Is the Moon there when nobody looks at it?

[RonLevy]

Please help me with this. Can anyone direct me to the specific mathematics that is interpreted as saying that "the Moon does not exist when nobody looks at it."
Is there any book or discussion of the actual math and physics of this?
What specifically was Einstein reacting to when he said:
"I cannot believe that the Moon exists only because a mouse looks at it." ?
Please feel free to write or send me anything you wish about this subject. I have no axe to grind, and I only would like to understand this better. Thank you.-Ron

 

[tardis]

To add to the question, what would constitute "looking". Would a video camera that displays the image on a screen in an empty sealed basement that no one can enter be considered "looking?

What if the images were captured digitally and were later destroyed without anyone looking at it?

or perhaps someone does look at it later.

The issue of looking, taping and viewing presents an interesting discussion topic.

Tardis

 

[DrChinese]

Please help me with this. Can anyone direct me to the specific mathematics that is interpreted as saying that "the Moon does not exist when nobody looks at it."
Is there any book or discussion of the actual math and physics of this?
What specifically was Einstein reacting to when he said:
"I cannot believe that the Moon exists only because a mouse looks at it." ?
Please feel free to write or send me anything you wish about this subject. I have no axe to grind, and I only would like to understand this better. Thank you.-Ron

Welcome to PhysicsForums, Ron!

I keep a page on my site which explains this in more detail:

Bell's Theorem with Easy Math

This is partially based on a paper by N. David Mermin called: "Is the moon there when nobody looks? Reality and the quantum theory" (1985). As you might guess, my page is probably a bit easier to follow for most people, especially as to the math.

The fact is: Einstein (sadly) died before Bell's Theorem appeared. He likely would have changed his opinion had he known about it. Experiments support the ideas of Quantum Mechanics in this area quite solidly.

 

[Spin_Network]

Welcome to PhysicsForums, Ron!

I keep a page on my site which explains this in more detail:

Bell's Theorem with Easy Math

This is partially based on a paper by N. David Mermin called: "Is the moon there when nobody looks? Reality and the quantum theory" (1985). As you might guess, my page is probably a bit easier to follow for most people, especially as to the math.

The fact is: Einstein (sadly) died before Bell's Theorem appeared. He likely would have changed his opinion had he known about it. Experiments support the ideas of Quantum Mechanics in this area quite solidly.

There are some recent:http://www.physics.uq.edu.au/people/andrew/publications/2005/weakvalue.pdf

workings on the experimental setup?

I like your pages on the setup principle, though simplistic it has the essence of answering some questions, whilst I must admit it has lead to me asking "more-than" the original question!

 

[Antiphon]

The moon is there when nobody is looking at it. You don't have to look at
something for it to exist. QM never said you did.

 

[DrChinese]

The moon is there when nobody is looking at it. You don't have to look at
something for it to exist. QM never said you did.

No one is actually talking about the moon. At least, I'm not. But if you are saying there are values for particle attributes independent of actual measurement, then I am going to disagree with you.

I believe this position is as consistent with experiment and theory as it is possible to state: the act of observation changes reality, even after the fact.

 

[RonLevy]

Hello Tardis, Dr.Chinese, and Spin Network, Thank you for your prompt replies. It is my pleasure to meet you. I downloaded David Mermin's paper, but could not open the file. How is the question of whether the Moon exists when nobody looks at it tied into EPR and Bell's Theorem?
Can you show me the equations that can be interpreted as showing that the Moon(or anything else) does not exist when nobody looks at it. I am familiar with issues about observer-created reality. Is this issue about the Moon a result of scaling up a quantum physics fact to macroscopic sizes, sort of like how this is done with Schrodinger's Cat? If so, what is it specifically that is being scaled up? Thanks, and Best Regards,-Ron

 

[εllipse]

No one is actually talking about the moon. At least, I'm not. But if you are saying there are values for particle attributes independent of actual measurement, then I am going to disagree with you.

I believe this position is as consistent with experiment and theory as it is possible to state: the act of observation changes reality, even after the fact.

Why doesn't this statement naturally lead to application with macroscopic bodies, such as the moon. The moon is composed of fundamental particles, is it not?

I have read a little about a particular Copenhagen stance considering macroscopic objects as different entities than fundamental particles. Something about a macroscopic measuring device being able to collapse the wave function, so there is some kind of interplay between the macroscopic world and the microscopic world and both are needed to create the human experience. Is this sort of what you're saying? That since the moon is macroscopic it is capable of having a definite position even when not being measured? It just seems to me that if you take the statement that fundamental particles don't have definite positions unless they're being measured and follow it to its logical conclusion, the moon also can't have a definite position unless it's being observed. ?

 

[Antiphon]

No one is actually talking about the moon. At least, I'm not. But if you are saying there are values for particle attributes independent of actual measurement, then I am going to disagree with you.

I believe this position is as consistent with experiment and theory as it is possible to state: the act of observation changes reality, even after the fact.

Actually, I was very careful to say that the thing [moon] "exists" and not
that it "is there" implying a particular position. As you know Dr. C, to exist
in QM is to have a unit probability of being somewhere in the universe
without actually being anyone place most of the time.

It's a freaky business and (quoting myself from another thread) the person
who figures out the physical basis of quantum superposition will be a rock
star on par with Einstein.

Edit: As far as the macroscopic-composed-of-microscopic goes, Ellipse, to my
way of thinking the best answers so far are given by the folks who say that
a large object perturbs (or observes if you will) itself and this is what gives
rise to the emergence of more classical persistence of position.

 

[Spin_Network]

No one is actually talking about the moon. At least, I'm not. But if you are saying there are values for particle attributes independent of actual measurement, then I am going to disagree with you.

I believe this position is as consistent with experiment and theory as it is possible to state: the act of observation changes reality, even after the fact.

So, if I observe the Moon, does this "effect" the motion of tides here on Earth?

What would such consequences be if everyone that can observe the Moon at the same instance, did so. Would there be a verifyable difference in Tidal action?

What I am asking is the number of observers influential on imparting "effects" to the observed ?

 

[Antiphon]

So, if I observe the Moon, does this "effect" the motion of tides here on Earth?

What would such consequences be if everyone that can observe the Moon at the same instance, did so. Would there be a verifyable difference in Tidal action?

