Is the Moon there when nobody looks at it?

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In summary, the conversation revolves around the concept of observer-created reality in quantum mechanics and its potential application to macroscopic objects like the moon. The discussion also touches upon the relationship between macroscopic and microscopic worlds and the role of measurement in determining the existence and properties of particles. The conversation references Bell's Theorem and a paper by N. David Mermin as sources for further reading on the topic.
  • #36
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
 
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  • #37
RonLevy said:
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 :cool: 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. :wink:
 
  • #38
bayan said:
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.
 
  • #39
RonLevy said:
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.
 
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  • #40
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
 
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  • #41
RonLevy said:
... 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.

RonLevy said:
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.

RonLevy said:
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).
 
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  • #42
RonLevy said:
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).
 
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  • #43
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
 
  • #44
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.
 
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  • #45
Gerinski said:
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?
 
  • #46
Sherlock said:
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)
 
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  • #47
Gerinski said:
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?
 
  • #48
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
 
  • #49
reilly said:
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

EnumaElish said:
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 ...
 
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  • #50
Gerinski said:
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.
 
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  • #51
EnumaElish said:
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.

I think so too...

There's one more scenario for which I'm not sure of the answer:

If there's nobody in the lab to see if the light turns on or not, and it is not recorded in any way, I'm not sure if the light will lit on or not.
Since nobody is attempting to get any information of what happens in the pot, why should the atoms bother to collapse their superposition into any definite state? They might stay with a 0% - 100% superposition but without actually collapsing into the definite excited state?
 
  • #52
Gerinski said:
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?
My guess would be that it has to do with the frequency of the
radio waves, the frequency of the laser light, and the resonant
frequency of the trapped beryllium ions.

Here's my take on the experiment from the link you provided:
If a beryllium atom is oscillating or resonating
due to excitation by a certain radio wave
frequency when light from a laser pulse hits it,
then the chance of it scattering the light from the
laser pulse back to the detector is very small.

It takes about 256 milliseconds for the radio waves
to get most all of the 5000 beryllium ions in the
electromagnetic trap resonating.

On average, if left undisturbed, about 19.5
atoms (or .0039% of the total) are added to the
resonating group each millisecond.

The atoms that are resonating stop resonating
after interacting with the laser light. During any
particular 2.4 millisecond pulse virtually all the atoms
that are resonating will stop resonating.

If you hit the beryllium atoms with 64, 2.4 millisecond
laser pulses at regular intervals during a 256 millisecond
run, then there's about 1.5 milliseconds between each
pulse for a certain number of atoms to resonate
again -- which would be a barely detectable percentage
of the whole group.

The longer the interval between laser pulses, the fewer atoms
will be directly detected as not resonating -- and then this is
subtracted from the total in the trap to get the percentage of
atoms that are resonating (or 'boiling' re the 'watched pot'
metaphor) wrt a particular delta t.

Gerinski said:
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.
I don't think you can use radio waves to get that info.
But, I'm not sure about that.

Gerinski said:
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)
This isn't really so perplexing the way you're stating it, is it?
I mean, of course the parameters of our physical existence
determine what we apprehend and how we apprehend it.
This by itself makes us no more special than any other
measuring device.
 
  • #53
Gerinski said:
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)
Yes, the 'pot' will be 'boiling' in this case, but not because you
set up the light to record the result. The red light isn't
the measuring device. The laser light is.
It takes at least 256 milliseconds for all of the trapped atoms
to resonate. So, if you don't zap them with the laser for the
duration of a 256 millisecond run, then your detection light
will light. And, if you didn't set up the detection light, they'd
still all be resonating after being exposed to an appropriate
radio frequency for 256 milliseconds. At least, that's the
assumption that I'd make.
Gerinski said:
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).
Yes, the light won't light in this case, but here's the
reason I'd give:
The non-harmonic (I'm guessing) interaction of the laser light
with the trapped ions effectively destroys the resonance
created by the radio frequency.

Gerinski said:
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)
No. The laser light stops (interferes destructively with)
the 'boiling' process.

Gerinski said:
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)
Yes, in this case the light won't light -- because you've zapped
the atoms with a 2.4 millisecond laser pulse every 4 milliseconds.

