Schrodinger's Cat.

[Das Platyvark]

Basically, I'm looking for an explanation here. I know the premise, how it works, but this seemed like the place to come for my biggest question on it: What, if anything, makes Schrodinger's Cat science, rather than philosophy? It seems to me that the premise of it's state of existence being anything till observed makes sense as a philosophical concept, but where does this intersect with science? (If I'm making some major blunder here in my ignorance, forgive me.)

[LaZodiac]

Technicaly its neither because it was meant as a joke/parody of how ridiculous quantum mechanics is. Taking it straight it's definitly a philosophical thing, like the "tree falls in a forest" line.

[Cobra_Ikari]

Basically, I'm looking for an explanation here. I know the premise, how it works, but this seemed like the place to come for my biggest question on it: What, if anything, makes Schrodinger's Cat science, rather than philosophy? It seems to me that the premise of it's state of existence being anything till observed makes sense as a philosophical concept, but where does this intersect with science? (If I'm making some major blunder here in my ignorance, forgive me.)

The only thing I could think of with that in it is the double slit experiment.

[Serpentine]

Wiki it. It's a little complicated, but it was basically Schrodinger saying "this idea of quantum physics is stupid!" If it seems unscientific to you, then you've sorta got the point.

[Grinner]

Many thought experiments like that are philosophic, but they usually end up filed under "Science".

The Boltzmann Brain (http://en.wikipedia.org/wiki/Boltzmann_brain) comes to mind presently.

[Weezer]

Here's (http://www.tu-harburg.de/rzt/rzt/it/QM/cat.html)a link to a translation of Schrodinger's original paper, it's actually pretty accesible, little to no funky math, mostly him laying out the situation of quantum mechanics and the various interpretations in pretty plain language. The cat comes up in section 5.

[factotum]

As I understand it, the "science" comes from the dual nature of quantum physics--basically, if you use the equations to predict if a particular quantum event has happened, you will always get two results, one saying it has, one saying it hasn't. I'm no expert on quantum theory, though!

[golentan]

Yeah. What the others have said. What made you think it was science? It's experimentally unverifiable, because observing the cat is observing the cat and violates the experiment. It's a philosophical exercise (specifically an attempt at Reductio Ad Absurdum) which comes up a lot in scientific discussions. And discussions of zombifying cats. And how to decide which path you should take (My girlfriend and I came up with the Schrodinger Murphy Formula: if there are two or more options where you know that at least one is incorrect and one is correct, all options are both correct and not correct until you make your selection. Which will then become the incorrect option).

[Feytalist]

The only thing I could think of with that in it is the double slit experiment.

The double slit experiment only really illustrates the many worlds theory of quantum mechanics, but it is pretty cool anyway.

[Cobra_Ikari]

The double slit experiment only really illustrates the many worlds theory of quantum mechanics, but it is pretty cool anyway.

My knowledge of quantum mechanics is...extremely lacking, it's been 6 years since I took a physics class, but I seem to remember one being able to explain parts of the other. *shrugs*

[Feytalist]

My knowledge of quantum mechanics is...extremely lacking, it's been 6 years since I took a physics class, but I seem to remember one being able to explain parts of the other. *shrugs*

Possibly. I've actually never heard a formal explanation of why either could work, just the pop culture versions :smalltongue:

[Killer Angel]

What, if anything, makes Schrodinger's Cat science, rather than philosophy? It seems to me that the premise of it's state of existence being anything till observed makes sense as a philosophical concept, but where does this intersect with science?

As already stated, it's a philosophical concept, applied to science.


Technicaly its neither because it was meant as a joke/parody of how ridiculous quantum mechanics is. Taking it straight it's definitly a philosophical thing, like the "tree falls in a forest" line.

Technically, there's no sound.
Sound is vibration, transmitted by a medium (usually air) and perceived by a receiver (usually ears). Remove the receiver, and there will be no sound, only vibration.

[Asta Kask]

My cat objects to this topic.

[Grinner]

My cat objects to this topic.

