28 January 2023

The Day Without Yesterday by John Farrell: How did Lemaitre do it?

My first post on John Farrell's The Day Without Yesterday 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) The second post looked at the intellectual environment and ended like this:

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?

This question is really interesting to me, and John sets it up brilliantly throughout the book before asking it explicitly in the penultimate chapter (pp. 186-7):

... Lemaître's insights were in fact key in almost all the important milestones of early modern cosmology... He was the first to see how the Einstein and de Sitter models were but two limited cases of a larger body of expanding universe models; he was the first to see that such models had to evolve from a super-dense state; and perhaps most importantlyfrom the very beginninghe was the first to tie the predictions of relativity about cosmology to actual astronomical observations. How did he do it?

I wrote previously that Lemaître is a scientific hero. It's not enough to point to his scientific accomplishments, which are historic by any account. I think his greatness is magnified by the fact that he stood apart, clear-eyed, amongst a cadre of brilliant minds who were somehow unable to see what he could see. I don't think you can read The Day Without Yesterday without feeling admiration and even awe toward the priest-scientist.

Before we look at how John tackles the "how did he do it" question, let's take a side trip to compare Lemaître's accomplishments to those of Watson and Crick. Here are some facts about the unveiling of the structure of DNA:

  • it was world-altering;
  • it answered big important questions;
  • it satisfyingly explained a lot of key observations;
  • it depended on brand-new technology;
  • it birthed a subdiscipline of science;
  • it's, well, famous.

Those things are all true of big bang cosmology. But Watson and Crick simply don't evince the kind of foresight that Lemaître showed repeatedly. I think Watson and Crick deserve some credit for boldness but, to me, nothing else in their story stands out. (Nothing positive, that is.) They were just the first. There was no powerful undercurrent of resistance to the idea. Others could have and soon would have figured out base pairing. Rosalind Franklin was probably just months behind. Once everyone saw the double helix, they were immediately convinced.

That story is different from big bang cosmology in every important way. Lemaître was unique. How?

Here are the possibilities John discusses:

1. Lemaître was young. The last post noted that Lemaître's contemporaries all grew up with Newtonian physics, and operated with a "neo-Newtonian" perspective. Lemaître grew up with Einstein's physics.

2. Lemaître was a more integrated thinker. He combined the local (e.g. stars and their evolution) with the global (the universe). He came to cosmology from theoretical physics but knew the math, the physics, and the astronomy. The latter point seems to have distinguished him from Einstein.

3. Lemaître was a believer. John devotes his final chapter to an account of how Lemaitre navigated his own faith/science relationship, and much of the focus is on Lemaitre's deep disappointment with the misuse of his work by the pope. It's a great chapter, an inspiring end to the book, and the reason why I think The Day Without Yesterday is more than just a fascinating biography of a scientific hero. But my question is: how did Lemaître see what others couldn't? And I think it's worthwhile to consider how his faith could have given him an advantage.

It's impossible to know the man's mind and heart, but it seems to me that Lemaître's view of the universe, as a creation of the Christian god, made him fearless. (John quotes another scholar making this suggestion.) In our age of rampant misinformation and shameless fearmongering, fueled to a depressing extent by various mutations of Christianity, it is hard to imagine that there was once a hero of science, who was a priest of the Catholic Church, who was so confident in his Creator God that he had no fear while considering how the universe came to be. In other words, it seems there was no answer to the question "did the universe originate in a single hyperdense point?" that was a threat to him. Remarkably, it seems that many of his unbelieving colleagues were more afraid of the answer.

Lemaître's story should inspire believers and unbelievers alike. He doesn't seem in any way to have been a radical, but his ideas were intensely radical. Yes, the ideas were soundly based on math and data, but they boldly challenged foundational ways of thinking that were essentially universal (and ancient). Lemaître knew this, but he was unafraid. I don't think we can ever know how he thought and felt about the fact that his colleagues, including Einstein, were stubbornly blind. And while it doesn't seem he was ever demeaned or hindered on account of his faith, I still think we owe him deep respect for his somewhat lonely pursuit. One way to do that is to tell his story: John has done that beautifully. And another might be to remember him whenever we sense that a new view or idea or theory is pushing us in ways we don't like. We can think of how Einstein himself needed that reminder, while we remember the hero Lemaître who led the way.

So, the next step for you is to read the book. The next step for me is to see if John is willing to answer some questions or add some comments/insights. Stay tuned!

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