In 2016, Ronald Kleiss and I were asked to present a course on the science canon for the Higher Education for the Elderly (HOVO). Several short-lived lifelong learning programmes have meanwhile succeeded the former HOVO programme. In the preparation of the session, we mostly found trampled paths. We did not much fancy that, and in a corny mood, Ronald introduced the tabé canon, an anagram to the Dutch word bèta for science, and sounding like tabee, Dutch for goodbye.
Many theories seem good at first glance but are not as good on second thought. An example is phlogiston, a colourless, odourless, tasteless, weightless substance that emerges from combustion. Relatively soon after the theory was launched, attention shifted to what is put into combustion: oxygen. Now, much later, combustion products play an important role again, albeit that phlogiston can take many forms, such as NO2 and CO2, to mention some present-day tormentors.
Some theories are just fiction spiced up with fraudulent observations, like cold fusion, for which the last grants in the US recently expired. Then, there are theories about things that evade measurement. For instance, there was a professor of parapsychology at Utrecht Universiteit until 2014. Other theories were not so much fundamentally disproved but primarily refined. Instead of the earth at the centre of the universe, it became the sun, and presently, any place is a good centre of the universe.
The most interesting category is where, with growing insight, validity fluctuates. My personal favourite is the vacuum. In the nineteenth century, the notion emerged that electromagnetic radiation (say light) propagates as waves in the æther. Einstein’s theory of relativity rigorously expelled this idea. Present-day quantum field theory sees, for example, light particles as wave-like excitations of an omnipresent vacuum field.
I draw two lessons. First, the truth can be time-dependent. Secondly, sticking to a theory, even though the present evidence is against it, is not always a bad idea. But often, a bad idea is just that. Only sticking to one’s truth is also not always best. The big question is to estimate when to jump on a newly departing train or when to explore the already-known station further. If you know, tell me.
