It is a commonplace that XXth century physics has produced powerful new theories, such as Relativity and quantum mechanics, that upset the world view provided by XIXth century physics. But every physicist knows how difficult it may be to explain the basic aspects of these theories to people having a non-physical professional training. The main reason of this is that both Relativity and quantum mechanics are based on fundamental ideas that are not hard to grasp in themselves, but deeply contrast the primary categories on which our everyday thinking is based, so that it is impossible to place relativistic and quantum results within the framework suggested by ordinary intuition and common sense. Yet, despite this similarity, there are some relevant differences between the difficulties arising in Relativity and in quantum mechanics. In order to understand this point better, let us focus our attention on Special Relativity first (analogous arguments can be forwarded by considering General Relativity). Here, the strange links between space and time following from the even more strange assumption that the velocity of light is independent of the motion of the observer conflict with the very simple conception of space and time implicit in our daily practice (and explicitly stated in classical Physics, think of Newton’s “absolute space” and “absolute time”): but this conflict regards geometrical space-time models, not the very roots of our language, hence our thought. Then, let us consider quantum mechanics. Here it is a basic notion that properties of physical systems are nonobjective, in the sense that a property cannot be thought of as existing if a measurement of it is not performed. As Mermin  writes,
“it is a fundamental quantum doctrine that a measurement does not, in general, reveal a preexisting value of the measured property”.