No, beacuse the gravity of the moon is there (and is the same) even when you don't look at
it- more evidence that you don't need a human observer to make a thing
manifest in a particular position.

 

[DrChinese]

Is this issue about the Moon a result of scaling up a quantum physics fact to macroscopic sizes, sort of like how this is done with Schrodinger's Cat? If so, what is it specifically that is being scaled up?

That is a good way of describing it, yes.

What is being scaled up is the idea that particles have definite attributes independent of observation. The Heisenberg Uncertainty Principle (HUP) restricts the "simultaneous reality" of various particle attributes according to its relations. Observation of position affects momentum, for example. QM treats HUP as fundamental; therefore the existence of attributes varies according to the nature of the observation. All known experiments satisfy the HUP.

EPR (Einstein) tried to use measurements on entangled particle pairs as a way to outsmart the HUP. However, the HUP came through as QM would predict, after Bell came along and showed the way. You see, many thought the HUP was simply an experimental limitation; Bell concluded it was fundamental to the nature of reality. Most people do not look at Bell in terms of the HUP, but that is in fact at the base of the debate.

I do not mean to imply that anyone really knows what an observer is - i.e. must it be a conscious mind? I only mean to say that the act of observation is somehow fundamental to the outcome as to what reality becomes.

 

[DrChinese]

No, beacuse the gravity of the moon is there (and is the same) even when you don't look at
it- more evidence that you don't need a human observer to make a thing
manifest in a particular position.

Talking about the moon confuses the issue greatly, because it is a macroscopic object. The combined uncertainty of the particles composing the moon is not a factor in macroscopic observations. The question is not whether the particles composing the moon exist. It is whether those particles have distinct values independent of individual observation. The answer is that they don't. That does not mean that the particles don't obey gravity - because they do. They also bond into atoms. Etc.

But no individual atom escapes the rules of the HUP. This is fundamental to QM. And this is the debate. People simply talk about the moon as a metaphor. It is not intended to be literal.

 

[DrChinese]

How is the question of whether the Moon exists when nobody looks at it tied into EPR and Bell's Theorem?
Can you show me the equations that can be interpreted as showing that the Moon(or anything else) does not exist when nobody looks at it.

Referring to my paper:

Einstein said: "I think that a particle must have a separate reality independent of the measurements. That is: an electron has spin, location and so forth even when it is not being measured. I like to think that the moon is there even if I am not looking at it."

If you look at my Table 1, you will see 8 cases ([1]...[8]) listed with all permutations for the hypothetically real polarization attributes at 3 angle settings - 0, 120 and 240 degrees. The existence of these 8 permutations is what is being debated. If there is reality independent of observation, then all 8 exist. But QM/HUP denies this explicitly! In fact, the mere assumption that there are 8 permutations leads to a burdensome requirement that was not previously suspected, and this requirement is called Bell's Inequality. Bell's Inequality cannot be supported experimentally, although the predictions of QM/HUP can. This is Bell's Theorem.

 

[RonLevy]

Hi Dr. Chinese, Please help me understand if this Moon-existence issue results from the whole take on the Copenhagen Interpretation, or not. I think I see now how it is related to EPR and Bell's, because the moon-existence thing is related to the question of whether there is or is not a "deep reality" independent of observations. Let me be straight with you: After spending the last 4 months trying to learn The Quantum Theory, (including the Bra-Ket notation), I came across a startling argument for the existence of God, (I am an agnostic.), which is that "If the Moon continues to exist when nobody looks at it, that this is because there is a conscious observer who is continuously observing the moon 24 hours a day." Naturally, I would like to see exactly where this follows logically from the science that yields the notion that "the moon does not exist if it is not observed by anyone."
What do you think about this? If the moon-existence paradox, (MEP), is actually a kind of "non-issue," so that MEP follows from a metaphor that conveys the essence of the Copenhagen Interpretation, then that is one thing. However, if, as you have pointed out, it leads straight back to The Heisenberg Uncertainty Principle, which has never failed an experimental test, that seems a lot stronger. Ron

 

[RonLevy]

Have finally gotten Mermin's paper to open, and am studying it and Dr. Chinese's discussion on his site. This is deep stuff. Fascinating and amazing stuff. Thanks. If you guys think I'm mixed up or confused, please tell me. I have no axe to grind or point I need to make. I just want to learn it and understand it.
-Ron

 

[vanesch]

I believe this position is as consistent with experiment and theory as it is possible to state: the act of observation changes reality, even after the fact.

If you *really* want to be politically correct, you should say that in quantum theory, the act of observation changes PERCEIVED reality, even after the fact.
The whole discussion (amongst those who accept of course current predictions of QM) resides in what is the underlying reality, and what part of it is perceived. It is only in the case you identify the underlying reality with the perception you have, that you can make such a statement.
In mathematical terms, this comes down to saying that the quantum state represents "reality", and that observation (projection) affects "reality" or that observation only comes down in picking one of the terms as the *perceived* reality.

 

[bayan]

How can something not exist if it does exist? There are somethings that maths simply fails to explain.

If no one looks at the sun for about 8 minutes 20seconds and when we look back would sun be there or would it not be there?

If it happenes to moon it will surly happen to sun!

 

[εllipse]

I came across a startling argument for the existence of God, (I am an agnostic.), which is that "If the Moon continues to exist when nobody looks at it, that this is because there is a conscious observer who is continuously observing the moon 24 hours a day."

Why are you so certain that the moon must have a definite position when it's not being observed? It *does* exist, as someone pointed out earlier, fundamental particles/waves always exist, they just don't always have a definite position. So why wouldn't quantum theory naturally lead to the fact that if there are no moon observers, there is no definite position for the moon.

However, I have come across a similar type of argument, that perhaps the one thing that separates an observer from the quantum world is a soul. I really don't understand why wave functions should ever collapse, but they obviously do when humans are involved, so should that lead to the conclusion that there is something humans possesses which isn't built up from the quantum world? Oh well, .

 

[LURCH]

If you *really* want to be politically correct, you should say that in quantum theory, the act of observation changes PERCEIVED reality, even after the fact.
The whole discussion (amongst those who accept of course current predictions of QM) resides in what is the underlying reality, and what part of it is perceived. It is only in the case you identify the underlying reality with the perception you have, that you can make such a statement.
In mathematical terms, this comes down to saying that the quantum state represents "reality", and that observation (projection) affects "reality" or that observation only comes down in picking one of the terms as the *perceived* reality.

