Talk:Schrödinger's cat/Archive 2

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Archive 5

The wiretap example

I'm no expert, but I fail to see how this kind of wiretapping detection as described here can be possible.

The receiver would by itself necessarily be a measurement system, and would thus destroy the superposition of the incoming signal if it was present.

To put it more concisely:

1. There is no wiretap. A superposed signal is sent; the receiver intercepts it, collapses the wavefunction, and reports the resulting state — random, but not superposed.
2. There is a wiretap. It intercepts and retransmits the signal, collapsing the wavefunction in the process. The receiver then measures the resulting (singular) signal.

However, from the receiving party's point of view, each state in #1 has the same probability as the corresponding state in #2, so the receiving party is left with no means to distinguish between them.

Now, on the other hand, if two identical signals were sent, it might be possible to distinguish between the states by observing the interference pattern on the receiving end — if I understand this correctly. But this is not the way the system is described in the article. Sikon 12:13, 24 June 2007 (UTC)

Old-style Daguerreotype, light-sensitive film on one wall, a light on the opposite wall, and a possibly sleeping cat in the middle

We use the two-hour set up where the cannister possibly releases the gentle sleeping agent. So, all we know is that the cat may have slept sometime in the middle, or it may not have. And this is a way to find out using 1839—or earlier!—technology. The Daguerreotype was announced in 1839. And there were light sensitive coatings before that, such as silver nitrate.

So, if the light-sensitive wall is primarily shadowy, that means the cat was pacing back and forth for most of the two hours. If it’s not so shadowy, then the cat was sleeping for a goodly amount of time in the middle.

(And hopefully, either case, when we open up the box, the cat won’t be too angry at us humans. And just maybe, maybe, it will even find a way to cut us some slack.) FriendlyRiverOtter 21:35, 5 July 2007 (UTC)

I don't know where you are going with this. A hardcore Copenhagenist would just say that the film is in a superposition of different images until a human looks at it.1Z 09:13, 6 July 2007 (UTC)

Which again, is absolutely preposterous! Okay, so you have got my attention. Please continue with the story. What does a Copenhagenist say is the next step in understanding how the universe works? And more importantly, what do you say is the next step? FriendlyRiverOtter 03:26, 19 July 2007 (UTC)

I don't find it particularly plausible, but is is hard to disprove empirically. 1Z 12:16, 19 July 2007 (UTC)

I don't find it particularly plausible either, but being as charitable to Niels Bohr as we can, he likes the Copenhagen Interpretation because . . . . .

Yes, I wonder about that too. Perhaps he was simply unable to accept the idea that human conciousness was subject to quantum mechanical laws, or maybe he was repelled by the 'messiness' of having the universe split into a superposition of states every time an 'observation' is made. Does anyone know what Bohr's reasoning was? --Chetvorno^TALK 08:38, 30 January 2008 (UTC)

confusing

The Spanish version of this, translated into english via google translate, is eaiser to understand than this.203.109.224.42 11:45, 7 July 2007 (UTC)

Hello All,

I've never posted anything on wikipedia before, so here is #1. I didn't want to make the edit myself, but IMO, the "Extension" section should be deleted. The whole point is that there is none other than 2 possibilities for the state of the cat. I hope this does not offend the person who wrote it, but to some extent it shows a misunderstanding of the thought experiment.

OK, let's just put this in simple English...

I was extremely confused by this article. Can someone just explain to me this paradox in simple terms? Without too much scientifical jargon and what not?--71.62.178.53 02:59, 12 August 2007 (UTC)

• Yes, please. Just looking at it is enough to give me a headache. Elwin Blaine Coldiron 21:44, 5 October 2007 (UTC)

i swear, Schrodinger just had two tabs of strong Sandoz acid and started going on about raving cats and .. nerve gases. Zerocannon 03:15, 11 October 2007 (UTC)

To my best understanding, this is how the whole thing runs out. Quantum Physics works a little differently than standard physics. When someone talks about two or more events happening, they are really talking about probability. There is a chance that the cat is dead, but the cat has a chance of being alive as well. Therefore, they say the cat is dead and alive at the same time. This is because you cannot observe the cat because it is totally isolated and therefore you have to assume that there is a chance that the cat will die and a chance that the cat won't die. ShogoFan3000

Nope: superpositions are real and experimentally observable. S's C is supposed to satirise the idea that they can only be collapsed by human observers. 1Z 22:12, 30 October 2007 (UTC)

Yup, 1Z is right. If it was just a matter of the cat being alive or dead, with certain probabilities then no one would have a problem with it. The paradox comes from the fact that quantum theory says the cat is both alive and dead (before some looks into the box -- afterwards the different interpretations disagree even more).--Michael C. Price ^talk 20:15, 31 October 2007 (UTC)

To put in even simpler terms, you put a cat with poison in a box, or lead box, and close the lid, and you have no idea whether or not it's dead. 88.104.59.93 (talk) 20:30, 6 June 2008 (UTC)

Not quite. In simple terms: if you set up a box so what happens in it depends on the outcome of a small quantum event, reality in the box will split into separate realities, one for each of the possible outcomes. However the different realities evolve from then on separately, so there is no way for any observers or cats in one reality to detect the others, or that the splitting has occurred. --Chetvorno^TALK 23:52, 6 June 2008 (UTC)

And the really important point is that this is only true if you accept the Copenhagen interpretation of quantum physics. Schrodinger's cat was intended to illustrate that the Copenhagen interpretation has some very strange consequences. Maelin (Talk | Contribs) 05:38, 7 June 2008 (UTC)

Splitting occurs in both the Copenhagen and Many Worlds interpretations. In the CI, the splitting stops and one of the alternatives is somehow 'chosen' when an 'observer' or 'consciousness' observes the result (when the box is opened). In the MWI, the splitting continues when the box is opened, with the rest of the universe, and any observers, splitting and becoming part of the alternate realities. --Chetvorno^TALK 07:10, 7 June 2008 (UTC)

