Another explanation of that poor, poor cat

  • Thread starter petmar
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Better than the original explanation?

  • YES! I love it!

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  • NO WAY!

    Votes: 3 75.0%

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  • #1
petmar
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Heisenberg's Uncertainty Principle/Schrodinger's Cat
Couples engaged in a romantic relationship usually have large amounts of physical contact with one another. However, when someone seems near, physically, to them, they begin acting normally again, even if blushing a bit. We therefore see that the couple has a probability wave function associated with them. Whenever an observer goes to see what they're doing, their wave function collapses and becomes a stable state. This is exactly the same concept that is illustrated in the Schrodinger's cat thought experiment. In this case, a cat is placed in a box along with a Geiger counter, a bottle of poisonous gas hooked up to the Geiger counter, and a radioactive particle source. If the source decays and triggers the counter, the poison is released and the cat dies. However, if the source doesn't decay, the cat lives. This is only a thought experiment, and no cats have ever been killed in one of these experiments. However, be that as it may, you have to open the box to see if the cat is still alive. If you do this, however, you collapse the probability waveform into one of two states: either the cat is alive or dead. While the box remains closed, the cat could be either alive or dead, but once opened, the cat has to choose a state. Just the same, the couple in question may or may not be making out, but when approached, they either will or will not be doing so.
 

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  • #2
jcsd
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Haven't you heard of a little thing called 'decoherence'?
 
  • #3
petmar
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no...

i haven't.
what is it?
 
  • #4
jcsd
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Decohernce shows why large systems exhibit classical rather than quantum behaviour shwing that a) Schroedinger's cat while an intersting thought experiment is one that could never be performed as the wave function in the box would decohere in a fraction of a second and b) that your kissing couople can only be treated classically.
 
  • #5
chroot
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A quantum system is very delicate. A system that is in a superposition of states will collapse into a stationary state on its first interaction with the outside world. That means it takes only one little photon, or one happenstance atom to come nearby and disrupt the system and collapse its wavefunction.

It's hard enough to isolate a microscopic object from other objects to observe its quantum properties. It's absolutely impossible to isolate a macroscopic object.

The common example is a playing card. If you balance a perfect playing card very precisely, exactly on its edge, it should actually fall to both the left and right simultaneously. The reason it doesn't, of course, is that there are billions of jiggling atoms inside it, all "measuring" the others, and there are air molecules and photons of heat radiation and so on all interacting with it from the external world. The action of all this is called "decoherence." The reason we don't observe quantum phernomena macroscopically is because it's impossible to isolate a macroscopic system well enough to protect its fragile wavefunction.

The only way to get macroscopic quantum behavior is at very low temperatures, where the thermal jiggling and radiation are diminished. Low temperature liquid helium, for example, becomes superfluid -- a sort of macroscopic quantum playground with billions of atoms all in the same quantum state, moving together without viscosity. Superconductors are another macroscopic quantum playground, but the slides are different colors.

- Warren
 
  • #6
LURCH
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Originally posted by chroot
A quantum system is very delicate. A system that is in a superposition of states will collapse into a stationary state on its first interaction with the outside world. That means it takes only one little photon, or one happenstance atom to come nearby and disrupt the system and collapse its wavefunction.


This is the part of the experiment where I always get hung up. The generally accepted proerties of gravitation include the traits of being impervious to interveening matter (cannot be blocked) and unlimited range. So it would seem that, through gravitation, every quantum system is in constant interaction with outside world. There is never a time when the unstable isatope is not being "observed" or "measured", is there?
 
  • #7
chroot
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Originally posted by LURCH
This is the part of the experiment where I always get hung up. The generally accepted proerties of gravitation include the traits of being impervious to interveening matter (cannot be blocked) and unlimited range. So it would seem that, through gravitation, every quantum system is in constant interaction with outside world. There is never a time when the unstable isatope is not being "observed" or "measured", is there?
Well, gravitation is not part of the standard model. ;) It's a good question, one I'll have to think about.

- Warren
 
  • #8
jcsd
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Originally posted by LURCH
This is the part of the experiment where I always get hung up. The generally accepted proerties of gravitation include the traits of being impervious to interveening matter (cannot be blocked) and unlimited range. So it would seem that, through gravitation, every quantum system is in constant interaction with outside world. There is never a time when the unstable isatope is not being "observed" or "measured", is there?