I think the whole point is that QM tells us that perceived reality is the only reality. This also goes right to the question regarding Conscious-mind observer vs. video recorder. Perhaps the statement in the OP could better be expressed as, "YOUR Moon only exists when you are looking at it". If the video camera is looking at the Moon, then the Moon exists for it, but you cannot prove that it exists for you. Of course, if you are not looking at the camera, then I suppose you can't even say that "the Moon exists for the camera", because the question then becomes "what camera?", since the camera also does not exist for you when you're not looking at it, right?

Why are you so certain that the moon must have a definite position when it's not being observed? It *does* exist, as someone pointed out earlier, fundamental particles/waves always exist, they just don't always have a definite position. So why wouldn't quantum theory naturally lead to the fact that if there are no moon observers, there is no definite position for the moon.

But for the Moon to exist as "moon", many articles/waves must be in definite positions. Those that make up the material in the loose dust on the surface must be above those that make up the carbonaceous rocket and magma underneath, with perhaps some others making a tiny metal core at the center. If all of these bits have only "existence" without a particular location, then they cannot be assembled together in their proper places to form a Moon.

However, I have come across a similar type of argument, that perhaps the one thing that separates an observer from the quantum world is a soul. I really don't understand why wave functions should ever collapse, but they obviously do when humans are involved, so should that lead to the conclusion that there is something humans possesses which isn't built up from the quantum world? Oh well, .

I think that it only looks that way to a human.

 

[RonLevy]

If the Moon did not exist when nobody looked at it, then wouldn't the gravitational attraction disappear too? If that happened, the tides would change (at least). Does our experiencing of the gravitational effects of the Moon amount to an indirect way of making a measurement (observing the Moon)?

 

[vanesch]

If the Moon did not exist when nobody looked at it, then wouldn't the gravitational attraction disappear too? If that happened, the tides would change (at least). Does our experiencing of the gravitational effects of the Moon amount to an indirect way of making a measurement (observing the Moon)?

There's a serious problem with applying quantum ideas to gravity. It might even be the key to the solution of the riddle. But let's for a moment assume that that is not a difficulty.
The tides would not "change" because by observing those tides, or their effects, you are indirectly observing the moon's position. So in the same way as the moon would maybe "jump around but only appear to be in the right spot when you observe a few photons bounced off its surface", the moon would maybe "jump around but only appear to be in the right spot when you observe a few tidal effects". So as long as you *observe* a consistent set of things, you will not conclude about an anomaly. That doesn't mean that things have to be that way (only), but that means that they have to give rise to consistent observations.

 

[vanesch]

I think the whole point is that QM tells us that perceived reality is the only reality. This also goes right to the question regarding Conscious-mind observer vs. video recorder. Perhaps the statement in the OP could better be expressed as, "YOUR Moon only exists when you are looking at it". If the video camera is looking at the Moon, then the Moon exists for it, but you cannot prove that it exists for you. Of course, if you are not looking at the camera, then I suppose you can't even say that "the Moon exists for the camera", because the question then becomes "what camera?", since the camera also does not exist for you when you're not looking at it, right?

Yup, that's right, it is a way to look at things (I adhere to that view). Well, no, I adhere to the view that the camera exists in BOTH states (with and without a picture of the moon), but that I only observe ONE of these states.

But for the Moon to exist as "moon", many articles/waves must be in definite positions. Those that make up the material in the loose dust on the surface must be above those that make up the carbonaceous rocket and magma underneath, with perhaps some others making a tiny metal core at the center. If all of these bits have only "existence" without a particular location, then they cannot be assembled together in their proper places to form a Moon.

In fact, for the Moon to exist as moon, many particles must not be in definite positions. There are many quantum states of the overall system that would be a sufficiently accurate description of what we vaguely call "Moon", and there's a whole body of theory (decoherence theory) which tries to demonstrate that the interactions of that system with its environment keep it in those states most of the time.

I think that it only looks that way to a human.

Worse, it only looks that way to YOU. All other humans have a different view, but YOU only see them in their only aspect where they have only seen ONE of the states

 

[RonLevy]

Dear Vanesch, To see if I understand: You and others are saying that it is not a question of whether or not the moon exists, but instead, by The Heisenberg Uncertainty Principle the question is whether the Moon occupies a specific spot in x,y,z,t space-time if it no one makes an observation? -Ron

 

[reilly]

This business of "Is the moon there..." is one of the oldest issues known to mankind, and has virtually nothing to do with QM, nor with empirical science. You have your platonic ideals to Hume's extreme skepticism, with which I pretty much agree. As several have pointed out, we observe the moon all the time -- it is, from time-to-time directly visible. When it's not, its gravity has a well defined and well predicted effect on the earth; similarly with the sun, ... Thus it is prudent to assume that the moon is indeed there all the time. Astronauts have confirmed this to a point; during their time their experience told us all that the moon was solid at the surface, was round, ...
The point is that there are other possible configurations, cf. optics and potential theory, that can provide a model of the moon that accounts for what we know of it -- great homework assignment.

So why do we assume the moon is in fact a solid body, much like other planets and moons in the solar system? Its the best Occam game in town. We work with what we call common sense and intuition and assumption -- all of which have changed radically since Plato's time -- sort of like "It's the economy stupid" a memorable statement of recent political affairs.

If you really think about it, there are a huge number of assumptions required to assert that "A is really there" or "B is not there." The key one, to which virtually all of us subscribe, is that there's something out there that generates the signals which we perceive -- and there's no way to find out whether or not that's true, because we rely totally on our perceptions to live, to understand, to do science, and so forth. Over the centuries we have become highly sophisticated, or so we like to think, and we've adopted a perspective on science, made authoritative via Popper's idea of falsification -- hardly a euphonious word --, with which David Hume would agree. And, of course, to date our common assumption of an external world has survived in admirable form. It boils down to: if you cannot observe or measure something by any means, for a short or long time, then you have no empirical way to assert existence during the time of observation -- this is true of legal evidence and reasoning as well as scientific evidence and reasoning. But the assumption of continuity of existence -- including possible alterations by one means or other -- has served us well. But make no mistake: reality is a human invention, a convenient assumption beyond proof.

