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Schrodinger's cat

Contributor(s): Ivy Wigmore

Schrödinger's cat is a famous hypothetical experiment designed to point out a flaw in the Copenhagen interpretation of superposition as it applies to quantum theory.

This is a somewhat simplified version of the virtual experiment:

A living cat is placed into a steel chamber along with a hammer, a vial of hydrocyanic acid and a very small amount of radioactive substance. If even a single atom of the radioactive substance decays during the test period, a relay mechanism will trip the hammer, which will in turn, break the vial of poisonous gas and cause the cat to die.

Nobel Prize-winning Austrian physicist Erwin Schrödinger created this mental experiment in 1935 to point out the paradox between what quantum theorists held to be true about the nature and behavior of matter on the microscopic level and what the average person observes to be true on the macroscopic level with the unaided human eye.

The Copenhagen interpretation of quantum physics, which was the prevailing theory at the time, proposed that atoms or photons exist in multiple states that correspond with different possible outcomes and the possibilites, called superpositions, do not commit to a definite state until they are observed.

Erwin SchrödingerErwin Schrödinger

Schrödinger's thought experiment was designed to show what the Copenhagen interpretation would look like if the mathematical terminology used to explain superposition in the microscopic world was replaced by macroscopic terms the average person could visualize and understand.

In the experiment, the observer cannot know whether or not an atom of the substance has decayed, and consequently, does not know whether the vial has broken and the cat has been killed. According to quantum law under the Copenhagen interpretation, the cat will be both dead and alive until someone looks in the box. In quantum mechanics lingo, the cat's ability to be both alive and dead until it is observed is referred to as quantum indeterminacy or the observer's paradox. The logic behind the observer's paradox is the proven ability of observation to influence outcomes.

Schrödinger accepted that superposition exists; during his lifetime, scientists were able to prove its existence by studying interference in light waves. Schrödinger wondered, however, about when the resolution of possibilities actually occurs. His thought experiment was intended to make people ask themselves if it was logical for observation to be the trigger. Wouldn't the cat be either dead or alive, even if not observed?

Throughout the years, Schrödinger's cat analogy has been used to illustrate emerging theories of how quantum mechanics works. In the Many Worlds interpretation of quantum law, for example, the cat is both alive and dead. In this interpretation, the observer and the cat simply exist in two realities -- one in which the cat is dead, and one in which the cat is alive.

What scientists have learned about the nature of matter at the microscopic level and its relationship to what humans observe at the macroscopic level has not yet been fully explored. The role of the observer remains an important question in the study of quantum physics and is an endless source of speculation and conjecture in quantum computing and pop culture. Schrödinger himself is rumored to have said, later in life, that he wished he had never met that cat.

This was last updated in July 2017

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Wouldn't the cat run out of air and die anyway?
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This really isn't about a cat or a vile it's about knowing whether subatomic particles are in a certain place at a certain time. E=Mc2 States that nothing is special. what's happening in the universe it is happening exactly as it would happen. As with most of the stuff the real issue is not whether the cat is alive or dead or the subatomic particle being in a certain space at a certain time the real issue is that we bring human perception into the equation where it does not belong. Human perception is not special and bringing it to bear in this topic is a violation of relativity. Determining the physical state of a subatomic particle bearing the determination of human perception makes human perception special in that weather human knows whether or not the cat is alive or dead the cat being alive and dead or the subatomic Particle being in a specific position because humans know where it is it's all irrelevant. If the file is intact the cat is alive, done, it has nothing to do with whether a person perceives or does not perceive or know what's inside of a box as this does not change what is factually true. From string theory and a multi-verse decided on human choice to this these theories are factually physically a violation of relativity which is a physical law not a Theory.
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Evolution is through.
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Consider this: we are not only observers, we are participants, and co-creators! With this in mind, let's now take this thought experiment even further...

Although the one(s) setting up the experiment know certain detatils about the cat, I now enter the experiment after it has been set-up. I am told about the basic conditions of the experiment, but I am not told any details about the cat. But before any other consideration, I immediately pull the cat from this ungodly experiment, thus saving its life! Now, I have positively affected the outcome through my consideration of the poor animal's plight.