While your cat is undoubtedly an insightful creature, I'm afraid it simply has no say on the matter, given its obvious bias. :smalltongue:

[Heliomance]

The double slit experiment only really illustrates the many worlds theory of quantum mechanics, but it is pretty cool anyway.

Pretty sure the double slit experiment has nothing to do with many worlds theory. All it shows is the wave/particle duality of photons.

The biggest problem with Schrodinger's Cat (aside, of course, from the fact it was intended as an absurdism in the first place) is that the cat is observing itself.

But yes, while a cat in a box does indeed have a definite state of alive or dead, regardless of whether we know that state, it is true that some sub-atomic particles really do exist in multiple states until they are observed (though the definition of observation is not the same as in common parlance - the observer need not be sentient or even alive. A single photon is entirely capable of being an observer.)

[Elemental]

Pretty sure the double slit experiment has nothing to do with many worlds theory. All it shows is the wave/particle duality of photons.

The biggest problem with Schrodinger's Cat (aside, of course, from the fact it was intended as an absurdism in the first place) is that the cat is observing itself.

But yes, while a cat in a box does indeed have a definite state of alive or dead, regardless of whether we know that state, it is true that some sub-atomic particles really do exist in multiple states until they are observed (though the definition of observation is not the same as in common parlance - the observer need not be sentient or even alive. A single photon is entirely capable of being an observer.)

Damnation. I was about to make that point, but you ninja edited your post.
But yes... Particles observe things. The only way to be really sure something exists in a state of flux resulting from non-observation is to remove it from all interaction. Which you just can't do with a cat because they're too complex.

[Yora]

And that's the important part: Schrödinger was not objecting to quantum physics in general, but only to the notion that it is the human mind that shapes reality. Which is a theory actually proposed by other quantum physicists at the time. Based on the assumption that human minds have been created with unique properties by god.
Which, as Schrödinger points out, is scientifically unsound.

Not only does the cat observe the poison, the geiger counter is also an observer of the isotope that may or may not decay.
There is the commonly accepted understanding that an observer affects the process he is observing. If you want to listen to sound? You have to stand in the sound waves. If you want to measure the temperature of water, you have to put a thermomether into it, which itself is warmer or colder than the water and changes it's temperature. In the same way, a geiger counter placed next to radioactive material will affect the material with it's own electromagnetic and gravitational field. Which will make a tiny difference.
But the idea Schrödinger was objecting to is, that it does not make a difference until a person looks at the geiger counter to see if it detected something.

The double slit experiment doesn't prove anything either. It only illustrates that light behaves in a wave that does not make any sense to our concepts of waves or particles. It only tells us, that there is something going on which we don't know yet.

[Kindablue]

Physicists propose 'Schrödinger's virus' experiment: Laser technique could put virus in two overlapping quantum states. (http://www.nature.com/news/2009/090910/full/news.2009.903.html)

[Heliomance]

And that's the important part: Schrödinger was not objecting to quantum physics in general, but only to the notion that it is the human mind that shapes reality. Which is a theory actually proposed by other quantum physicists at the time. Based on the assumption that human minds have been created with unique properties by god.
Which, as Schrödinger points out, is scientifically unsound.

Not only does the cat observe the poison, the geiger counter is also an observer of the isotope that may or may not decay.
There is the commonly accepted understanding that an observer affects the process he is observing. If you want to listen to sound? You have to stand in the sound waves. If you want to measure the temperature of water, you have to put a thermomether into it, which itself is warmer or colder than the water and changes it's temperature. In the same way, a geiger counter placed next to radioactive material will affect the material with it's own electromagnetic and gravitational field. Which will make a tiny difference.
But the idea Schrödinger was objecting to is, that it does not make a difference until a person looks at the geiger counter to see if it detected something.

The double slit experiment doesn't prove anything either. It only illustrates that light behaves in a wave that does not make any sense to our concepts of waves or particles. It only tells us, that there is something going on which we don't know yet.

The fun thing about the double slit experiment is that if you send the photons through one at a time, such that there is no possible way they could interfere with each other, you end up with an interference pattern anyway!