Schrodinger's Cat? Perhaps I'll drum myself of the respectable scientific community, but I have never understood "the problem" since I first heard of it many years ago. In no small measure, my take on this matter has been fortified by many years of day-to-day work with statistics and probability, which I've also taught at the undergraduate level. If you don't know, you don't know. Of course I work with the assumption that we have yet to encounter a cat which in, other than some mystical or a specific medical sense, simultaneously is alive and dead. Why in the world would we assume the cat's state in Schrodinger's experiment takes on a wholly different aspect than one we see in the "real" world? Cats, humans, other animals are either alive or dead -- except, perhaps in unusual medical circumstances -- are either alive or dead. There is, certainly, a probability that the cat is either alive or dead, the two allowed states. And the probability is conditioned on the state of the radioactive system, which does or does not decay. To me, standard probability theory does an Occam-like job with Schrodinger's cat.(Not dissimilar to assuming, in an unwatched horse race, that A won, because just before crossing the finishing line B stopped and tried to turn around. Arguably this could happen, but...)

Suppose you did many EPR experiments with detectors at different distances from the source, or many scattering experiments with detectors spanning the space allowed to the scattered particle. (I mean one set of counters per experiment; not multiple scattering configurations.) You, of course, will find events in different configurations, and different places. That is you will map out the density of events in the appropriate configuration space, and thus you will map out the probability of events. This approach is equally valid in the classical and quantum worlds --measure and count. (Recall that the low energy cross section for charged particle scattering, the Rutherford cross section, is equally valid classically and quantum mechanically. Granted, this scattering phenomena occupies a small portion of the space of all possible scattering experiments. Nonetheless it is suggestive that a straightforward application of basic probability to such low energy scattering is quite appropriate.)


Finally, the results discussed above, define perfectly additive measures, as do all spaces of disjoint events -- a single measurement cannot simultaneously give both a spin up and a spin down result. For a basic probability measure to exist, discrete or continuous or mixed, an additive measure is necessary and sufficient. Thus, a global perspective puts QM on a standard probability basis, and therefore allows a "knowledge interpretation", a la Sir Rudolph Peierls.

Regards,
Reilly Atkinson

 

[Spin_Network]

Dear Vanesch, To see if I understand: You and others are saying that it is not a question of whether or not the moon exists, but instead, by The Heisenberg Uncertainty Principle the question is whether the Moon occupies a specific spot in x,y,z,t space-time if it no one makes an observation? -Ron

Try this up to the minute paper:http://arxiv.org/abs/quant-ph/0509061

It should enlighten you

 

[bayan]

If no one looks at the sun for about 8 minutes 20seconds and when we look back would sun be there or would it not be there?

What would happen in this case? wouldn't the same apply to sun?

 

[DrChinese]

If you *really* want to be politically correct, you should say that in quantum theory, the act of observation changes PERCEIVED reality, even after the fact.

I stand corrected, my many worldly friend!

 

[DrChinese]

Dear Vanesch, To see if I understand: You and others are saying that it is not a question of whether or not the moon exists, but instead, by The Heisenberg Uncertainty Principle the question is whether the Moon occupies a specific spot in x,y,z,t space-time if it no one makes an observation? -Ron

That is correct, the moon does not have specific quantum attributes independent of observation. That does not mean that the moon does not exist. Nor does it mean that the particles of the moon are thought (per QM) not to exist.

The "moon not there" phrase is simply a metaphor. It would seem obvious that if particles exist, then their quantum attributes must also exist simultaneously at all times. However, what is "obvious" is also subject to debate and refutation.

 

[Q_Goest]

From an undergraduate physics course 20 years ago, I seem to remember the professor suggesting that if something such as the moon was not observed, then it doesn't simply 'disappear' (or instantly go into superposition), it would only slowly go into a state of superposition because of its mass. It would take billions of years before any appreciable difference was made to its location. I seem to remember the wavefunction of matter is a function of its mass. Can someone elaborate on that?

Also, I don't believe "looked at" and "observed" are equivalent in this sense. Simply not looking at something doesn't allow matter to go into a superposition of states. For matter to go into a superposition of states, one needs to prevent interactions of all kinds such as exchange of radiation, etc... which makes it essentially impossible in practice to isolate something as large even as a marble, let alone the moon. Not sure if this says that if there is no conscious life in the universe, the moon would begin to go into a superposition or not.

vanesch said: There's a serious problem with applying quantum ideas to gravity. It might even be the key to the solution of the riddle. But let's for a moment assume that that is not a difficulty.

This is my understanding also. From my limited knowledge there is no real theory that links how gravity affects the superposition of matter, is that correct?

 

[reilly]

Gentlemen -- As my hero, David Hume, would say: if nobody observes A (no gravity), prove that it exists. QM presupposes existence.

Regards,
Reilly Atkinson

 

[reilly]

Gentlemen -- As my hero, David Hume, would say: if nobody observes A (no gravity), prove that it exists.

QM presupposes existence.

And, in fact, if you think about the various possible states that QM affords, these states describe something, that by definition, exists. Another question, then is how can QM describe something that does not exist?

Why would the moon go into a superposition if we stopped looking -- what is the physical mechanism that would cause such a thing? (I've taught QM, and can assure you that I and most other physicists I know would not say such a thing as did your prof. Did he give any reasons?)

Regards,
Reilly Atkinson

 

[RonLevy]

To all interested persons:
Do you think the statement: "The Moon does not exist when nobody looks at it" is a dramatic way of saying "The Moon does not exist in a definite place when nobody looks at it" ? Or is this still too oversimplified?

Am I correct in supposing that to every point in space,(x,y,z) there is a number which is the probability of the Moon being there? (If you looked there several times)
So that there would sort of be a function, F, such that:

{probability that The Moon is Here} = F(x,y,z) ?

But if ever F(x,y,z) = 1, that you wouldn't ever know the Moon's momentum there (at the same time)?
-Ron

 

[selfAdjoint]

To all interested persons:
Do you think the statement: "The Moon does not exist when nobody looks at it" is a dramatic way of saying "The Moon does not exist in a definite place when nobody looks at it" ? Or is this still too oversimplified?