Delete the word 'consciousness' in my post above. Von Neumann and Wigner proposed versions of the CI in which superpositions don't collapse until perceived by a conscious observer (1), but they don't seem to have any support now. --Chetvorno^TALK 22:10, 8 August 2008 (UTC)

To put in even simpler terms, you put a cat with poison in a box, or lead box, and close the lid, and you have no idea whether or not it's dead. Since this keeps coming up, it might be worthwhile stating in the article that is definitely not what Schroedinger's cat is all about.--Michael C. Price ^talk 06:18, 7 June 2008 (UTC)

It is like the double-split experiment - shine light from a single source at a screen - between the two put another screen with two slits or holes in it. The pattern on the initial screen shows interference - light/less light dark/less dark/light/less light/dark... like a cross-section of the ripples of a wave. The lighter areas are where there has been a greater probability of light hitting the screen, the darker areas where there was less likelihood. (Similarly, a photograph is an interference pattern).

If you fire the light particles (photons) (or any particle really) one at a time at the screen so that there is a 50/50 chance the particle will go through either slit you will still get the interference pattern. If you try to determine which slit the particle went through you disturb the particles in their journey and the interference pattern is washed out. The wave function only exists whilst you are observing only the result on the screen - the wave function collapses when you determine something of its course from the source. In essence the particle has gone through both slits unless it is determined which slit it has gone through.

Translated to the cat scenario, there is a 50/50 chance the radioactive source will release one particle in a given time - essentially then, in that time a particle has both been released and not released - killing the cat and not killing the cat - and only opening the box will determine which is the result.

Of course this scenario is a falacy. It does not distinguish between passive observation and active observation. Passive observation is where you are in a room with the light on, and active observation is where you are in a dark room with a torch.

With passive observation, the light from a star or reflected from a tree etc. will not be paricularly affected whether you look at the star or tree.

With active observation the act of shining the light for the observation changes what you are observing - just as observing a particle can only be done by whacking it with another particle (thus collapsing the wave function).

With the cat scenario opening the box is supposed to be the active observation which collapses the wave function. It is active observation - but the wave function has already collapsed.

For 'active observation', one can substitute 'interaction'. The wave function actually collapses at the point where one particle interacts with another. In the cat scenario the wave function collapses as soon as the radioactive particle (if it is emitted) interacts with another particle. This determines whether or not the particle has been emitted in the given time period.

So the many-worlds interpretation in any long-term sense is a false conjecture. Take the instance of a pencil with a fine point, stood on that point. The wave function will determine that the pencil will fall in every conceivable direction - and so it does, initially. But unlike the many-worlds scenario - which determines that a new universe comes into existence, each at right-angles to the one in which the pencil is placed on its point - for each possible direction the pencil might fall - the direction of the pencil's fall is determined by the first interaction of the particle in the pencil (or with a particle in the immediate vicinity of the pencil) with another particle - at which point the wave function collapses and the direction of fall is established. --JohnArmagh (talk) 07:14, 7 June 2008 (UTC)

If I understand it right, this is one interpretation, the Objective collapse interpretation. But there is room for others. The motivation for the other interpretations is that the quantum mechanics equations (Schrodinger's equation) say nothing about collapse. All they say is that when a superposition interacts with the large scale world, the branches of the superposition become undetectable (decoherent from each other. So there is no way to distinguish a real collapse from this decoherence, since afterward the only evidence we have access to is from one branch. The other branches may still be out there, undetectable. So there seems to be no way to tell how long superpositions last, or if they collapse at all.--Chetvorno^TALK 01:13, 9 August 2008 (UTC)

Every time somebody does this thought experiment, God kills a kitty or not. Please, Think (or not) in kitties —Preceding unsigned comment added by 190.135.147.15 (talk) 03:41, 4 August 2008 (UTC)

Intent

Was Schrodinger's intent to illustrate how this was in reality ridiculous, or was he serious in saying that this was possible? My school teacher told me that Schrodinger never actually believed that the cat would exist in two states and was really mocking the existing theories. Is this right? Or was he really showing the majesty and complexity of the subject in an attempt to wow the layman with "dumbed-down" science for the man on the street and ignite debate amongst scientists? —Preceding unsigned comment added by 86.17.211.191 (talk) 14:19, August 29, 2007 (UTC)

The intent was to show that QM was incomplete or unfinished. --Michael C. Price ^talk 18:15, 29 August 2007 (UTC)

Very sorry - I know this isn't a forum but I'm not that clever with the sciences (I'm an arts man) and really want to understand this. So was he therefore demonstrating the incompleteness of QM by saying that the current understanding was giving us a scenario that was utterly ridiculous (in essence, an expirement that was giving results that just looked completely wrong)? It's just that everyone I know thinks of this as something highly profound and majestic, whereas I was taught that Scrodinger came up with it almost as a mockery and never intended for people to actually believe the cat would exist in two forms until observed etc etc. Many thanks for your time and thinking. 86.17.211.191 12:20, 1 September 2007 (UTC)

Schro's intent was to mock the conventional understanding of QM, but not everybody else took it like that. --Michael C. Price ^talk 14:31, 1 September 2007 (UTC)

Much obliged Sir. 86.17.211.191 19:58, 6 September 2007 (UTC)

Ensemble Interpretation Edit

I removed text that were an editor’s, unreferenced personal opinion on alleged deficiencies in the EI view to the shrodinger cat problem. The EI, by its very construction, resolves the cat problem. That is, the EI was designed to specifically avoid the difficulties associated with cat states. Objections to the EI in general, should be left to the EI page. Kevin aylward 11:54, 12 September 2007 (UTC)

"The EI, by its very construction, resolves the cat problem" Editor's unreferenced personal opinion. 1Z 12:00, 12 September 2007 (UTC)

Sure I have neglected to source the assertion, but get real now, anyone with even the slightest concept of the EI, can see that it, *if* correct, it trivially dispenses with the cat states. It is what the EI was designed to deal with. I will dig out a relevant quite just for completeness. It might even be sourced on the EI page, I will have look when I get time.