Roger Penrose has speculated that quantum gravity may indeed cause the collapse of the wavefunction when a macroscopic system is in a delocalized state, which could provide a mechanism for GRW theory (spontaneous collapse), but importantly as chroot says gravity doesn't have a palce in the standard model yet, so it's just speculation.
 
  • #9
petmar
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erm...

first of all, the idea was just to show what a probability waveform was all about.

secondly, and more importantly, if gravity affects all systems, then why is it that even at the smallest levels, quantum phenomena still occur? wouldn't they be influenced enough by gravity to not occur?
 
  • #10
Jonathan
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That's what I was just wondering as I read this thread, it never occurred to me that it doesn't make sense for gravity to not be included in the list of things that'll destroy a wave function. I may not be able to sleep over this!
 
  • #11
jcsd
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Originally posted by petmar
first of all, the idea was just to show what a probability waveform was all about.

secondly, and more importantly, if gravity affects all systems, then why is it that even at the smallest levels, quantum phenomena still occur? wouldn't they be influenced enough by gravity to not occur?

It's unknown, but here's some wild speculation on my part, perhaps the gravity of microsco[ic system is so small that it's indistinguishable from quantum fluctuations.
 
  • #12
Isn't the dead cat just an explanation to show that on such scales we can't know for sure so must assume both are true, basically that proabilities are fundamental to QM at these scales? If so it still seems a very roundabout way to say we can't know so must assume both.
 
  • #13
jcsd
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Originally posted by jammieg
Isn't the dead cat just an explanation to show that on such scales we can't know for sure so must assume both are true, basically that proabilities are fundamental to QM at these scales? If so it still seems a very roundabout way to say we can't know so must assume both.

It's just a thought experiment, the conclusion that the cat can be in a supposition of states is rejected.
 
  • #14
pelastration
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Originally posted by petmar
...and more importantly, if gravity affects all systems, then why is it that even at the smallest levels, quantum phenomena still occur? wouldn't they be influenced enough by gravity to not occur?

Correct.

Of course the cat is dead or alive. It's only the human measuring problem.
Uncertainty in relation to measuring is OK (there are many manufacturing limits related to machinery limits and material limits when you make for example tennis-racquets) , but making from that measuring-problem a general projection on "concepts" is quiet questionable. These are different things.
It's like saying as an tennis-racquet inventor to the tennis manufacture: This is the concept design in general but I don't know exactly how you must fix the strings 10 to 15 to that part of the tennis frame ... so please start production and finish it ... and start to deliver to Nike".

Some months ago Osher (postings a reaction on superstringtheory.com) pointed out that : "There are two meaning of Uncertainty, (1) error, like x2 - x1 or dx, and (2) standard deviation or its square variance which is the only technically correct definition used by mathematical probability and statistics people. Error itself is replaced by standard deviation precisely because it is so fluctuating (negatively and positively) that it often cancels itself out or else overexaggerates in random directions, but standard deviation isn't a major tool for engineering or for that matter for physical laws because most physical laws relate VARIABLES (even RANDOM VARIABLES) rather than their statistical population standard deviations or population means. Einstein, Schrodinger, Bohr, Heisenberg, all made the mistake of not understanding that."

Maybe it's better to rename Quantum Mechanics to Qualm Mechanics.
 
  • #15
chroot
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Actually, pelastration, quantum uncertainty has nothing to do with our limited measurement technology. This is one of the most common misunderstandings. It's not that we just can't build a good enough measuring device -- it's that no such device can exist.

- Warren
 
  • #16
I am convinced now that this thought experiment was originated by someone trying desperately to explain basic probability theory applied to QM in such an elaborate and indirect "thought experiment" kind of way that it has led to more confusion and been confusing me for some time and if the cat isn't dead yet I would like to kill it at this point.
 
  • #17
marcus
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recent paper about the cat

http://arxiv.org/gr-qc/0306007 [Broken]

"Schroedinger's Cat and the Clock: Lessons for Quantum Gravity"

a short paper with some original ideas by Robert Oeckl, a post-doc working with Carlo Rovelli

as I recall Oeckl did his doctorate in Non-commutative Geometry with Shawn Majid in the UK, has now wandered over into Loop Gravity.

the cat has some meaningful connection to time and to gravity

what Oeckl says may relate to what was being discussed here
 
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  • #18
jcsd
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Also pelastration, the measurment problem is not the same thing as uncertainty, the measurment problem is the problem in QM that a measurment isn't a mathematically defined concept.
 
