is caused by consciousness. It seems that this is one of the simplest solutions. Yet even then there still seems to be a problem.

In order to observe something it must exist. Yet if a thing does not exist until we observe it then obviously we can never observe it at all, since we would have to observe it before it was observable in order to bring it into existence. This seems to me an important and often ignored aspect of the problem. How is this timing problem explained in QM? Or is it as yet just another unknown? Or, it just struck me, might this be something to do with non-locality? Or, another thought, is this something to do with Feynmans 'advanced' and 'retarded' waves allowing (what appears to be) instantaneous interaction?

 

[Tournesol]

In order to observe something it must exist.

before or at the time of observation

 

[gptejms]

I think 'collapse of the wavefunction' is not such a mysterious thing as it is made out to be.What do you do when you do a measurement----you just reduce the \Delta x or the position uncertainty of the particle(so that you know the position of the particle (reasonably well)),whereas the momentum uncertainty becomes high.So what you do when you make a measurement is simply this-------you reduce the particle's position uncertainty whereas you increase its momentum uncertainty(given any initial wavefunction)--it's as if you have a gamma ray microscope in your hands and you 'observe' the particle---in doing so you inevitably disturb the particle,so whatever interference/diffraction pattern you would have expected in absence of the measurement is disturbed.The 'collapse' is a literal collapse in the position sense---the challenge is to show that this can come out of a unitary process.'If ' we can do that(may be we could take the measurement to be introduction of some sort of a potential which changes the wavefunction and localizes the particle in the position sense) then the need for mysterious things like consciousness,MWI etc. goes away---note the 'if ' in the statement.

 

[Canute]

before or at the time of observation

The entity must exist before the observation if it takes time for information to travel from the observed entity to our consciousness. The alternative, that the entity does not exist before we observe it, is that the observation and the collapse of the wave function must be an example of non-locality, instantaneous correlation across intervening spacetime. A third alternative is that the observation is causal backwards through time, which is why I mentioned retarded waves. Is there a fourth alternative?

 

[Tournesol]

The entity must exist before the observation if it takes time for information to travel from the observed entity to our consciousness.

The entity does nto need to exist before it the first microscopic interaction with the apparatus that eventually leads to our being aware of it.

 

[Pi_314B]

One could understand this whole thing if one were to accept that all things are conscious, down to and including fundamental entities. I.E A fundamenal entities knows what it is to the extent that it is. This goes to say that reality is conceptual only ... physical realty is conceptually based.

 

[sd01g]

To keep a proper perspective on the double slit experiment, fire a large caliber bullet through the double slits. Notice how both slits become one large hole. Also notice that no interference pattern is produced. Point made: Quarks rule.

 

[Canute]

The entity does nto need to exist before it the first microscopic interaction with the apparatus that eventually leads to our being aware of it.

Are you suggesting that the entity can interact with the apparatus before it exists?

 

[vanesch]

Sorry, didn't see that post for a long time !

Vanesch,you(or all MWI adherents) seem to reserve the word measurement till the point a conscious creature comes in.Upto the point it's a detector interacting with the particle,it's all linear superposition, but when the observer comes in, linear superposition(via unitary evolution) still continues but the world splits and the unobserved branch goes into some mysterious other world.How does the particle being observed or the system of particle + 'observer' come to know that the observer is conscious,so I must now split up?

Nothing special happens physically. I'd object to "and the unobserved branch goes into some mysterious other world", because, according to MWI, it is just as well "there" as the observed branch ; only, it seems to be a rule of conscious observation that you can only subjectively experience one branch (that your consciousness can only be associated to ONE coherent bodystate, and not to all the quantum states your body is in), and that this branch is chosen randomly according to the Born rule.
So from the moment that your body gets entangled with something else (which is the case when you "learn" about a measurement result: your body gets entangled with the carrier of the message), it seems to be the rule that your subjective experiences are only associated with ONE of the terms, and that this assignment is statistically following the Born rule.
It could simply be the "law of consciousness associated with physical structures (bodies)".

Also coming to the cat paradox--say the cat observes itself to be alive--now the human observer comes in after some time---how do you explain from theory that he should necessarily find the cat to be alive and not dead(apart from common sense)?

Solipsism ! The conscious cat can observe a totally different world than you ! Maybe the cat's consciousness is still associated with a live cat in another branch, and your consciousness is associated with one of your bodystates which is entangled with the dead cat's body. You're now simply living in two different branches.
Or even weirder: the opposite: the cat's consciousness was in the "dead cat" branch, so the cat is dead now according to its consciousness, but YOU see a live cat. It doesn't have its original consciousness, but (because of the hard problem of consciousness) there's no way you can find that out.
This is the Wigner's friend kind of situation.

cheers,
Patrick.

