Schrodinger's cat is a thought experiment, sometimes described as paradox, devised in 1935 to illustrate the physicist's problem with the interpretation of quantum mechanics. Intended to point out the absurdity of a scenario in which the cat is both alive and dead, the case became a milestone in interpreting quantum mechanics, spawning multiple theories and interpretations. Also having an issue with the multiple states of being, Einstein wrote to Schrodinger in 1950:
"...one cannot get around the assumption of reality, if one is honest. Most of them simply do not see what sort of risky game they are playing with reality - reality as something independent of what is experimentally established. Nobody really doubts that the presence or absence of the cat is something independent of the act of observation."