Question about Uncertainty

[Membrain]

I think you're attributing the wave function collapse to some physical properties of the electron, and including the wave function in the so-called wave-particle duality.

 

The wave function is a description of the electron, not the electron itself. The electron exhibits both classical wave and particle properties. If the electron is in some undetermined state, you "collapse the wave function" when you measure it to be in one particular state, but that state may still exhibit wave properties, e.g. you may have a superposition of the spin states, but measuring the spin, which collapses the wave function, won't necessarily preclude the electron from demonstrating interference, which is a wave property.

Please allow me to parse your language a bit to see if I can't gain some understanding. Some of what you say confuses me not so much due to jargon as much as perhaps what appears to be contradictions.

 

For example, the sentence "The wave function is a description of the electron, not the electron itself". I paraphrase this to say:

 

The wave function is a description of the electron, and

the wave function is a not a description of the electron

 

Confusing, eh? So am I interpreting something incorrectly?

 

Thanks again for patience. The questions come from a lack of understanding and nothing more.

[Membrain]

I think it depends on the approach, but normally I would for sure say that the exact wave does not have a definite physical existence in the old fashioned sense - like a water wave of sound wave.

 

In quantum mechanics the wavefunction is not measurable.

This is where it seems like there is sort of a philosophical question being answered. Are quantum mechanics physicists saying that, "If we can't measure something, it doesn't exist"?

 

If so, this to me seems like an ontological leap.

 

Please everyone, feel free to chime in on this question.

[swansont]

Please allow me to parse your language a bit to see if I can't gain some understanding. Some of what you say confuses me not so much due to jargon as much as perhaps what appears to be contradictions.

 

For example, the sentence "The wave function is a description of the electron, not the electron itself". I paraphrase this to say:

 

The wave function is a description of the electron, and

the wave function is a not a description of the electron

 

Confusing, eh? So am I interpreting something incorrectly?

 

Thanks again for patience. The questions come from a lack of understanding and nothing more.

 

 

Yes. If I write down your description and print out a picture of you on a sheet of paper, that sheet of paper is not you.

 

But it's QM. It can be confusing.

[Membrain]

Yes. If I write down your description and print out a picture of you on a sheet of paper, that sheet of paper is not you.

 

But it's QM. It can be confusing.

So is what you are saying:

 

The wave function is a description of the electron, but

the wave function is a not an electron

 

This makes sense, yes?

[fredrik]

> "If we can't measure something, it doesn't exist"?

 

Ask yourself this. If you really can't measure something, wether directly or more often indirectly. In other words, this something really doesn't effect you, because if it did, it would in general sense be measurable, because in my world effect and measurements are sort of similar. I make a measurement on X by interacting with X and registering the outcome of the interaction. This interactions depends on both me and X. And since me (my self) is my "a priori given reference" I can deduce information about X. Note that ignorance does not cause such things. Ingorance means you may still be effected, but you don't "pay attention" to it. All our observations are filled with noise. So beeing ingorant might possible be said to mean that we mistake something for normal noise, while a more perceptive observerer would have seen an anomality in the noise - which in itself is sort of fuzzy evidence or support for that "something" more, that as of yesterday was unknown, are likely to exist out there.

 

The question is more, what does "exist" mean? I've been thinking alot about this too and I have come to a conclusion that the concept of exist and real has an intrinsic fuzz factor in themself. I think in some strange way, the only existence most people find to nuaturally not question, is the "self". Anything beyond the self, and it does start to get fuzzy. When you think about this for a while I think the likely conclusion is that it IS fuzzy, whithout even talking about QM.

 

Yet it's as natural to WANT to clear the fuzz. That seems to be the key to development of life, and possibly also arrow of time, though the details remains unclear.

 

If we can't measure something, what is the meaning in terms of effect, that this something does exist?

 

Logic is extremely important but I think the "new physics" of the last 100 years, and more important of the next 100 years will require some kind of fuzzy or probabilistic logic. Not merely new strange mathematics with the same old logic. Bring on the new logic and I am sure the new math will come, and in the light of the new logic it will seem very natural, and the old stuff will seem very simplistic.

 

This is how I personally see it. I think physicists have been too ignorant about philosophy for a long time. The new logic doesn't come without philosophy.

