He is also famous for a thought experiment that has become known as Schrödinger's cat. The Heisenberg principle states the position and the velocity of a particle cannot be exactly measured with perfect accuracy. Similarly, quantum mechanics shows probabilities of position and velocity and all values are possible, some values being more possible than others, and does not exist until the observer measures it. Schrödinger tried to explain that this did not apply to larger things. He proposed a system where a cat was locked into a closed container with a small amount of radioactive material, a geiger tube, and a device that kills the cat if radiation is detected by the geiger counter. It only takes one disintegrating atom to kill the cat, but whether or not the atom decays is left to chance and probability. According to the rules of quantum mechanics, the cat is neither dead nor alive until someone opens the box to check. Schrödinger argued that this was a silly way to explain quantum mechanics to situations where it doesn't apply.
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