Subatomic particles and the observer

[Kenneth Boon Faker]

I have read that when an electron is observed, it behaves differently to when it is not being observed.

Could someone please expand on this, or indeed correct me. In what way does an observed particle behave differently to a particle that isn't being observed by somebody's consciousness?

 

[mfb]

To observe a particle you have to interact with it.
Interacting with particles means changing their properties.

This is nothing magical, it applies to classical objects as well, a typical interaction is just less important there.

This has nothing to do with consciousness. A photon detector can observe it in the same way a human eye can.

 

[Kenneth Boon Faker]

Hi mfb, many thanks for reply. I just want to get some clarity on this, as it's puzzled me for some time.

Physicist Pascual Jordan writes: "Observations not only disturb what has to be measured, they produce it. ... We compel [the electron] to assume a definite position. ... We ourselves produce the results of measurement."

And Paul Davies writes, "According to Bohr, the fuzzy and nebulous world of the atom only sharpens into concrete reality when an observation is made. In the absence of an observation, the atom is a ghost. It only materializes when you look for it. And you can decide what to look for. Look for its location and you get an atom at a place. Look for its motion and you get an atom with a speed. But you can't have both. The reality that the observation sharpens into focus cannot be separated from the observer and his choice of measurement strategy."

From my understanding of everything I've read about quantum theory, the observing mind plays a role in the unfolding of what is being observed. The consciousness of the observer is crucial in determining the measured outcome.

mfb, are you saying that a photon detector overcomes the problem of "you can't have both" (i.e. you can know its location AND know how it is moving)?

Can anyone help enlighten me please, in light of the above quotes?

Many thanks,
Kenny

 

[ChrisVer]

From my understanding of everything I've read about quantum theory, the observing mind plays a role in the unfolding of what is being observed. The consciousness of the observer is crucial in determining the measured outcome.

This in general is up to how you interpret the theory, not how it manifests itself. And in general the quotes are very simplistic, as I wouldn't call the atom a "ghost", as this gives somekind of entity to the probability density distributions of QM.

mfb, are you saying that a photon detector overcomes the problem of "you can't have both" (i.e. you can know its location AND know how it is moving)?

No it does not in principle- the Heisenberg inequality is an intrinsic property of for example the momentum and position [for any non-commuting operators]... however the uncertainties you get from the detector measurement are huge compared to the Heisenberg's inequality limit.

 

[mfb]

From my understanding of everything I've read about quantum theory, the observing mind plays a role in the unfolding of what is being observed. The consciousness of the observer is crucial in determining the measured outcome.

No it is not. If you send short wavelength radiation to an atom, you'll get a good estimate for its position. If you send long wavelength radiation to it, you'll get a good estimate for its velocity. Again: This has nothing to do with consciousness.

mfb, are you saying that a photon detector overcomes the problem of "you can't have both" (i.e. you can know its location AND know how it is moving)?

No you cannot. The atoms does not even have a single well-defined location and velocity at the same time. Let it interact with short wavelength radiation and it will get a somewhat fixed position from this interaction, but a large spread in its velocity. Let it interact with long wavelength radiation and it will get a somewhat fixed velocity from this interaction, but a large spread in its position.

These are simplified descriptions, of course, but that is the general idea.

No it does not in principle- the Heisenberg inequality is an intrinsic property of for example the momentum and position [for any non-commuting operators]... however the uncertainties you get from the detector measurement are huge compared to the Heisenberg's inequality limit.

It is easy to set up measurements that get close to this limit. Every double-slit experiment does so indirectly.

 

[rootone]

Einstein was never happy with quantum mechanics.
"Is the Moon There When Nobody Looks?"
As far as I know though he did eventually accept that quantum theory fits with observation.
https://maltoni.web.cern.ch/maltoni/PHY1222/mermin_moon.pdf
It isn't anything to do with consciousness, inanimate machines can also be observers.

 

[Kenneth Boon Faker]

Many thanks for your feedback, it's much appreciated.

That article about Einstein's famous quote about the moon is particularly interesting.

To me, the following quote from the article sums up the intrinsic limitations of our understandings of how subatomic particles behave : "Because the quantum theory is intrinsically incapable of assigning values to both quantities at once, it must provide an incomplete description of the physically real."