Am I correct in supposing that to every point in space,(x,y,z) there is a number which is the probability of the Moon being there? (If you looked there several times)
So that there would sort of be a function, F, such that:

{probability that The Moon is Here} = F(x,y,z) ?

But if ever F(x,y,z) = 1, that you wouldn't ever know the Moon's momentum there (at the same time)?
-Ron

The probability distribution would hold as long as nobody looked. But when somebody did, she would always see the moon at a definite position. Physics isn't ready yet to deal with the fact that the same thing is true of momentum, i.e. there is no orbit when nobody is looking.

 

[Spin_Network]

To all interested persons:
Do you think the statement: "The Moon does not exist when nobody looks at it" is a dramatic way of saying "The Moon does not exist in a definite place when nobody looks at it" ? Or is this still too oversimplified?

Am I correct in supposing that to every point in space,(x,y,z) there is a number which is the probability of the Moon being there? (If you looked there several times)
So that there would sort of be a function, F, such that:

{probability that The Moon is Here} = F(x,y,z) ?

But if ever F(x,y,z) = 1, that you wouldn't ever know the Moon's momentum there (at the same time)?
-Ron

There are some forms of interpretations that really are at the crux of things.

Example, I can "observe/detect" the moon by looking at it, just by looking I do not perform a "measure", that is calibrated with intent to gauge a position with respect to another 'position' of something else.

Observation does not mean "measure" by default. A simple example of "observation", I can observe a speck of dust by focusing a glance upon it, if I disregard everything else, the background it rests upon, or any other distractions, then this observation has no other necessary paramiters. By choosing to disregard its distance from me, and its distance from the next speck of dust, I can perform a minimum "observation", ie..it exists because I see it, there is no "here or there" as I am not performing a "measure", and therefore I can and will observe this speck of dust with sure CERTAINTY?

The act of "Measure" though, introduces the paramiters of Uncertainty by accounting factors. I have to account for the fact that I cannot be in two separate locations in a single timeframe. A detector that is calibrated for Measuring, follows the same Laws as an Observer who performs an act of "measure" rather than an act of just "observation" .

A video camera can be proof of "observation" over "measure", video camera's are not configured for measure, they are configured as purely "observational" device's only!

An act of observation need not collapse the wavefunction, whereas an act of Measure will definitely need the wavefunction to collapse, its a default process, not a confirmation of realty?

 

[RonLevy]

Dear selfAdjoint and Spin Network,

The probabilities of Quantum Physics seem different than the probabilities of the macroscopic world: the probabilities of the Quantum World do not seem to reflect the same thing as "classical ignorance" about a throw of dice, but rather seem to be a kind of "speed limit" on what can ever be known in some cases,
so if we were to construct a wagering on the outcome of a quantum measurement (Las Vegas-style), like say a wager based on a Bell-type inequality where one of the outcomes was expected to be 5/9, how would the wager be decided?

If you bet $10 on whether the Moon was someplace and a $10 bet on whether the orbit was there, when nobody looked, who wins and how much do they win?

Actually, it is amazing that someone has not yet set up a profitable Quantum Theory Casino, based on the outcomes of quantum measurements, except for the problem of how tough it seems to be to understand what's going on, including the problem for The Casino operators to understand it. Maybe the physicists could do this to raise money to help out the grad students and pay for the next Super Super Collider.

Or is this line of thinking pathological, and a sign that I'm all mixed up?

I'm wondering if any of you could find a way to re-phrase the issue about the Moon in terms of a bet on the outcome.

(Maybe there is actually a way to write a whole Physics Book using this approach, where you pass the course only if you have any money left at the end of the exam.)


Ron

 

[Spin_Network]

Dear selfAdjoint and Spin Network,

The probabilities of Quantum Physics seem different than the probabilities of the macroscopic world: the probabilities of the Quantum World do not seem to reflect the same thing as "classical ignorance" about a throw of dice, but rather seem to be a kind of "speed limit" on what can ever be known in some cases,
so if we were to construct a wagering on the outcome of a quantum measurement (Las Vegas-style), like say a wager based on a Bell-type inequality where one of the outcomes was expected to be 5/9, how would the wager be decided?

If you bet $10 on whether the Moon was someplace and a $10 bet on whether the orbit was there, when nobody looked, who wins and how much do they win?

Actually, it is amazing that someone has not yet set up a profitable Quantum Theory Casino, based on the outcomes of quantum measurements, except for the problem of how tough it seems to be to understand what's going on, including the problem for The Casino operators to understand it. Maybe the physicists could do this to raise money to help out the grad students and pay for the next Super Super Collider.

Or is this line of thinking pathological, and a sign that I'm all mixed up?

I'm wondering if any of you could find a way to re-phrase the issue about the Moon in terms of a bet on the outcome.

(Maybe there is actually a way to write a whole Physics Book using this approach, where you pass the course only if you have any money left at the end of the exam.)


Ron

The outcome of a theoretical Quantum Casino "cr#p" game?..how cool would that be apart from the logistical 'rules' of the game (both observers and gameplayers would need to agree on wether rules conform to reality?), I can see an outcome for Quote:I'm wondering if any of you could find a way to re-phrase the issue about the Moon in terms of a bet on the outcome.

One can ask the Quantum Croupier to forfit his/hers £10 if, standing next to a Relative Player, both look up to the Moon and ask the simple Question:Do you "see" the Moon from here?..if the Quantum Croupier denies this 'Observation', then the game is a non-starter!...I mean what's the point of staking money on an object that is being physically denied as an Observation?

Here is a simplistic valuable notionable fact:You can Observe something without performing a Measure upon it, you cannot measure something fully without actually "Just" Observing it?

Thinking time?

Q)Why is it that you do not need measuring impliments in Relative Observations, the act of "Just" observing can confirm an existence upon something, but in QM you cannot measure hidden-objects, unless you actually use measuring impliments?..to measure something in QM that you cannot observe, you actually need measuring devices!

One of the main implements in LQG is the measuing devise, the 'length' is the basic paramiter needed to gauge Quantum Gravity, this 'length' can be thought of as a having its existence at a finite size many orders of magnitude below the limit of "observation". So actually, by default the measuring implement uses undefined "observations", but at the same time relays some interaction within a detector, and relays this as a confirmation of "observation", when in fact it is NOT such an act?