[Asta Kask]

While your cat is undoubtedly an insightful creature, I'm afraid it simply has no say on the matter, given its obvious bias. :smalltongue:

He says it's okay if you use the neighbor's cat. Who is an evil territory-stealing thief.

[Manga Shoggoth]

Technically, there's no sound.
Sound is vibration, transmitted by a medium (usually air) and perceived by a receiver (usually ears). Remove the receiver, and there will be no sound, only vibration.

Technically nothing! "Sound" has a number of different definitions depending on who you are talking to. That's why the "tree falling in the forest" arguement is essentially unsolvable.

The usual one for physics is something like: Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas.

More colloquial definitions may add things like frequency ranges and receptors.

[dehro]

why has nobody yet mentioned sheldon cooper, I wonder...

[Elemental]

why has nobody yet mentioned sheldon cooper, I wonder...

Because he's not the topic of conversation.
And as for the whole virus thing, I have a feeling it won't work the way they want it to. But, I'm not a theoretical physicist, so I'm going to have to wait and see if my hunch is correct.

[Bhu]

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

peek here

[Elemental]

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

peek here

That's the exact spanner I was thinking of.

[Serpentine]

The idea of a forest with nothing to hear a tree falling has always disturbed me about that question... What sort of a forest doesn't have a single ear within it? Creepy.

[Elemental]

The idea of a forest with nothing to hear a tree falling has always disturbed me about that question... What sort of a forest doesn't have a single ear within it? Creepy.

Correct. There aren't any like that.
Well, not without blending science and fantasy, but that always ends with overly done magitech, which annoys me.

[Gnomish Wanderer]

A single photon is entirely capable of being an observer.

I just wanted to say that in quantum mechanics observer can simply mean any force that acts upon it, such as gravity or heat, and if you remove those you can even get a photon or atom to exist in multiple states, based on that oscillating microchip experiment.

[Feytalist]

The fun thing about the double slit experiment is that if you send the photons through one at a time, such that there is no possible way they could interfere with each other, you end up with an interference pattern anyway!

Which illustrates the many worlds theory. Or used to. I think that theory has been pretty much laughed out of the room by now. These days it just illustrates that we don't quite know everything about light particles yet, as someone else said.

[Killer Angel]

Technically nothing! "Sound" has a number of different definitions depending on who you are talking to. That's why the "tree falling in the forest" arguement is essentially unsolvable.

The usual one for physics is something like: Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas.


Thus eliminating the receiver? In that case, things are different...
Of course insects exist: :smallbiggrin:


The idea of a forest with nothing to hear a tree falling has always disturbed me about that question... What sort of a forest doesn't have a single ear within it? Creepy.

[Manga Shoggoth]

Thus eliminating the receiver? In that case, things are different...
Of course insects exist: :smallbiggrin:

Oh, yes indeed - Hence the reams of discussion.

After all, do insects hear in the same way as us? If they do, do they hear in the same frequency range as us?

The same problem exists if you consider cats and dogs as receptors - cats can hear higher frequencies than humans, dogs can hear lower ones. If a cat or dog can hear it, but a human can't, is it still a sound?

If I keep winding the frequency up (or down, for that matter), when does a pressure wave cease to be a sound? After all, the only difference is the frequency.


The idea of a forest with nothing to hear a tree falling has always disturbed me about that question... What sort of a forest doesn't have a single ear within it? Creepy.

If you read David Eddings, there is conversation between two of the wizards about the tree falling in the forest. The two women listening derail it in a simillar way. It's quite an amusing scene.

[Elemental]

If you read David Eddings, there is conversation between two of the wizards about the tree falling in the forest. The two women listening derail it in a simillar way. It's quite an amusing scene.

I do indeed remember that scene. Sorceress of Darshiva wasn't it?
Beldin was trying to get Durnik into philosophy, and Ce'Nedra responds by saying that the trees would be aware if one of them fell.
Which brings me to a question appropriate for another thread.
I'll post it there.