  • #19
pelastration
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Thanks Croot,

the problem is that from a measuring problem a world/reality image is created that is based on super-position. Super-position is anti-unity as a concept. From the top there is causality, hierachy, ... not anarchy. The start maybe chaotic but the further developments - on the brane - were historical consequent. Uncertainty only exists is the human ignorance and the lack of logic explanation.
 
  • #20
chroot
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Originally posted by pelastration
Thanks Croot,

the problem is that from a measuring problem a world/reality image is created that is based on super-position. Super-position is anti-unity as a concept. From the top there is causality, hierachy, ... not anarchy. The start maybe chaotic but the further developments - on the brane - were historical consequent. Uncertainty only exists is the human ignorance and the lack of logic explanation.
Umm.. I'm pretty certain you've just gone off the scientific radar now. Good luck.

- Warren
 
  • #21
pelastration
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Good luck too Chroot. The future is uncertain ... I am certain of that ... it's embedded inside your worldview. ;-)
 
  • #22
petmar
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the world must be ending... ;-)

Originally posted by chroot
Actually, pelastration, quantum uncertainty has nothing to do with our limited measurement technology. This is one of the most common misunderstandings. It's not that we just can't build a good enough measuring device -- it's that no such device can exist.

- Warren
here here! warren, for once, we agree.
 
  • #23
pelastration
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... can not exist. ,-)

“I think there is a world market for maybe five computers” Thomas Watson, Chairman of IBM, 1943

“There is no reason anyone would want a computer in their home” Ken Olson, founder of DEC, 1977

“Computers in future may weigh no more than 1.5 tons” Popular Mechanics 1949


Lord Kelvin (1824-1907), President of the Royal Society

“Landing and moving around on the moon offer so many serious problems for human beings that it may take science another 200 years to lick them”

“X-rays are a hoax”

“Radio has no future”
“Heavier than air flying machines are impossible”

http://www.nau.edu/rufis99/masterton/tsld003.htm [Broken]
http://www.brainyquote.com/quotes/quotes/t/thomasjwa103740.html

-----
I think that a particle must have a separate reality independent of the measurements. That is an electron has spin, location and so forth even when it is not being measured. I like to think that the moon is there even if I am not looking at it.
Albert Einstein

God does not play dice.
Albert Einstein

Intellectuals solve problems, geniuses prevent them.
Albert Einstein

The more success the quantum theory has, the sillier it looks
Albert Einstein

http://www.brainyquote.com/quotes/authors/a/Alberteins125184.html
 
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  • #24
Intellectuals solve problems, geniuses prevent them.
Albert Einstein

The more success the quantum theory has, the sillier it looks
Albert Einstein

Sounds like a man with a plan, but things change, not all things are true for all times.:smile:
 
  • #25
ranyart
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Some years ago I came to the 'observer dependence' principle, which is currently being brought into mainstream Loop Quantum Gravity theories.

Some time ago I had posted in [superstringtheory.com], and I got a lot of response from people in private e-mails, what I had touched upon was the original Shroedinger's Cat experiment, ie..was it a fact that Shroedinger used a Cat as a representation of conscious human observer?..and was this a failing of is ability to comprehend the situaiton if one replaces the cat with a Human?

If one replace's the cat with a Human, then looking from within the Box, one can ask of an outside observer:if the lid opens then I am/was alive before the event of lid opening. How does one know if one is alive?..Desmond Carter once said..I think therefore I am!

This is a self assertion everybody can comprehend, we cannot think outside the Brain box and assertain: I think for you, therefore you are!

The original Shroedinger experiment leaves one to ask this, if the cat is dead, once the box is opened, then it may be that when the box is closed (isolated), then you the outside observer is/am Dead.

If you share the box with the Cat, do you both share the same wavefunction?

As conscious observers we can only ask of others (cats included) what we ask of our selves, and we cannot isolate a box and its contents, without isolating ourselves from the box, this is the measurement problem, and extends from nearby Quantum Realms, to far far away locations in a universal Box!

The quantum dot's wavefunction cannot be influenced by a far away Galactic superlarge Attractor, in the same way that a Super-attractor can be influenced by the wavefunction of the very last atom, at the farthest edge, of a single Hair, on the very tip of your nose!:wink:

According to Stastistical Mechanics, if you think, therefore you PROBERBLY are! which can be interpreted as: even if you do not think?, you have an equal chance of still being dead or alive, QED.