 

[gptejms]

Nothing special happens physically. I'd object to "and the unobserved branch goes into some mysterious other world", because, according to MWI, it is just as well "there" as the observed branch ; only, it seems to be a rule of conscious observation that you can only subjectively experience one branch (that your consciousness can only be associated to ONE coherent bodystate, and not to all the quantum states your body is in), and that this branch is chosen randomly according to the Born rule.
So from the moment that your body gets entangled with something else (which is the case when you "learn" about a measurement result: your body gets entangled with the carrier of the message), it seems to be the rule that your subjective experiences are only associated with ONE of the terms, and that this assignment is statistically following the Born rule.

Do MWI-ists assume that the consciousness also splits up when a measurement is made--if it does not,the other you in the other world is a poor dead fellow(and he does not even matter).

It could simply be the "law of consciousness associated with physical structures (bodies)".

According to your model the world splits only when a measurement is made--before that the system under observation is in a superposition in this very world.By calling it a law of consciousness or whatever nothing really is answered.How do you explain the probability aspect when the world just splits into two everytime a measurement is made.

Solipsism ! The conscious cat can observe a totally different world than you ! Maybe the cat's consciousness is still associated with a live cat in another branch, and your consciousness is associated with one of your bodystates which is entangled with the dead cat's body. You're now simply living in two different branches.

See the problem here is this--cat's consciousness is associated with only the live branch i.e. it has not split into two,whereas yours has split into two(the other you in the other world is also alive).So there is a contradiction--one consciousness splits,the other does not.

Or even weirder: the opposite: the cat's consciousness was in the "dead cat" branch, so the cat is dead now according to its consciousness, but YOU see a live cat. It doesn't have its original consciousness, but (because of the hard problem of consciousness) there's no way you can find that out.
This is the Wigner's friend kind of situation.

This of course is weird--a new consciousness for the live cat.

The only way,perhaps, you can resolve the contradiction mentioned above is to say that the cat's consciousness also splits into two and in the dead cat's branch,the consciousness is still there,but it's just there as an out of body soul like existence!You'll agree that this is weirder.

 

[vanesch]

Do MWI-ists assume that the consciousness also splits up when a measurement is made--if it does not,the other you in the other world is a poor dead fellow(and he does not even matter).

Pick your flavor !

According to your model the world splits only when a measurement is made--before that the system under observation is in a superposition in this very world.

It still is in a superposition. The so-called "splitting of worlds" was only some verbial addition to put more dramatic spin to the story, but what it just comes down to, is a term in the "wavefunction of the universe". What term ? One in which your body state appears as a product. There's much more drama in the words than in the formulas. Let * stand for my consciousness, and @ stand for yours.
At a certain point, we have observed each other and we're in the following state:

|mybody*> |yourbody@> (a |1> |U>+ b|2>|V>)

I took an entangled system to give the issue more spin (!).

Suppose I will observe the 1/2 system, and you will observe the U/V system.

After I interact with the 1/2 system, this gives:

|yourbody@> (a |mybody1>|1>|U> + b|mybody2>|2>|V>)

but now the body to which my consciousness is associated, due to the interaction of the measurement, doesn't appear in a product state anymore, so my consciousness has to be assigned to one of both terms (the law of consciousness, if you want to).

|yourbody@> (a |mybody1*>|1>|U> + b|mybody2>|2>|V>)

This means that my consciousness observed the result "1" (and this happened with a probability |a|^2), and it is associated with a body state of my body that has "1" in its physical brain as a souvenir of the measurement.

Now, you will interact with the U/V system:
a |mybody1*>|1>|yourbodyU>|U> + b |mybody2>|2>|yourbodyV>|V>

Again, your conscious body state doesn't appear in a product, which is forbidden. Your consciousness will be assigned one of your bodystates at random, say V, to make it spicy:

a|mybody1*>|1>|yourbodyU>|U> + b |mybody2>|2>|yourbodyV@>|V>

This happens to your consciousness with probability |b|^2

This means that I will experience a body which remembers "1", and which will observe YOUR body which remembers "U". We are both in agreement (even if the body state I'm interacting with is not associated with your consciousness anymore, but I'll never observe that).

It means that you will experience a body which remembers "V" as a measurement result and it also means that you will interact with a body state of mine which remembers "2" (even if it is not the body state that *I* am aware of - you'll never notice the difference).