 

/Fredrik

[fredrik]

> > The wave function is a description of the electron, but

> > the wave function is a not an electron

>

> This makes sense, yes?

 

This is of course true. But still, what is more "real"? Your collected information of the electron, or the electron itself - wich you at this point really don't know what it is?

 

Unlike macroscopica objects, some of these small particle, we know ONLY by indirect interactions. We know them only by their effect. In our mind the electron can be anything we want it be, as long as it interacts the way we have observed it, because anything that looks like the electron, interacts like an electron and talks like an electron, I will definitely classify as a very probable electron, indistinguishable from any other electron. This is so, until we observe anomalities in noise(or our ingnorance) or something...

 

/Fredrik

[SyedAmeen]

jan.25.2007

 

Did you read about the Heavy Neutrinos.The Oscillations of these heavy neutrinos?

neutrino e-,neutrino muon,neutrino tau

That is what ignorons(assumped faster than c particles ,entanglement creates.)with cosmic entities.But the frequency of charge +ignorons could still be immeasureable,that is what neutrinos are.The ennergy induced momentum tensors results forced forced fermion to boson transformation,which is th real PHOTON.

Here Quantum Field Theory is facing a renewed interest in rediscovery of photon.So the Wave function faces new approach.

Dr.syed Ameen (Ph.D.)

see links listed in myspace.com view blog,click

http://www.myspace.com/syedameen

[Membrain]

> "If we can't measure something, it doesn't exist"?

 

If we can't measure something, what is the meaning in terms of effect, that this something does exist?

 

Logic is extremely important but I think the "new physics" of the last 100 years, and more important of the next 100 years will require some kind of fuzzy or probabilistic logic. Not merely new strange mathematics with the same old logic. Bring on the new logic and I am sure the new math will come, and in the light of the new logic it will seem very natural, and the old stuff will seem very simplistic.

 

This is how I personally see it. I think physicists have been too ignorant about philosophy for a long time. The new logic doesn't come without philosophy.

 

/Fredrik

Not to be pushy, but is there a definitive answer to the question?

 

Yes, No, Not Sure or Other?

[fredrik]

> The wave function is a description of the electron, but the wave function is a not an electron

 

About this particular question I could answer a clear Yes, and still feel good.

 

It's kind of clear that there is a difference between X, and the representation of X - set aside the question which is more "real" than the other, which may be another question.

 

/Fredrik

[fredrik]

> "If we can't measure something, it doesn't exist"?

 

About this question. I would like to say that it depends on what "can't measure" means, and what exists means.

 

But to give a short answer, I would still choose to say that the answer to the question is No, if we by exists subjective or conditional opinions.

 

/Fredrik

[fredrik]

To expand it... I would reprhase to say that

 

If we can't measure something, it existence is "ambigous".

 

Because I think non-ambigous and non-existent are quite different things.

 

Many things that exist are ambigous.

 

/Fredrik

[swansont]

> The wave function is a description of the electron, but the wave function is a not an electron

 

About this particular question I could answer a clear Yes, and still feel good.

 

It's kind of clear that there is a difference between X, and the representation of X - set aside the question which is more "real" than the other, which may be another question.

 

/Fredrik

 

(quoting Fredrik, but still addressing Membrain's query)

 

My main objection was to the phrasing that the electron collapsing to a point when you do a measurement, vs the wave function collapsing.

 

The wave function collapsing means you had a superposition of states in the basis and you've reduced that to one. That need not mean that you have localized the electron, though - the superposition could have been in an energy or spin state. You don't really know much more about the location of the electron after the measurement. The electron has not collapsed, per se, you have just forced it into a definite state.

[fredrik]

Membrain, another advice is to do a checkup on the topic of "bayesian logic". That can be understood easily without complex math, and provides a very philosophically plausible framework to view the wavefunction stuff in. This is sometimes also called hte "logic of science".

 

There is a concept of conditional probability, where you do not only ask what's the probability of X, you rather ask what is the probability of X, given Y. And each interaction/measurement is an update of your sort of dynamic "a priori" knowledge. Wave collapse should IMO best be interpreted as a revision of your point of view.

 

When say, and electron interacts. The a priori knowledge (condition) of the electron is different from yours. Obviously how an electron experiences the world is different than how photon experiences the world, alot thanks to the fact that they posess different self-conditions.

