Walking the Planck

June 17, 2020

Planck’s principle is bleak. It says that scientists rarely change their minds. Instead, they die, and younger scientists, brought up with an updated set of theories, replace them. Put succinctly, it states that “Science progresses one funeral at a time.”

Here’s the quote from Max Planck’s Scientific Autobiography (published posthumously in 1950):

An important scientific innovation rarely makes its way by gradually winning over and converting its opponents: it rarely happens that Saul becomes Paul. What does happen is that its opponents gradually die out, and that the growing generation is familiarized with the ideas from the beginning: another instance of the fact that the future lies with the youth.

This is incidental evidence that the 1950s promised to be a good time to be young, with regard to the cycles of youth I mused about yesterday. (Zweig had made a similar claim in favourably comparing the early 1940s to the 1890s.)

Certainly there were anxieties about youth as the baby boom took off, but Planck reminds us that there was hope too — for the future, if not for the minds of the older generation.

Polanyi seems more sanguine about the speed of scientific progress. In The Republic of Science (1962, PDF), he argues that Planck was himself the beneficiary of a relatively rapid paradigm shift:

Scientific opinion imposes an immense range of authoritative pronouncements on the student of science, but at the same time it grants the highest encouragement to dissent from them in some particular. While the whole machinery of scientific institutions is engaged in suppressing apparent evidence as unsound, on the ground that it contradicts the currently accepted view about the nature of things, the same scientific authorities pay their highest homage to discoveries which deeply modify the accepted view about the nature of things. It took eleven years for the quantum theory, discovered by Planck in 1900, to gain final acceptance. Yet by the time another thirty years had passed, Planck’s position in science was approaching that hitherto accorded only to Newton. Scientific tradition enforces its teachings in general, for the very purpose of cultivating their subversion in the particular.

Two things here:

  1. The tension between scientific dissent and scientific authority is exactly the tension I described between the avant-garde and her critics.
  2. Thirty years is a generation, but that’s how long it took for Planck’s canonisation. It only took eleven years for the acceptance of a paradigm-shifting idea, which is genuinely pretty good. Polanyi’s point is that progress had been much more rapid under science than, for example, it had been under the Catholic Church, because science encouraged and assimilated dissent, rather than discouraging or silencing it. Under Church dogma ideas might languish for centuries, if they were lucky enough not to be doomed to oblivion. (Not that there weren’t merits to the church; I’ll write more about religion later, starting here.)

Thomas Kuhn coined the term “paradigm shift” in his incredible Structure of Scientific Revolutions (suspiciously also 19621). Such shifts, he writes, can be hard:

Just because it is a transition between incommensurables, the transition between competing paradigms cannot be made a step at a time, forced by logic and neutral experience. Like the gestalt switch, it must occur all at once (though not necessarily in an instant) or not at all.

How, then, are scientists brought to make this transposition? Part of the answer is that they are very often not. Copernicanism made few converts for almost a century after Copernicus’ death. Newton’s work was not generally accepted, particularly on the Continent, for more than half a century after the Principia appeared. Priestley never accepted the oxygen theory, nor Lord Kelvin the electromagnetic theory, and so on. The difficulties of conversion have often been noted by scientists themselves. Darwin, in a particularly perceptive passage at the end of his Origin of Species, wrote: “Although I am fully convinced of the truth of the views given in this volume …, I by no means expect to convince experienced naturalists whose minds are stocked with a multitude of facts all viewed, during a long course of years, from a point of view directly opposite to mine. … [B]ut I look with confidence to the future,—to young and rising naturalists, who will be able to view both sides of the question with impartiality.”

At this point Kuhn quotes the same passage from Planck that I quoted above. It seems salient that paradigm shifts are essentially binary. But also note the timescales: a century, half a century, then Planck’s eleven years. They seem to be getting faster…

What if paradigm shifts, which once occurred only inter-generationally, had begun to occur intra-generationally? In Copernicus’ time (1473–1543), it took more than three generations. In Newton’s (1643-1727), it took nearly two. By the turn of the twentieth century, it took about a third of one generation. How many times might a scientist born today change his mind? Does the question not seem to be asked fairly often?

Could, in short, Planck’s principle have been true in his time (1858–1947), but be true no longer?

What if this is an indicator that adult plasticity via juvenescence is increasing over time, with real consequences for the speed of cultural change?

Of course, however plastic individuals may (or may not) have become, institutions, incentives, or groups of individuals might impede such shifts. So plasticity is not the whole story. But I’m beginning to wonder whether something hasn’t changed in the past few centuries.

  1. I noted a lot of similarities between Kuhn’s view and Polanyi’s, and I am evidently not the only one; I may need to investigate this.

I'm Bryan Kam. I'm thinking about complexity and selfhood. Please sign up to my newsletter or see more here.