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

Well, as you can see, I don't think it's so weird. But,
I could be missing something.
 
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  • #54
Quantum Weird - Want more!

These Quantum Theory "weird" experimental results and strange implications of theory are a striking feature of this branch of science. Would any of you be able to contribute your own paradoxes and points?
 
  • #55
Sherlock said:
The atoms that are resonating stop resonating
after interacting with the laser light. During any
particular 2.4 millisecond pulse virtually all the atoms
that are resonating will stop resonating.

Hi Sherlock. Your understanding of the experiment is wrong and therefore you miss the quantum aspect.

The laser does NOT in any way bring back excited atoms to the unexcited state (I believe excited is a more appropiate word than resonating, although it doesn't matter).
This is clear, if you shine the laser after 128 ms, you find 50% of the atoms excited, and these will remain excited. This 50% do NOT go back to the unexcited state. The proof is that if you measure shortly again, you will find more than 50%, never less.
Only the 50% which "choose" to be unexcited will remain unexcited (for these, it's not that they "go back" to unexcited, because they were never excited. They just had a certain probability of being excited (actually 50%) and it's this probability which returns to zero).

What the laser does is just to "force" each atom to define its state as either unexcited or excited, and which one the atom will take is defined by the probability % quantum superposition of both states.

What the laser does (e.g. if fired at 128 ms) is to take the group of atoms, which are all of them in a state of 50% probability of being unexcited + 50% probability of being excited, and split them in 2 groups, one of them with a 100% probability of being unexcited + 0% of being excited, and the other group with a 0% probability of being unexcited + 100% of being excited.

You can not explain the experiment results without resorting to the quantum superposition of states (atoms must be in 2 different states simultaneously) and to the incompatibility of observation with this superposition (we can not observe this superposition, observation collapses the superposition into any of the definite states).

Sherlock said:
Quote:
Originally Posted by Gerinski
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)


No. The laser light stops (interferes destructively with)
the 'boiling' process..


I'm not so sure. Other experimental setups, such as the "delayed choice double-slit experiment" and particularly the variant with the "quantum eraser" have proved that it's not the fact of putting an interacting detector or not what defines the result of an experiment, but wheter we can extract any information or not from that detector. Exactly the same setup with the same detectors yield different results if we are attempting to learn the result or if we are not.


Maybe this discussion has become ortodox enough for the moderators to bring back this thread to the Quantum Physics forum, where more expert people could clarify our doubts ...
 
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  • #56
Gerinski said:
Hi Sherlock. Your understanding of the experiment is wrong and therefore you miss the quantum aspect.

The laser does NOT in any way bring back excited atoms to the unexcited state (I believe excited is a more appropiate word than resonating, although it doesn't matter).
This is clear, if you shine the laser after 128 ms, you find 50% of the atoms excited, and these will remain excited. This 50% do NOT go back to the unexcited state. The proof is that if you measure shortly again, you will find more than 50%, never less.
Only the 50% which "choose" to be unexcited will remain unexcited (for these, it's not that they "go back" to unexcited, because they were never excited. They just had a certain probability of being excited (actually 50%) and it's this probability which returns to zero).

What the laser does is just to "force" each atom to define its state as either unexcited or excited, and which one the atom will take is defined by the probability % quantum superposition of both states.

What the laser does (e.g. if fired at 128 ms) is to take the group of atoms, which are all of them in a state of 50% probability of being unexcited + 50% probability of being excited, and split them in 2 groups, one of them with a 100% probability of being unexcited + 0% of being excited, and the other group with a 0% probability of being unexcited + 100% of being excited.

You can not explain the experiment results without resorting to the quantum superposition of states (atoms must be in 2 different states simultaneously) and to the incompatibility of observation with this superposition (we can not observe this superposition, observation collapses the superposition into any of the definite states).

...

I'm not so sure. Other experimental setups, such as the "delayed choice double-slit experiment" and particularly the variant with the "quantum eraser" have proved that it's not the fact of putting an interacting detector or not what defines the result of an experiment, but wheter we can extract any information or not from that detector. Exactly the same setup with the same detectors yield different results if we are attempting to learn the result or if we are not.

