Quantum mind by physicists, some of which regard the "alive and dead" cat superposition as quite real. Schrödinger's famous thought experiment poses the question, ""when" does a quantum system stop existing as a superposition of states and become one or the other?" In the same way, it is possible to ask whether the brain's act of making a decision is analogous to having a superposition of states of two decision outcomes, so that making a decision means "opening the box" to reduce the brain from a combination of states to one state. But even Schrödinger didn't think this really happened to the
Introduction to quantum mechanics by a small amount, where only one line was expected. Pauli formulated his "exclusion principle", stating that "There cannot exist an atom in such a quantum state that two electrons within [it] have the same set of quantum numbers." A year later, [[George Eugene Uhlenbeck|Uhlenbeck]] and [[Samuel Goudsmit|Goudsmit]] identified Pauli's new degree of freedom with the property called [[spin (physics)|spin]] whose effects were observed in the Stern–Gerlach experiment. Bohr's model of the atom was essentially a planetary one, with the electrons orbiting around the nuclear "sun." However, the uncertainty principle states that an electron cannot simultaneously have an exact location