Saving Newton or destroying Newton? Popular and professional physics publishing in the 1920s

The below is based on a paper that I’m going to be giving at the 24th International Congress of History of Science, Technology and Medicine (iCHSTM). It’s an academic conference, but there are also public events and stuff (if you happen to be in Manchester at the end of July). And there’s a blog, where this post originally appeared.

History is a tricky business. For the majority of those who study it, our main source of information is words. These were written down long ago (or perhaps not so long ago, depending on your preferred time period) and were chosen by particular people for particular purposes. There are endless complications. Is it possible to tell if somebody was speaking from the bottom of their heart or deliberately manipulating their audience? How are we to uncover what happened before, during and after the act of communication? Just what are we supposed to do with all these words?

I suppose we could start by looking at some context. For my paper at ICHSTM, the context is early-twentieth-century British physics. This was a period of quite dramatic change in the discipline – the last few years of the nineteenth century had seen the discovery of X-rays, radioactivity and the electron (disclaimer: J. J. Thomson conceived of this not as the ‘electron’ but as a similar-but-different ‘corpuscle’). This was followed by the quantum and relativity theories, which really shook things up. The atom was broken up, matter was disintegrating, energy was jumping around in tiny packets, and time and space were sort of the same thing. The natural world was no longer as it had first seemed. It was all very exciting.

But when it came to talking about these changes, putting them into words, there were certain difficulties. Depending on how you interpreted the new ideas, there was the suggestion that they overturned a lot of previous knowledge, including Newton’s laws of mechanics. This didn’t sit that well with the idea of science as progressive, building on the work of those who had come before. Physics in particular was supposed to be sturdy, providing the foundations of all other sciences. But instead we had a discipline whose very foundations could seemingly be destroyed at any moment. Just as damaging, physics was apparently breaking ties with the father of modern science himself, Sir Isaac Newton. The implications for public trust in science were rather worrying, and physicists needed to take this into account when they spoke about their work.

In 1930, the physicist James Jeans published a best-selling popular science book, called The Universe Around Us. Here, describing how one can use the speed in orbit and distance from the sun of any planet in order to determine the sun’s gravitational pull, Jeans noted that this ‘provides striking confirmation of the truth of Newton’s law of gravitation’. And while Einstein had ‘recently shewn that the law is not absolutely exact’, this amount of inexactness was only revealed in Mercury’s orbit, ‘and even here it is so exceedingly small that we need not trouble about it for our present purpose’.  In the following few pages, Newton’s law was ‘confirmed’ twice more, and Jeans found himself again levying ‘toll on the mathematical work of Newton’.  When he moved away from celestial space on to notions of time, Jeans yet again found that ‘it is a matter of complete indifference for our present purpose whether we use the law [of gravity] in Newton’s or in Einstein’s form; for stellar problems the two are practically indistinguishable, and there is abundant evidence . . . in favour of either’.  For practical purposes, Jeans noted that he was happy to use either theory, or even any other ‘not entirely dissimilar law’.

But did Jeans really think Newton was still relevant, or was this a deliberate attempt to present physics in a certain way, at a time when it was in danger of losing its precious connections to the beloved 17th century scientist? How do we uncover the true meaning of his words? Perhaps by looking at another aspect of Jeans’ career, his position from 1919 to 1929 as Physical Secretary of the Royal Society. In this capacity, Jeans had a considerable amount of influence over what was published in the Proceedings of the Royal Society of London (Section A), one of the most prestigious physics journals in Britain. He decided whether papers should be immediately published, immediately rejected, or sent to a reviewer. And in this capacity, Jeans was no friend to older ideas and methods.

Responding to a paper that tackled atomic structure without incorporating recent ideas in quantum theory, Jeans declared that in such a problem classical mechanics led nowhere at all. This angered the communicator (although not author) of the paper, the Cambridge mathematician and self-styled curmudgeon Joseph Larmor. He confided in his friend Oliver Lodge, declaring that Jeans was now banning Newtonian atomic theory from the journal. While this was certainly an exaggeration, Jeans’ work at the Royal Society does indicate a hefty bias towards ‘modern’ physics. This is evident not just in his comments on papers, but also his choice of referees, with papers being passed on to ‘modern’ reviewers.