(If I have missed a counter-argument in the article, or that anyone may be aware of, which can provide a better understanding then please feel free to share it).

Thanks again all, this is a very useful website that I have encountered.

Kenneth

 

[cosmik debris]

Many thanks for your feedback, it's much appreciated.

That article about Einstein's famous quote about the moon is particularly interesting.

To me, the following quote from the article sums up the intrinsic limitations of our understandings of how subatomic particles behave : "Because the quantum theory is intrinsically incapable of assigning values to both quantities at once, it must provide an incomplete description of the physically real."

(If I have missed a counter-argument in the article, or that anyone may be aware of, which can provide a better understanding then please feel free to share it).

Thanks again all, this is a very useful website that I have encountered.

Kenneth

I'm not sure when Jordan wrote the comment you quoted but I suspect it was a long time ago. Science has moved on and quoting people like Einstein, Heisenberg etc is OK for historical reasons but it was the beginning of a paradigm shift in scientific thought, there were bound to be some misunderstandings as the subtleties were tackled.

Cheers

 

[Nugatory]

To me, the following quote from the article sums up the intrinsic limitations of our understandings of how subatomic particles behave : "Because the quantum theory is intrinsically incapable of assigning values to both quantities at once, it must provide an incomplete description of the physically real."

That is essentially the claim that Einstein and coauthors made in the EPR paper in 1935. Subsequent discoveries (Bell's theorem in 1965, abundant experimental proof that Bell's inequalities are violated in nature) have shown that this claim is based on a non sequitur ; the theory is incapable of assigning values to both quantities at once, but it doesn't follow that the theory is necessarily incomplete. Instead, any theory that does assign values to both quantities at once is necessarily incorrect.

 

[Lord Jestocost]

Physicist Pascual Jordan writes: "Observations not only disturb what has to be measured, they produce it. ... We compel [the electron] to assume a definite position. ... We ourselves produce the results of measurement."

In “Quantenphysikalische Bemerkungen zur Biologie und Psychologie” (Erkenntnis 4: 215-252, 1934) Pascual Jordan elucidates his thinking using as an example the measurement of the unknown linear polarization state on a quantum of light. One can do nothing else but letting the quantum of light pass a polarization filter. It will either pass or not. But that does not mean that one detects the polarization state that existed before (for this, there is no possibility at all when considering a single quantum of light). Instead, one “forces a decision” on the quantum of light: it should now adjust its polarization plane either corresponding to the filter or perpendicular to it. If this decision has been made, one knows which position the polarization plane now has; but one has not learned anything about the original state; our knowledge applies to a state created only by the fact that we have forced the decision in question during the observation process. By means of measurements, one only brings about that decisions are made, but one is not able to influence the outcomes of these decisions.

(I have tried to “freely” translate a passage on page 226 of Jordan’s paper)

 

[bhobba]

From my understanding of everything I've read about quantum theory, the observing mind plays a role in the unfolding of what is being observed. The consciousness of the observer is crucial in determining the measured outcome.

Here is a MUCH better understanding:
https://www.scottaaronson.com/democritus/lec9.html

Formally its simply an extension of normal probability theory. I can explain why you would want to extend it but first let's just get these unfortunate common misconceptions from populations out of the way.

Its not generally talked about but what ordinary probability means - does it involve consciousness, all sorts of subtleties, is an issue as well. QM has the same issues only worse:
http://math.ucr.edu/home/baez/bayes.html

The observing mind may or may not play a role - we do not know. Its pretty much a backwater view these days without going into its history and why it lost favor. If you want to understand that one start a new thread - but just for you to think about computers are a lot more advanced than when QM appeared - do they count as consciousness?

Thanks
Bill

 

[bhobba]

but it doesn't follow that the theory is necessarily incomplete. Instead, any theory that does assign values to both quantities at once is necessarily incorrect.

Just to elaborate on what Bohmian Mechanics (BM) says because until you understand what Nugatory correctly said it can be a bit confusing. He said you can't assign values to both things like momentum and position at once. That does not imply it can't have them - in fact BM says they do. What you can't do is actually know it. Weird hey - but true.

Thanks
Bill

 

[bhobba]

That article about Einstein's famous quote about the moon is particularly interesting.