The many worlds interpretation allows one cat to be dead, and still be able to comprehend its own existence away from its death, which some people think why Shroedinger used the Cat, it is the old saying that a Cat's:have nine lives..or many worlds..some where its dead..and some where it lives.
 
  • #26
jcsd
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Raynart, what you posted sounds simlair to the 'Wigner's friend' version of Schoredinger's cat, in which a human is place in the box to observe whether the cat dies or not. However you should be very careful aout jumping to conclusions as what you have also posted sounds a lot like 'psycho-parallelism' which is almost universally rejected as explanation of the paradox.

Basically the idea that the cat is in a suppositon of states is rejected as it does not conform to our everyday experince of cats.
 
  • #27
selfAdjoint
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Well, our everyday experience of cats that we can't see is that they might be anywhere and in any state. So on the interpretation of the wave function that it expresses our state of knowledge about something (I admit this interpretation has technical problems), the everyday cat is then in a superposition of states, which is collapsed to an eigenstate when we see the cat.
 
  • #28
jcsd
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Yes, but do we ever see an evidence that implies that cats are non-localized? (I asked my cat if she is ever in an uncollapsed state but she just miaowed).
 
  • #29
ranyart
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Originally posted by jcsd
Yes, but do we ever see an evidence that implies that cats are non-localized? (I asked my cat if she is ever in an uncollapsed state but she just miaowed).

Yes..but wait a mo!..I remember seeing an article in Nature that shows that Cats and Mice have a correlation within their brains?

I will dig the article out, I remember the Cat somehow influences the mouse using, well as I recall ESP?..or an equivilent phenonema, but I know it related to Quantum Entanglement States between the Cat and Mouse.

But for now, I will refrain from posting this until further orders!:smile:
 
  • #30
Quantum entaglement is a good example of today's cat, just another experiment that came up with odd results and as a result all kinds of way out there conclusions were drawn from it and of them the most profitable turned out to be a theory of parrelel universes, why?
Becuase it's the one that captures the imagination and emotions the most not reason, it's the one that would make the most sales in Hollywood. Same with the cat I think, it's just harder to go back into the history of it and see it's origins, but the key is if someone in your physics class where to suggest the cat thing today and not back then and nobody had ever heard of it before and he said that it was impossible to know from the observer's point of view so the cat is both alive and dead, we would probably immediately see it as lacking in explanation and want to know what they meant, and so they would go on to explain that instruments don't exist to see the quantum world directly just as we can't see the cat directly and so we have to use mathematical probabilities and formulas to really work with these things and it gets real complicated with probabilities but even more so with lack of detailed explanations and people trying to capitalize on real science to extend to media and make money off of hype.
 
  • #31
jcsd
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Jammieg, the Schroedinger's cat experiment has never been perfomed as due to decoherence, you could not expect to get anything other than a classical result. It is a thought experiment and is one orginally cretaed to attamept to show the absurdity of the Copenhagen interpretation.

Qantum Entanglemnt was predicted before it was tested and infact Schroedinger's cat would represent a many particle entangled system, which is why it decoheres.

For the third time, the idea that the cat is in a suppostion of states in genereally rejected, which poses the question: why don't macroscopic objects exhibit quantum behaviour? with probably the best answer being: decoherence.
 
  • #32
JKLM
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Of course we can't measure the uncertainty principle the idea is that the different possibilities exist in separate universes or exsist at the same time the second you open that box the cat becomes either dead or alive. However, there was an experiment done with light put through a small hole and how the shadows and the illuminated parts blended I don't quite remember the particulars. Anyway it shows the effect of the uncertainty principle in real life
 
  • #33
jcsd
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Originally posted by JKLM
Of course we can't measure the uncertainty principle the idea is that the different possibilities exist in separate universes or exsist at the same time the second you open that box the cat becomes either dead or alive. However, there was an experiment done with light put through a small hole and how the shadows and the illuminated parts blended I don't quite remember the particulars. Anyway it shows the effect of the uncertainty principle in real life

We can measure the uncertainty principle quite easily as a matter of factas it places a limit on our abilty to predict the outcome of experiments and this limit is easily measured. The idea of mutiple universe is only one intepretation of QM and not the convential one either.

You mean the two-slit diffraction experiment, which in the way you've described it, doesn't indicate uncertainty at all as you've described in a way which can be fully explained by classical theories.
 

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