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Schrodinger's Cat vs. The Principle of Explosion

  1. Sep 17, 2013 #1
    onsider the following link:


    Now, consider Schrodinger's Cat. Does this not imply the following statements?

    - A) The cat is alive before the box is opened.
    - B) The cat is not alive before the box is opened.

    Aren't both of these statements supposedly true?

    Now, consider the following proof based on the principle of explosion:

    1) The cat is not alive before the box is opened or Santa Claus exists. (From A))
    2) The cat is alive.
    3) Santa Claus exists (because 2) contradicts A) and 1) must be true - just like the Wikipedia link states).

    Therefore, is the principle of explosion wrong or is something wrong with the notion of Schrodinger's Cat? (Or something else?)

    Last edited: Sep 17, 2013
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  3. Sep 17, 2013 #2


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    No, it does NOT imply the two statements you give. What it implies is that the cat is in an "indeterminate" state of "neither alive nor dead" but some combination of the two.
  4. Sep 17, 2013 #3
    I'm not a physics major. I'm a philosophy major studying logic and have only read about quantum physics in my spare time. That's why I wondered... Is that okay with you? Is it the lack of face-to-face communication and therefore I'm misinterpreting you, or is it for some strange reason a touchy subject...
    Last edited: Sep 17, 2013
  5. Sep 17, 2013 #4


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    This is a physics forum, not a philosophy forum. People tend to give straight-forward, factual, answers to questions (as Halls did in this case). There is no "touchiness" involved, just the possibility that you don't like the answer.
  6. Sep 17, 2013 #5
    If it's not meant to be helpful, then why should I cooperate? (Of course, I realize that maybe it was meant to be helpful and I am misinterpreting him/her...)
    Last edited: Sep 17, 2013
  7. Sep 17, 2013 #6

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    Nope. It means you don't know what has transpired until you open the box.

    You have ascribed a local variable that remains hidden until the box is opened. There are no local hidden variables. Bell's Theorem. There are *lots* of threads on Bell's Theorem in this forum.
  8. Sep 17, 2013 #7


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    Halls provided a succinct and accurate/correct answer to your question. I cannot imagine how he could have been more helpful.
  9. Sep 17, 2013 #8
    Then let's just chalk it up to the fact that Internet communication can be misleading...
    Last edited: Sep 18, 2013
  10. Sep 20, 2013 #9


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    jason_m, Schrödinger's cat is just a thought experiment, designed to illustrate some counterintuitive issues in quantum mechanics;

    • superposition ("dead and alive cat") before measurement
    • measurement (that a superposition - "dead and alive cat" - will be observed as either "dead or alive cat" after a measurement).
    Schrödinger's cat is nowadays often presented in various introductions to quantum mechanics. In my opinion you will get more meat out of the double-slit experiment(s), as it brings you more face to face with quantum mechanics.
    Last edited: Sep 20, 2013
  11. Sep 20, 2013 #10
    no, the thing, goes beyond science, philosophy, go to the root of existence, but some people argues "well it coincides with observation, empirical method and so on" but observation rest on concepts and i ask, what are concepts ? concepts that sustain physics, philosophy any thing that you can think, logics etc.
    then, is a thin ice, that can break any moment.

    Last edited: Sep 20, 2013
  12. Sep 20, 2013 #11


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    I can't make any sense at all of this statement. What is your point? What are you saying?
  13. Sep 20, 2013 #12
    what is a FACT ?

  14. Sep 20, 2013 #13
    How can the cat be in a mixed state? Can a hidrogen atom be partially in the S1 state and partially in the P(2,1) state?

    In that case one would think when in the S1 state it can be transfer a quantity of energy smaller than the 10.2 eV ( the energy to go from S1 to P(2,1) ) because you can "partially" put the atom in P(2,1) which is false.

    That's false not because of the photon but because of the electron. Photons are the manifestation of the interaction between EM and matter but it's just EM what travels, there is nothing like the mass that can help you to say "this region of EM field it's a photon"... but in fact this is another subject of debate...