We now know both Einstein and Bohr were wrong - I personally side more with Einstein.

My view is quite close to the pioneer who I think really understood QM best - Dirac (it is often thought Dirac was a Copenhagenist siding with Bohr - actually Bohr thought Dirac a bit weird - he was not the only one - but that's just by the by - he really held a much more subtle view closer to Einstein):
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.485.9188&rep=rep1&type=pdf

Things have progressed a lot since Dirac's time - exactly as his view would suggest and much of what was not clear then is a lot clearer now - although problems still remain. Best to start a new thread if you want to understand it better.

Thanks
Bill

 

[ZapperZ]

I have read that when an electron is observed, it behaves differently to when it is not being observed.

Could someone please expand on this, or indeed correct me. In what way does an observed particle behave differently to a particle that isn't being observed by somebody's consciousness?

I want to emphasize something slightly different here based on the topic of this thread that you created. Please note that what you are asking for are properties of quantum objects, and this is not restricted to just "subatomic particles". Many people have the misunderstanding that quantum effects occur only for such entities, and that is wrong and should be corrected.

We have seen interference effects on objects as big as buckyballs, and have seen quantum superposition on supercurrent entities consisting of 10¹¹ particles! These are waaaaaay past being the size of "subatomic" particles.

So, to you and others who are still under the impression that "subatomic" particles are the only ones exhibiting these quantum properties, please reset and reboot.

Zz.

 

[bhobba]

So, to you and others who are still under the impression that "subatomic" particles are the only ones exhibiting these quantum properties, please reset and reboot.

You Dirac lover . He always thought that way - and he was spot on.

As Feynman showed even classical physics has its basis in QM ie his path integral approach implies the principle of least action. Actually Dirac originally showed it but Feynman of course really advanced it.

Thanks
Bill

 

[Kenneth Boon Faker]

I like your answers, they are very informative. Thank you.

I've just read the following in a book that a friend lent me. What are you opinions on it?

"We can know either the momentum of a particle or its position, but not both. We must choose which of these two properties we want to determine. This is very close to saying that we create certain properties because we choose to measure those properties. Said another way, it is possible that we create something that has position, for example, like a particle, because we are intent on determining position and it is impossible to determine position without having some thing occupying the position that we want to determine. Did a particle with momentum exist before we conducted an experiment to measure its momentum? Did a particle with position exist before we conducted an experiment to measure its position? Did any particles exist at all before we thought about them and measured them? Did we created the particles that we are experimenting with? Incredible as it sounds, this is a possibility that many physicists recognise."

 

[bhobba]

Did a particle with position exist before we conducted an experiment to measure its position? Did any particles exist at all before we thought about them and measured them? Did we created the particles that we are experimenting with? Incredible as it sounds, this is a possibility that many physicists recognise."

We have no idea. There are various views on if it, or even if it matters - mine is - who cares? Its not quite shut up and calculate - it more like let's proceed and see what happens - exploring interpretations is OK - not exploring them is OK as well. Just don't be too worried about it - what's going on will emerge one way or the other.

Like I said I am with Dirac - it will gradually progress and we will know more in the future - what that will be and what it says about questions like the above - only time will tell. For example in Dirac's time that it was just an extension of probability theory wasn't known - but is now. Things will gradually become clearer.

Thanks
Bill

 

[Khashishi]

I've just read the following in a book that a friend lent me. What are you opinions on it?

You ought to have given the name and author of the book.

Exist is such a hard word to use in quantum mechanics. Fields are more fundamental than particles. There is an electron field which governs the behavior of electrons and positrons. Particles and antiparticles are excitations of the field, so whether they exist depends on what you mean by exist. The number of particles is not necessarily definite. Does sound exist? It is just collective motion of particles.

Note that sound can be described by quasiparticles called phonons. Phonons don't have exact positions because sound waves are spread out in space.

 

[ZapperZ]

I like your answers, they are very informative. Thank you.

I've just read the following in a book that a friend lent me. What are you opinions on it?

