How Do You Know if a Snake Is Dead or Alive
One of the original questions was: A basic rule of logic is that something cannot contradict itself. It is impossible for P to exist true and not true. Doesn't Schrödinger'southward cat violate this law and therefore invalidate logic?
Schrödinger proposed this thought-experiment to demonstrate how ridiculous quantum super-position is. Basically the multiple states of a single atom (decayed and not decayed) causes a cat to be in multiple states (living and expressionless).
Physicist: The resolution to this comes from a careful await at what is meant by the "state" of something. Turns out, logic is condom from Lil' Schrödinger's claws.
There'due south a big departure between "reasonable" and "logical". To see the deviation, find a at-home, reasonable person and talk to them, then (this is more difficult) discover a professional logician and try to talk to them.
Talking to professional Logicians: among the more frustrating conversations you'll ever have.
It'south pretty reasonable to say that a single affair must be in one state or another, specially if those states are mutually exclusive. It's obvious. It's common sense. In fact, information technology's so reasonable/obvious/sensible that disagreeing with it would be a good mode of beingness laughed out of every fancy scientific discipline salon of the 19th century (or at least the occasional salon with sober members). Logic, on the other hand, has nothing to do with physical reality (neither does being reasonable for that affair).
Logicians first with a big bucket of postulates and symbols and statements, and and then run with them. None of it needs to be "physically motivated" or even remotely intuitive.
Clearly, this reads "P is perhaps truthful if and only if P is not definitely untrue" and likewise "P is definitely truthful if and but if it is non possible for P to not be true".
The statement that things must be one mode or another (specifically, that each state is mutually sectional of the others), is a whole new logical statement on its own. The statement fifty-fifty has a proper name: "counterfactual definiteness". Overly-complicated terms like that are just made up then that people will think that physicists are wizards-of-smartness. A better term for things needing to be in a definite state is "realism". While realism is "obviously true", is isn't necessarily truthful (not "logically true"), and point of fact: isn't true.
In that location's a famous no-get theorem in quantum physics called "Bell'due south theorem" that says that, given the results of a diverseness of experiments involving entanglement, "local realism" is impossible. This ways that things always being in single states requires the exchange of some kind of faster-than-light signals. Or conversely, if no effects can travel faster than light, and so things must exist immune to be in multiple states.
It's pretty natural to bound to the conclusion that things are communicating faster than low-cal. Losing realism is philosophically, even mathematically, a bitter pill to swallow. Unfortunately, at that place are a lot of issues with faster than lite stuff (similar this one!).
It turns out that the universe doesn't seem to have any problem dropping realism. Things are perfectly happy being in multiple states at the same time: particles being in multiple positions or energy states, single events happening at multiple times, or (admittedly reaching a little past our grasp) beingness in multiple states of living and dead. The last of grade has never been observed in the lab (and probably never volition be), but this is a well-studied property otherwise. We've seen multiple-stated-ness in every physical system we're capable of measuring the effect in. And then far, there doesn't seem to be whatsoever limit to the scale at which quantum weirdness shows upwardly.
In short, information technology does make sense to say that things must be in a single land or another, but it isn't necessarily "logical". The universe couldn't intendance less about what makes sense.
Respond gravy: This bit threatened to derail the flow of the post.
Realism is technically a argument that limits the exact nature of what kind of states are immune. For example, only the states 
We see this all the time in the polarization of lite, for example. A diagonally polarized photon is in a single state, 
The answer to whether Schrödinger'southward cat is in multiple states becomes a resounding "Yes! Unless some very specific measurement is ready, in which example: no!".
Source: https://www.askamathematician.com/2013/04/q-why-is-schrodingers-cat-both-dead-and-alive-is-this-not-a-paradox/
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