Miss-Interpreting Quantum Collapse.

[Robin]

Just having another look:

Ingrid Hansen Smythe:



What does she mean by "messing up the results"? Do physicists regularly "mess up their results"? By "switching on the light"?? Surely they have learnt not to do that by now!!!

She obviously means, as Feynman says "the photons disturb the electrons".

Does she mean that in order for an experimenter's thoughts to shape reality (assuming for the moment that that is actually what happens), he would necessarily have to turn on the lights - so as to justify her claim that "it is the photons messing up the results, not the Observer's mind"

But she is not claiming that the experimenter's thoughts are shaping reality, I am rather confused as to why you think she is. She is simply stating, as Feynman says, that the photons are disturbing the electrons. That is a simplification, but it is not wrong.

 

[Dancing David]

Hi Dancing David,
No need to apologise,
The point is IMO, Richard Feynmann never said nobody understands the theory of quantum mechanics, he said nobody understands quantum mechanics.

I think it is safe to say that we understand the theories of classical mechanics as well as the underlying mechanisms.

Oh really, okay, what makes gravity suck?

The same can be said for relativity.

Not really, why is c invariable ?

However, this cannot be said for quantum mechanics.
Now, I am not a physicist, so ultimately you are not disagreeing with me, rather you are disagreeing with Richard Feynmann, Brian Greene and many other respected physicists.

Nice dodge Skwinty, I am saying that we do not understand the underlying mechanisms, we model them.

 

[schrodingasdawg]

Right, but it's certainly not obvious that we should think of the evolution of the wavefunction as a description of what happens to the system, because (as you agreed earlier), it's far from clear what the wavefunction is a mathematical representation of.

I'm afraid I don't understand your argument. Regardless of what the wave-function is a representation of (e.g. it is real, statistical properties, etc.), it still models whatever it represents.

 

[Skwinty]

Oh really, okay, what makes gravity suck?

Simply stated: Mass tells space-time how to curve and curved space-time tells mass how to move.
Pretty understandable to a layman.

Not really, why is c invariable ?

Well, simply stated again. The invariance of c is one of the postulates of relativity. If you accept that, gravity becomes understandable.

We can invoke words like wave/particle duality and translate this into incredibly precise mathematical formalism that has amazingly accurate predictive power, but this is incredibly difficult to understand at deep meaniful level to a layman, or a physicist. This is where I suspect Feynmans statement " Nobody understands quantum mechanics." comes into play. This is still applies equally well today.

Bohr said and I paraphrase: If you think quantum mechanics is a slam dunk, then you most certainly don't understand it.

Nice dodge Skwinty, I am saying that we do not understand the underlying mechanisms, we model them.

Well, I see you agree that we don't understand.
A quote from Brian Greene: "Maybe some time in the future some clever person will see clear to a new formulation that will reveal the whys and whats of quantum mechanics. And then again, maybe not. The only thing we know with certainty is that quantum mechanics absolutely and unequivocally shows us that a number of basic concepts essential to our understanding of the familiar everyday world fail to have any meaning when our focus narrows to the microscopic realm.As a result we must significantly modify both our language and our reasoning when attempting to understand and explain the universe on atomic and subatomic scales"

 

[Dancing David]

Simply stated: Mass tells space-time how to curve and curved space-time tells mass how to move.
Pretty understandable to a layman.

Psst, that is a model not how reality actually works.

Well, simply stated again. The invariance of c is one of the postulates of relativity. If you accept that, gravity becomes understandable.

So it is statement given to be true, not really an understanding of how reality actually works?

We can invoke words like wave/particle duality and translate this into incredibly precise mathematical formalism that has amazingly accurate predictive power, but this is incredibly difficult to understand at deep meaniful level to a layman, or a physicist. This is where I suspect Feynmans statement " Nobody understands quantum mechanics." comes into play. This is still applies equally well today.

Psst, it applies to much of science.

Bohr said and I paraphrase: If you think quantum mechanics is a slam dunk, then you most certainly don't understand it.


Well, I see you agree that we don't understand.
A quote from Brian Greene: "Maybe some time in the future some clever person will see clear to a new formulation that will reveal the whys and whats of quantum mechanics. And then again, maybe not. The only thing we know with certainty is that quantum mechanics absolutely and unequivocally shows us that a number of basic concepts essential to our understanding of the familiar everyday world fail to have any meaning when our focus narrows to the microscopic realm.As a result we must significantly modify both our language and our reasoning when attempting to understand and explain the universe on atomic and subatomic scales"

And we really don't understand much of the reality of physics in general.

You have not explained why gravity sucks, you have modeled it.
You have not explained why c is invariant, you have postulated it.

 

[schrodingasdawg]

As a physics student, I should tell my friends that I'm going into modeling.