[The Extinguisher]

Which illustrates the many worlds theory. Or used to. I think that theory has been pretty much laughed out of the room by now. These days it just illustrates that we don't quite know everything about light particles yet, as someone else said.

No, it shows that the photons are both particles and waves, and that they are interfering with themselves.

There's nothing about the many worlds theory (which tries to answer the same questions as the "collapsing the wavefunction" theory), and everything about wave-particle duality.

[Cobra_Ikari]

The idea of a forest with nothing to hear a tree falling has always disturbed me about that question... What sort of a forest doesn't have a single ear within it? Creepy.

If you had asked me to guess a place, I would have thought here (http://en.wikipedia.org/wiki/Red_Forest), but apparently, it's actually got a lot of wildlife. Huh.

[TheCountAlucard]

But, I'm not a theoretical physicist, so I'm going to have to wait and see if my hunch is correct.B-but by observing it, you're changing the outcome!

[golentan]

{{Scrubbed}}

[Manga Shoggoth]

{{Scrubbed}}

Isn't that pretty much what I said?


{{Scrubbed}}

If you don't define your terms, there is no clear basis for arguement, because you may be arguing about completely different things under the same name. I once had a huge arguement with someone because sge was using a word (Organic, as I recall) in one way, and I was using it in another.

In the sciences especially, definition of terms is crucial. How many people remember the difference between speed and velocity, for example?

I am merely pointing out that the "tree in the forest making a sound" discussion depends entirely on how you define a sound.

[Serpentine]

If you had asked me to guess a place, I would have thought here (http://en.wikipedia.org/wiki/Red_Forest), but apparently, it's actually got a lot of wildlife. Huh.The most I was thinking of was a petrified forest, but even those'd still have bugs at the very least, and probably reptiles and birds.

[Balain]

I remember watching some show hosted by Stephen Hawkings. They were talking abut some lab that did an experiment where they were able to observe one atom in two different locations at the exact same time.

[shawnhcorey]

First, I would like to say that all science is philosophy. When you go to university, study hard, graduate, get your master's, then write a thesis, you get a Ph.D. (http://en.wikipedia.org/wiki/Doctor_of_Philosophy), a philosophiae doctor. That's Latin for a doctorate of philosophy. All the sciences are philosophies.


The fun thing about the double slit experiment is that if you send the photons through one at a time, such that there is no possible way they could interfere with each other, you end up with an interference pattern anyway!

You get the interference pattern because quanta have both particle and wave properties but are neither. During the experiment, a body will go through both slits and immediate become two superposition, entangled bodies. They will proceed independently to the detectors where one is measured. When it is measured, the superposition will collapse and the other will disappear. All the properties will be associated with the one that is measured.

BTW, the experiment has been done with 60-atom and 80-atom buckyballs (https://en.wikipedia.org/wiki/Buckyball) with the same results.


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

Sorry, the Heisenberg Uncertainty Principle has little to do with this. Try quantum superposition (http://en.wikipedia.org/wiki/Quantum_superposition) instead.

Schrödinger thought experiment about a cat may have been to point out the silliness that humans have a unique perspective on the universe but macro-objects, that is, much bigger than quanta but still very small compared to humans, have been put in a superposition state (http://www.scientificamerican.com/article.cfm?id=quantum-microphone). This shows that even everyday objects like cats can exist in two (or more) states at the same time and will continue to do so until they are measured.

One further clarification. Although observed implies a human is the one observing, measured means it is measured by a detector, any device to measure and record a property of the phenomenon in question.

And the falling tree will make a sound. Physics, which is a philosophy, says so. :smallwink:

[Grinner]

First, I would like to say that all science is philosophy. When you go to university, study hard, graduate, get your master's, then write a thesis, you get a Ph.D. (http://en.wikipedia.org/wiki/Doctor_of_Philosophy), a philosophiae doctor. That's Latin for a doctorate of philosophy. All the sciences are philosophies.

All sciences are philosophies. Not all philosophies are sciences.

Ideally, they would be, but many are hinged on speculation.

