Are dead and alive alike

Quantum mech. Atomic model

As early as 1935, the physicist Erwin Schrödinger published "Schrödinger's cat", a thought experiment that problematizes the direct transfer of quantum mechanical terms to the macroscopic world: a cat is in a box, together with a small amount of radioactive substance. This is chosen so that it is equally likely within an hour whether one of the radioactive atoms will decay or no decay will take place. In addition, there is a detector, a hammer and a jar with a poisonous substance in the box. As soon as an atom changes its state, the decay is registered by the detector. This moves the hammer, which then destroys the container with the poisonous substance. The cat dies.


As long as the box is locked, it is not clear from the outside whether the atom has decayed or not. It is in a superimposed state. But it is precisely on the decay of the atom that the “liveliness” of the cat in the thought experiment depends. As long as the box is not opened, the cat is also in an "intermediate state" - it is 50% alive and 50% dead. “Superposition” of these two states. According to the rules of quantum mechanics, the state is only clearly defined when the system interacts with the environment, i.e. when a "measurement" is carried out. In the case of a quantum mechanical superposition, this leads to the respective particle assuming an unambiguous state again, namely by chance one of the states contained in the superposition.
The paradox is that, according to the thought experiment, a cat as a macroscopic system with the rules of quantum mechanics could be brought into a superimposed state of "alive" and "dead" until one of the states is only determined through observation. However, this contradicts our view and everyday experience. “Schrödinger's cat” shows that quantum mechanical laws cannot simply be transferred to everyday systems.
It behaves differently in the microscopic range. Quantum objects such as B. photons or electrons assume several states at the same time. For example, in a double slit experiment, a photon can penetrate both one and the other slit at the same time. However, if one wants to observe exactly how the photon passes through the two slits, the path of the photon is determined by the measurement and the result of the experiment is different.