"We can know either the momentum of a particle or its position, but not both. We must choose which of these two properties we want to determine. This is very close to saying that we create certain properties because we choose to measure those properties. Said another way, it is possible that we create something that has position, for example, like a particle, because we are intent on determining position and it is impossible to determine position without having some thing occupying the position that we want to determine. Did a particle with momentum exist before we conducted an experiment to measure its momentum? Did a particle with position exist before we conducted an experiment to measure its position? Did any particles exist at all before we thought about them and measured them? Did we created the particles that we are experimenting with? Incredible as it sounds, this is a possibility that many physicists recognise."

There are MANY things that are wrong here:

(1) There is nothing that says that one can't measure BOTH position and momentum. However, it is the idea of the SPREAD in repeated measurement of the same thing that is of issue here. This spread represents the variation in the values of position and momentum if you measure the same situation repeatedly. In classical physics, reducing the spread in the value of the position doesn't affect the spread in the value of momentum. In QM, it does! The relevant concept in QM here is the Heisenberg uncertainty principle (which you should do a search on in this forum).

(2) This has nothing to do with whether the particle exists or not before a measurement. It has to do with a particular set of PROPERTIES of that particle. QM indicates that ALL the possible values for a particular property are there before a measurement, and that these values are not determined until it is measured. So they are there. It is just that they haven't been picked out yet. The relevant QM concept is the principle of quantum superposition.

Zz.

 

[Nugatory]

I've just read the following in a book that a friend lent me. What are you opinions on it?

Not exactly wrong (because it is too vague to be assigned an unambiguous truth value), but a waste of time if your goal is to understand quantum mechanics.

Try to get hold of a decent first-year textbook... Almost the first thing it will cover is the mathematical relationship between states of definite position and states of definite momentum.

 

[PeterDonis]

a book that a friend lent me

Please give specifics: which book, what chapter/page?

 

[StevieTNZ]

Maybe good old 'Sneaking a Look at God's Cards' ( https://www.amazon.com/dp/069113037X/?tag=pfamazon01-20 ) is an appropriate place to start, then move into basic Maths with https://www.amazon.com/dp/0465062903/?tag=pfamazon01-20 ?

 

[Lord Jestocost]

"We can know either the momentum of a particle or its position, but not both. We must choose which of these two properties we want to determine. This is very close to saying that we create certain properties because we choose to measure those properties. Said another way, it is possible that we create something that has position, for example, like a particle, because we are intent on determining position and it is impossible to determine position without having some thing occupying the position that we want to determine. Did a particle with momentum exist before we conducted an experiment to measure its momentum? Did a particle with position exist before we conducted an experiment to measure its position? Did any particles exist at all before we thought about them and measured them? Did we created the particles that we are experimenting with? Incredible as it sounds, this is a possibility that many physicists recognise."

To my mind, one should avoid such a kind of formulation by using the terms "particle" and "create". It would be better here to follow John Marburger:

“This is the gist of Bohr’s concept of complementarity. It is not so much that the underlying stuff does not possesses position and momentum simultaneously, it is that we will never have any way of verifying it. This has nothing to do with waves and particles. It has to do with how we get knowledge about the microscopic world. We do not have this problem with large-scale things because the incompatibility of detectors for position and momentum is a tiny effect. For microscopic things, we can choose what we want to measure about Nature, but some properties are incompatible in that they simply cannot be measured at the same time, no matter how hard we try. Bohr says that such properties are complementary.”

“Please note that I have said nothing of whether the underlying stuff is waves or particles. In the Copenhagen Interpretation of microscopic Nature, there are neither waves nor particles. There is an underlying non-visualizable stuff that has the power to make clicks in different kinds of detectors. We can use the mathematics of Schrödinger or of Heisenberg to predict how frequently a particular kind of detector, tuned to a particular value of the property it detects, will be triggered by a given apparatus. A complete description of the underlying stuff that makes the clicks, according to Bohr, can only be obtained by repeated observations of different complementary properties.”

“We do not – cannot – measure waves in the underlying stuff. We can only measure detector clicks. But when we hear the click we say “there’s an electron!” We cannot help but think of the clicks as caused by little localized pieces of stuff that we might as well call particles. This is where the particle language comes from. It does not come from the underlying stuff, but from our psychological predisposition to associate localized phenomena with particles. That predisposition is reinforced by the fact that in large scale Nature there are particles whose trajectories we can trace to an accuracy limited by the size of Planck’s constant. This is how the Copenhagen Interpretation frames the wave versus particle issue.”