Second, the added bit to the EI on the cat is not relevant to this shroedinger cat page. It does not make any additional statements about the cat, or address the cat problem. The EI paragraph is simply there to make a statement that in the EI, it does not have the cat paradox. The EI page is the page that any claimed deficiencies in the EI should be addressed Kevin aylward 14:40, 14 September 2007 (UTC)

Superpositions are highly relevant to S's C. Some superpositions aer called "Schrodinger's cat" states as the page states. Anyone with even the slightest concept of QM would see that. 1Z 13:15, 15 September 2007 (UTC)

I reiterate the same point that Kevin aylward makes: The EI page is the page that any claimed deficiencies in the EI should be addressed and would extend it all interpretations. This article is trying to pass judgement on each interpretation -- this isn't the place for it. We should just say how each interpretation deals with the cat; leave the pros and cons of each interpretation to their respective articles. --Michael C. Price ^talk 00:52, 1 October 2007 (UTC)

I've removed the too-brief critiques of the various interpretations. They'd been annoying me for awhile, especially since they were resistant to being NPOVed. (You can't do justice to an entire interpretation in a single sentence.) Any reader who's interested in this can follow it up on each interpretation's page where they are dealt with in greater depth. --Michael C. Price ^talk 01:12, 1 October 2007 (UTC)

You don't make an article balanced by removing criticism from it. How about 1 positive point and 1 negative point under each heading? (In fact this is the way a short summary , such as a lede would be written anyway) 1Z 08:39, 1 October 2007 (UTC)

You don't make an article balanced by making 1 positive point and 1 negative point under each heading. But that misses the more important point that Kevin aylward and myself made. This is an article about S's cat, not about interpretations of quantum mechanics, which is a different subject (hence the different page(s)). Place your condensed critiques there, or at each individual interpretation's page. --Michael C. Price ^talk 10:54, 1 October 2007 (UTC)

I don't see why having only positive points would be more balanced.

S's C was intended as a critique of an interpretation of QM, so it is is relevant to interpretation.

"The essential problem of the interpretation of quantum mechanics is that exhibited by the Schrodinger cat experiment" http://eve.physics.ox.ac.uk/Personal/steane/interpret.html

1Z 12:44, 1 October 2007 (UTC)

I thought I had removed the positive points as well. If not then do remove them also. There really is no problem about writing an article about S's cat and not critiquing the interpretations. Just describe how each interpretation handles the cat and leave it at that. --Michael C. Price ^talk 13:16, 1 October 2007 (UTC)

You don't think "this makes the Schrödinger's cat paradox a trivial non issue" is positive? In any case, I don't see how removing the postive is going to be possible in principle. If you state

how a particular interpretation address S's C and stop there, it is going to sound like untrameled success. 1Z 13:48, 1 October 2007 (UTC)

SIGH --Michael C. Price ^talk 08:50, 3 October 2007 (UTC)

Please try to understand the difference between balance and an unlimited right to reply.1Z 11:57, 3 October 2007 (UTC)

Please try to understand the difference between balance, NPOV and wikilinks to other articles, and the insertion of one confused, isolated point by a maverick scholar. --Michael C. Price ^talk 12:23, 3 October 2007 (UTC)

Explain it to me then. Why does a positive recommendation without any criticism count as balanced?1Z 12:46, 3 October 2007 (UTC)

You have talent for always missing the point. --Michael C. Price ^talk 12:53, 3 October 2007 (UTC)

It's nothing like yours for not answering questions. 1Z 13:01, 3 October 2007 (UTC)

No point answering when you don't listen. Your previous point was already answered. --Michael C. Price ^talk 13:03, 3 October 2007 (UTC)

Would it be reasonable to point out that the above editor is currently being decried for his, shall we say, inadequate referencing on the Talk:Ebionites page, and is currently the subject of a request for arbitration, primarily on the basis of his circular argumentation, failure to apparently understand the concept of WP:Undue weight, and perhaps a few other concerns as well? John Carter 18:07, 3 October 2007 (UTC)

Cripes, this section is a bit err unnecessary? Anyway without wanting to add petrol etc - why does this bit of the article state: Taking this interpretation, one forever discards the idea that a single physical system has a mathematical description which corresponds to it in any way. Is this correct? Surely the whole point of is that mathematics can describe physical systems in a prabablistic rather than a deterministic way. I cannot interpret the statement in any meanigful way. Could it be expanded upon somehow, or else simply deleted? Or is that's what's being fought over here like dogs and err cats? If so, yes, delete it! It's nonesensical.
LookingGlass (talk) 23:42, 11 February 2008 (UTC)

"Taking this interpretation, one forever discards the idea that a single physical system has a mathematical description which corresponds to it in any way."

What? How does understanding the wavefunction as that of a probability deny the possibility of mathematical description? I second that this is poorly supported and should be explained or deleted. Bleedingcherub (talk) 09:32, 27 April 2008 (UTC)

Classical probability is just a lack of knowlege of initial conditions; the world still evolves deterministically. QM introduces a new, fundamental randomness into the universe that destroys determinism. The continuous evolution of a system is interrupted by discontinuous events in which, mysteriously, one of a number of possible states is selected (in S. Cat, whether the particle decays). People want to know, what is the actual mechanism that picks one or another state? --Chetvorno^TALK 20:56, 3 June 2008 (UTC)

The minimalist Ensemble interpretation, if I understand it right, just avoids this problem by saying QM doesn't specify what happens in individual experiments. This is probably the meaning of the phrase "one forever discards the idea that a physical system has a mathematical description", although it seems a little sweeping. --Chetvorno^TALK 21:53, 3 June 2008 (UTC)

Can we include medium descriptions of various interpretations?

