The great dream of physics is the "theory of everything", a theory that describes both the world of the smallest particles and the world of large masses. So far, we know quantum mechanics for the world of the smallest particles, and the theory of relativity for the world of the largest masses - and it does not seem possible to unite both theories. The world of quanta is too bizarre: states can overlap, particle properties are only known with a certain probability, and a particle can be found everywhere before the measurement - and only manifests itself in one place when the measurement is made. There are numerous paradoxes that show us how bizarre the quantum world is. The best known are probably Schrödinger's cat and Einstein's spooky action at a distance. But are these properties and paradoxes really properties and paradoxes of the quantum world? If we look at them more closely, we see that many of the properties we ascribe to the quantum world are in fact properties of only one particular interpretation of the quantum world, namely the so-called Copenhagen interpretation. If we look at the quantum world from the point of view of other interpretations, then these paradoxes dissolve into nothing. But what are then really properties of the quantum world? Especially in the last few years, numerous experiments have been carried out which bring us closer to answering this question and which show what could be the common denominator for a unification of quantum mechanics and the theory of relativity.