So both of us consciousnesses, in our own little subjective experiences, are convinced that there was some real observation (I think it was 1 and U, you consciously think it was 2 and V), and everything I can try to find out about it, by asking YOUR BODY, will give me the impression that I'm right ; to you, exactly the same thing will happen. But we each now live in our separate terms (branches - worlds).

cheers,
Patrick.

 

[gptejms]

Pick your flavor !

Let * stand for my consciousness, and @ stand for yours.
At a certain point, we have observed each other and we're in the following state:

|mybody*> |yourbody@> (a |1> |U>+ b|2>|V>)

I took an entangled system to give the issue more spin (!).

Suppose I will observe the 1/2 system, and you will observe the U/V system.

After I interact with the 1/2 system, this gives:

|yourbody@> (a |mybody1>|1>|U> + b|mybody2>|2>|V>)

but now the body to which my consciousness is associated, due to the interaction of the measurement, doesn't appear in a product state anymore, so my consciousness has to be assigned to one of both terms (the law of consciousness, if you want to).

|yourbody@> (a |mybody1*>|1>|U> + b|mybody2>|2>|V>)

This means that my consciousness observed the result "1" (and this happened with a probability |a|^2), and it is associated with a body state of my body that has "1" in its physical brain as a souvenir of the measurement.

Now, you will interact with the U/V system:
a |mybody1*>|1>|yourbodyU>|U> + b |mybody2>|2>|yourbodyV>|V>

Again, your conscious body state doesn't appear in a product, which is forbidden. Your consciousness will be assigned one of your bodystates at random, say V, to make it spicy:

a|mybody1*>|1>|yourbodyU>|U> + b |mybody2>|2>|yourbodyV@>|V>

This happens to your consciousness with probability |b|^2

So both of us consciousnesses, in our own little subjective experiences, are convinced that there was some real observation (I think it was 1 and U, you consciously think it was 2 and V), and everything I can try to find out about it, by asking YOUR BODY, will give me the impression that I'm right ; to you, exactly the same thing will happen. But we each now live in our separate terms (branches - worlds).

Patrick.

So the consciousness has not split---yours is one branch(1 and U) and mine is in the other branch(2 and V).Or is it in both?After all the fellow that tells you that he observes U(the other me) is a meaningful live fellow!The you in my branch is also alive for me to tell me that 2 was observed.Don't you agree that this all very weird and can not be taken seriously.
You didn't answer the probability part.

 

[vanesch]

So the consciousness has not split---yours is one branch(1 and U) and mine is in the other branch(2 and V).Or is it in both?

As I said, pick your flavor. Of course it cannot be in both: we don't observe consciously to be in a superposition (that's the whole riddle to be solved!). Now, you can say that when a conscious body gets entangled with something else (by interaction), the actual consciousness will be assigned to ONE of the term in the superposition, according to the Born rule (take that as a postulate, it answers your probability question). You are now free to assign a NEW consciousness to the other states or not. These are different flavors of the interpretation. It doesn't really matter, because you can never know if a living being has a consciousness or not. If you want it to have one, just assign a "new" consciousness to the other branches then (which, itself, will not know it is a "new" one because the bodystate it is associated with will remember everything from the "old" body, except of course a different measurement result).
[/quote]

After all the fellow that tells you that he observes U(the other me) is a meaningful live fellow!The you in my branch is also alive for me to tell me that 2 was observed.Don't you agree that this all very weird and can not be taken seriously.
You didn't answer the probability part.

I agree that this is very weird, however I don't see why it cannot be taken seriously. (who said again: "we all agree that your theory is crazy. We are discussing if it is crazy enough!") After all, if quantum theory is correct (and there is a unitary evolution - a hamiltonian) for every interaction in the world, there's almost no way to avoid this. There is no logical error in this, and it explains all our conscious subjective experiences.
I did answer the probability part (and that's where my view is NOT the one of the average MWI supporter): it is a postulate: "when the body associated with a consciousness, gets entangled with something else, the consciousness will now be associated with ONE of the body states in the entanglement, with a probability that is given by the Born rule". Take it as the MWI version of the projection postulate.
EDIT: the hard-core MWI fan will hope that we do not have to *postulate* this but that it comes out "naturally" of the formalism ; I think that this cannot be done, and that's where I'm a heretic wrt MWI.