“It is not true that the underlying stuff sometimes behaves like a wave and sometimes like a particle. It always behaves like itself, but we sometimes choose to measure one property, sometimes another.”

Citations from: Marburger, J. (2002, March 2). On The Copenhagen Interpretation of Quantum Mechanics. In The Copenhagen Interpretation: Science and History on Stage. Symposium conducted at National Museum of Natural History of the Smithsonian Institution.

 

[mark!]

Einstein was never happy with quantum mechanics.
"Is the Moon There When Nobody Looks?"
As far as I know though he did eventually accept that quantum theory fits with observation.
https://maltoni.web.cern.ch/maltoni/PHY1222/mermin_moon.pdf
It isn't anything to do with consciousness, inanimate machines can also be observers.

This was Einstein's reaction to the Copenhagen interpretation of quantum mechanics. The scientific community still isn't entirely sure about how to interpret quantum mechanics, because we don't quite understand the wave function collapse.

Its not generally talked about but what ordinary probability means - does it involve consciousness, all sorts of subtleties, is an issue as well. QM has the same issues only worse:
http://math.ucr.edu/home/baez/bayes.html

In his treatise 'The Mathematical Foundations of Quantum Mechanics', John von Neumann analyzed the measurement problem. He concluded that the entire physical universe could be made subject to the Schrödinger equation. The 'Participatory anthropic principle' of John Archibald Wheeler (the physicist behind the term 'black hole') says that consciousness plays some role in bringing the universe into existence. This principle, that consciousness causes the collapse, is the point of intersection between quantum mechanics and the mind/body problem, and researchers are working to detect conscious events correlated with physical events that, according to quantum theory, should involve a wave function collapse; but, thus far, results are inconclusive.

By including consciousness into the picture, you're leaving the domain of science, because you're taking human subjectivity (and thereby an interpreting observer, unlike a computer) in account. This does not mean that consciousness can't be affiliated with the quantum world in any possible way however, don't you agree @mfb?

This has nothing to do with consciousness. A photon detector can observe it in the same way a human eye can.

 

[StevieTNZ]

By including consciousness into the picture, you're leaving the domain of science, because you're taking human subjectivity (and thereby an interpreting observer, unlike a computer) in account. This does not mean that consciousness can't be affiliated with the quantum world in any possible way however, don't you agree @mfb?

I'm sick and tired of people saying consciousness has nothing to do with Quantum Mechanics, when it is a valid interpretation.

 

[bhobba]

I'm sick and tired of people saying consciousness has nothing to do with Quantum Mechanics, when it is a valid interpretation.

We all know some are passionate about certain interpretive issues. If it persists the thread will likely be shut down - correctly. Can we all just show a bit of tolerance. All that was needed to be said is its still a legit interpretation just out of favor with most for various reasons.

Thanks
Bill

 

[bhobba]

This was Einstein's reaction to the Copenhagen interpretation of quantum mechanics. The scientific community still isn't entirely sure about how to interpret quantum mechanics, because we don't quite understand the wave function collapse.

Collapse is actually not part of QM eg Many Worlds.

We are making progress, but slowly - no interpretation is better than any other - can we please just discuss the differences and try not to put our own spin on it?

I know its hard, and there are a lot of misconceptions such as QM has collapse. We can work through them but there is no generally agreed answer - accept that at the start and all of us can learn - especially the OP.

Thanks
Bill

 

[Nugatory]

I'm sick and tired of people saying consciousness has nothing to do with Quantum Mechanics, when it is a valid interpretation.

It is a valid interpretation, but a B-level thread that starts "In what way does an observed particle behave differently to a particle that isn't being observed by somebody's consciousness?" isn't about that interpretation - at best it's based on a pop-sci caricature of that interpretation, and more likely it's based on a complete lack of awareness of the distinction between the mathematical formalism and its interpretation.

Thus, although it's something of a lie to children, it's reasonable to say in these threads that whatever the original poster has heard about the role of consciousness is just plain wrong.

 

[rootone]

If the moon only exists when we can see it, there is no reason is expect it to come back after it has disappeared,
It does come back though and very predictably.
I think that is enough to conclude that the Moon exists. whether or not it can be seen.