    In brief, I think the Schrödiger cat paradox just means that before we open the box, we only have statistical knowledge about what's inside the box.
  15. Sep 20, 2013 #14
    Quantumness that's no longer coherent?
  16. Sep 20, 2013 #15
    Ok let's be real no cat has ever been dead and alive alltogether , the cat either lives until the box is opened or dies at some given exact time and is dead when we open the box , it' s not about the cat not about the box , it's rather about our lack of knowing when that happens , or I should say lack of a way to even get that answer without disturbing the outcome.

    There could be chances to open up the box and see the cat being dead already which would rather indicate that the particle has decayed sometime ago and the only way to conclude that would be to make an autopsy of the cats dead body to tell an approximate time of death.Then there are chances of decaying the particle while opening the box which kills the cat , and then there are chances that nothing bad happens and the kitty ends up ok.Which one will happen in a given situation is a casino bet.
    Further opinions are 100% philosophical , spiritual etc as there are no more ways of knowing the answer as nature forbids it. Why who knows , God , Buddha , nobody a matter of opinion , well I have my own and I think its right but then again many of us do so I am not going to endorse that here. :)
  17. Sep 20, 2013 #16


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    The point of the paradox is to indicate the opposite. There is a state called superposition which is neither this nor that for a quantum system. If such were not the case, Bell tests would yield different experimental results. (As well as many other things.)
  18. Sep 20, 2013 #17


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    The problem with threads and questions in this topic is that people tend to mix many different aspects of QM and confusing them to be one. I see in this thread alone, the mixing up of the concept of "superposition", "realism", and "contextuality". And no, I am NOT doing philosophy either because these concepts are also defined in physics and there are experiments that are testing such things (which is why it is NOT philosophy).

    There have been several papers in the Noteworthy Papers thread in the General Physics forum that have dealt with such issues:


    It is confusing when different concepts are mixed in, and this often cause the responses to go in all different directions.

    If the issue is the idea of superposition, which is what I believe it is, I've highlighted, numerous times, the Delft/Stony Brook paper (do a search on PF) and also Tony Leggett's treatise on this. It is one of the strongest demonstration of this principle.

  19. Sep 20, 2013 #18
    Instead of doing something useful and trying to understand the answer given, you are wasting time debating the useless point of whether or not the topic is a touchy one. - Clearly an philosophy major...
  20. Sep 21, 2013 #19
    I don' t think @dauto there was any need to feel superior to a philosophy major , doesn't seem you yourself would be the next Einstein, clearly a response like that doesn't indicate you being any better than the OP with his misunderstanding.

    As to the the OP and what Zapper said already , we need to have distinction between different terminology.
    There is the principle of superposition , clearly no doubt about it, but a macro object like a cat or for the sake of an argument any object you can touch is not in and cannot be in a superposition let alone because of the surrounding medium that ti normally is in.
    Millions of atoms , room temperature etc.
    In the case of Schroedingers cat it is more the fact that we cannot know the outcome without a high chance of making it a certain way when doing the " peek" in the box , just because when it comes down to a few radioactive atoms or whatnot measuring is also interacting and vice versa.
    The atom knows very well in what position it was before we saw it being in a different one but ofcourse that is an abstraction as it would imply an atom to be conscious which is not the case.

    To add just a little bit of philosophy to this our lack of determining the result without disturbing it rather comes from the fact that we are conscious creatures but we also are a macro being in other words we can only interact with macro object , nobody sees an atom directly that why we need " tools" special ones to look into the quantum world and these tools are also the ones which interact and disturb the quantum world.
    If atoms would be humans then we could very well see in what state each one of us is in at a given moment.But that just a side note.
  21. Sep 21, 2013 #20


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    Right on.

    People get very confused about Schrodinger's Cat I think largely because of populist gibberish like What The Bleep Do We Know Anyway.

    Copenhagen, the interpretation that was the most prevalent when Schrodinger's Cat was proposed, assumes the existence of a commonsense classical world out there independent of observation exactly like is assumed in classical physics. It assumes we know about quantum systems via 'marks' left in that classical world - that are called observations, measurements etc. QM is a theory about such 'marks'. In Copenhagen the solution to Schrodinger's Cat is trivial, utterly trivial. Quantum effects make their appearance here in the classical world at the particle detector. It either detects a particle or not - nothing weird at all going on from that point on. The cat is alive or dead when you open the box, or even if you don't open the box - consciousness is not involved to collapse anything.