Maybe this discussion has become ortodox enough for the moderators to bring back this thread to the Quantum Physics forum, where more expert people could clarify our doubts ...

I found a link to the Itano et al. experiment as well as another
paper that might help us. Haven't had time to read them yet.
I suggest keeping this thread here and maybe starting another
one on interpretations of the quantum zeno effect in the
quantum physics forum. But, first I'd check in the archives
and the faq and the journals of the advisors and mentors to
see what's already been said here about it. (I haven't had
a chance to do this yet either.)

http://en.wikipedia.org/wiki/Quantum_Zeno_effect

Experimentally, strong suppression of the evolution of a quantum system due to environmental coupling has been observed in a number of microscopic systems. One such experiment was performed in October 1989 by Itano, Heinzen, Bollinger and Wineland at NIST. Approximately 5000 9Be+ ions were stored in a cylindrical Penning trap and laser cooled to below 250mK. A resonant RF pulse was applied which, if applied alone, would cause the entire ground state population to migrate into an excited state. After the pulse was applied, the ions were monitored for photons emitted due to relaxation. The ion trap was then regularly "measured" by applying a sequence of ultraviolet pulses, during the RF pulse. As expected, the ultraviolet pulses suppressed the evolution of the system into the excited state. The results were in good agreement with theoretical models.

http://tf.nist.gov/general/pdf/858.pdf

(NOTE: if this link doesn't work, then just go to the parent
directory http://tf.nist.gov/general/pdf/
and scroll down till you find the link for 858.)
_____________________

Quantum Physics, abstract
quant-ph/0105138
From: Julius Ruseckas [view email]
Date: Mon, 28 May 2001 12:18:36 GMT (69kb)

Real measurements and Quantum Zeno effect
Authors: Julius Ruseckas, B. Kaulakys
Categories: quant-ph
Comments: 3 figures
Journal-ref: J. Ruseckas and B. Kaulakys, Phys. Rev. A 63, 062103 (2001)

In 1977, Mishra and Sudarshan showed that an unstable particle would never be found decayed while it was continuously observed. They called this effect the quantum Zeno effect (or paradox). Later it was realized that the frequent measurements could also accelerate the decay (quantum anti-Zeno effect). In this paper we investigate the quantum Zeno effect using the definite model of the measurement. We take into account the finite duration and the finite accuracy of the measurement. A general equation for the jump probability during the measurement is derived. We find that the measurements can cause inhibition (quantum Zeno effect) or acceleration (quantum anti-Zeno effect) of the evolution, depending on the strength of the interaction with the measuring device and on the properties of the system. However, the evolution cannot be fully stopped.

http://arxiv.org/PS_cache/quant-ph/pdf/0105/0105138.pdf [Broken]
 
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  • #57
RonLevy said:
These Quantum Theory "weird" experimental results and strange implications of theory are a striking feature of this branch of science. Would any of you be able to contribute your own paradoxes and points?

As I-don't-remember-who said (was it Feynman maybe?) the whole wonder and paradox of the quantum world is encapsulated in the double-slit experiment.
Indeed, starting from such a simple experiment with a beam of light, a perforated panel and a screen, as scientists have gradually progressed in observing and interpreting what happens (and especially after introducing refined versions of the experiment such as the delayed-choice and the quantum-eraser), nearly all the mysteries and weirdness of the quantum world unfold in front of your eyes.

This is the thread line that most popular science books follow, but it's too long to describe properly in a place like this.

The best would be that you get some good popular science book/s (as the layman I am, I particularly liked John Gribbin's "In search of Schroedinger's cat" and its sequel "Schroedinger's kittens". David Deutsch's "The fabric of reality" is also great, although very biased in the interpretation of quantum theory towards his favourite "multiverse").
 
  • #58
is the thread
Is the Moon there when nobody looks at it?
there when nobody looks at it?

you know its there if nobody looks at it because you witnessed it being put there by its creator--you.

all that is needed to confirm the true "presence" of anything created "is" an impartial, non-biased, objective, non-action witness.

if you would like to go a little deeper, the "Moon" is always in motion, so when you ask "Is the Moon there?", what "there" are you referring to? The presence of the Moon being anywhere, or an exact location in orbit to where the moon was, or shall be?

