Quantum mechanics is unusual in that first, while it underpins essentially all of chemistry and most of physics, there are several different interpretations of it, although all agree that the Schrödinger equation is correct. The only problem is, what does it mean? A second point is that the Schrödinger equation is perfectly deterministic. By that, I mean, if you know the value of ψ for any set of variables, you know the value for any change of variables. The problem is, you never observe ψ, but rather you observe position, momentum, energy, or some other more measurable variable, and it is from this problem that all the interpretations arise.
In a post last year I mentioned I had published an ebook entitled "Guidance waves, an alternative interpretation of quantum mechanics", so you might ask, what made me do this? Why cannot I accept ordinary quantum mechanics? The first reason I have alluded to in a previous post. As a student in my honours year (and in those days, your future tended to depend on one big effort in honours finals) I had trouble following a lecture on the hydrogen molecule, and indeed I protested that the function being used should actually be more predictive of the helium molecule. What happened next was that I decided to explore the possibility that the molecular properties were determined solely by wave properties, on the basis that the Schrödinger equation was inherently a wave equation. Wave physics permitted some additional relationships, and I was surprised to get essentially the correct answer on my first attempt, inside a quarter of an hour. What bothered me next was it soon became apparent my lecturers did not understand quantum mechanics, and I was a few weeks short of finals. Finals were to some extent competitive; this was a sorting process, and in principle quantum mechanics was something I felt I was more capable of than the others, but what do you do when those marking your papers don't understand? I tried the library, but most of the books were already taken out. What I did find was the book by de Broglie. What I did not realize was that his was considered a minority interpretation. What I did realize was that the physics background given to chemists was totally inadequate for understanding quantum mechanics. Thus started my heresy! The second point that started my heresy was the Copenhagen Interpretation that the physics were determined by the act of observation. Rightly or wrongly, I always felt Einstein's comment that observation recorded what happened, and did not determine it. That Bohr seemingly over-ruled Einstein does not make Einstein wrong, at least in my opinion.
I still think one point of my initial concern stands. If you want to understand chemistry, I fail to see how you can get by without some understanding of Maxwell's electromagnetic theory. You do not have to be expert in manipulating his equations, but you should understand what is involved. Similarly, it is difficult to come to grips with quantum mechanics if you have no idea what a Lagrangian is, or what action is. I think advanced University chemistry courses need to pay some attention to these matters, and they did not when I went through.
Anyway, back to the issue. The second reason I feel the Copenhagen interpretation of quantum mechanics is wrong is Einstein's objection, in the EPR paradox. What this can involve is two entangled photons heading in opposite directions. If you determine the polarization of the first, and its polarization is determined by the act of observation, then the polarization of the second is defined instantly, and given relativity says no signal can exceed light speed, the second photon cannot know what the first one did. The problem with relativity is commonly dispensed with by arguing that you cannot send messages by this means, so relativity is not violated. To me, that is arm-waving. Either the second photon had its polarization pre-determined, or it fixed its polarization dependent on what the first one did, and it has to "know" that somehow. To me, that indicated the polarization was pre-determined. For me, to require an electromagnetic signal to travel faster than the speed of light violates both Einstein's relativity and Maxwell's electrodynamics, and I think special evidence is needed to justify that.
The third reason I feel the Copenhagen interpretation of quantum mechanics is wrong is the Schrödinger cat paradox. The idea that the physical values are determined by the act of observation, as opposed to being recorded by the act of observation, creates its own difficulties for me. The first is the obvious one: who observed the early Universe? To argue that all those photons with a variety of red shifts are created by the telescope is bizarre, but the cat paradox, for me opens another question that I have never seen addressed: what comprises an observation? A detection by a physicist is clearly an observation, but back to the cat: why cannot the cat observe itself? If it did, then the cat is always alive until it can no longer observe, in which case it is dead, classical physics reigns, there is no "half alive-half dead wave function", and there is no paradox. For me, the usual evasions of these apparent paradoxes (for they are only paradoxes within the Copenhagen interpretation) are pure sophistry.
All of which set me off in a search to justify my back of the envelope calculation of the properties of hydrogen. That in itself has been interesting, if a little frustrating at times, because what I found is that most people do not really want the standard interpretation questioned, even if they do not understand it at all.