While Jeans was writing a popular publication that stressed the continuing importance of Newton, he was using a professional publication to dismiss ‘Newtonian’ contributions to the field. He was helping to establish a new status quo of modern physics, at the same time as obscuring the extent of this change from the wider public. The words he published, and allowed others to publish, were carefully chosen to create two contradictory consensuses (consensi?).

Of course, you might argue that quantum theory was fully accepted by the 1920s, so of course Jeans would choose quantum theorists as referees and reject papers that attempted to bypass now-established theories and practices. And perhaps his popular book was simply a valiant effort to hide certain anti-Newtonian developments from a naïve public that frankly didn’t need to know this stuff. This is one interpretation. An alternative is that we now think quantum theory was accepted by the 1920s because of the very editorial policies employed by Jeans. We might also suggest that Jeans wasn’t helping a confused public, but rather manipulating them to protect his, and his discipline’s, own interests. Words can be powerful tools.

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Why do we call it ‘modern’ physics and why should anybody care about the reasons why?

A rambling mess about my PhD

About 4 years ago, I applied for a PhD to study the transition from classical to modern physics in Britain. I knew relatively little about physics, having dropped it at school because it was boring and I was never able to understand how a fridge works. And I wasn’t really familiar with the categories of ‘classical’ and ‘modern’ physics. But I thought the project sounded interesting, and I really didn’t like my job. Miraculously, I was given money to quit and move to Manchester (which is something I thoroughly recommend doing). And I quickly set about trying to find out what it is I was supposed to be studying. As is so often the case with history, I was given a ‘received interpretation’ and told to look into it.

Here’s how the basic story goes (bear with me):
As the end of the nineteenth century approached, physicists were pretty pleased with themselves. They had the aether, this weird stuff that was everywhere and explained everything (slight oversimplification). They had a nice theoretical framework for important technologies like steam power. They had decided, and mostly convinced everybody else, that their discipline underpinned all others. And they could namedrop Newton whenever they liked. But then, with the twentieth century just round the corner, weird things started happening. Wilhelm Röntgen discovered X-rays. Henri Becquerel discovered radioactivity. J. J. Thomson ‘discovered’ the electron (although he called it a ‘corpuscle’ and didn’t conceptually relate it to the electron that his theory-inclined peers had been discussing). It would seem that matter was stranger than we’d first thought. And of course it got stranger. In the early twentieth century, quantum theory emerged, postulating that energy jumped around in little packets. This was a BIG problem for physicists of the Victorian tradition, who liked everything to be continuous and connected. Yes, matter had been discontinuous for some time, and was getting more so, as the atom was split up into little pieces revealing a void of empty space within. But physicists had managed to reconcile continuity with atomism by arguing that all these broken up bits of matter were swimming in the aether. Everything was still connected. But when discontinuity infected energy as well, it got a little bit harder to argue for continuity. And then there was also relativity theory to deal with, messing up time and space irreparably.

At some point after all these developments, people started referring to some types of physics as ‘classical’ and others as ‘modern’. And it stuck. Pretty soon we were looking back at the year 1900, conveniently situated between two centuries, and seeing a revolution in thought. X-rays, radioactivity and subatomic particles were all ‘classical’ – they didn’t defy the laws of Newtonian mechanics. Relativity and quantum theory were too weird – they became ‘modern physics’. Nowadays these categories seem quite obvious. Except that some people don’t really consider relativity theory to be modern physics, but rather an extension of ‘classical’ mechanics. So there’s clearly something of a problem here.

