I've always found classical Newtonian physics, the Special Theory of Relativity, and (to a lesser extent) the General Theory of Relativity to be understandable at an intuitive level, but quantum phenomena just baffles me, even when I think I "understand" it.
PS. IvoDankolov: I find it difficult or impossible to think intuitively about quantum phenomena.
Ever heard of chaotic systems? Any dynamic system that shows extreme sensitivity to initial conditions is chaotic. For instance smoke curling from a cigarette, planetary orbits over time, weather, water dripping from a tap - all of these show extreme sensitivity to initial conditions.
Here is the fun thing. In quantum mechanics everything evolves linearly. Therefore extreme sensitivity to initial conditions is entirely impossible. We only think that we observe that. Yet the world is full of cases where we can demonstrate such sensitivity!
Thanks. A perfect example of the outright weirdness of quantum phenomena.
I read the first section of that paper ("Why quantum chaos?"), and its proposition makes no sense to me. None other than Poincare PROVED (proved!) ages ago that the motion and position of just three little points attracted to each other according to Newton's formulas are extremely sensitive to infinitesimal changes in their initial motions and positions (i.e., the system is chaotic in the classical sense). And as you point out, the world is full of cases that demonstrate such hyper-sensitivity. Yet, according to this paper, such a system is impossible in nature. I don't get it.
Instinctively, I have to believe there must be a more fundamental underlying explanation for this and other apparent contradictions... it's just that at the moment no one knows what this explanation might be.
>Here is the fun thing. In quantum mechanics everything evolves linearly. Therefore extreme sensitivity to initial conditions is entirely impossible
I'm not sure if that is true. You can have dense sets created by Linear Operators if you're in a infinite dimensional setting (which you _are_ in QM). That's what Hypercyclic Operators are.
In any case, although the wave function evolves linearly, the _square_ of the wavefunction obviously does not (by the product rule). Since all observations are going to be based on square of the wavefunction, or the product of it with it's gradient, all observable quantities will typically evolve nonlinearly.
What do you make of this problem with distant entangled particles?
The double slit experiment and interference in general?
The Heisenberg uncertainty principle? (Or as I'd like to call it, Heisenberg's horribly mislabeled-in-order-to-confuse-students principle)
A shot in the dark - many of the problems with coming to terms with quantum mechanics arise from trying to impose on it that it should somehow behave like classical mechanics, or that somehow we humans stand above it and look down upon it, and heaven forbid that we're part of a qunatum system).
Exactly, we humans try to learn new things by relating to what we already know. This leads to trouble when we encounter new subjects that have no connection to previous experiences, because we have a hard time relating to it. However, the problem with people finding QM esoteric and weird is a bit more nuanced than that.
In most of the other areas of knowledge we can make progress because they do resemble reality in ways that we are familiar with. For example rotation in classical mechanics or special relativity can be somewhat confusing to a beginner, but if we think a little bit deeper than what we are used to then we can see that the results make sense and match what we experience. And also this experience is consistent at different scales. Now you move to QM and the first thing that hits you is that reality "breaks" after some point in the size scale, beyond that everything is different, with uncertainties, probabilities and a bunch of other odd properties. Learning QM is an exercise in mind-stretching, even for the most capable of us. For me the problem is not that it is different, but why is different. Why do we have such a gap between the large scale and the small scale? That is what baffles me.
Quantum mechanics is very simple and intuitive, after you remove the annoying physics (and the long history of misunderstandings that courses in the subject seem duty-bound to cover) from the mathematics. See http://www.scottaaronson.com/democritus/default.html
PS. IvoDankolov: I find it difficult or impossible to think intuitively about quantum phenomena.