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Miss-Interpreting Quantum Collapse.

Congratulations. You've just re-invented the Everett Interpretation, also called Many Worlds.

No, actually, that's rather precisely NOT what I'm saying. I'm saying that if you could actually model the entire system, you'd find that it time evolves into a specific state without "collapse" or chance. But we can't model the entire system, and the initial state of the entire system is essentially random (and different each time a measurement is performed), so we get what appears to be random results.
 
Nope. Wavefunctions and their collapse are part of the real world, they are not simply a mathematical conveniece. If a particle is floating aroun dall by itself, it can exist in a superposition of many different states. When it interacts with another particle it cannot stay in that superpostion because each different state it is in would lead to a different outcome. Instead the superposition collapses down to a single state, with the probability of each state being determined by the wavefunction. The collapse is not dependent on conciousness and is a real phenomenon. No rugs need to be brushed.

If you can prove that collapse is real, then you've just disproven the Everett Interpretation. I'm pretty sure that nobody has done so. Our perception of collapse is real. But that doesn't mean that collapse "really" happens.

Furthermore there are lots and lots of situations where multiple particles interact but do not collapse. If this were not possible, then phenomena like quantum entanglement could not exist.

Of course, this is a little simplified and it is possible to get particles not to collapse under certain conditions. This is where weird things like superconductivity and quantum computing come from, but isn't really relevant to a basic understanding.

You can change "a little simplified" to "simplified to the point of being wrong".

Cheers,
Ben
 
No, actually, that's rather precisely NOT what I'm saying. I'm saying that if you could actually model the entire system, you'd find that it time evolves into a specific state without "collapse" or chance. But we can't model the entire system, and the initial state of the entire system is essentially random (and different each time a measurement is performed), so we get what appears to be random results.

Oh. In that case you're wrong. Sorry.

Linearity implies that once a quantum mechanical system goes into superposition it can never stop being in superposition. This is not a failure to model the system in full detail, this is a basic prediction of quantum mechanics. So basic, in fact, that the contradiction was evident before quantum mechanics was worked out in any great detail. Hence the mystery in the fact that it does appear to stop being in superposition. (The "collapse".)

Several possible explanations exist for how it is that we see collapse happening, even though collapse can't happpen within quantum mechanics. There is no test that can distinguish between these explanations (which are called "interpretations of quantum mechanics"). Therefore one can only decide between them on philosophical grounds. (I personally like the Everett Interpretation because it is the only one that says that quantum mechanics applies to everything, including the observer.)

But whatever interpretation you prefer, it is an observational fact that we perceive collapse happening, and quantum mechanics predicts that collapse can't actually happen.

Cheers,
Ben
 
Linearity implies that once a quantum mechanical system goes into superposition it can never stop being in superposition. This is not a failure to model the system in full detail, this is a basic prediction of quantum mechanics.

I'm afraid you're simply wrong. First off, every state is always a superposition state. The phrase is only meaningful with respect to a particular basis (commonly energy eigenstates, but that's not a requirement). But states that start out as energy eigenstates don't need to stay that way, which means that they time evolve into other states. Superposition or not, a quantum state is still just a vector in a phase space, and that vector can change continuously under the Schrodinger equation without having to "collapse" to a particular basis.

Consider, for example, a free quantum spin with a magnetic moment (ie, an electron). Let's say it's in a state with spin up along the z axis. This is a superposition state of up and down spins along the x axis, or a superposition of up and down states along the y axis (all equivalent expressions). Now let's suppose we apply a magnetic field along the y axis. The energy of the y-axis eigenstates are now different, and the phase difference between them changes over time. This is equivalent to the spin rotating in the field. If we look at how the spin state evolved in a different basis (namely, the x-axis or z-axis basis), we find that the amplitudes of these superpositions will change. The spin will rotate from up along the z axis (and an even mix of up and down x-axis states) to up along the x-axis (and an even mix of up and down x-axis states). Given an initial quantum state for our spin, we can use a magnetic field to change it into anything we want. That includes turning a "pure" state into a "superposition" state, or vice versa. So the claim that superposition states cannot become pure states without collapse is simply wrong. Depending on the system, it can be quite easy to do.

But whatever interpretation you prefer, it is an observational fact that we perceive collapse happening, and quantum mechanics predicts that collapse can't actually happen.