Through my observations, participation, and 'status' as Co-creator, I can also affect whether the cat is male or female, young or old, black or orange, nice or mean, etc. Those who selected the cat without my observing it, have in their minds these details, but there perceptions are subject to a 'parallel-reality'. I AM aware that my thoughts are potentially very powerful and faster-than-light (it has no mass). Therefore, because of this superluminal aspect of thought, my desires can travel back in time and produce a new reality that will be perceived in the present as 'coincidence'.

Remember, "There is no single outcome unless it is observed. We know that superposition actually occurs at the subatomic level, because there are observable effects of interference, in which a single particle is demonstrated to be in multiple locations simultaneously. What that fact implies about the nature of reality on the observable level (cats, for example, as opposed to electrons) is one of the stickiest areas of quantum physics."

By the way, if this experiment were to be actually carried out without my knowledge until I was brought in in the middle of it, after saving the cat's life I would keep it. And the karma of those setting up this unglodly scenario would produce them being reincarnated as laboratory rats.

- Brad Watson, Miami
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Violation of the law of relativity human choices not special decision-making is not special what is happening in the physical world is happening with no influence from human decision or knowledge
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That was terrific. My brain is so limited, I can only skim the surface of this thinking, but you saved the cat and predicted karma that I would love to see.
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If Schrodinger was so clever why didnt he put a window in the box?
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So this theory is a fancy way to describe the old idiom: If a tree falls in the woods and there is no one to hear it, does it make a sound?
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stltrp:

I have always felt the conclusion to this thought experiment, contains a fallacy in the logic, in spite of stature of the author. Even though we spent about 2 weeks on quantum theory in college physics, the proposition and conclusions have seemed somehow dishonest.
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the problem with this thought experiment is that the person observing said experiment is trying to view events in the universe as if he were outside the universe and not a part of it . Its like looking into A fish bowl and trying to quantify whats going on inside. the problem and confusion of this is that the observer is in the fishbowl as well, and not considering himself as part of the equation. the word cosmos means everything there is in existance including the cosmologist, Therefor I do not understand why it seems strange to anyone that the observer being part of the equation would effect the outcome.
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How long does the experiment go on? Would the cat not potentially suffocate or starve to death?
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The tree falling in the uninhabited forest makes no "sound". It will cause vibrations with the potential to become sound if detected.
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I completely disagree with this experiment. They cat can not be dead and alive at the same time. The discovered outcome will not change the previous happenings.
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I don't understand a word of this.
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To the person who says they disagree with this, you completely miss the point. This is a thought experiment. Obviously the cat cannot be both dead and alive at the same time. But, for the purposes of the thought experiment, in the context of the wave function, that is exactly what happens. This is merely an illustration of how complicated quatum mechanics truly is.
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Can someone please find out if the Schrodinger's cat experiment (or whatever it is) is similar to the concept of the falling tree, at least on a more philosophical level???

If a tree falls in the forest and no one is around, does it still make a sound?
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I think a tree doe not even exist at all, unless observed.
This may suggest that an awareness  exists in the Universe itself- this way the Moon can exist even when you are not looking at it.
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Post 463786
28 Jul 2013
4:05 AM z
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I completely disagree with this experiment. They cat can not be dead and alive at the same time. The discovered outcome will not change the previous happenings.

