Erwin Schrödinger proposed a paradox

Erwin Schrödinger was a Nobel prize-winning physicist. Schrödinger proposed a paradox in 1935 to illustrate a point in quantum mechanics about the nature of wave particles.

At the center of quantum theory is the idea of a wave function. A wave-function describes all the possible states subatomic particles can have, including energy, momentum, and position. A wave-function for a particle reveals there is some probability that it can be in any allowed position. However, you can only know the position by observing it. Without observation, you have to say that it can be doing any of the things, even if the probability is small.