Standing next to a detector that relays a detected click, is no conformation of an observation?..its a confirmation of a "measured" sound, not an act of vision! There is definate difference in visual Observation as opposed to visual Measure.

I have a simple experiment that can confirm "relative" Observation as the prime act over and above the performing act of "Quantum" Measure.

 

[EnumaElish]

If no one looks at the sun for about 8 minutes 20seconds and when we look back would sun be there or would it not be there?

Do trees falling in the forest make a sound if nobody is listening? How do you know? Will the sun rise tomorrow morning? How can you be sure? Etc.

 

[Sherlock]

I think I see now how it is related to EPR and Bell's, because the moon-existence thing is related to the question of whether there is or is not a "deep reality" independent of observations.

It has to do with an understanding of the meaning of terms like
"moon" and "fundamental particle ". The moon exists
on a natural scale that's amenable to our sensory perception.
Fundamental particles 'exist' on a natural scale that is *not*
amenable to our sensory perception. In other words, we really
don't know what the qualitative appearance of nature is at the
level of quanta.

The actual physical referents of "fundamental particle" are
mathematical schemes and instrumental preparations and results.
The Copenhagen Interpretation limits the discussion to that.

Is there a qualitative level of reality deeper than the math
models and the experimental results. Sure, at least that's the
assumption. But, we have only very sketchy ideas about it from
the limited number of experiments that have been performed -- a
more or less incomplete *quantitative* 'picture' of reality at the
quantum level.

So, a certain fundamental particle doesn't exist unless and until
it can produced experimentally. A specific particle doesn't
exist independent of the operations that produce it. It's
existence is defined that way, because we have no perception
of it independent of that.

On the other hand, the moon can be seen by anyone with
normal sensory capabilities. We photograph it directly, we've
even walked on it, so there's no problem in developing a
common statement regarding it's natural qualitative
characteristics.

The HUP, a quantification of the relationship between
complementary variables, is about the limits of describing
the natural qualitative characteristics of phenomena that
we *can't* sense in terms of phenomena that we *can*
sense.

 

[reilly]

Other things to ponder. When we say that we see or observe the moon, we are technically dealing with double scattering events. That is, the photons that impinge upon our retina were emitted by the sun, and reflected-scattered by the moon. Then, in order for sight to occur, the photons participate in the photo-dissociation of rhodopsin molecules in the rod and cones in our retina. It's well know in the vision business, that the photodissociation processes amount to working with a random sample of the incoming photons. Our visual system presents a moving average of photon signals, which come partly from the fundamental quantum process of association, and partly from the the thermally and electrically random characteristics of the rod and cone systems -- which are sort of like stacked plates. So what we see is the moon averaged over time, short periods to be sure. Certainly the uncertainty of when and where is substantially larger than any quantum uncertainty, and the limits of the Heisenberg Uncertainty are washed out, as they must be, as pointed out by Bohr, for observations of macroscopic systems. Further, we see the moon where it was, not where it is. And, our observations certainly have virtually no effect on the moon -- sure there are probably a few photons backscattered to the moon, reflected from our eyes, or forehead, or ..but their mechanical effect is at best a few ev, hardly enough to change anything.

Indeed, if you are highly rigorous, then the probability of seeing the moon, with "center", x,y,z,t is not quite 1. even if the moon's trajectory is totally determined. But, let's be clear, the deviation from 1 is likely to be 10-n, where n is fairly large, and this deviation can be explained almost entirely in classical terms. (A photograph suffers from the same problem, but I suspect that the photographic n is less than the direct vision n- and, of course when we view the photograph both n's are at play

A primary assumption of all science is that the external world we perceive is always there, whether we observe it or not. As far as I know this assumption has never ever been falsified; it certainly cannot easily be verified. That being said, the basic laws of physics, conservation laws, for example, tell us the observed or not, macroscopic entities exist, and are not appreciably altered by the act of or lack of observation. At the microscopic level, it's a bit trickier -- have Brownian motion at a thermal level, and all the wierdness of QM at an even finer level. There are those of us who look at the probabilistic nature of QM as dealing with the observer's state of knowledge, in which the idea of collapse of the wave function, or probability function is the same for classical and quantum physics, and corresponds to the (rapid) change in neural structure and neural signals corresponding to learning. (As I've pointed out before, QM measurements and classical measurements produce similar measureable spaces, and, hence well defined probability spaces.)


And finally, recall that for most of us, physics is a highly pragmatic subject. We tend to leave issues like "deep reality' to the philosophers. We change our minds when prompted by empirical results, and are willing to live with the tensions created by less than complete certainty or consistency -- a few conflicts make for what might be called creative tension. Certainly this was the case from the 1890s to the 1930s.

Regards,
Reilly Atkinson

 

[Sherlock]

... I came across a startling argument for the existence of God, (I am an agnostic.), which is that "If the Moon continues to exist when nobody looks at it, that this is because there is a conscious observer who is continuously observing the moon 24 hours a day."

The only thing startling about this argument is the idea that
anybody would actually use it. :-)

What are you being agnostic about? "God" is just a word that
has no particular verifiable meaning. People use it to 'account'
for anything and everything. It's a non-issue.

Naturally, I would like to see exactly where this follows logically from the science that yields the notion that "the moon does not exist if it is not observed by anyone."

There's no science that yields that notion.

If the moon-existence paradox, (MEP), is actually a kind of "non-issue," so that MEP follows from a metaphor that conveys the essence of the Copenhagen Interpretation, then that is one thing. However, if, as you have pointed out, it leads straight back to The Heisenberg Uncertainty Principle, which has never failed an experimental test, that seems a lot stronger.

Yes, the (MEP) is a non-issue. It comes from a misinterpretation
of statements like "the photon doesn't exist until it's measured
or observed." The measurement or observation is a set of
instrumental operations, and (along with the mathematical
schemes that are used to organize and relate those operations
in a quantifiable, unambiguous form) this is what the photon
(or any particle or quantum) *is*.

Back in the day when quantum theory was being developed,
the developers (faced with experimental results that sometimes
seemed to imply wave phenomena and other times particulate
phenomena -- as with light, but now they were dealing with
matter) had the perplexing task of deciding just how they
were going to talk about all the new experimental results.