If Schrodinger’s Cat is something that captures people’s imagination, and it certainly seems to be, let’s roll with it. Let’s use it as an in to talk about quantum physics in broader, more general terms, just like an experienced college professor might do. This is something we humans are good at, moving from a specific example to broader principles.

What I would find useful would be a couple of sentences on each interpretation, in plain English as much as we can, with footnotes to more technical sources, including perhaps other pages on wikipedia. I could even go for a medium sized paragraph on each interpretation, and if someone's not interested they can just skip that section.

I really think it’s okay to discuss something that’s discussed in greater length elsewhere on wikipedia, just like it an astronomer professor might talk about something in class that’s discussed in greater length in a physics class.

Teach. Please teach. For those of you who really know quantum physics, you have an occasion of an interested audience. And that’s an opportunity you don’t always have. FriendlyRiverOtter 20:55, 23 October 2007 (UTC)

Yes, but let's not provide half-baked and glaringly incomplete "critiques" of interpretations of quantum mechanics here. --Michael C. Price ^talk 18:43, 24 October 2007 (UTC)

You know, I’d almost rather someone be taking chances and trying to put it in plain English. FriendlyRiverOtter 20:41, 28 October 2007 (UTC)

A little knowledge can be a dangerous thing. [1] Better to drink deep from the Pierian spring of other, more relevant articles. --Michael C. Price ^talk 09:42, 29 October 2007 (UTC)

Can we start at the 8th grade level and allow our account to have some arc to it?

And a little while later, we’re progressing to the 10th grade level, and a little while after that, we’re at the college freshman level. Then the college junior level, then beginning grad student, then mid grad student. And the beauty of it is that someone can read as deeply as they can understand, and then they are struggling at their challenge level and really learning something.

And they might take a break when it feels right and maybe come back to our article at a later time.

And we continue with the advanced grad student level, the post doc level, all the way up to the most current, cutting edge research and thought going on right now. We try and summarize very recent articles, and we debate and discuss these. And when necessary, we allow the end of our article to remain a little bit ragged. Our goal being to include excerpts and links to the absolute best on Schrodinger’s Cat . . . and, and to quantum physics in general. And if someone is saying similar things in another wiki article, that’s okay. That’s perfectly fine. We can kind of run in friendly and healthy competition. FriendlyRiverOtter 20:48, 28 October 2007 (UTC)

"And if someone is saying similar things in another wiki article, that’s okay. That’s perfectly fine." Wikipedia strives to be a normalised database.--Michael C. Price ^talk 09:44, 29 October 2007 (UTC)

This is a great article!

This is by far the best Wikipedia page I have ever seen. —Preceding unsigned comment added by 68.99.242.160 (talk) 02:45, 17 December 2007 (UTC)

I agree, this is an excellent article. For me (an electrical engineer who has never taken QM) the explanations were wonderfully lucid. The explanations of the different interpretations were a little brief, but I can always refer to the main articles. Thanks and kudos! --Chetvorno^TALK 09:22, 30 January 2008 (UTC)

Too bad most of the interpretation pages are a mess. Bleedingcherub (talk) 09:36, 27 April 2008 (UTC)

And not such a great article now all the diagrams have been removed.--Michael C. Price ^talk 15:28, 27 April 2008 (UTC)

Yeah, it was better with the pictures, although I don't feel strongly enough to revert it. Maybe I'll try getting my cat to play 'dead' long enough to get a snapshot of him, and photoshop it up with some pictures of geiger counters to make some replacements. --Chetvorno^TALK 10:44, 28 April 2008 (UTC)

What's up with the pictures?

This article's pictures are ridiculous- it feels like an Uncyclopedia page. 69.121.179.87 (talk) 02:17, 4 January 2008 (UTC)

I think the pictures are cute.--89.142.61.231 (talk) 17:02, 6 January 2008 (UTC)

Yeah, wow... those are REALLY bad pictures... It makes the article look like a joke. 130.127.92.78 (talk) 05:24, 22 April 2008 (UTC)

Oh, for christ's sake, who put the pictures back in? After what we went through last time? Maelin (Talk | Contribs) 05:54, 23 April 2008 (UTC)

Okay, I've removed two of them. I'm going to see if I can get a better one made up to replace the third one. Maelin (Talk | Contribs) 05:57, 23 April 2008 (UTC)

They're back again. Please hurry with the update!--Old Moonraker (talk) 10:40, 23 April 2008 (UTC)

It was decided long ago to leave the current pictures in *until* replacements were found. --Michael C. Price ^talk 12:00, 23 April 2008 (UTC)

It wasn't, actually. Nothing was decided long ago, we just argued about it and gave up. Just leave the least awful of them in until we get a better one sorted out, we don't need three. I'm trying to organise something with an artistic friend of mine. Maelin (Talk | Contribs) 15:30, 23 April 2008 (UTC)

I got bored waiting. Done it. Note: this is the image we previously agreed was acceptable. --Michael C. Price ^talk 13:37, 28 April 2008 (UTC)

The impenetrable box

As I understand it, the experiment is a thought experiment because it is impossible to construct a 'box' that will isolate the interior wavefunction from the exterior. Is this impossible in principle? Or is there any prospect of actually performing an equivalent experiment in the future? The article says only, "...the machine proposed is not known to have been constructed." --Chetvorno^TALK 16:19, 31 January 2008 (UTC)

Impossible at the moment. Possible in principle, but a long way off. --Michael C. Price ^talk 15:50, 23 April 2008 (UTC)

Thanks! --Chetvorno^TALK 23:51, 23 April 2008 (UTC)

There's no real point in that. The box doesn't have to be impenetrable, just opaque to the observer, in order for the (approximate) waveform to apply. Actually, the experiment relies on the observer going cleanly from a state of "I have no idea" to "Dead"/"Alive" 65.96.201.130 (talk) 03:58, 8 March 2009 (UTC)

Would performing the experiment settle the controversy?