It is only in cases where we have an absence of any prediction from quantum mechanics that we "observe" collapse. You never get collapse in a situation where quantum mechanics gives you an answer, and the only reason quantum mechanics doesn't give you an answer (since it's deterministic) is because you can't do the calculation for practical reasons.
 
OK, so let's talk about physics.

Nominated.

Mate, as a science communicator (and currently a science teacher), I often endeavour to try to find ways of communicating science in a fashion that people who don't have the relevant background can understand. You have an excellent way of describing what you know, and I'm jealous of your abilities.

Thanks.

Athon
 
Nominated.

Mate, as a science communicator (and currently a science teacher), I often endeavour to try to find ways of communicating science in a fashion that people who don't have the relevant background can understand. You have an excellent way of describing what you know, and I'm jealous of your abilities.

Thanks.

Athon
Oh, you math jocks just drool over stuff like that, don't you? I'll bet when you were kids you would huddle in the garage playing with your calculators and telling dirty equations.

(Seriously, it was quite good and deserving of a nomination. And Athon should know, as he is a former winner himself.)
 
Can you explain to me why the quote is utter rubbish?
Yes. Because she has confused a gedankenexperiment that Heisenberg used to describe the uncertainty principle with the truth. In fact, the reason that quantum parameters that are uncertain because they are conjugate with measured quantities is not because the measurements are disturbed- it is because the quantities themselves are of indeterminate value. It's not that they have a value but we can't measure it, it's that they don't have a value. Or in the case of continuous conjugate parameters like position and momentum, they don't have a precise value. It's a little easier to understand with spin, which has discrete values- or perhaps it's more confusing, since this type of thing is completely unlike what we experience.

All it looked like she was trying to say is the same thing that you and the others have said - the process of measurement necessarily involves interacting with the particle which necessarily leads to collapse to an eigenstate.
No. She said that the process of measurement necessarily disturbs it- that's not the point. The point is that measurement makes the conjugate parameter indeterminate, not merely unmeasurable. We can actually tell the difference, there is an experiment called the "Aspect experiment," a realization of an earlier gedankenexperiment devised by Einstein, Podolsky, and Rosen, and called the "EPR experiment" in their honor, that allows us to do so.
 
The quote looks fine to me too. She did say "crudely simplistic terms" and I interpret it as referring to decoherence which is a perfectly legitimate objection as far as I can see. Of course, more context would be helpful. Is the article on-line, and is there is a link?
The idea is indeed very, very close to decoherence, but decoherence varies from that idea because it does not assert that indeterminate parameters have values but those values are unmeasurable.
 
Nominated.

Mate, as a science communicator (and currently a science teacher), I often endeavour to try to find ways of communicating science in a fashion that people who don't have the relevant background can understand. You have an excellent way of describing what you know, and I'm jealous of your abilities.

Thanks.

Athon
Beat you by a day or so!
If he wins I get the credit, okay. ;)
 
No. She said that the process of measurement necessarily disturbs it- that's not the point.

That's EXACTLY the point. A measurement process can only happen when there's an interaction. Interactions change energy eigenstates, so any previous energy eigenstates of the system (the only basis states which can be non-time-dependent) are no longer eigenstates of the system, and so the system MUST time-evolve in response to the measurement process. And how exactly it time evolves is uncertain not because of quantum uncertainty, but because you never know the quantum state of your measuring device.

The point is that measurement makes the conjugate parameter indeterminate, not merely unmeasurable.

That can happen even without a wave function collapse. In fact, that's precisely what I described above: take a spin in a z-axis eigenstate, rotate it with a magnetic field applied along the y axis, and you can turn it into an eigenstate of the x axis and a superposition of z-axis eigenstates (which is really what you mean when you say it's indeterminate). But that requires no "measurement", and no collapse, because you can model the whole thing entirely.
 
I'm too thrashed to write tonight. I'll try to get to this tomorrow. Also, I'll have to do the "wave/particle" thing before I can talk about the interpretations. More later.
 
Here's the link to the eSkeptic article, just so it's clear where this is from.

