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I would be grateful for any comments regarding two variations of Schrödinger's Cat experiment I’ve been pondering.

In the first, wishing no harm to the animal, I remove the cat and replace it with a very simple clock. The clock could be mechanical, chemical or atomic in nature, and is just the simplest way to measure time after an event occurs. It is totally enclosed within the box and will start when the radioactive decay event is detected.

Sometime after the experiment begin I look into the box. Sometimes I would expect to see the clock had not been activated but other times it has. In those cases, what will the clock show? Common sense (AKA classical phyiscs) would say it would show an apparent random value but, if I repeated the experiment enough time, I would see it was related to the probability the radioactive substance has decayed. What I would not expect is the clock to consistently showing that it started only when I looked inside the box. If the quantum state only collapses when I look, how come the clock might say it started minutes ago?

EDIT: I am particularly interested in the apparent paradox of an event triggering an event in the past. How, in quantum terms, would this be explained?

Variation 2 is also simple but a bit more dramatic. Here the cat is replaced with a (very small) explosive device – just enough to blow the box part. If I never look inside the box and hence the quantum state is never observed, does the box never explode? If it does explode before I look inside, why? And if, after a long time, the box has not explored and I then look inside, does this mean it’s very like the box will exploded at that moment and I get my hair singed!

Your thoughts please. Bryan.


marked as duplicate by StephenG, Cosmas Zachos, user191954, Jon Custer, ZeroTheHero Oct 17 '18 at 21:52

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

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    $\begingroup$ I voted to close as a duplicate, but in fact if you read the "related" list of questions (on the right when you view your question) there are a whole load of detailed answers explaining your issues with this thought experiment. Go through them carefully. $\endgroup$ – StephenG Oct 17 '18 at 8:21
  • $\begingroup$ I was specially interested in the time element of the question, which I cannot find in any other question. Can you point me to one? $\endgroup$ – BryTack Oct 17 '18 at 15:02
  • $\begingroup$ I don't actually see how this question is a duplicate with the other questions. There is confusions regarding the opening of the box and the state collapsing. These sorts of issues are addressed in the supposed duplicate question. However, OPs questions about what the clock would read and if/when the box would explode I would argue are interesting twists on Schrodinger's cat which don't seem to be immediately addresse in the linked and related questions. $\endgroup$ – jgerber Oct 18 '18 at 3:52

I think the easiest resolution of the Schrodinger cat situation is to think that the state of a macroscopic system is never in a superposition of states, you can search about decoherence to understand this a little bit better.

So in this case, you have a cat in a box, a bit of radioactive material, a geiger counter and some poison that is released if the geiger counter detects a particle from the radioactive decay. It is fine to talk about an atom being in a superposition of states, the atom can be sufficiently isolated so that it is truly in a superposition of states. But the geiger counter is never in a superposition of states, independently of wheter you look at it or not(since observation has nothing to do with an actual person looking, or any kind of consciousness oberving), it either detects a particle or it doesn't, so the poison is either released or it isn't, which makes the cat not both dead and alive, not neither dead nor alive, but as expected, either dead or alive.

So even if you change the set up, it won’t matter. For whichever macroscopic system you choose to use to activate the clock or the bomb, there is no sense in talking about superposition of the macroscopic system, so no paradox arises, as expected.


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