The different interpretations all agree about what is observed when the box is opened, right? Or are there subtle differences to be observed that could distinguish between the different interpretations? --Chetvorno^TALK 16:19, 31 January 2008 (UTC)

Nope, cause if the cat was dead after all, a whole bunch of animal lovers will be wanting to put you in a similar box. Besides, there a re a whole bunch of different theories stating that the cat is both dead and alive, just one in each universe, a new universe forms for each type of occurrence.68.122.8.52 (talk) 04:52, 20 April 2008 (UTC)

It's not a "controversy". It's a thought experiment. The goal is to demonstrate that, if we accept the Copenhagen interpretation, then we are forced to accept that under the cat experiment, the cat would be both alive and dead at the same time. The idea is to illustrate that the Copenhagen interpretation has highly questionable implications. Maelin (Talk | Contribs) 05:44, 23 April 2008 (UTC)

So the answer is yes? There is no way to decide between the interpretations based on what is observed when the box is opened. Oh, that's why they are called interpretations. Duh. --Chetvorno^TALK 06:33, 23 April 2008 (UTC)

Would it be useful to consider a transition state for the cat? Since death by exposure to hydrocyanic acid will involve a measurable time interval, for the sake of this discussion, let’s assume it will take 30 seconds for the cat to perish. If a light on the outside of the box is illuminated at the same instant the relay releases the hammer (to alert an observer) and precisely 15 seconds later a small, opaque cover is opened exposing a small glass window, an observer looking through this window could view the subject cat in a state transitioning from live to dead. At that instant, the cat would be half alive and half dead. Comments? —Preceding unsigned comment added by 68.157.140.49 (talk) 01:18, 15 May 2009 (UTC)

And no one has thought to perform the experiment in this manner....?

Why not take the cat and other parts of the setup and put them in a TRANSLUCENT box so you can see what happens? Is it somehow impossible? —Preceding unsigned comment added by 68.212.254.117 (talk) 03:50, 22 March 2008 (UTC)

Yes. That totally defeats the purpose of the experiment. Go read the article again until you understand why you can't use a translucent box. — Val42 (talk) 04:02, 22 March 2008 (UTC)

Because according to quantum physics and mechanics, just by looking at the cat you'll be modyfing it's state, so you can't look, even from a transparent box, because you'll change the quantum state of the cat. — makecba (talk) 22:45, 22 March 2008 (GMT -3)

Does the experiment require an impenetrable box, so no form of matter or energy could get through? --Chetvorno^TALK 06:48, 23 April 2008 (UTC)

No. (see my response to Impenetrable Box) 65.96.201.130 (talk) 03:58, 8 March 2009 (UTC)

Would it be useful to consider a transition state for the cat? Since death by exposure to hydrocyanic acid will involve a measurable time interval, for the sake of this discussion, let’s assume it will take 30 seconds for the cat to perish. If a light on the outside of the box is illuminated at the same instant the relay releases the hammer (to alert an observer) and precisely 15 seconds later a small, opaque cover is opened exposing a small glass window, an observer looking through this window could view the subject cat in a state transitioning from live to dead. At that instant, the cat would be half alive and half dead. Comments? —Preceding unsigned comment added by 68.157.140.49 (talk) 01:13, 15 May 2009 (UTC)

Cecil Adams' poem

Perhaps there should at least be a link to this in the article: http://www.straightdope.com/classics/a1_122.html —Preceding unsigned comment added by 76.21.8.213 (talk) 04:37, 22 April 2008 (UTC)

Oh, I see it is linked way down in External Links. 76.21.8.213 (talk) 04:39, 22 April 2008 (UTC)

Cat vs human

The article says that the cat is simultaneously alive and dead "until we look at it". That implies an enormous difference between cats and humans: that cats aren't sentient and humans are, because the cat is watching and still there would be no certainty of the state of the poison, not even for the cat?

However, in the box there is a 'detector' (the cat) watching the poison. Therefor there is a 100% certainty for that detector which state the poinon is, and it is not simultaneously alive and dead.

Either that, or the world would be extremely relativistic: for the cat, the poison is either released or not released, but for any other detector (we), the poison is both at the same time. There is in that case no difference between cats-humans and humans to each other. That means that every human would live in an extremely different world, not just contracted or time-dilated, but just entirely different, as for one human certain objects have a certain location/speed, while for other humans, it may only be a probability that the object exists.

We should invent a new saying: as weird as quantum mechanics. Apography (talk) 09:41, 1 May 2008 (UTC)

Whether you treat the cat -- or poison -- as an observer or not is an interpretational issue. --Michael C. Price ^talk 10:27, 1 May 2008 (UTC)

That's what I've never understood about this experiment. The cat is a living creature. If it's still alive, there's an inside perspective because it knows it's alive. Maybe not conscious enough to be self-aware, but it still has neural functions and reacts to its surroundings. It seems to me that just because the humans who put it into the box don't know whether it's alive or dead, it doesn't mean that it's BOTH. Maybe to them, but not to the cat. It seems to me like this doesn't explain anything, and the cat is a poor example. It would be a better example to use an inanimate object that would be destroyed or not destroyed. Or, this experiment is a GREAT example of why people love to put so much stake in things they don't know, thinking it's fact. If the only reason we assume it's both alive and dead is because we don't actually know, isn't it equally as likely that the cat disappeared, or mutated into a ball of sentient energy, or has been replaced by a stack of pancakes? That's just as realistic as saying something is alive and dead at the same time. 74.76.142.137 (talk) 18:29, 2 June 2008 (UTC)

The article may be a little vague about the conditions of the experiment. The reason we assume the cat is both alive and dead is not just "because we don't actually know". In the first place, the box must be impenetrable, so no information can get out. Secondly, the setup of the experiment must make the large scale state of the box (dead or live cat) dependent on a quantum event, the decay (or not) of a particle. Under these conditions, quantum mechanics says a peculiar physical state will exist inside the box until it is opened: each of the alternate 'histories' resulting from possible outcomes of the event will unfold in parallel in the box. Possible outcomes; no pancakes or balls of energy. They will be 'decoherent', in separate 'Hilbert spaces', so they will not interact.