 

This alone can't explain physics of course, but it is IMO sound logic. Or at least, reasonably sound. And I think it will help you digest the "problem" of the "collapse".

 

It is much more logical to respond to the information you have, than to the information you could have had. IMO the information concept is fundamental in modern physics and I am sure also in future models.

 

Need to go marinade a chicken

 

/Fredrik

[Membrain]

To expand it... I would reprhase to say that

 

If we can't measure something, it existence is "ambigous".

 

Because I think non-ambigous and non-existent are quite different things.

 

Many things that exist are ambigous.

 

/Fredrik

OK, thanks. Now I'll try to work this into the original question: Does uncertainty refer to us being uncertain where an electron is.

 

To use your terms: Is the electron ambiguous?

[Membrain]

(quoting Fredrik, but still addressing Membrain's query)

 

My main objection was to the phrasing that the electron collapsing to a point when you do a measurement, vs the wave function collapsing.

 

The wave function collapsing means you had a superposition of states in the basis and you've reduced that to one. That need not mean that you have localized the electron, though - the superposition could have been in an energy or spin state. You don't really know much more about the location of the electron after the measurement. The electron has not collapsed, per se, you have just forced it into a definite state.

Concerning the "uncertainty" of quantum mechanics: is the uncertainty referring to our uncertainty where the electron is between measurements? Or also, perhaps our uncertainty as to the electrons real "shape" and "movement" since when we try to measure, we influence the measurement?

[fredrik]

> To use your terms: Is the electron ambiguous?

 

Others may want to jump on me for this, but I would say, a little bit Yes, but not completely ambigous. Of course, "ambigous electron" is still ambigous itself I am still looking for a satisfactory formalism, meantime it's fuzzy.

 

/Fredrik

[fredrik]

> is the uncertainty referring to our uncertainty where the electron is between measurements?

 

There is uncertainty also "during" measurement.

 

> Or also, perhaps our uncertainty as to the electrons real "shape" and "movement" since when we try to measure, we influence the measurement?

 

I think that's a better way of putting it I think. One simply can not make

a measurement without have at least a slight influence. Which in

the philosophical domain can be interpreted as a slight blurring

between the "self" and the non-self, at least during the interaction.

Because the interaction kind of belongs to both. It's a transient overlap

between the self and non-self.

 

In an abstract sense once could imagine a particle having something

like a "self" too. That's the analogy.

 

/Fredrik

[swansont]

Concerning the "uncertainty" of quantum mechanics: is the uncertainty referring to our uncertainty where the electron is between measurements? Or also, perhaps our uncertainty as to the electrons real "shape" and "movement" since when we try to measure, we influence the measurement?

 

There are experiments that have shown that information not known to us is, in fact, unknown. The concept is known as "local hidden variables"

 

Take, for example, a particle of spin zero, and let it decay into two particles, which must have complimentary spins (call them spin up and spin down) that must add to zero. This is known as entanglement. If we measure the spin of one of these particles, we also gain knowledge of the other. So we do a measurement, and find one particle to be spin up, and immediately know the other must be spin down. Now, one might think that the particle was spin up the whole time, and we just didn't know until we measured it, but experiments have been done that show this not to be the case. The spin orientation is actually undetermined. The classical notion must be discarded.

 

for further rading, you might want to read up on the Einstein Podolsky Rosen (EPR) paradox, and local hidden variables. But it is very much not elementary physics

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

[Membrain]

> To use your terms: Is the electron ambiguous?

 

Others may want to jump on me for this, but I would say, a little bit Yes, but not completely ambigous. Of course, "ambigous electron" is still ambigous itself I am still looking for a satisfactory formalism, meantime it's fuzzy.

 

/Fredrik

OK, thanks. Now I'll try to combine everything together:

 

Is the electron ambiguous to the degree that we are uncertain about it?

 

And is the ambiguity and uncertainty based upon measurement?

 

So if we are not measuring it, it is 100% ambiguous and 100% uncertain?

 

Or, are we even uncomfortable with making ambiguity and uncertainty the same thing?