Then again, so are a few sciences... :smalleek:

[Androgeus]

The idea of a forest with nothing to hear a tree falling has always disturbed me about that question... What sort of a forest doesn't have a single ear within it? Creepy.

Didn't plant life precede animal life? You could have a forest with out any wildlife then. Although would you get forests with out animals? for some reason all the trees I can think of use animals to pollinate and distribute their seeds. I'm no paleontologist though.

[irenicObserver]

But yes, while a cat in a box does indeed have a definite state of alive or dead, regardless of whether we know that state, it is true that some sub-atomic particles really do exist in multiple states until they are observed (though the definition of observation is not the same as in common parlance - the observer need not be sentient or even alive. A single photon is entirely capable of being an observer.)

So, in a more pedantic sense does that make the observer the interacter? The only possible way for something to register is by its context interacting with the surrounding environment. The "observer" is merely the thing that would possibly conduct the information to another body.

I tend to blather when it comes to attempting to grasp these things sorry.
I do indeed remember that scene. Sorceress of Darshiva wasn't it?
Beldin was trying to get Durnik into philosophy, and Ce'Nedra responds by saying that the trees would be aware if one of them fell.
Which brings me to a question appropriate for another thread.
I'll post it there.

Link please so I may follow?

[Serpentine]

Didn't plant life precede animal life? You could have a forest with out any wildlife then. Although would you get forests with out animals? for some reason all the trees I can think of use animals to pollinate and distribute their seeds. I'm no paleontologist though.Hm. True... But I'm pretty sure back then thre were no trees. Just ferns and similar.

[Heliomance]

So, in a more pedantic sense does that make the observer the interacter? The only possible way for something to register is by its context interacting with the surrounding environment. The "observer" is merely the thing that would possibly conduct the information to another body.
Sounds about right, yes.



Link please so I may follow?

It's a dead tree book, not web-based.

[Yora]

So, in a more pedantic sense does that make the observer the interacter?
That's the point. Observing is an interaction. By being present, the observer changes the environment, which affects the result of the experiment. In most situations, it does not make much of a difference, but in subatomic physics or social sciences, it changes everything.

[Elemental]

If you were referring to the question I asked, I can provide a link to the thread I asked it on.
Link. (http://www.giantitp.com/forums/showthread.php?t=230984&page=12)

@V And It's been linked.

[irenicObserver]

Which brings me to a question appropriate for another thread.
I'll post it there.

Well yes, *ahem*.

[mattrwh]

That's the point. Observing is an interaction. By being present, the observer changes the environment, which affects the result of the experiment. In most situations, it does not make much of a difference, but in subatomic physics or social sciences, it changes everything.

I was watching this crazy documentary where they basically said that while there has to be an observer to collapse the wave function, making it measurable or however the hell that part of quantum physics works, there is no scientific proof that we are the observer in those situations, given that we can't locate the "observer" in the human brain. It was a pretty trippy show.


In response to the thread, I think that it depends on whether you view theories of quantum physics as being scientific, or theories that emphasize our lack of understanding of the universe. If its the latter, then you probably wouldn't consider schroedinger's cat as a scientific thought experiment.

[Kindablue]

I was watching this crazy documentary where they basically said that while there has to be an observer to collapse the wave function, making it measurable or however the hell that part of quantum physics works, there is no scientific proof that we are the observer in those situations, given that we can't locate the "observer" in the human brain. It was a pretty trippy show.

You need light to use a microscope, and in this case what you're looking at is so small that the particles of light themselves interact with it and screw up your measurement. More broadly, there has to be something to bounce off whatever you're measuring and back to you to get information, but at the scale where things don't get any smaller (atomos being Greek for uncuttable or indivisible), that seems to be impossible.

[Asta Kask]

While that is true, there are experimental data that indicate that the problem goes deeper than just our clumsy tools. At a fundamental level, the thing we call an electron cannot have a defined momentum and position at the same time.

[Manga Shoggoth]

While that is true, there are experimental data that indicate that the problem goes deeper than just our clumsy tools. At a fundamental level, the thing we call an electron cannot have a defined momentum and position at the same time.