This splitting of reality, or mixed states, has long been observed on an atomic scale; as interference patterns that indicate that a single electron is in two or more places at once. What is not known is whether these separate realities persist when the differences between them have evolved in time from just a few particles to the point of large macroscopic differences, such as a live cat versus a dead one. Everything in QM says they do. However, because of decoherence, any cats or observers or scientific equipment in one reality cannot detect the others. --Chetvorno^TALK 21:53, 2 June 2008 (UTC)

Would it be useful to consider a transition state for the cat? Since death by exposure to hydrocyanic acid will involve a measurable time interval, for the sake of this discussion, let’s assume it will take 30 seconds for the cat to perish. If a light on the outside of the box is illuminated at the same instant the relay releases the hammer (to alert an observer) and precisely 15 seconds later a small, opaque cover is opened exposing a small glass window, an observer looking through this window could view the subject cat in a state transitioning from live to dead. At that instant, the cat would be half alive and half dead. Comments? —Preceding unsigned comment added by 68.157.140.49 (talk) 01:26, 15 May 2009 (UTC)

The issue is not that, once the hammer falls, the cat takes time to die and thus is "half dead" at some point. The issue is that (in the Copenhagen interpretation) "reality splits", and the two incompatible outcomes or histories, "hammer falls/cat dies" and "hammer does not fall/cat lives", exist simultaneously in a superposition in the box. If the cover is taken off the window so an observer can see in, the superposition will collapse and all evidence of one of the histories will disappear retroactively, leaving only the other outcome. --Chetvorno^TALK 11:45, 9 July 2009 (UTC)

observer doesn't split, only a few brain cells

I don't like the way that this is traditionally explained as "the observer splits". The observer doesn't split into 2 completely separate people that start living their lives from that day forward in different ways. No, a few memory brain cells in the observer have different values about whether the cat was alive or dead and how the person felt about seeing a dead cat. The observer still went home, made dinner, got drunk and went to sleep. Then he got up the next day and did another 30 cat experiments, not really caring that much what happened :) Seriously, though, it's an important distinction. A dead cat doesn't split a world, it just splits a few aspects. The split is real, but the observer will probably still end up having chicken for dinner in either world. 81.154.198.63 (talk) 23:51, 9 May 2008 (UTC)

Whether the observer splits or not is an interpretational issue. --Michael C. Price ^talk 05:42, 10 May 2008 (UTC)

If I understand it correctly, in the many-worlds interpretation the observer actually does split, along with the rest of the universe. --Chetvorno^TALK 23:39, 15 May 2008 (UTC)

The observer splits when the observation is made. The rest of the universe splits as it comes into causal contact with the observer and/or cat (i.e. the splitting spreads at the speed of light or less). --Michael C. Price ^talk 18:53, 16 May 2008 (UTC)

Article is misleading, gives impression splitting is only a mental phenomenon

The above 2 discussions ('Cat vs. Human' and 'Observer doesn't split') indicate that the article as it now stands is misleading people. They're getting the idea that the splitting of states in the box is somehow only a mental phenomenon, or the experiment only demonstrates the philosophical idea that nobody knows what happens in a box until it is opened. I think the main problem is the 2nd paragraph, it should either be rewritten or removed. Thoughts? --Chetvorno^TALK 18:24, 3 June 2008 (UTC)

You are right. The 2nd paragraph of the article is erroneous. It is not describing the Schrodinger cat thought experiment, it is describing a philosophical question about knowledge of unobserved events. In contrast, the Schrodinger cat thought experiment crucially relies on a quantum effect generating a quantum superposition. How about changing it to:

"In simple terms, the thought problem involves a cat placed in an opaque box with a sealed vial of poison that will be triggered by a random quantum event. Since these kinds of events exist in superpositions before observation (i.e. a mixture of "happened" and "didn't happen"), the cat would enter into a superposition of "alive" and "dead" states--at least until someone opens the box to make an observation."

I know this wording isn't nearly as simple as what the article currently has--but I don't see any way to describe this experiment without mentioning the concept of a superposition. Reducing the problem to a simple "we don't know what's going on inside a sealed box" totally misses the point. --Kebes (talk) 16:21, 4 June 2008 (UTC)

I suggest you delete the 2nd paragraph -- isn't it all covered in the diagram text? --Michael C. Price ^talk 09:38, 5 June 2008 (UTC)

I have deleted the 2nd paragraph, since a more accurate explanation is given by the diagram (which is what most newbies will probably read first, anyway).--Michael C. Price ^talk 13:07, 5 June 2008 (UTC)

I concur. I was just trying to think of something to put in its place. --Chetvorno^TALK 18:44, 7 June 2008 (UTC)

This is me, discussing some changes

• Tag for expert

My intention in adding this tag was to address and as a precaution about the repeated questions on the practical explanation of the subject that seemed to come up on the talk page; I would especially want to point out that the tag I added specifically referred to attention for the introduction of the article.

• Links

Roughly speaking, I suppose I should have mentioned more specifically that I removed most of these links meaning to balance the article away from the rather un-academic attitude most readers seem to be approaching the subject with (at least judging by, again, a—granted—rather un-scientific observation of a trend in the anonymous questions and edits).

Specifically, my concern in removing the Commons link was only about that it didn't seem to add any clarity or context to the article and that it seems to shift the focus of the article negatively or at least distractingly away from, again, reading with an academic tone; having said that, though, I'd understand having the link if I'm missing some specific reason or policy.

