Hello folks, When you study a pendulum or the path followed by a ball falling under gravity the first thing you have in mind is the experimental result, because you can actually see it. It is easy to measure or find the position and velocity of those systems. If we talk about a particle with position, mass and velocity we have enough information to predict his movement. When you study quantum mechanics frequently you read about Hilbert infinite spaces, differential equations, , eigenvalues, eigenvectors, imaginary numbers, integrals, operators, matrix calculus, but, Where is the data? To make this clear, let's talk about a triatomic molecule, something like our solar system with two planets. Let's say we have 3 protons in the nucleus and 3 electrons. Where can I find the experimental data on this system? What is the total list of observables that is possible to meassure? I mean, I know from spectroscopy you can measure the difference between energy levels. And from x ray difraction you can learn about its structure, What about the "eigenstates"? Can I measure the "eigenstates"? We have energy levels, with stern gerlach experiments I guess you can measure spin too. What else is measurable? My goal is to have first the experimental data, and only then reading about this or that model "hartree fock" and so on. I don't like to read about a simplifying model before actually knowing the experimental result, it looks completely absurd to me.