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Schrodenger's cat

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#26 star drop

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Posted 07 May 2013 - 11:06 AM

I know I am in way over my head here, but I gotta ask someone! what is it that I am not seeing about this cat? If an atom decays, the cat is dead. well , that's easy enough. and if an atom does not decay, the cat is not dead. that seems to be another easy. so where is the overlap of the cat being BOTH dead and alive at the same time? is it the speed in which an atom MIGHT decay?
as I said, I am trying to understand something probably way over my head, so if someone cares to answer, please try to use layman's terms.

Thanks, Theo

If I may run with the question further I would like to delve deeper. In general terms very large atoms don't hang around very long. They sometimes emit multiple alpha particles at the same time. When these particles are in the process of forming in the large nucleus just before being emitted, what makes them special from the rest of the nucleons, can quantum theory explain why the helium nuclei are not ejected one by one as is the customary case? As they form are they quasi dead in respect to both the parent nucleus and the forming helium nucleus? Particle or wave, explain it either way in layman's terms if possible.

#27 TVG

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Posted 07 May 2013 - 02:37 PM

What would happen in a similar experiment to the double slit if the same particle was measured multiple times with different expectations for a wave or a particle each time. In other words does the wave of probability collapse only once per particle per observance and that particle must remain in that state forever or does each new observance of the particle bring about a new state of existence. Sorry if that is a stupid question, but I am enjoying this thread immensely, even if it is way over my head.

Todd

#28 dickbill

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Posted 07 May 2013 - 03:09 PM

The 'cat in the box' is not the best example, it's probably the slit experiment that examplifies best the problem, according to the physicist Richard Feynman.

Take a single photon moving in the direction of a screen with 2 slits before he finally hits a screen or a camera.
If this photon is like the bullet of a gun, it will go through one slit since it cannot be at two different places in the same time. If instead the photon behaves like a wave, like we get on water, it will go through both slits at the same time and produce an interference pattern on the screen and camera.
Now, even if a photon is a particle, in quantum theory it can be in two places at the same time (with a probability given with a function), and produce an interference pattern like a wave. Even if you send photons one by one, one at the time, they will still produce an interference pattern, that is, until you don't 'observe' them.
If you put a detector under each slit to detect which slit the photon went through, the interference figure is destroyed. But as long as the photon is not observed, his position in space is really a superposition of possibilities, or states. That's because of the quantum nature of the photon, as opposed to a macroscopic object like a bullet with no quantum indetermination. That is, whether you observe a bullet or not, it will go through one slit only, not both.

Anyways, in the story with the cat, the quantum undertermination is supposed to be transfered to the cat which in this case, can be in a superposition of states dead or alive, as long as you don't observe it. The cat has become entangled with the original quantum event.

it's better described here
http://en.wikipedia....um_entanglement

For those interested in the nature of the mind, we could ask if a quantum entanglement could somehow be transfered to 'brain activity'? the experiment i was refering above (human meditators focusing their mental attention on a remote slit apparatus), came from a blog site called 'Entangled Minds'. Now you understand the connection. Whatever we can think of it (of the Mind, forget the cat), i think it's a valid question to ask, and valid to test it by experimentation.

PS: i'm not the author of the blog.

#29 Mister T

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Posted 07 May 2013 - 08:08 PM

he's not dead yet

he's almost dead

actually I'm feeling better

#30 llanitedave

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Posted 07 May 2013 - 11:11 PM

You're not fooling anyone.