Yes. Because she has confused a gedankenexperiment that Heisenberg used to describe the uncertainty principle with the truth. In fact, the reason that quantum parameters that are uncertain because they are conjugate with measured quantities is not because the measurements are disturbed- it is because the quantities themselves are of indeterminate value. It's not that they have a value but we can't measure it, it's that they don't have a value. Or in the case of continuous conjugate parameters like position and momentum, they don't have a precise value. It's a little easier to understand with spin, which has discrete values- or perhaps it's more confusing, since this type of thing is completely unlike what we experience.

No. She said that the process of measurement necessarily disturbs it- that's not the point. The point is that measurement makes the conjugate parameter indeterminate, not merely unmeasurable. We can actually tell the difference, there is an experiment called the "Aspect experiment," a realization of an earlier gedankenexperiment devised by Einstein, Podolsky, and Rosen, and called the "EPR experiment" in their honor, that allows us to do so.

You seem to be focussed on what she means by messing up, but I think the relevant point is a step back. The premise for movies like "The Secret" and "What the Bleep do we Know" seems to be that measurement consists of a conscious observer becoming aware of the result. And I think that is what she was attempting to counteract. She does refer to Schrodinger at the start of the quoted paragraph.

I do agree that her description can be read as though the photons interfere with or disturb an accurate measure. But I also think it can be read as a recognition that even "turning on the light" forms part of what leads to waveform collapse (without getting into a discussion on what that is). And that does seem to be what her footnote is referring to as well.

Linda
 
Joe Vitale was on Larry King tonight talking about "the secret" and he said that Jessica Lunsford (The 9 year old girl who was kidnapped, molested repeatedly, tortured and buried alive) actually "caused" that to happen to her because she unconsciously attracted the pedophile to her life.



When I heard this I felt sick to my stomach. I just wanted to punch that fat bald freak in the face.
 
I do agree that her description can be read as though the photons interfere with or disturb an accurate measure. But I also think it can be read as a recognition that even "turning on the light" forms part of what leads to waveform collapse (without getting into a discussion on what that is). And that does seem to be what her footnote is referring to as well.

Linda

I just wanted to add that I understood (or thought I did) what she should be trying to say, so I'm attempting to clarify whether the disagreement is about what she should be trying to say or if it's about whether she does a poor job of it.

Linda
 
If you can prove that collapse is real, then you've just disproven the Everett Interpretation. I'm pretty sure that nobody has done so. Our perception of collapse is real. But that doesn't mean that collapse "really" happens.

It wouldn't disprove anything. The whole point of the many worlds interpretation is that the collapse is the point where different universes diverge. From our point of view it looks exactly the same as simply seeing a superposition collapse to one value. Proving the collapse is real would say nothing about which interpretation of tha collapse is correct.

I think to go any further will simply get into pointless philosophical discussions about what is "real". I see it from the point of view that collapse is seen to happen, therefore it is real, in the same way that I see wavicles as real things that can act as either particles or waves, rather than either particles or waves being real. Different people view different things as real and disagree over which bits are just convenience to make it look nicer. All the maths is the same and the answers are the same, so all these arguments are purely semantic. At the moment we simply have no way to tell what is actually the "real" answer.

Furthermore there are lots and lots of situations where multiple particles interact but do not collapse. If this were not possible, then phenomena like quantum entanglement could not exist.

That's exactly what I said.
 
Joe Vitale was on Larry King tonight talking about "the secret" and he said that Jessica Lunsford (The 9 year old girl who was kidnapped, molested repeatedly, tortured and buried alive) actually "caused" that to happen to her because she unconsciously attracted the pedophile to her life.



When I heard this I felt sick to my stomach. I just wanted to punch that fat bald freak in the face.

Oof some people waste valuable resources.
 
Missing the point?

"The Secret" video claims that people can influence the universe in very tangible ways merely by feeling the right feelings, and tries to back it up with vague claims that "quantum physics" allows this sort of thing to occur. Ms. Hansen Smythe's point, I think, is that one cannot reasonably use quantum physics to back up these claims.

What's interesting is that this forum demonstrates how easy it is to make bogus claims about quantum physics. Just trying to talk about it instantly causes an argument, so those who make outrageous claims for quantum effects get a free ride between the doubts of laymen and the difficulty for experts of describing phenomena which have no macro-world analogues.

Quibbles about whether or not the author hit the quantum nail squarely on the head or not are irrelevant to the more central idea of her article, which is that "The Secret" is a literally incredible collection of alarmingly immoral nonsense.
 

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