In the words of Heisenberg, "The solution of the difficulty
is that the two mental pictures which experiments lead us to
form -- the one of particles, the other of waves -- are both
incomplete and have only the validity of analogies which
are accurate only in limiting cases. It is a trite saying that
'analogies cannot be pushed too far,' yet they may be
justifiably used to describe things for which our language
has no words. Light and matter are both single entities,
and the apparent duality arises in the limitations of our
language.

"It is not surprising that our language should be incapable
of describing the process occurring within the atoms, for,
as has been remarked, it was invented to describe the
experiences of daily life, and these consist only of processes
involving exceedingly large numbers of atoms. Furthermore,
it is very difficult to modify our language so that it will be
able to describe these atomic processes, for words can
only describe things of which we can form mental
pictures, and this ability, too, is a result of daily
experience. Fortunately, mathematics is not subject
to this limitation, and it has been possible to invent
a mathematical scheme -- the quantum theory -- which
seems entirely adequate for the treatment of atomic
processes; for visualization, however, we must content
ourselves with two incomplete analogies -- the wave
picture and the corpuscular picture. The simultaneous
applicability of both pictures is thus a natural criterion
to determine how far each analogy may be 'pushed'
and forms an obvious starting point for the critique
of the concepts which have entered atomic theories
in the course of their development, for, obviously,
uncritical deduction of consequences from both
will lead to contradictions. In this way one obtains
the limitations of the concepts of a particle by
considering the concept of a wave. As N. Bohr
has shown, this is the basis of a very simple
derivation of the uncertainty relations between
co-ordinate and momentum of a particle. In the
same manner one may derive the limitations of the
concept of a wave by comparison with the concept
of a particle."

At least that's what Heisenberg said. It pertains to
two pillars of orthodox quantum theory, complementarity
and the uncertainty relations.

(My personal feeling is that 'deep reality' is all about
waves.)

There are tons of papers about the uncertainty
relations. As you are (and I am) learning, this
is a fascinating subject to explore.

But, to bring it back to your consideration(s), may
I presume to make two suggestions:
1. Throw out the garbage and just be an atheist.
2. If you can see something, then don't worry
about it not existing when you're not looking at
it (assuming that you don't need medication
and aren't frequently under the influence of
mind-altering substances).

 

[metacristi]

Please help me with this. Can anyone direct me to the specific mathematics that is interpreted as saying that "the Moon does not exist when nobody looks at it."
Is there any book or discussion of the actual math and physics of this?
What specifically was Einstein reacting to when he said:
"I cannot believe that the Moon exists only because a mouse looks at it." ?
Please feel free to write or send me anything you wish about this subject. I have no axe to grind, and I only would like to understand this better. Thank you.-Ron

Einstein was reacting against the central role assigned by the copenhagenists to the process of 'measurement' (for which they had not provided a clear definition). The problem was that from their approach it could be derived, though Heisenberg and Bohr did not sustain this view, the seemingly crucial role of the conscious observers into creating reality (see also 'Schrodinger's Cat' paradox).

Nowadays this problem of early copenhagenism (a real problem, apart of its rather idealistic 'flavor') has been 'fixed' somewhat, we have now a more acceptable picture of what can count as a 'measurement' (see the consistent / decoherent histories interpretations of QM, basically revised forms of copenhagenism, accepted by more and more physicists as their main approach in what the interpretation is concerned).

However the interesting fact is that the idealist interpretation 'to exist is to be observed / perceived' is far from being discarded, for example the ontological form of idealism proposed once by the bishop Berkeley (still fully tenable logically) is consistent at limit with such an interpretation of QM (additionally when no one looks it is God who perceive the Moon, keeping it 'real').

Indeed no one can disprove the different forms of idealism, holding that to exist is to be perceived, so there is no reason to totally discard such an interpretation. However this 'research program' has no epistemological privilege, at least currently, under the actually accepted definition of rationality we just have more reasons (though not counting as 'sufficient reasons' settling the problem once and forever) to prefer a form of realism as the first choice program (the coherent / decoherent histories interpretations do respect this, anyway in a far stronger way than copenhagenism where realism is dropped almost altoghether-even when accepting their solutions to the 'Schrodinger's Cat' paradox).

 

[RonLevy]

To everyone who was kind enough to offer their help with my puzzlement about "Does the Moon exist when nobody looks at it," please accept my sincere thanks for your replies. You have given me much to think about, and I am grateful.-Ron

 

[Gerinski]

As already remarked by many, the statement that "the moon may not exist when nobody is looking at it" is purely a metaphor and nobody should waste much time discussing at the specific case of the moon (especially when -as also said by many- the use of the word "exist" is particularly misguiding).

A good example of what the metaphor stands for is the famous experiment of "the beryllium quantum pot that never boils if it's observed".

Not going to describe it fully here, you may google search on it if you don't know much about it, but it's about a pot containing around 5000 beryllium atoms exposed to a radiation shower that brings them all to "boiling" -actually a higher energy state- in about 256 milliseconds.

However this boiling -which is the expected thing to happen for atoms under the radiation shower- occurs only if the atoms are not observed during the 256 milliseconds period.

The more the atoms are observed, the longer they take to boil. If the atoms are observed frequently enough -every 4 milliseconds- the pot will never boil.

This shows that objects -matter, and events in general- evolve differently when observed than when unobserved (at least in the quantum realm), and this is what the metaphor of the moon stands for.

The reason why the pot never boils if observed, is that those atoms which at the moment of being observed (let's say after 128 milliseconds) "choose" to take still the unexcited (non-boiling) state, need to start again from scratch, and need again 256 milliseconds to boil, not just 128 milliseconds more.

 

[Sherlock]

As already remarked by many, the statement that "the moon may not exist when nobody is looking at it" is purely a metaphor and nobody should waste much time discussing at the specific case of the moon (especially when -as also said by many- the use of the word "exist" is particularly misguiding).

A good example of what the metaphor stands for is the famous experiment of "the beryllium quantum pot that never boils if it's observed".

Not going to describe it fully here, you may google search on it if you don't know much about it, but it's about a pot containing around 5000 beryllium atoms exposed to a radiation shower that brings them all to "boiling" -actually a higher energy state- in about 256 milliseconds.

However this boiling -which is the expected thing to happen for atoms under the radiation shower- occurs only if the atoms are not observed during the 256 milliseconds period.