 

[Skwinty]

As a physics student, I should tell my friends that I'm going into modeling.

You must admit, humans have come very far based on postulates, models and zero understanding.

 

[Robin]

Simply stated: Mass tells space-time how to curve and curved space-time tells mass how to move.
Pretty understandable to a layman.

And how do they do that?

This is where I suspect Feynmans statement " Nobody understands quantum mechanics." comes into play. This is still applies equally well today.

But he also said that nobody knows the mechanism of gravity. That applies equally well today.

So we understand QM as well as we understand gravity. In other words we can do the maths for each.

 

[Skwinty]

And how do they do that?.

Once you accept the basic principles of general and special relativity then the implications of space-time can be deduced with logical reasoning. The speed of light was calculated and measured for example.

But he also said that nobody knows the mechanism of gravity. That applies equally well today.

I need to read more of Feynmans work.
I haven't come across that before.

So we understand QM as well as we understand gravity. In other words we can do the maths for each.

I agree that mathematics is the language of science and without those skills ones comprehension and appreciation are severely limited.

My take on this was that we have a deeper understanding of classical and relativity mechanics than we do of quantum mechanics.

The weirdness of quantum mechanics is much more difficult to understand.
When the theory of gravity and quantum mechanics are so incompatible, physicists look to modifying quantum mechanics through string theory and not general relativity.
String theory seeks to explore beyond the planck scale and that is in the subatomic realm and not the macroscopic.

This is the aim of string theory is it not?

 

[BillyJoe]

She obviously means, as Feynman says "the photons disturb the electrons".

So physicists DO have to turn on the lights to see what's going on? And, in doing so, they DO "mess up" their results? They get no meaningful results because they have to turn on the lights to see what's going on and, in the process, mess them up?

But she is not claiming that the experimenter's thoughts are shaping reality, I am rather confused as to why you think she is.

I did not say so. I said "assume for the moment" that the experimenters thoughts shape reality. If that is the case, why does the author assume they they can only do so if they "turn on the lights" (like those silly physicists continually messing up their results!)? Because, if they don't need to, the authors reason why their thoughts cannot shape reality fails.

She is simply stating, as Feynman says, that the photons are disturbing the electrons. That is a simplification, but it is not wrong

Which photons? The ones that mess up his results when he turns the light on? They should really should stop doing that!

 

[Robin]

So physicists DO have to turn on the lights to see what's going on? And, in doing so, they DO "mess up" their results?

Electrons scatter light. So in order to detect which slit the electron goes through a light source is introduced. A flash is detected at the slit where the electron passes through. But when this occurs the interference pattern is not in evidence any more and there are just two "bars" where the electrons are detected, indicating that the electrons are acting like particles rather than waves and are now passing through specific slits.

This in itself is not very surprising since we should not expect the interaction between electrons and photons to be one sided.

So they alter the light source to see if they can detect which slit the electron passes through without disturbing it. But at the very point where the wavelength of the light makes it impossible to tell which slit it passes through, the interference pattern is seen again.

And it is impossible to set up the experiment in any way that it is possible to detect which slit the electron passes through without losing the interference pattern. That is the surprising part.

They get no meaningful results because they have to turn on the lights to see what's going on and, in the process, mess them up?

On the contrary, they get a very meaningful result because they introduce a light source to detect which slit the electrons pass through.

Whether "messing the results" is the appropriate term is perhaps debatable, maybe "unmessing the results" would be more appropriate for what is happening.

But any plain language account of this will obviously be an approximation.

Which photons? The ones that mess up his results when he turns the light on? They should really should stop doing that!

The photons from the light source that was introduced to detect which slit the electrons pass through, obviously.

I am interested - are you now saying that Feynman is talking nonsense in "Six Easy Pieces" when he says the photons disturb the electrons?

 

[Fredrik]

I'm afraid I don't understand your argument. Regardless of what the wave-function is a representation of (e.g. it is real, statistical properties, etc.), it still models whatever it represents.

Right, it models what it represents, and if it doesn't represent the properties of the system...

 

[Robin]

Deleted.

 

[Robin]

I need to read more of Feynmans work.
I haven't come across that before.

It is in the chapter on gravity in "Six Easy Pieces". I can find the full quote if you want.

 

[Skwinty]

It is in the chapter on gravity in "Six Easy Pieces". I can find the full quote if you want.

That would be great, thanks Robin

 

[BillyJoe]

Robin,

Ah, now I get it!
She is using metaphor!



"turn on the light" = direct a beam of photons at the electrons that may of may not be entering the slit.
"mess up the results" = change the result from an interference pattern to a scatter pattern

Now, pray tell, how is the lay public supposed to understand that?
I mean I'm serious about this - how is the public supposed to understand what she wrote in her article and see it as a refutation of the mind shaping reality claim.