(Bolding mine...)

It's more that they cannot be measured together with any certianty - The more accurately you measure the momentum, the greater the uncertianty in the position, and vice versa. What Hisenberg's equation gives us the absolute limit of the uncertianty - your measurements can be no better than this.

And, of course you cannot get round this by measuring one and then the other as the very act of making the measurement will change the system.

[Killer Angel]

That's the point. Observing is an interaction. By being present, the observer changes the environment, which affects the result of the experiment. In most situations, it does not make much of a difference, but in subatomic physics or social sciences, it changes everything.

And, in this specific case, the observer will certainly hear the falling tree, so the question would be moot...

[Asta Kask]

(Bolding mine...)

It's more that they cannot be measured together with any certianty - The more accurately you measure the momentum, the greater the uncertianty in the position, and vice versa. What Hisenberg's equation gives us the absolute limit of the uncertianty - your measurements can be no better than this.

And, of course you cannot get round this by measuring one and then the other as the very act of making the measurement will change the system.

From the books I've read, I'd say you're wrong. What you're proposing is essentially a 'hidden variables' system and IIRC that has been disproven.

[Manga Shoggoth]

From the books I've read, I'd say you're wrong. What you're proposing is essentially a 'hidden variables' system and IIRC that has been disproven.

It is possible that they've changed things since I did my degree (wouldn't be the first time...), but the definition then was that it was impossible to know (ie, measure) both the position and momentum of a particle at the same time with any accuracy, and that the Hisenberg equation represented the ultimate limit of knowledge, even with "perfect" equipment and conditions.

Though I hate to invoke wikipedia, my textbooks are at home (and not as easy to link to):


In quantum mechanics, the Heisenberg uncertainty principle (http://en.wikipedia.org/wiki/Heisenberg_uncertainty_principle) states a fundamental limit on the accuracy with which certain pairs of physical properties of a particle, such as position and momentum, can be simultaneously known. In layman's terms, the more precisely one property is measured, the less precisely the other can be controlled, determined, or known.


My problem was with your use of "define", which means something else. You can't define the position or momentum of a particle - you can only measure them.

[Asta Kask]

What I mean is, there isn't some particle there that's localized in one space with a given momentum. Whatever is there is not exactly localized and has no given momentum. If you could measure without interacting, you would still get an uncertainty.

[The Extinguisher]

It is possible that they've changed things since I did my degree (wouldn't be the first time...), but the definition then was that it was impossible to know (ie, measure) both the position and momentum of a particle at the same time with any accuracy, and that the Hisenberg equation represented the ultimate limit of knowledge, even with "perfect" equipment and conditions.

Though I hate to invoke wikipedia, my textbooks are at home (and not as easy to link to):




My problem was with your use of "define", which means something else. You can't define the position or momentum of a particle - you can only measure them.

It's not really a measuring thing though.

As far as I can remember, it's actually based on the wave particle duality of everything. You look at two ends, you can consider a wave, which has no exact position but an exact speed (and therefore momentum), and then you look at a particle which has an exact position (a point in space) but no exact momentum, because it's just a point in space.

Since nothing is either a wave or a particle, but both, the position and momentum fall somewhere between exact and unknowable.

[Asta Kask]

I have started a Twitter group to stop this barbaric cruelty: #CatsagainstSchrödinger

I contend that we can easily perform the same experiments with less valuable subjects, like grad students.

[Mono Vertigo]

I have started a Twitter group to stop this barbaric cruelty: #CatsagainstSchrödinger

I contend that we can easily perform the same experiments with less valuable subjects, like grad students.

Grad students? Are you kidding?
Lawyers and bankers make much better subjects.

[Manga Shoggoth]

I have started a Twitter group to stop this barbaric cruelty: #CatsagainstSchrödinger

I contend that we can easily perform the same experiments with less valuable subjects, like grad students.

If I was on Twitter, I'd join it.

Technical Architects would make good subjects too, and we have plenty at work that aren't doing anything else...