 

[bhobba]

If the moon only exists when we can see it, there is no reason is expect it to come back after it has disappeared, It does come back though and very predictably. I think that is enough to conclude that the Moon exists. whether or not it can be seen.

This view raises all sorts of issues of a philosophical nature such as what is exist - the interpretation does not deny the moon has a quantum state regardless of being observed by a conscious observer or not - is being in a quantum state existing? The modern issue is what is a conscious observer? Is a computer that passes the Turing test a conscious observer - they now possibly exist - but even if we are not quite there yet there is little doubt it will eventually happen:
http://www.bbc.com/news/technology-27762088

And what exactly is organically conscious? A monkey, a dog, an amoeba?.

Its a valid interpretation - I actually dislike it personally - as I said it's not much in favor these days - but that has nothing to do with anything - we need to point out its issues here - as well as positives - not personal opinions - it certainly breaks the Von-Neumann chain (if the OP does not know what that is from his readings let us know and someone will elucidate - or better still look it up) at an interesting point which is why it was introduced by him in the first place. If someone wants a post on the history behind it I am happy to do so but I am not sure it will particularly help - and again looking it up for yourself is a good exercise..

Thanks
Bill

 

[Derek P]

If the moon only exists when we can see it, there is no reason is expect it to come back after it has disappeared,
It does come back though and very predictably.
I think that is enough to conclude that the Moon exists. whether or not it can be seen.

Or some sort of hidden Moon-Creator field with a very good memory :)
Which, come to think of it, is very similar to some interpretations !

 

[Kenneth Boon Faker]

Please give specifics: which book, what chapter/page?

The book is called "The Dancing Wu Li Masters: An overview of the New Physics" by Gary Zukav, published by Rider in 1979.

The 'Participatory anthropic principle' of John Archibald Wheeler (the physicist behind the term 'black hole') says that consciousness plays some role in bringing the universe into existence. This principle, that consciousness causes the collapse, is the point of intersection between quantum mechanics and the mind/body problem, and researchers are working to detect conscious events correlated with physical events that, according to quantum theory, should involve a wave function collapse.

Am I right saying that this kind of conclusion has been drawn from the implications of Schrodinger's wave equation? The wave function gives a description of the things that could happen to an observed system. Before we interfere with (i.e. setup an experiment to observe) an observed system, it continues to generate possibilities in accordance with the Schrodinger wave equation. But as soon as we make a measurement, the probabilities of all the possibilities, except one, because zero, and the probability of that possibility becomes one, which means that it happens. This is when the wave function collapses.

How else can the wave function collapse without an observer looking at the observed system and then concluding that the wave function has collapsed?

 

[Nugatory]

The book is called "The Dancing Wu Li Masters: An overview of the New Physics" by Gary Zukav, published by Rider in 1979.

... Which is not an acceptable source under the physics forums rules.

Am I right saying that this kind of conclusion has been drawn from the implications of Schrodinger's wave equation? The wave function gives a description of the things that could happen to an observed system. Before we interfere with (i.e. setup an experiment to observe) an observed system, it continues to generate possibilities in accordance with the Schrodinger wave equation. But as soon as we make a measurement, the probabilities of all the possibilities, except one, because zero, and the probability of that possibility becomes one, which means that it happens. This is when the wave function collapses.

That the wave function collapses is one way of interpreting what Schrodinger's equation is telling us. It is by no means the only way, and indeed it is possible to interpret Schrodinger's equation without introducing the notion of collapse at all. To be fair, however, I have to add that none of the ways of interpreting the mathematical formalism of quantum mechanics are completely satisfactory to everyone, so giving up on the notion of collapse is not to going to bring any miraculous clarity to the problem. If you search for "quantum measurement problem" you will find many ways of stating the underlying problem, many interesting ways of thinking about it, but no definitive answers... search some of our old threads in which interpretations are discussed to see for yourself.

How else can the wave function collapse without an observer looking at the observed system and then concluding that the wave function has collapsed?

The discovery of quantum decoherence about a half-century ago went a long ways towards answering that question. As always, there is no substitute for actually learning the mathematical formalism of QM, but David Lindley's "Where does the weirdness go?" is a pretty good layman's introduction to the subject.

In any case, as this thread was started with misunderstandings from a source that never should have been used as the basis for a Physis Forums discussion, this thread is closed.