While I have been advocating efforts to find alternative theories, I do not wish to give the impression that I think most theory is wrong. There has to be a reason for anyone to seek an alternative theory, because without any grounds it is simply a waste of time, as illustrated by the periodic attempts by various people to defy the second law of thermodynamics and build a perpetual motion machine. Theories may come and go, but I have great faith in the lasting values of the second law.
Most other theories are far less robust but the question then becomes, what are reasonable grounds for seeking new theories, or at least revising current ones? One obvious answer is, a discrepancy between theory and observation. That is fine, except it raises a problem: how does the potential theoretician find the discrepancy? The experimentalist who finds it may well report it, but the experimentalist wants to get published and not buy a fight with referees, so if it is reported it is very rare for it to be highlighted and it tends to be lost somewhere in the discussion, maybe even embedded as casually as possible two thirds the way through a rather densely written paragraph. Worse, many discrepancies, when first found, tend to be ambiguous in interpretation, because since they were not sought, the experiment was not designed to specifically demonstrate what nature is trying to tell us, but rather to test some other hypothesis. Accordingly, the potential baby is lost in a sea of bathwater.
The reader of this blog should not simply take my word for that, which so far is simply an assertion. An illustration is required. My ebook,
Elements of Theory ends with 73 problems, so my challenge to you is, try one. (If you have read the book, thank you, but this challenge is not for you.)
Woodward and Hoffmann have stated that there are no exceptions to their rules. One reason (somewhat simplified) why this should be correct is as follows. The signs of the wave functions correlate with the signs of the amplitude of the wave, and the square of the amplitude, within the Copenhagen Interpretation, indicates the probability of an event occurring. If plus overlaps with plus, there is reinforcement, but if plus overlaps with minus, there is cancellation, and the square of zero is zero. With zero probability, that event cannot occur. Accordingly, at a first level analysis,
only permitted products can form. In practice, we do not expect perfect wave interference, so very minor contributions of the wrong products are possible.
Given that, here is the challenge. First, have any exceptions been found? This is important, because if so, it would show that something is wrong with theory. However, it does not follow that anybody finding such exceptions would recognize their significance, which means that finding them in the literature, if they exist, could be a real challenge. It may be that the only real way to find them is to ask as many people as possible, to dredge their memories and experience, so to speak. The second part of the challenge is, is there any theoretical reason why there could be an exception?
In a future blog, I shall give my answer to these questions, but before that I am particularly interested in other chemists' opinions, and in particular, any observations of which I am unaware.