The more the atoms are observed, the longer they take to boil. If the atoms are observed frequently enough -every 4 milliseconds- the pot will never boil.

This shows -once again- that objects -matter, and events in general- evolve differently when observed than when unobserved, and this is what the metaphor of the moon stands for.

The reason why the pot never boils if observed, is that those atoms which at the moment of being observed (let's say after 128 milliseconds) "choose" to take still the unexcited (non-boiling) state, need to start again from scratch, and need again 256 milliseconds to boil, not just 128 milliseconds more.

Are the atoms being exposed to the radiation shower during
the time(s) that they're being observed? If so, then what is
happening during the observations to cause them to go
to a lower energy state?

 

[Gerinski]

Are the atoms being exposed to the radiation shower during
the time(s) that they're being observed? If so, then what is
happening during the observations to cause them to go
to a lower energy state?

The radiation shower is continuous, even while the atoms are being observed.

The observation is done by shining a laser beam through the "fog" of beryllium, and the scattering of the laser tells how many atoms were boiling and how many were not (because non-boiling atoms absorb some energy from the laser and boiling ones don't).

When observed, each atom can only be in any of either states, boiling or not-boiling, but nothing in between. They can only be in between (in a quantum superposition of both states) while not observed. This is the key.

During an unobserved 256 milliseconds radiation shower, every atom will evolve from a quantum superposition of states 100% not-boiling + 0% boiling, to a superposition of 0% not-boiling + 100% boiling.
At 128 milliseconds, the superposition is 50%-50%, at 64 milliseconds it's of 75%-25%, and so on.

When observed, each atom must abandon the superposition and "choose" between any of both states.

If you only observe after 256 milliseconds, all the atoms could get to the 0% not-boiling + 100% boiling superposition, so you find all of them boiling.

If you observe after 128 milliseconds, they are in a superposition of 50%-50%, therefore half of them will choose the non-boiling state and the other half the boiling state.

But for the 50% who take the non-boiling state, the superposition returns to 100% non-boiling + 0% boiling. Therefore they need again 256 milliseconds unobserved to evolve to 0%+100%, they have to start from scratch again.

Therefore if you observe them very repeatedly -every 4 milliseconds-, causing them to return to the 100% non-boiling + 0% boiling, they can never make it to boil even if the radiation shower is never stopped.

The interesting fact is that both the radiation shower (it is radio waves radiation) and the laser beam, are BOTH electromagnetic radiation being showered to the atoms. However the radio waves shower does not cause the collapse of the superposition, and the laser does. Why?
The only difference is that we use the laser to observe, while we don't with the radio waves. We look at the laser scattering to get information on which is the state of the atoms. Presumably, if we used the same radio wave shower to get that information, they would also never boil.

Therefore it seems unavoidable that it's our getting knowledge of the world what makes it be like it appears to us. This is the deep dilema (and personally I don't like it. I don't like to think that we are so special)

 

[EnumaElish]

if we used the same radio wave shower to get that information

Is that technically possible?

Therefore it seems unavoidable that it's our getting knowledge of the world what makes it be like it appears to us. This is the deep dilema (and personally I don't like it. I don't like to think that we are so special)

What if the laser was shone by a cat (or a chimp), would the result be any different?

 

[reilly]

Gerinski-- Do you have any references for the boiling beryllium experiment? In particular, can you observe without a laser, which creates a presumably non-trivial perturbation for the system?
Regards,
Reilly Atkinson

 

[Gerinski]

Gerinski-- Do you have any references for the boiling beryllium experiment? In particular, can you observe without a laser, which creates a presumably non-trivial perturbation for the system?
Regards,
Reilly Atkinson

Is that technically possible?

The experiment was carried out by W. Itano and D. Wineland and their paper was published in Physical Review in 1990, I tried to get to it but it's pay contents...
But you can read a bit about it here

http://www.textfiles.com/bbs/KEELYNET/BIOLOGY/mind11.asc

I have no idea if it might be possible to observe the atoms using the radio waves themselves, or in any other way other than the laser.
But I can think of a hypotetical refined version of the experiment, and I would like someone who knows better than me to confirm if my guesses are correct or not:

Let's imagine that you could set up the device so that when all the atoms get to the excited state (boiling), a red light is lit on the lab wall. I have no idea how to do it, but all being hypotetical let's imagine that non-excited beryllium was non conductor and excited beryllium became superconductor, allowing when all of the atoms are excited to let through just enough electrons to lit the light.
The light is in fact an observation device, but able only to observe when ALL of the atoms are boiling, we can't observe anything in between until then.

Now guessing:

1. If we don't shine laser at all, after 256 milliseconds the light will lit on (the fact of letting the atoms reach the 0% - 100% superposition state will be enough to collapse them on the boiling state and lit the light, because we have set up the light in order to be able to observe that event)

2. If we shine the laser every 4 milliseconds and watch the scattering result (acquiring information on the state of the atoms), the light will never get lit (because we are continuously bringing back all the atoms to their starting 100% - 0% superposition state).

3. If we shine the laser every 4 milliseconds but do not watch nor record in any way the scattering result, the light will lit on after 256 milliseconds (just as if we did not shine the laser at all, because we can't get any information)

4. If we shine the laser every 4 milliseconds and do not watch the result, but record it so that we could watch it later on, the light will never lit on (because information can eventually be retrieved from the recorded data)

I'm not 100% sure that I'm right but I guess so. Weird ...

 

[EnumaElish]

If we shine the laser every 4 milliseconds and do not watch the result, but record it so that we could watch it later on, the light will never lit on (because information can eventually be retrieved from the recorded data)

To go a step further, suppose that a single copy of the data is made "blindly," then enclosed in a steel vault with a lock that is electronically linked to the stock exchange market. A self-destruct mechanism ensures any tampering will result in destroying everything inside the vault. The lock would open only if the Dow Index were to fall under 10,000 exactly two years from the date the experiment was conducted. If the Dow were to stay above 10,000 then the vault would self-destruct in a mini thermonuclear explosion on that day two years in the future. Can this be the way to make a lot of money? (And I mean A LOT.)

P.S. Upon careful consideration, I now think that as long as there is the tiniest probability of the Dow being under 10,000 on the specified day, the light will stay off. I am moving on to the next promising project that involves getting rich by using quantum states.