In response to the above, that's exactly the point he's making. The ABSURDITY of Quantum Physics. He's just finding a way of making people who aren't physicists understand the theory behind it. Nothing is known for sure until a proven outcome.
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So, if I step on a caterpillar without realizing and later notice the guts on my shoe but think it's from a grasshopper, does a caterpillar get its wings?
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A theoretical physicist was stopped by the police on his way home. After inspecting his licence, the officer asked to look in his trunk, and the professor cooperatively popped the release. Moments later, the officer returned and asked, "Sir, are you aware the cat in your trunk is dead?"  To which the professor replied, "Well, it certainly is now!"
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If a tree falls, it makes sound waves - the definition of sound. The ear simply detects the waves and sends impulses to the brain, which then interprets them as sound. If a light is turned on and a blind person doesn't see it, it is still light.
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Some people missed the point of Schrodinger's illustration. Yes, it's true that the cat might run out of air and die, the hammer might not work, and somebody might have accidentally put water in the vial instead of HCN. The purpose of the theoretical experiment is to show the uncertainty of quantum physics. Some of what we know about quantum physics is experimental, and a lot of it is determined by mathematical processes, which remain theoretical until proven in the laboratory.
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Correct this article. The small amount of radioactive substance in the box with the cat is _not_ the hydrocyanic acid. Get it right, or don't post it. The flask of acid is in the box with the cat, and situated under a hammer. The hammer is connected to a mechanism that uses a Geiger counter to detect any decay in the radioactive substance -- this is the quantum event at the heart of the paradox -- and either drops the hammer on the flask, releasing the acid and killing the cat, or not, depending on the quantum state (decay event or no decay event) of the radioactive material. Superposition says that at some point, the material both decays and does not decay, with quantum realities existing simultaneously (and thus the cat is both alive and dead), as long as the quantum state of the system is not observed....thus the paradox. The cat cannot be both alive and dead.
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Obviously, you people can not see past was is obvious and provoke your inner consciousness. It's a thought experiment. Not a literal one.
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The purpose of this experiment is to show that nothing has a certain, specified conclusion until physically observed and scientifically proven. Schrodinger was saying that you can't prove the cat is dead or alive until you open the box. Therefore, you must accept that there is a 50% outcome for either chance, which is why the article says the cat is both alive AND dead. Nobody can say for certain the cat is alive/dead without opening the box. If the cat is dead, the cause of death, whether it's suffocation, poison, or starvation, is irrelevant to the experiment. Schrodinger never actually conducted this experiment, he only proposed it.
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Not sure that your interpretation is correct. It isn't that he was showing the absurdity of quantum physics. What he was trying to explain was how, in quantum physics, the theory exists that something can exist in multiple states (the cat being dead and/or alive) and that the sheer act of measuring an observation (checking to see the state of the cat) will affect the outcome. Until the measurement is made, there is no way to know exactly what the state of something is, and thus it is understood to exist in multiple states, as per quantum physics.
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ok you geeks since the brain operates and emits electricty, even if you think about the results IE. the cat can be thought of as neither dead or alive, and observation disrups the results then it can be said that if you are thinking about it you have altered the results by electricty emited by your brain waves, unless you are outside the box then it would be brain particals.
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Schrödinger's Cat Chow - 50% Off This Week... >..<
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"There is no single outcome unless it's observed". I wasn't in the forest when the tree fell, yet I know it made a sound.
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My issue with this experiment setup is time. Given enough of it, an atom will decay. That doesn't affect what it's meant to represent, but something that is equally likely/unlikely needs to be the catalyst.
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asda
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I think the whole point of this or the moral is that let's say you want to ask a girl out on a date but have doubts about it or are afraid she'll say no. You are to remember this story about the cat. They could not really tell if the cat was dead or alive until the box was opened. And, you will not actually know if the girl you want to ask out on a date will say no until you do ask. Get it? You will not ever know the answer to something -whatever it is- until you open the box (or ask the question) . That is the point of Schrodinger's Cat.
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There is a difference between "the cat is dead and alive" and "I don't know"
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Similar to the previous poster's comment, there is a difference between our knowledge of something and its existence. The cat is either dead OR alive, regardless if we know it. Seems simple.