[Membrain]

There are experiments that have shown that information not known to us is, in fact, unknown. The concept is known as "local hidden variables"

 

Take, for example, a particle of spin zero, and let it decay into two particles, which must have complimentary spins (call them spin up and spin down) that must add to zero. This is known as entanglement. If we measure the spin of one of these particles, we also gain knowledge of the other. So we do a measurement, and find one particle to be spin up, and immediately know the other must be spin down. Now, one might think that the particle was spin up the whole time, and we just didn't know until we measured it, but experiments have been done that show this not to be the case. The spin orientation is actually undetermined. The classical notion must be discarded.

 

for further rading, you might want to read up on the Einstein Podolsky Rosen (EPR) paradox, and local hidden variables. But it is very much not elementary physics

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

OK, thanks. I looked at the EPR Paradox and have a question:

 

Concerning entangled electrons:

 

I have an interesting metaphor for the indeterminate positions of the entangled electrons involving flipping coins.

 

Let's say that two entangled electrons are created. My understanding is that they are in an indeterminate states until you measure one of them and then the other one takes on the opposite spin of the first.

 

This made me think about flipping a coin: when a coin is flipped it is in an indeterminate state until it stops moving, and then we can determine its state. I saw a similarity in that the electrons can be considered to be like coins endlessly flipping until we measure them, and then like a coin come to rest, we can determine a state. But prior to the measurement they are like coins spinning.

 

Does anything about this make sense when it comes to uncertainty, probability, and indeterminacy?

 

And forgive me if this is really dumb!

[fredrik]

I think these are good valid, but fuzzy questions. I can never be sure you are asking the same questions (same intent) I do, even if the words look similar if you know what I mean. By the universal token we are already discussing, your words are merely your representaton of your real quesitons. This is why I for one, can not possibly give you a definite answer to these questions. I can only try to express my point closest point of view that i think is related to what you are asking.

 

I have the feeling that you are struggling with reality and it's non-deterministic nature.

 

IMO, the key is to understand how the "preceived reality" is formed from interpretations of of interactions. An interaction is always interpreted from a certain point of view.

 

If we start out thinking about an electron as some spinning rigid particle (á la Newtons mechanics) we start out with a premature, and as can be seen - wrong - assumption. This is why one must be extremtly careful when assuming an a priori structure on the unknown. Starting to interpret interactions based, on a formalism based on an premature and oversimplified assumption often leads to inconsistencies.

 

So I think that while we talk about say an electron we should do that only in a loose sense and keep in mind that this is techically an interpretations.

 

If we are "not measuring it" (in some way) as you say, then think about it... what reason do we have to even talk about? You obviously mean that we have a massive body of a priori knowledge generated from elctron Interactions in the past? So you are really asking question about something we don't measure, but adding ALOT of "fuzzy conditional information" in application of accepted science. My main point that most things IS fundamentally uncertain for a number of I think natural reasons.

 

To consider a classical analogy of game theory. Instead of particles interacting, asking yourself how they interact. Consider a team of expert poker players, and ask yourself how they will play.

 

In the case of poker game, little thought is needed and I am sure anyone would agree that each player acts, upon what cards he has, and what information he THINKS they other player has. He does not act upon what the other players in fact do have. Inherent in the whole dynamics of the game, is the fact that the parties does possess different information. For example, there is only one ace of spades. And before anyone has seen ace of spades, there is a probability that they will get it. But it could be that one of the players already has received this card, but this will not change the way the other players play because this information is unkown to them. So in this case it is clear that interactions are not goverened by what cards everyone does in fact HAVE - as seen by "god". Interactions are governed by local information.

 

Therefore to ME at least, "information" is more fundamental than reality. I think the information is the fact, and this obsession with reality is IMO a sort of simplistic concept. I think one need to face the fact that some things are fuzzy. From a human perspective this is obviously a stress condition, and I think it is why we are searching for all these theories to describe a "reality" consistent with what we see. Our intelligence is fighting this fuzzy, and we are doing a pretty good job so far. But I think we must not fool ourselves. A good theory makes reality more comprehensible and reduces the chaos stress in our brains. I think we all feel that "not knowing" is a pretty damn annoying state. So often, even an approximation makes us feel better.

 

/Fredrik

[fredrik]

This may not answer your question by here is some more comments...