With the first few links (A Lazy Layman's Guide to Quantum Physics, Quantum Mechanics and Schrodinger's Cat, and The many worlds of quantum mechanics), I couldn't find either obvious academic credentials and credibility or added information specifically on the subject (as opposed to on 'quantum physics' in general) that wasn't already encapsulated in the article. (Per the external links guidelines; specifically, the basic definition of acceptable links)

I have noticed that I was too hasty in removing the "EPR Paper" link; I assumed it was just the abstract and that you couldn't access the actual paper without a subscription.

Otherwise, the last three links (lyrics, comic, comic) would seem to belong, if anywhere in the "... in popular culture" article; the lyrics and the first cartoon only reference the subject, and the second seems only to discuss it in the context of some existing story.

Sorry about the length here, I'd have to say that my level of involvement here seems to ebb and flow without much control on my part.

Thanks, ~Wikimancer X *\( ' ' ^) 07:29, 7 June 2008 (UTC)

Thanks for the explanation. I missed that you were specifically calling attention to the introduction (and which I agree needs attention). I'll move the pop links to the popular culture article. The only change I think is wrong is the removal of the commons media link. --Michael C. Price ^talk 08:54, 7 June 2008 (UTC)

Edits around June 7, 2008

Trying to gather my thoughts about recent changes to the first 3 sections. --Chetvorno^TALK 18:53, 7 June 2008 (UTC)

It's mostly re-arrangements, so most of the material should still be there. But the introduction was just getting too long (they are really meant to be brief), so I moved a lot of it into a new section. Hope it helps. --Michael C. Price ^talk 21:03, 7 June 2008 (UTC)

The new section is good. However, I question whether it should include background information and the connection to EPR. Maybe the 2nd section should be devoted to a plain language description of the experiment. The historical info is great, but I somehow feel it belongs in the 3rd section, with that wonderful Einstein quote. --Chetvorno^TALK 20:42, 20 June 2008 (UTC)

I've increased the size of the caption text, which is the closest we have to a "plain language description" and I don't really want to copy this into the article itself (unless that's the consensus?). -- but, as we have seen, plain language description can easily miss the point of the experiment, which is quite subtle and technical.

I agree there is an uneasy overlap between the 2 sections. Not sure how to resolve this at the moment -- perhaps they should be merged?--Michael C. Price ^talk 07:23, 21 June 2008 (UTC)

Does article overemphasise the cat?

Some parts of the article imply that the presence of the cat is an important part of the experiment. As far as I understand them, few of the interpretations rely on the agency of a 'conscious' observer, and none require one inside the box. One such dubious sentence: "...our intuition says that no observer can be in a mixture of states, yet it seems only cats can be such a mixture." Why "only"? --Chetvorno^TALK 03:55, 21 June 2008 (UTC)

The "only" looks like an error. Now rephrased. --Michael C. Price ^talk 07:17, 21 June 2008 (UTC)

New lead image

If you have comments or suggestions for improvement of the new lead image please place them here (slow turnaround) or on my talk page (fast turnaround). Dhatfield (talk) 16:17, 26 June 2008 (UTC)

Thanks for this edit. The new image is undoubtedly clearer than the old, but it's missing the representation of "superposition", possibly the key concept. Would it be possible to do this while retaining the clarity? --Old Moonraker (talk) 17:32, 26 June 2008 (UTC)

My thoughts also --superposition is the key concept, which is not represented in the diagram. The previous image represented the concept of superposition by showing the two cats superimposed. This has now been lost. --Michael C. Price ^talk 21:50, 26 June 2008 (UTC)

I agree. --Chetvorno^TALK 23:00, 26 June 2008 (UTC)

It is quite easy to superimpose them with transparency, but clarity does suffer, particularly in the poison vial-hammer area. I will do a new version and the community can decide. Dhatfield (talk) 11:24, 27 June 2008 (UTC)

Thanks for your comments - done. Dhatfield (talk) 11:40, 27 June 2008 (UTC)

Ah, much better. Thanks. Didn't Bohr say that truth and clarity are complementary? --Michael C. Price ^talk 14:42, 27 June 2008 (UTC)

Excellent. It was really nice to work on such an iconic image. If there are any further comments, or if you have requests for further images, please post them at Wikipedia:Graphic_Lab/Images_to_improve#Schrodinger's Cat. Cheers. Dhatfield (talk) 11:39, 28 June 2008 (UTC)

Explanation for laymen?

I am not a layman in physics, but I am certainly nowhere near an expert. And even less in quantum mechanics. To me it just sounds... hmm... "ridiculous". I mean, I could travel into a jungle and die. Nobody will find my body EVER. And quantum mechanics states that maybe I am NOT dead? That's how it sounds to me. I would VERY MUCH appreciate someone to explain the cat so that laymen can understand. In my mind, either I'm dead, or I'm not. Either the cat is dead or it's not. If I die right now, but no one finds my body until a week later, does that mean that during that week I am both alive and dead? 68.200.239.84 (talk) 01:01, 19 July 2008 (UTC)

I'm not sure that a "lay" explanation is possible. It's been tried before here and then deleted because of inaccuracies. Try this: you'd be dead in the the universe where you're just a decaying corpse (found or unfound), but alive in those universes where you:

• didn't go to the jungle
• went to the jungle but

• didn't die
• died momentarily before reviving.

--Michael C. Price ^talk 04:54, 19 July 2008 (UTC)

This is fucking ridiculous. Years ago, scientists mock people who believe in other dimensions (and often by extrapolation, beings from other dimensions) and now they include the idea in their theories?

That's right; scientists have found that whether something is viewed as "fucking ridiculous" or not is not a useful guide to the truth. Live with it. --Michael C. Price ^talk 08:49, 11 August 2008 (UTC)

The Cat is supposed to be ridiculous. It's a reductio ad absurdum.

