In every academic field, an absolutely essential component is to create a set of “technical terms” (i.e., jargon) so that those outside the field don’t understand what you are saying but you still sound impressive. Physicists, however, have been faking all their experiments since around 1927 (alternatively, physicists and those of us who might be called mathematical physicists, are all insane; as I am insane from the study and use of physics I can’t tell which is true). We have cleverly hidden this not just using jargon, but by using both (more or less) “normal” language to mean things that have little or no relation to the normal meanings AND by taking technical terms from classical physics and using them to mean bizarre things.
Example 1: Most people have heard of Heisenberg’s uncertainty principle. Simplistically, it is a sort of a set of mathematical ratios that tell us the more certain we are when we measure something like spin, position, momentum, or any other “observable” property of a quantum system, the less certain we are of related “observable” properties of the system. The common example is position and direction: the more we know about the position of e.g., an electron, the less we know about its direction.
Fewer know the small set of basic postulates of quantum mechanics, one of which says something like everything there is to know (or all the information about) a quantum system is contained in our mathematical representation of its state. By “mathematical representation”, I mean something like the way we use numbers and math to describe values like speed, velocity, mass, position, etc.
Intuitively, this seems to say that we can write down a description of a quantum system such that we know everything about that system. However, the (in)famous uncertainty principle tells us we can never know anything exactly about any property of a quantum system, and the more we know about some property the less we know about others. What gives?
Example 2: An extremely important property of particles is what physicists call “spin”. Now, this would seem to be intuitive. Better still, we often refer to spin with phrases like “spin up” and “spin down” or “spin along the x-axis”, making it more obvious that by “spin” we really do mean rotation of the particle. But we don’t. In fact, we refer to another property of such systems (orbital angular momentum) which in classical physics is equivalent to spin: the “orbit” of something like a planet or a bullet along its axis. When something “orbits” along its own axis, this would seem to mean (and in classical physics it does) “spinning”. In quantum mechanics, these two ways of describing how something can spin correspond to very different things, and the seemingly more intuitive term “spin” is almost impossible to mentally visualize.
Example 3: I used the term “observable” above. In quantum physics, one finds references to “observables”, and these are defined as measurable properties of systems in quantum mechanics. And, as the observables are things like position and momentum, it would seem that we wouldn’t need such a term. After all, in classical physics we don’t refer to the position of an arrow or the momentum of a car as “observables”. These and other properties of physical systems are observed, and we have names for them (mass, speed, velocity, momentum, etc.) that we use to represent the values of our measurements/observations. Why would we need a term for the things we measure rather than, as in classical physics, just use the darn names of the properties we measure? Because “observables” in quantum mechanics are mathematical operators/functions, not values. They’re Hermitian matrices.
Example 4: Why on earth do we represent so-called “observables” by the mathematical functions? Because when, in quantum physics, we refer to the “state” of our system, the system we are referring to has no physical existence. It isn’t real. It’s a mathematical entity that dwells in an abstract mathematical space that isn’t 3-dimensional, or 4-dimensional, or 10-dimensional, but usually infinite-dimensional. So, when we “measure” these systems, we have to use mathematical functions because there is only a mathematical system to “measure”.
Example 5: What do we mean by “measure”? Answer: don’t ask.