    So what is its importance - why is Schrodinger's Cat considered a valid tool to help elucidate issues with QM? Its not what you usually read in the popular press. Its simply this - the classical world that Copenhagen assumes is composed of quantum stuff. So how does a theory that assumes the existence of something the theory itself should explain actually accomplish this feat and explain it. We need a fully quantum theory of measurement. That's the issue.

    Since then a lot of work has been done on just that and decoherence has shed a lot of light on the issue - but it does not resolve it to everyone's satisfaction - it's hotly debated.

    If you want to understand the issues check out:

    I hold to the ignorance ensemble interpretation. I wont defend it because it usually ends up in a heated debate. Instead I urge the OP to go through the paper and form his own opinion.

    Doing this will give you a correct understanding of the issue - which unfortunately popular accounts will not give you - and even some under graduate texts like Griffith skirt around whats really going on, instead concentrating on how to solve problems.

    If you really want to understand QM, I mean really understand it, the book to get is Ballentine - QM - A Modern Development:

    Last edited: Sep 21, 2013
  22. Sep 21, 2013 #21
    No, it doesn't, and that's the point. If you think the atom "knows" its position before the measurement, you don't understand quantum mechanics. Bell's inequality was designed to test this very point and experimental results confirm that, indeed, the atom doesn't "know" its own position before it is measured.
  23. Sep 21, 2013 #22
    As I understand the question, this thread is not supposed to be about interpretations of Quantum Mechanics. It is about whether quantum mechanics states that the cat might in principle (forget about the inpracticality of creating a macroscopic superposition for a moment) be alive and not alive at the same time, triggering the Explosion theorem. The answer of course must be no. So what gives? Quantum mechanics is actually stating that a live cat and a dead cat are not opposites. They are in fact perpendicular to each other in a space of possible states that is more than one dimensional. That space has other possible states besides dead or alive, and those states will have non-zero components in both the dead and the alive direction making both things partially true at the same time. Opening the box changes the state forcing the cat to be either dead or alive. Is that weird? Sure... But who cares? experiments have confirmed this fundamental aspect of Quantum Mechanics at every turn, and experiments beat philosophy any day of the week.
  24. Sep 21, 2013 #23


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    That's my impression of the original post #1 too. My impression was that the OP was asking about the concept of quantum superposition. And it sure would be good to get some feedback from the OP, so we do not end up talking to ourselves about interpretations. There are plenty of other threads for that, and plenty more will come; that's a safe prediction I can make without using any equation :biggrin:.
  25. Sep 21, 2013 #24

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    By way of analogy, general relativity shows that the universe is markedly non-Euclidean. Did this disprove Euclidean geometry? Of course not. Back on topic, did experiments that show that Schrodinger's cat paradox is valid suddenly cause every logical (and illogical) thought by mankind to suddenly become false and true at the same time? Of course not.

    That reality motivates developments in mathematics and logic does not mean that new developments/observations in science can falsify old mathematics and logic. That's not how mathematics and logic work. Euclid's geometry and Aristotle's logic are still quite valid, despite developments by modern physics.
  26. Sep 21, 2013 #25

    Why would that be a 'no'? How else are we to view what we observe but as quantum fields(and matter as excitations of same fields)? The standard model got recently re-confirmed with the evidence of the Higgs boson and there really is no other understanding of reality and the experimental evidence in that respect is overwhelming(to say the least). As has been noted in other threads, decoherence alone does not adequatelly explain single outcomes and hence all single-state objects, incl. cats. If anything, the statement 'all matter is constantly in a state of superposition' fits better the theoretical framework and there are no known conflicts except maybe someone's prejudices. Whereas the statement - 'all matter is never in a state of superposition' is in contradiction with both theory and experiment.

    Edit: There is one resolution to this impasse and it's well known among the physicists - it's called the MWI. Many a physicist adhere to it for that reason alone.
    Last edited: Sep 21, 2013
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