18 January 2023

The Day Without Yesterday by John Farrell: "conservatism and hesitation"

In my first post on John Farrell's The Day Without Yesterday, I identified two themes the book raises for me: the intellectual milieu into which modern cosmology came to be, and the reasons why Georges Lemaître was able to "lead Einstein and the rest of his generation into a new, truly dynamic model of the universe." (p. 53) Let's look at that milieu.

The first chapter of the book describes the first time Lemaître and Einstein met in person. Lemaître had published a paper suggesting that the universe was dynamic, indeed that it could be expanding. On meeting Lemaître, Einstein brushed the priest off, even referring to the idea as "abominable." Wow.

Now, John suggests that Einstein was not being a jerk but was instead expressing his personal distaste (revulsion even) to the very notion that the universe was expanding. And this matters because:

The modern world's comprehension of the universe is one of the most fascinating subjects in the history of science. But the history of modern cosmology is one of constant doubt, second-guessing, obstinacy, missed opportunities, distraction, and outright denial. (p. 13, emphasis mine)

To me, that list starts like a normal recitation of human imperfection, hardly remarkable to anyone who has worked in science. Until the end. Obstinacy is bad enough (if fully human) but outright denial? That sounds a bit more serious. And it is.

Chapter 2 traces Lemaître's life up to 1927 when he endured Einstein's rebuff, while outlining developments in astrophysics that culminated in Einstein's maddening responses to work by an obscure mathematician named Friedmann. John tries to prepare us (p. 32):

Einstein's hasty objection and retraction concerning Friedmann's work seem to suggest a stubbornness based on more than simply what he knew of the stellar velocities of the time. They suggest a prejudice, an ingrown view of the cosmos inherited but never really questioned.

Chapter 3 ("A Universe That Evolves: The History of an Idea") takes us on a journey through human thought that shows that the idea of an evolving universe was frustratingly far from the Western mind for centuries. It seems that a static universe, not so different from now-laughable Greek models of crystalline spheres, was wired into the minds of even the legit geniuses of cosmology in 1927. John transitions to the meat of Lemaître's work with this more generous assessment of the problem in Einstein's head:

It's somewhat odd to see in retrospect how conservatism and hesitation manifest themselves in the history of sciencesometimes, as we saw in some elements of Greek thought, for centuries. Perhaps because of the general nature of this conservatism, it's unfair to ask why Einstein was content to plug the cosmological constant into his equationsin reaction to their clear suggestion that the universe as a whole could not be static. Einstein was preceded by generation after generation of thinkers who believed the same thing. (pp. 52-53)

"Conservatism and hesitation." Stubbornness. Prejudice. "Outright denial." What was going on?

The book discusses three possible explanations, which need not be mutually exclusive.

In the case of a dynamic universe, and especially one that had an "origin" in a singularity, there is the possibility that some minds had a religious prejudice one way or the other. Lemaître was (unfairly) confronted with the suspicion that his "primeval atom" theory was a way to identify a moment of creation. So, we know that the prejudice was there. But my impression is that the initial stubbornness was not aimed at an origin or singularitythose aspects came later. Einstein, especially, was resistant to a universe that changed at all. Once everyone agreed that the universe was expanding, there was a different discussion about the big bang and its implication of a beginning. During that debate, there were religious believers defending an eternal static universe. So, if religious conviction was a barrier to accepting the new model of the cosmos, it hindered people in all different directions.

Somewhat more technically, John notes that Einstein's generation had "grown up" with Newtonian physics. As had three centuries of astronomers and physicists. The expanding universe was initially revealed in the mathematics of Einstein's general relativity. But according to John, Einstein and his contemporaries "tended to approach the problems of the new cosmology in neo-Newtonian terms." That was a significant barrier. Lemaître was apparently immune, and that's for the next post.

The big one is what John calls "prejudice, an ingrown view of the cosmos inherited but never really questioned." I suggest that's the one for all of us to take note ofscience regularly offers up a view or an explanation that just doesn't fit with what we think we know. I can think of a few examples from biology: species that aren't fixed, genes that jump, RNA interference, reverse transcriptionthose are all concepts now known to describe straightforward reality but that pushed hard against things we thought we knew. In at least some of those cases, the initial observations just didn't fit into an existing framework. Something new had to be builta model or a theoryto hold the data. Once that was done, it all seemed easy. John paints a picture of great minds that, initially, just didn't have a place to put an expanding universe. Maybe you had a similar struggle when you first heard this fact. It's weird and non-intuitive, and we have the benefit of knowing that it's settled science supported by numerous observations.

This, then, is a great reason to read the book and to think about what Lemaître was up against. Some of the greatest minds in human history were overtly resistant to a new model of the universe, a model that was (at least in retrospect) clear from math and physics known at the time. If it could happen to them, it could happen to anyone, and of course it has happened constantly through intellectual history. I think we owe it to Lemaître to reflect on how it will happen again. It has to. Data doesn't wait for minds to be ready.

And yet somehow Lemaître's mind was ready. How? Why? That's the next post.

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