An answer to the latter can be found, I speculate, at NASA.
An answer to the former can be found, I know, "in here". (I/you)
 
  • #59
I would like to give a sort of personal view (founded in interprtation of modern philosophy) about this issue, that I am developing for a work to get a degree in physics. I belive, that the whole problem has to do with the fact that our mesurments are so precise that we have to give up some "classic" notions about, not the actual existence of reallity (denying its existens would be, at this point absurd) but the way it exists. We can no longer hold the view that we can have any konwledge of "absolute" reality without interacting with it. That is, in case independent reallity exists, it makes no sense talking about it, and as Wittgenstain use to say "Of that which we can talk about, the best thing to do is keep silent" What we can talk about is "conceptually designated reallity" (The book "Choosing Reality" by Alan Wallace is grate to explain this point), and for that we have to accept that separation between observer and object was an ilussion, in the first place. If anyone is interested in book or references about the philosophical aspect, I would be more than happy to help.
 
  • #60
If a particle doesn't have a definite position until observed, but is in a "superposition of positions", then why is it that the result of an observation is dependent on the position where the observation is performed. If a particle does not have a definite position, why is it that I'm more likely to, upon observation, find a particle in a given position and never in another.
For example, say that i know that a particle came into my room, but i don't know exactly where it is. Suppose i make an observation on a randomly chosen portion of the room, to check whether the particle is there. There is a positive probability that it is in the area i chose. The bigger the area i choose, the bigger the probability that the particle is there. But consider that i search outside the room. I'm 100% sure i saw the particle come into my room, that means 0% probability that it's not in my room. So the particle is in a superposition of positions because i don't know where it is, but does it mean that it is in a superposition of the positions available inside the room, or in a superpositions of all available positions in the universe? Certainly i can imagine the particle could have traveled outside the room, and so it's a non-zero probability that the particle is outside the room. But certainly there are positions outside the room where the particle cannot be. The particle having entered my room, could not have traveled at the speed of light to 1 billion miles away, in less than X minutes. therefore i can send a signal traveling at the speed of light to a friend of mine who will verify whether or not the particle is 1 billion miles away. But, of course, the particle couldn't possibly be there, it would be against the laws of physics. So it seems to be that a particle that has entered my room is not in a superposition of all possible positions in the universe, but only a given subset.
Having said that does it mean that, if i saw the moon a minute ago, even though i don't know where it is now, it certainly cannot be next to Pluto, because it couldn't have gotten there.
How can we even distinguish particles? Atomic, subatomic particles. If we can't distinguish the particles then what use is an observation? When measuring the spin of a particle, how do i know that some other particle didn't get in there, and it's that particle's spin that I've measured?
Suppose that i look for my particle outside my room and i meet a particle that's exactly like it. How do i know if it is or isn't my particle? If it is and i think it is then how does my observation change the world? If it isn't and i think it is, does my observation change the world in the same way?
Suppose I'm always able to distinguish my particle. Doesn't that imply hidden variables? I mean after all, that would imply that no other particle is like mine and does not have the same properties as my particle, which already says something about every other particle, namely, that it is not like my particle.

One alternative is that you can make an observation, and have an impact on the universe, but not know what the impact was. So it doesn't take a conscious being to make an observation, because you wouldn't be conscious of the result anyway. And then inanimate things, like a rock,can make an "observation". It can "observe" the position of another rock by hitting it. Then, what that means is that when rock A hits rock B, it causes rock B to have a definite position. Suppose i never saw one rock hit another. Supposedly rock B should not have a definite position, but rock A made sure it did, regardless of whether anyone made an observation; hidden variable.
 
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  • #61
I used the moon as an example to illustrate the same question in the Quantum Physics Section of PF.

quantumcarl said:
If no human has observed the moon or been able to calculate its existence through studying its physical effects... does the moon exist under the terms and formulations of quantum mechanics?

this got quite a few replies from some excellent sources on PF not unlike this thread!

Here's the thread:
https://www.physicsforums.com/showthread.php?t=106188
 
  • #62
I did a google search and I found this article
http://www.ruf.rice.edu/~hpu/Phys311_source/mermin_moon.pdf [Broken]
 
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