#31 cavefrog

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Posted 07 May 2013 - 11:45 PM

well at least I got it that the cat can be let out of the box , fed, and sent on his way because he is only a distraction.
some things said are starting to fall in place. superposition is something I have not come across. this is my first exposure to it. the double slit experiment, I have read about before. I think I came across it in ham radio, but I seem to have a misconstrued understanding. I had the belief that the slit experiment was supposed to determine if "something" was a particle or a wave. I do think that something was a photon. again, a photon in my understanding has not been determined to be a particle or a wave, which makes it unknown whether it has mass or not. or maybe both?
fluctuating back and forth? is this where the superposition comes in? to add to this is a statement that I came across lately, that Heisenburgs uncertainy principle has often been confused with the "observers effect". again, as I understood, Heisenburgs uncertainy principle says something like a particles speed and position cannot both be determined at the same time. one can only know either speed OR position , but not both.
so... maybe none of this has anything to do with the subject, but if determining a particles state is dependent upon being observed at a particular monent... sure sounds like obsevers effect to me.
the way a lot of this stuff is linked together makes it all very confusing. I was running in circles with absolute zero questions too. but like I said, I grasp alittle here an there.
does any of this make any sense? or am I totally discombobulated?

somehow I feel its all connected!!!! :>)

Theo

#32 Rick Woods

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Posted 08 May 2013 - 12:19 AM

You're not fooling anyone.


Look, isn't there something you can do?

#33 Pess

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Posted 08 May 2013 - 08:00 AM

What would happen in a similar experiment to the double slit if the same particle was measured multiple times with different expectations for a wave or a particle each time. In other words does the wave of probability collapse only once per particle per observance and that particle must remain in that state forever or does each new observance of the particle bring about a new state of existence. Sorry if that is a stupid question, but I am enjoying this thread immensely, even if it is way over my head.

Todd



You are reading far too much into the thought experiment. One event=one outcome.

All The Cat Thought Experiment was meant to show that if you link a quantum event to a macro event than superimposition applies equally to both the quantum AND macro world.

The implications of this idea is staggering. What it means at its most core level is that the physical world as we we perceive it doesn't exist until we sense some portion of it.

In other words, we form the Universe by our observation of it....

Pesse (I see it, therefore I am it) Mist

#34 dickbill

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Posted 08 May 2013 - 11:31 AM

"..All The Cat Thought Experiment was meant to show that if you link a quantum event to a macro event than superimposition applies equally to both the quantum AND macro world..."
Yes, that's the point of the tought experiment, except my understanding is that you cannot link a quantum event to a macro event and therefore a macroscopic system cannot be in a superimposition of states.
I mean any macroscopic system which entropy will change will provoke the probability function to collapse. And if the entropy has changed, the arrow of time has been activated.
If the entropy has not changed, it's because nothing has happened.
I wonder if it could be reworded as: as soon as the quantum event 'feels' the arrow of time, it ceases to exist as a superposition of states.

#35 Pess

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Posted 08 May 2013 - 11:37 AM

...except my understanding is that you cannot link a quantum event to a macro event


The entire point Schrodeniger was making is that you CAN have a macro object in a superimposition state.


"arrow of time has been activated' Hunh?

Time is not an arrow, nor can it be described in isolation any more than you can talk about the length of an object and ignore its width and height.

Pesse (Spacetime is a better nom de plume) Mist

#36 dickbill

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Posted 08 May 2013 - 04:31 PM

I was refering to the definition popularized by Stephen Hawkins:"the arrow of Time points in the direction of increasing entropy".
That's in his 'Short History of Time' If i recall.

Schrodinger wanted to play games with this story with the cat. When he invented the story, maybe he was frustrated, or just drunk. Beside, the endresult of the experiment could be used to make a reductio ad absurdum: since not cat can be dead or alive, then no macroscopic system can be in a superposition of states and no macroscpic system can be entangled with a quantum event, and you might say it was exactly THAT point Schrodinger wanted to make.

#37 Pess

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Posted 08 May 2013 - 05:00 PM

I was refering to the definition popularized by Stephen Hawkins:"the arrow of Time points in the direction of increasing entropy".
That's in his 'Short History of Time' If i recall.

Schrodinger wanted to play games with this story with the cat. When he invented the story, maybe he was frustrated, or just drunk. Beside, the end result of the experiment could be used to make a reductio ad absurdum: since not cat can be dead or alive, then no macroscopic system can be in a superposition of states and no macroscpic system can be entangled with a quantum event, and you might say it was exactly THAT point Schrodinger wanted to make.