My job (if you can call it that) was to go back to the first few decades of the twentieth century and look at how physicists were actually using these terms, and for what purpose. Why was I doing this? What was the point? Well, that’s what historians do – they look at stuff that happened and say “Hey, this actually occurred slightly differently from what you thought. So? Um, well, you know, nuances.” You have to have some kind of purpose in your life. I do actually occasionally read very good arguments about why history is important, but then I forget them, like I forget everything, because I’m a bad academic in that respect. So I’m pretty sure there’s a fairly good reason for all of this, I just can’t quite remember. Maybe I’ll figure it out. Something to do with helping us think about why we think the things we think about science.
(While I was writing this, Rebekah Higgitt and James Wilsdon were writing something much more important about how history can be used by policy-makers, which answers some of the ‘why’ questions)

Moving beyond whether this is at all important in the larger sense, my research was certainly important for historians of early twentieth century physics (of which there are at least four). Because when you separate an entire discipline into ‘classical’ and ‘modern’, there is the temptation to only look at the ‘modern’ stuff. And then it all gets a bit Whiggish. But classical and modern physics weren’t two separate entities for quite a long time. Our retrospective artificial separation results in an incomplete picture and incorrect characterizations of the people involved. Certain ‘classical’ scientists and institutions get dismissed. We start to see them as obsessed with the ether and continuity, stubbornly clinging to theories that are clearly wrong. We fall into the trap of assuming that people believe ‘wrong’ theories because of stupid philosophical commitments, and that people believe ‘right’ theories purely because they’re correct. Our own biases cause us to only ask certain questions.

Not every historian makes this mistake – in the 70s Paul Forman argued that the development of quantum mechanics in German-speaking countries was directly influenced by the wider intellectual culture of Weimar Germany, which rejected notions of causality and determinism. It was such a good idea, that people now refer to this as the ‘Forman thesis’, which must be pretty cool for Forman. (I met Forman once, in a Chinese restaurant in Washington, but embarrassingly I hadn’t heard of him or his thesis before then. And, more embarrassingly, I fled the restaurant after about two minutes because the humid Washington air was making me miserable. I made excuses about my weak English constitution, went back to my poorly air-conditioned B&B and watched Jersey Shore for 2 hours. It was a high point in my academic career.)

People believe things for all sorts of reasons. And physicists in the early-twentieth century often believed multiple things that, from our current point of view, seem incompatible. It was not unheard of for a physicist to simultaneously praise quantum theory and the aether. So you can’t lump everybody into two categories, particularly if they weren’t even using the categories at the time.

So why did these categories come about? We can find some clues if we look more broadly at other stuff that was going on at the same time. Modernist literature and modern art both emerged towards the end of the nineteenth century. The Church of England had its own modernism, with Anglican Modernists challenging the orthodox view of Christ’s divine status. What these all had in common was a challenging of past authorities and a sense of disconnect with the past. Physics was facing this very problem.

God knows why all these various disciplines all started using the same terms – somebody was definitely copying somebody else. But it’s sort of not surprising that physicists latched on, as these categories are particularly useful for science. Unlike many other disciplines, science is supposed to be progressive, and it tends to make a big deal out of this fact. An artist can quite happily decide to start drawing faces that don’t look like faces, and then get into a philosophical discussion about what art even is, but they sort of get away with it. (Apologies for my description of art – I’m a philistine. Also a lot of modern artists and writers actually did initially struggle with the problem of rejecting old ideas, so what I’ve written isn’t entirely true) But when physicists start devising theories of motion that reject everything that had been believed for the past 200 years, then we have problems. Science had built up a reputation as this great route to knowledge, better than anything else, and physics puts itself at the very centre of this. We’re supposed to trust it. But how can we continue trusting it, when the physicists themselves admit that they’d been wrong all along about the very fundamentals of what they were doing?

We can see the classical / modern divide as a way around this. By designating Newtonian physics as ‘classical’, a word with grand connotations, physicists were able to push him to the side a bit without rejecting him completely. He wasn’t wrong, just different. So they were doing ‘modern’ physics, whilst ignoring ‘classical’ physics, but arguing that they were both physics and they were both good and please don’t lose faith in us, we’re doing our best.

The end.

I was going to put some actual historical evidence in this blog post, but I typed for too long, so never mind. Maybe another time.

P.S. postmodern physics