Maybe the real insight here to "perceptions vs reality" is how this story is believed to be some great insight when it really isn't.
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It was 1935 ... The Cat is Dead
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I think of this in poker. My opponent can have anything until I see his cards. I guess it has its advantages and disadvantages...
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I think the real question is why is there a hand on the table beside the man?
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Does he really wants to say that we cannot make sure that something actually happens unless we see it?! What a discovery! Or am I missing something here?
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Do you have a favorite Schrodinger's cat meme or cartoon to share?
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So he's the guy who invented the preferred form of torture used by the California Bar Examiners. Until you know you failed the exam, you have both failed it and passed it. I hate that damn cat.
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Well, if the hammer falls, one might hear it. If one does hear it, or it is recorded and one hears that, one can deduce that it broke the vial and, hence, without opening the box, know that the cat has perished. As to asking the girl out thing, just remember, a no is better than a missed yes!
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As to why the hand is on the table? It's to reach where you can't reach when you have an itch. Simple!
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There is a big difference between "the cat is dead and alive" and "I don't know if the cat is dead or alive." In other words, Schroedinger proved that the superposition theory was wrong (that was his actual intention by the way).
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The decay of the atom has a cause, but due to our ignorance, we can't say when. Determinism is true.
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isn't it also everywhere and nowhere?
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One must first have faith the builder of the box did not include a hidden door for the cat to escape.
one must have faith that there is even a cat in the box.
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Kitties of the world unite and get Schrödinger a dog...
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Is this related to multiple possible realities? Every possibility that can happen is happening in some alternate dimension of the universe? So really, Schroedinger's cat is really both dead and alive, depending on the reality you are in. We simply don't know which reality we are in until we open the box.
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The cat is either dead or alive. Not both. The cat exists only in one state regardless of my knowledge of the state of the cat. My not knowing the state of the cats existence does not alter it's existence unless I interfere by opening the box. My perception of the cat's state is altered, not the cat it's self.
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Is this basically ignorance is bliss?
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I wish the cat never met him.
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The main fault of this thought experiment leaves out one important consideration: opening the box will immediately put the cat into the opposite state. So we will know what the cat WAS at the moment the box was opened, but it is NOW the opposite.

This assumes an even more unnatural event: that cats can be resurrected from the dead.
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What will the cat eat and drink without either it will die before anything else will kill it
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It's a fucking ducking stool! BjD'
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The cat is dead and alive simultaneously, until it is observed to be one or the other, at which point its state manifests as having been so all along, at least so far as experiments have indicated...
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quantum theory is strange, and it is far beyond the commonsense, and i think tht's why people think of it as absurd.
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It's just stupid theory again
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The cat, if indeed found to be dead, will have eight other lives.
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Why a cat? There are so many other animals out there deserving of torture.
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100 cats in 100 boxes so we can get a greater amount of info to figure out who is putting the cats in boxes. All possibilities can only be comprehended based on previously acquired knowledge.
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That's absurd, or not.
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It makes sense it's basically saying until you break open an atom/other matter from the human eye you cannot see what's inside so there is no actual way of finding out the smallest thing in the universe as we can not see it because the laws of physics will not allow it therefore we can only have a 50/50 chance of the outcome/ millions of different possibilities.
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Unless I'm misunderstanding it, this is dumb... we can just put a camera in there to see whether the cat is alive or not.

We can also listen to hear whether or not the hammer has smashed to know whether the cat is dead or alive.

Life carries on regardless of whether or not we witness an event, right? That's how we can get calls that one of our loved ones was killed in a car accident, even if we haven't witnessed it, right? People can die alone in their apartments even if no one was with them to witness it.
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To clarify my last post, you can die alone in your apartment, and you're still dead, you don't have to wait till someone opens the front door to observe you to be truly dead. We can just play back the webcam or CCTV if there is one and see just how long ago you died, if you really need proof. Events do not have to be observed first before they have an outcome. You're dead either way.
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Placing a camera inside the box, assuming pre trial of the experiment, is similar to playing paper, rock, scissors and then suddenly deciding to add gun or bomb to the game. Think of Schrödinger's cat in the terms of only its present parameters... do not alter it in any way. This makes the only immeasurable outcome to be life... think about that, right?! Lol... Without altering the present parameters of the experiment, my only sure outcome is that if I wait 2 weeks to open the box, the cat WILL be dead! Death is certain, life is the mystery!!! ;)
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You see the most beautiful woman at a bar, will she yes or no to you asking her out?  

(Presently, she can say either no or yes, with both possibilities being possible)

(You will never know the answer until you participate/observe/take action, and your action is what caused the result/answer)