I certainly can't argue with you. What you say might be valid. But regardless of Schrodenger sobriety at the time, his logic is not flawed: If superimposition as a state of a quantum particle is a valid state, then it follows that if you link a quantum event with that quantum particle to a macro event than both MUST be in superimposition states.

So what was Schrodeniger being absurd about? Superimposition of quantum particles in general?

And if it is so absurd, why has the world of physics so embraced the analogy?

We exist in a sea of unformed energy.

I actually don't have any problem embracing this concept. Eastern disciplines have long talked about the energy of the Universe. Even Motivational speakers understand the idea of positive thinking.

The Universe is a blank slate of energy. We give it form and function by our perception of it. Viewing things in a negative light can lead to negative views of our own unique universe (bad karma, bad energy, Poison Qi).

Physics is just now seeing this in the concept of quantum uncertainty. Certainty can only come AFTER perception (measurement).

Pesse (To control the Universe, one only has to see it in the proper light..) Mist

#38 Rick Woods

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Posted 08 May 2013 - 05:36 PM

The Universe is a blank slate of energy. We give it form and function by our perception of it. Viewing things in a negative light can lead to negative views of our own unique universe (bad karma, bad energy, Poison Qi).

Physics is just now seeing this in the concept of quantum uncertainty. Certainty can only come AFTER perception (measurement).


I'm sure I'll be shot down here, but it seems to me that certainty is merely a function of our own perception of things. Things are what they are, whether we perceive them or not. If the cat is dead, it's dead whether we're sure of it or not. The falling tree made noise. Our perception of these events does not affect their objective reality (or lack of it). Why on earth would it?

I know, I know: We change the fact by observing it. But why do we think this? What makes us think things were one iota different before we observed them, than they were afterward?

What am I missing? It's been nearly 20 years since I read "Brief History of Time", and I've lost whatever edge I had back then on this stuff. But the cat, etc; it all just seems like sophistry to me.

OK, open fire. I can take it. :D

#39 deSitter

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Posted 08 May 2013 - 05:38 PM

The problem is, the cat does not have a prepared state. For example, the cat may be genetically resistant to cyanide. Classical statistical mechanics may cause the cyanide atoms to accumulate in the corner while the cat breathes free. Et cetera - I can invent a billion scenarios in which the cat is not connected to the microstate. There is no actual connection. The cat is simply a distraction. The states that are connected by superposition in an observable manner, must both be capable of being put into a prepared state - an eigenstate of the corresponding observable - and there is no operator of liveness or deadness. It's simply a pointless mind game. You can play the very same mind games with any logical system, including classical mechanics (tree falls etc).

-drl

#40 dickbill

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Posted 08 May 2013 - 08:10 PM

...and there is no operator of liveness or deadness. -drl


WHAT !, what are you waiting for?

#41 David Knisely

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Posted 09 May 2013 - 02:03 AM

I would hang old Schrodinger for the way he treated that cat! :) As for me, I long ago concluded that the photon is a particle whose behavior is dictated by the statistical probabilities given by quantum electrodynamics. In large numbers, statistically the distribution of photons does display some wave light properties, but individually (or in individual single-photon events), I consider them to be particles. That ended all my headaches about trying to make it into both a wave and a particle. Clear skies to you.

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#42 dickbill

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Posted 09 May 2013 - 08:36 AM

Clear skies to you too, but that's not correct. Photons sent one by one towards the two slits will still produce an interference pattern on the projection screen. To do that, the single particle photon must have been through the two slits at the same time. Same thing for single electrons sent one by one to the slits, they will produce an interference pattern....as long you don't try to find out which slit they went through.

#43 jchaller

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Posted 09 May 2013 - 12:01 PM

Looks like my cat - who prefers to sit on my lap when I have something better to do. He might disagree with me referring to him as "my cat".

