Is a cat in an isolated box that has a 50% chance of getting killed in the next hour due to a quantum event - such as a particle decaying with 50% chance, and which
will release a poison that will kill the cat. If the particle does not decay, then cat
will remain alive.
Schroedinger/Einstein claimed that after an hour with the
box lid closed, the cat must be either dead or alive, each with 50% probability - this is just common sense. Bohr/Heisenberg claimed that with the lid closed, the cat is neither alive nor dead, but 50% alive AND 50% dead at the same
time. That is the cat is in 2 mutually exclusive states at the same
time!
Bohr's position is the "Principle of Superposition" and is central to quantum physics.
Empirical experments show that Bohr was correct, and Schroedinger
wrong - up to a point. If the observer happens to be in the
box, he
will see what Schroedinger asserts. If the observer is out of the
box and cannot see inside the
box, then Bohr is right.
So Bohr and Schroedinger were both neither right nor wrong! What
irony. The answer is "who is asking". Is the observer privy (entangled) with the cat or not. Note: this is unrelated to the popular concept that "the observer influences the observed". There is no influence by the observer.