Silly me, all along I thought she was talking about the situation where physicists measure the position of an electron by shooting photons at it ("turning on the light") but, in the process changing the electrons position ("messing up the results"). Hence my mistake in thinking that she was talking about - and misunderstanding - the HUP.

In any case, it certainly did not occur to me that "messing up the results" could mean "changing the result from an interference pattern to a scatter pattern".

 

[Robin]

Robin,

Ah, now I get it!
She is using metaphor!

Not a metaphor. Just a simplification. Not a particularly good one, I will grant you but a simplification nevertheless

"turn on the light" = direct a beam of photons at the electrons that may of may not be entering the slit.

Turning on a light is literally what they do. Introduce a light source.

"mess up the results" = change the result from an interference pattern to a scatter pattern

Now, pray tell, how is the lay public supposed to understand that?

How, pray tell, is the lay public supposed to understand about interference patterns?

Nobody really knows what happens, so "messing the result" is no worse than most descriptions.

How would you have put it, to a lay audience?

Silly me, all along I thought she was talking about the situation where physicists measure the position of an electron by shooting photons at it ("turning on the light") but, in the process changing the electrons position ("messing up the results").

That is the process she is talking about, but you haven't got it quite right either. The photons don't "change the electrons position", they don't have any specific position until we attempt to measure it.

And of course I don't have it quite right either. Nobody does, because nobody actually knows what happens.

Hence my mistake in thinking that she was talking about - and misunderstanding - the HUP.

The uncertainty principle is not directly relevant to this, but it comes into play when they find that as soon as flash of light becomes too diffuse to determine which slit the electron passes through, the interference pattern comes back.

But she really only wanted to make the point that it was photons responsible for what happens and not thoughts, and in that she is perfectly correct.

 

[Fredrik]

If the particles interact with something between emission and detection, this can localize the particles to specific positions, and that will destroy the interference pattern. This is what happens in the double slit experiment with C70 molecules that I mentioned earlier. (Higher air pressure means less interference. Air messes up the results).

In a "successful" double slit experiment, one that does produce an interference pattern, the particles have made it through the slits, all the way to the detector (often a photographic plate) without getting significantly disturbed by photons or anything else. Each particle that reaches the detector would be putting it in a superposition of classical states if we could also prevent the detector from interacting with its environment. But we can't. It will scatter photons unless the room is completely dark, and it will emit photons if it isn't at absolute zero temperature. And even if it was, it would still interact gravitationally. These interactions will "mess up" the superposition of detector states. If the detector is a photographic plate, they will cause the discoloration to appear at a specific location rather than at a superposition of locations.

Is it correct to say that this "messes up the results"? The answer depends on what result we were hoping to get in the first place. If we wanted to determine the state that the system was in before the measurement began, then the result has indeed been messed up. But it makes more sense to include the requirement that the measuring device must be in a specific classical state as a part of what we mean by a "result". If we do, these interactions are the reason why experiments have results at all (at least in the MWI).

 

[Robin]

If the particles interact with something between emission and detection, this can localize the particles to specific positions, and that will destroy the interference pattern. This is what happens in the double slit experiment with C70 molecules that I mentioned earlier. (Higher air pressure means less interference. Air messes up the results).

In a "successful" double slit experiment, one that does produce an interference pattern, the particles have made it through the slits, all the way to the detector (often a photographic plate) without getting significantly disturbed by photons or anything else. Each particle that reaches the detector would be putting it in a superposition of classical states if we could also prevent the detector from interacting with its environment. But we can't. It will scatter photons unless the room is completely dark, and it will emit photons if it isn't at absolute zero temperature. And even if it was, it would still interact gravitationally. These interactions will "mess up" the superposition of detector states. If the detector is a photographic plate, they will cause the discoloration to appear at a specific location rather than at a superposition of locations.

Is it correct to say that this "messes up the results"? The answer depends on what result we were hoping to get in the first place. If we wanted to determine the state that the system was in before the measurement began, then the result has indeed been messed up. But it makes more sense to include the requirement that the measuring device must be in a specific classical state as a part of what we mean by a "result". If we do, these interactions are the reason why experiments have results at all (at least in the MWI).

But how do you describe the situation, in a few words, to make the point that she was making?

As I said before, perhaps "unmesses the results" might have been closer to the mark. But it all comes down to how you characterise the uncharacterisable.

Bohr called the state of the unmeasured electron "a great smoky dragon". Often people say "smeared out".

I don't think it is the best lay description of the double slit experiment I have heard, nor the worst.

She was trying to make a point in not too many words, that it is particles and not thoughts that is responsible for the change that happens.

If I was making that point, without going into the specifics of interference patterns and so on, I am not sure that I could have done any better.

 

[Robin]

In fact why don't we all try to re-write the passage in question, they way she should have put it and see if we can come up with something that couldn't be criticised?