#44 TL2101

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Posted 09 May 2013 - 01:49 PM

Is it true that on the double slit that if the detectors are on but the data is never collected that you will get an interference pattern.

In other words it is the data not the detector collapsing the the wave?

If this is true (must be I read it on the Internet) its implications are mind bending. :question:

#45 dickbill

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Posted 09 May 2013 - 06:00 PM

No it's the detection. It also makes sense, or let's say it's not surprising, since to detect the photon or electron, you need to make it interact with something, like another photon.

But let's go ad absurdum again, if the quantum event could be entangled with a macroscopic system, first the geiger, then the cat, when or when would that stop?
There is no reason the entanglement would stop at the cat, the box should be entangled as well, then the outside observer and everything else that is causaly related. An infinite chain of observers is then absolutely necessary: You know the cat is alive because you watch him, but how do YOU know that YOU are alive? somebody must be watching you and so on...

#46 deSitter

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Posted 09 May 2013 - 06:17 PM

dickbill, good point.

-drl

#47 TL2101

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Posted 09 May 2013 - 10:20 PM

No it's the detection. It also makes sense, or let's say it's not surprising, since to detect the photon or electron, you need to make it interact with something, like another photon.


That makes sense but what about the delayed choice experiment. Doesn't it hit a detector but is then erased showing an interference pattern?

The only reason I ask is there is a NASA physicist with a book that claims it is the act of knowing the data that collapses the wave function. He goes into quite a bit of detail about it.

Are all these physicists like Greene and others that write books for the general public a bunch of charlatans who can't be trusted? I am too old to learn physics so I have to trust someone for whats going on in the science community.

And why do physicists pick on cats? Shouldn't they use rats like other scientists? :grin:

#48 David Knisely

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Posted 10 May 2013 - 02:38 AM

Clear skies to you too, but that's not correct. Photons sent one by one towards the two slits will still produce an interference pattern on the projection screen. To do that, the single particle photon must have been through the two slits at the same time. Same thing for single electrons sent one by one to the slits, they will produce an interference pattern....as long you don't try to find out which slit they went through.


Nope, a single photon sent towards a two slit setup will appear at a single location on the screen behind the slit, and not as a "pattern". The next photon sent through the 2-slit system will hit the screen behind the slits at a different location on the screen, and the next one after that at a still different location, and so on. If one keeps this up and keeps track of where each one hit the screen, eventually, you will see a banded distribution of photon locations on the screen which mimics the two-slit diffraction pattern seen for wave mechanics. This is the probability distribution for the two-slit experiment. If you have a whole huge stream of millions of photons going towards the screen, then the two slit diffraction pattern does appear, but for single photons, all you can see are single tiny impact spot locations and all you can calculate is the probability that a photon will hit a given location on the screen. More will hit certain locations than others, and if you do the statistics, the distribution of the photon impact locations looks just like the double slit pattern for wave mechanics. Clear skies to you.

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#49 freestar8n

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Posted 10 May 2013 - 03:32 AM

I'm not sure how you get comfort viewing individual photons as "particles" when they don't follow ballistic trajectories. Those individual photons land in completely non-classical locations. The fact that individual locations behave according to the overall distribution expected from classical wave interference, and yet each one appears to "hit" at a single location, is what particle/wave duality is all about.

As for Schrodinger's cat - I view it as using words and analogies way outside the intended scope. A "particle in a box" with a separate observer "opening" it is an abstract and well defined concept - but a macroscopic cat in a macroscopic box with a macroscopic observer opening it is totally different. It is all a single system and there is no separation of the experiment from the observer and the observation. It's a single system "in a box" and there is no clear description of it that makes the observer distinct from the system being measured.

So if any conceptual paradoxes arise from pondering it - it doesn't really matter since it isn't following the rules of the game in the first place.

Frank

#50 Charlie B

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Posted 10 May 2013 - 08:14 AM

Two-slit experiment 2012!

I believe I would go with David on this point.

Charlie B






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