 

IMO, the basic mistake made when arriving at the "EPR paradox", is to confuse the conditional probabilities of Alice, Bob and the third hypotetical observer (the EPR authors) that seem to think that they can hold both Alice and Bobs point of views at the same time and compare their respective values, which of course makes little sense.

 

In general Alice's conditional probability is not the same as Bob's, or anyone elses. So there really isn't much of a paradox. The paradox is created by mixing up and comparing different conditional probabilites. Noone can hold two remotely different incompatible conditions at the same time.

 

I think the lesson here is that it is dangerous to analyzing something by "picturing" some definite global structure as seen by som God that has access to everybodys information at the same time, without influencing the system. That was the problem with the old days thinking. If there was such a God the whole concept of probability would get silly, because God would know it all anway.

 

This is why I think the extension to quantum mechanics, that will also solve the quantum gravity problem must let go of the old thinking altogether which only causes problems, even though the new thinking is admittedtly more stressful to the human mind! Even thouhg I have come to accept this new thinking and thinks it wipes the floor with the old thinking by orders of magnitude, I still feel an intrisic confusion that I suspect has to do with way the human brain works.

 

So start out by thinking that we are in a big well defined room (space) and now we are going to do QM in here... makes no sense, does it? That is a clear premature construct pulled out of nowhere. That whole starting point IMO conflicts with the good essence of QM. Anything we put into our theories must be defined in terms of interactions/observations. Any ad hoc frameworks that aren't proven to be completely general seems to violate the whole philosophy of QM.

 

/Fredrik

[swansont]

OK, thanks. I looked at the EPR Paradox and have a question:

 

Concerning entangled electrons:

 

I have an interesting metaphor for the indeterminate positions of the entangled electrons involving flipping coins.

 

Let's say that two entangled electrons are created. My understanding is that they are in an indeterminate states until you measure one of them and then the other one takes on the opposite spin of the first.

 

This made me think about flipping a coin: when a coin is flipped it is in an indeterminate state until it stops moving, and then we can determine its state. I saw a similarity in that the electrons can be considered to be like coins endlessly flipping until we measure them, and then like a coin come to rest, we can determine a state. But prior to the measurement they are like coins spinning.

 

Does anything about this make sense when it comes to uncertainty, probability, and indeterminacy?

 

And forgive me if this is really dumb!

 

As far as the analogy goes I think it's OK.

[gib65]

This made me think about flipping a coin: when a coin is flipped it is in an indeterminate state until it stops moving, and then we can determine its state. I saw a similarity in that the electrons can be considered to be like coins endlessly flipping until we measure them, and then like a coin come to rest, we can determine a state. But prior to the measurement they are like coins spinning.

 

As a metaphore, yes this works. But the uncertainty of a coin toss is an example of classical uncertain - that is, it is uncertain only because we haven't measured exactly the initial state of the coin toss, and we haven't done the necessarily physics and math to figure out exactly what side it's going to land on. In principle, however, this could be done and we could figure out which side it will land on. In QM, it's a whole different ball game. When we talk about the uncertainty of an electron's spin or momentum or position or whatever, we really mean that it has no definite spin, momentum, position, or whatever - at least, when it's not measured.

 

The double slit experiment is decisive in clarifying how to interpret this uncertainty. Did you read swansont's post about this? You should read up on this. This double slit experiment shows that the only logical interpretation of its results is that a single electron is sometimes in two places at once - not that we don't know which of the two places it's in, but that it is in those two places at the same time.

[Membrain]

The double slit experiment is decisive in clarifying how to interpret this uncertainty. Did you read swansont's post about this? You should read up on this. This double slit experiment shows that the only logical interpretation of its results is that a single electron is sometimes in two places at once - not that we don't know which of the two places it's in, but that it is in those two places at the same time.

Quick question on the double slit experiment for anyone to answer:

 

Do the electrons collapse back into a point on the target screen because they are in affect being measured?

 

If so, I also don't understand how the electron knows where to collapse. It seems to me that the illustrations show "waves" interacting with themselves and then creating this "interference pattern". I guess the way I'm looking at it is: if the electron wave did not collapse, would the target screen show the imprint of the entire "interference pattern" all at once, just getting stronger and stronger over time?

 

Thanks for the help. I searched and was unable to find this question answered.