Get it?
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they should put a human into the box instead of a cat and that is called a gas chamber. i hate the way humans are so flip about the lives of other living beings on the planet. #catlivesmatter
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For many of you who have commented you were both stupid and smart until you started typing........
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Rock paper and scissors makes up 33.33333 percent in comparison to Fitt percent chance However a CCTV would be no different than observations by naked eye. Still makes it the Observers paradox.
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Putting a camera in the box is still a form of observation. Holding the idea still true.
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Chuck Norris knows whether Shrodinger's cat is dead or alive. (but seriously, check out http://sciencequestionswithsurprisinganswers.org/2013/07/30/what-did-schrodingers-cat-experiment-prove/ - very enlightening)
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The Question should be is there still a cat in the box this doesn't really prove anything whether the cat is alive or dead there is still a cat in the box
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It's called a metaphor
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That theory may be a bit of a stretch, but a majority of you people won't even try to understand it! You say "Its no different than (insert stupid comparison here)" However, IT IS NOT LIKE THAT. Nobody knows if the cat has died until checking, so it is both dead and alive due to THE QUANTUM THEORY, not someones idea to say "I don't know what it is so I'll just say he is dead and alive!" This has more behind it than most of you think, I'm especially saying this to the "genius" who said its like getting a call about a deceased love one. OBVIOUSLY someone had to have known about the death for you to have received a call. Before you comment trying to make a false analogy, remember: Just don't.
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I apologize for my ignorance. I meant to say the QUANTUM LAW, not the QUANTUM THEORY.
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i understand the concept of it, but i never liked the description using the cat and box and vial.. it's much more headache then actually realizing the equation.. It means you can only see something when you look at it.. simple and fast..
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This experiment was supposed to illustrate why quantum mechanics can't be applied to regular stuff. So by assigning any importance to it in terms of quantum mechanics, you are by default showing that you don't understand the principle of quantum mechanics, I.e. That it applies only on subatomic levels. The cat is most definitely alive or dead, whether you look or not. You could study the radioactive material prior to putting the cat in the box and learn its half-life, or the cat could tear a hole in the side. It doesn't apply.
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We have learned a lot about "entanglement" and "measurement" since Schrodinger's day. Using modern insights into entanglement and nonlocality, the apparent paradox of Schrodinger's cat disappears. The cat is in an "entangled" state, in which the cat's state (alive or dead) is correlated with the state of the radioactive nucleus (undecayed or decayed). Schrodinger knew about entanglement, but neither he nor anybody else at that time understood the mathematics associated with it. The entangled "cat" state is not a simple "superposition" state. A superposed cat would be both dead and alive, and a superposed nucleus would be both decayed and undecayed, but the entangled Schrodinger's cat can be easily proven (using standard quantum mechanics) to be EITHER dead OR alive, not both. Furthermore, opening or not opening the box has nothing to do with this question. The entangled, or correlated, state already IS the "measured" state of the nucleus. So, whether the box is opened or not, the state of Schrodinger's cat is just what we expect: The cat's state is correlated with (and quantum-entangled with) the state of the nucleus: If the the cat is alive, the nucleus is undecayed; If the cat is dead, the nucleus is decayed. Thus, the macroscopically observable state of the cat "measures" (discovers) the state of the microscopic nucleus. This is provable with conventional quantum theory. Although others have also recognized this, one source of further details is: Art Hobson, "Resolving Schrodinger's cat," at arXiv 1607.01298 on the web. --Sincerely, Art Hobson, Emeritus Professor of Physics, University of Arkansas, USA, ahobson@uark.edu. See my book "Tales of the Quantum," soon to be published by the Oxford University Press.
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The quantum state cannot be predicted in advance, and any attempts to measure it affect its state.  A quantum state is a non-causal phenomenon, nothing more.  An individual radioactive nucleus could decay one millisecond from now, or 100 years from now.  There is no known causal phenomenon that predicts the path it will take in the future.  This is the essence of statistics -- an irreducible random phenomena.

Therefore, cat is not alive and dead.  The cat is alive OR dead.  One must observe to know -- there is no other way.  It's as simple as that.
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Thank you so very much for the explanation!
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Everyone loves this. E=Mc2 the law of relativity states that the observer is not special, and whether or not the vial is or is not broken became truth within the box where the vial is contained. It has no relevance on who is obersving or not from outside of the box. There is no duality, and even though a particle might be undetermined by an observer does not mean it is not on a determined course. In other words, the duality of its existance is only in the mind of an unrelated unefecting observer. That is all, nothing more. The observer is not special because nothing is special.
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This was a precursor to more elaborate discussions of the multiverse later in life. In retrospect, he would probably amend the thought discussion to account for additional cats for any other set of variables within that box that had multiple outcomes.
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