You might add: "and a new consciousness will be created and associated with each of the viable bodystates in the other terms", at your will.
You might also consider that there is only one consciousness, namely yours (mine!), and that all other bodies are just not associated with a consciousness. There's no way to find out as is philosophically well known. Probably the version with the "new" consciousnesses is the most "symmetrical", but it is just a matter of taste.

cheers,
Patrick.

 

[nameta9]

"Irreducible complexity". Maybe the problem is in the concept that observer plus system being observed cannot really be further decomposed without eliminating everything. An odd theory put forward to justify "creationism", but in this case may very well apply. The system as a whole is "irreducible", so you have irreducible complexity where you can't take any part away without modifying the system into something else.

 

[vanesch]

"Irreducible complexity". Maybe the problem is in the concept that observer plus system being observed cannot really be further decomposed without eliminating everything.

This is not just an "odd theory", it is fundamental in quantum theory (and well known). The hilbert state space of a composed system is the kronecker product of the individual hilbert state spaces: H = H_A (x) H_B.
Now, in order to be able to talk about the state of each system individually (A or B), the global state must be a product state of a state in H_A and a state in H_B. However, it is well known that the very large majority of states in H CANNOT BE WRITTEN IN SUCH A PRODUCT FORM (in that case, one says that systems A and B are entangled). In such a case, there's no way of assigning an individual state to system A and system B. There are *statistical* descriptions (using reduced density matrices) that can limit one's attention to A or to B, but they are not correct when both systems are considered (they do not correctly give the correlations between measurements).

cheers,
Patrick.

 

[nameta9]

This also confirms that the "marxist-sociological" theories that science is a social "construction" really applies. If you were the only observer in the universe, then the laws of physics would change (and probably wouldn't even exist) as it is all dependent on your subjective view and experience. The other "observers" confirm science, but all civilization as a whole could be looked upon as only one observer, hence the laws of physics don't exist. And "irreducible complexity" may even apply to all objects; hence even an atom if taken away an electron becomes something else (anyways it remains an odd theory).

Did the creationist oddballs know that stuff of hilbert ?

 

[vanesch]

This also confirms that the "marxist-sociological" theories that science is a social "construction" really applies. If you were the only observer in the universe, then the laws of physics would change (and probably wouldn't even exist) as it is all dependent on your subjective view and experience.

I don't understand this. Why would the laws of physics change or not even exist if I were the only observer ? What stops objective laws of physics from determining my subjective experiences ?

Did the creationist oddballs know that stuff of hilbert ?

As it isn't written in the Bible, I think they don't

 

[nameta9]

Vague concept not worded right. Imagine really if you were the only person in the entire universe. So you have books, instruments and laws of physics. But you completely depend on your "subjective-psychological" state. I think that under these conditions after some time, you would start losing all references as only "other" people / communications somehow provide a reference. I think a single pesron observer would end up "changing" the laws of physics because he wouldn't be able to reason straight for very long.

 

[vanesch]

I think a single pesron observer would end up "changing" the laws of physics because he wouldn't be able to reason straight for very long.

Now let us assume for a moment that there are other bodies, which act as persons act, but which are not conscious. Only, the behaviour of these bodies is exactly as if they were conscious, and you ARE indeed the only person in the world with a consciousness. What does that change from the actual situation you think you are in ?

 

[Canute]

Quite. Every theory must be consistent with solipsism being true, since if it is not then proving that theory true will involve proving solipsism false, and this cannot be done. This renders any theory that assumes solipsism to be false unprovable in principle. This seems a regularly overlooked issue in physics. For example, even if materialism is true we can never know this, since its truth cannot be known by experience, and to know it to be true by reason would involve falsifying solipsism. Btw, it can be argued that solipsism is not falsifiable because it's not exactly false, even if it's not exactly true either. Many people hold this view.

Earlier (Vanesch) you wrote - "Of course it cannot be in both: we don't observe consciously to be in a superposition (that's the whole riddle to be solved!)." I wonder though. Is this not just an assumption? It's my suspicion that we can observe ourselves to be in a superposed state, and that this is the answer to many riddles.

 

[vanesch]

It's my suspicion that we can observe ourselves to be in a superposed state, and that this is the answer to many riddles.

Well, maybe exceptionally (which would then account for a lot of "supernatural" phenomena :-).
But I fail to see how we observe ourselves to be in superposed states in the "standard" situation: it would mean that we observe outcomes of experiments in superposition: the answer on the voltmeter was observed to be 2, 5, 18 and 21 Volt at the same time. Sorry, but this happens to me only when I'm seriously drunk (ah, that's maybe the key: ethanol (and other substances) momentarily suspend the Born rule :-)