Mr Price's contribution is the many worlds alternative: it is not a fact or "what quantum mechanics says" in any uncontroversial sense. 1Z (talk) 14:10, 19 July 2008 (UTC)

Which is why no lay explanation is possible, because we have to get into the whole controversial interpretation business. --Michael C. Price ^talk 20:17, 19 July 2008 (UTC)

OK. What I understood from these replies is that it COULD be a "many worlds" explanation, but it may be something else. Am I correct in saying that quantum theory is not developed well enough and that even experts are mostly "grasping in the dark"? I had the impression too that the cat is ridiculous because of Stephen Hawking's remark of reaching for his gun. But is the cat REALLY a paradox? Apart from the very short time between someone being alive or dead, it seems to me that someone is either alive or dead (and I'm not even getting into "philosophical" topics, so lets keep this to animals (humans)). And it seems to me that, UNLESS there are multiple worlds, this (apart from the very short time I just mentioned) is pretty well "defined". I know that sometimes reality is stranger than fiction. Is this an explanation for the cat? That it MAY be an explanation that defies common sense? 68.200.239.84 (talk) 17:21, 19 July 2008 (UTC)

The idea that collapse occurs for objective reasons before the box is opened is another alternative.1Z (talk) 07:29, 22 July 2008 (UTC)

I won't paste it here, but I suggest you read the last paragraph of the origins and motivation section. --Michael C. Price ^talk 20:17, 19 July 2008 (UTC)

OK... the bizarreness. I understand the pointer. And I understand that physics sometimes is much stranger than "common sense". But I'm STILL a layman. And I asked a layman's explanation. Do even quantum physicists take Schrödinger's Cat seriously? While I'm willing to accept a "many worlds" explanation, I'm not ready to accept a situation in which the cat is both alive and dead and to lay the responsibility of someone else like me killing the cat soleley on me opening or not opening the box. So, I, an innocent bystander, could kill the cat just by opening the box? Is that what it is? If that's the case, then I, an innocent bystander, theorectically have the "power" to INNOCENTLY kill any and every living being by my observations... because it makes it seem like just because I witness something happening, it MAKES it happen. And, if that's the case, then *I* am the one who made it happen. Then *I* am the one who killed someone by my action of observation. So I am guilty of murder, JUST because I witnessed it and THEREBY made it happen? 68.200.239.84 (talk) 01:33, 22 July 2008 (UTC)

Being able to trigger a collapse, if you are, does not ential being able to choose the outcome of it. Without choice, it is difficult to see a moreal dimension1Z (talk) 17:09, 22 July 2008 (UTC)

What about playing Russian roulette with a gun against someone's head? It's very similar to opening the box. The end result is random but the only way you are not responsible is by not pulling the trigger or not opening the box, in a sense. What about someone sitting in a room slowly starving to death, and the only way getting inside is to open a door, whose knob is tied to the gun trigger? Shouldn't you open the door as soon as possible, as opposed to not wanting to be responsible, and instead letting the person inside starve? Sillybilly (talk) 22:56, 1 August 2008 (UTC)

The concept of guilt is very far from the topics of quantum mechanics. If you're trying to pick apart guilt and law and ethics, we can start with the bears catching the salmons and murdering them, and then wasting most of the fish's body and only eating the brains out and scattering the rest inside the forest. These fish are a nitrogen fertilizer source that the forest cannot exist without. Are the bears guilty? Would you be guilty for opening the box? Sometimes stuff just is, the way it is, without ethics in the picture, and assigning guilt or crime to an event is just a whole different topic, a separate issue and subject to some debate. Ethics originates in how people want to live, how they feel about the whole thing, what kind of society they want to live in. Ethics originates from people's souls, not in pure facts. It originates in how people feel. As far as a jury of 12 sane people randomly selected from the population is concerned, I think you'd be fine, they'd let you go, but they'd go after the animal torturing bastard who actually creates something this cruel, in real life, with a real cat inside it. There is a large divide between thinking about something, as a mental exercise, and actually doing it. So you can probably sleep well, and don't be paranoid to open boxes, it's not your fault if there is a dead cat in it, even if technically you caused it. In fact you should go ahead and open the box as soon as possible, because the probability of the kitty jumping out of it alive decreases as time goes on. Sometimes inaction is a crime, and you'd be guilty for not opening the box, though less guilty than the person who set it up in the first place. Sillybilly (talk) 04:12, 22 July 2008 (UTC)

He has a point. It's true that if the box is never opened, both branches of the superposition will continue inside, in one of which the cat is alive (presumably getting hungry), and in the other it is dead (its body decaying). While if the box is opened, the superposition will collapse and one of the branches will randomly become reality, while the other one will 'disappear'. If the one that 'disappears' is the one with the live cat, opening the box might be said to have 'killed' the cat in that history. Maybe QM will require us to get used to new moralities. However, it is not clear (to me) how 'real' the branches which disappear from the superposition are, or what happens to them when the superposition collapses. All this just applies in the Copenhagen interpretation; in the other interpretations there is no collapse so the issue doesn't arise. --Chetvorno^TALK_CONTRIB 08:48, 22 July 2008 (UTC)

No, they won't. The superposition is not collapsed by observation per se, it is collapsed by interaction - interaction of particles which have determined whether the radiation has been released with those which have yet to determine that. It just happens to be that, unlike the macroscopic world, where observation can be passive (just looking) or active (whacking something with something else to get a result), in the quantum realm one is limited to active observation, which is interaction. So by the time the 'box' is opened the decision has already been made by the interaction of particles which had taken place whilst the 'box' was still closed --JohnArmagh (talk) 14:02, 22 July 2008 (UTC)

That is one view, and a consistent one, but no one can assert with confidence at what point a wavefunction collapses, or even that it does at all, since collapse has never been observed. We observe decoherence, not collapse. --Michael C. Price ^talk 14:36, 22 July 2008 (UTC)