I’m writing a bit for the book-in-progress about neutrinos– prompted by a forthcoming book by Ray Jaywardhana that I was sent for review– and in looking for material, I ran across a great quote from Arthur Stanley Eddington, the British astronomer and science popularizer best known for his eclipse observations that confirmed the bending of light by gravity. Eddington was no fan of neutrinos, but in a set of lectures about philosophy of science, later published as a book, he wrote that he wouldn’t bet against them:
My old-fashioned kind of disbelief in neutrinos is scarcely enough. Dare I say that experimental physicists will not have sufficient ingenuity to make neutrinos? Whatever I may think, I am not going to be lured into a wager against the skill of experimenters under the impression that it is a wager against the truth of a theory.
As an experimentalist, I initially found that kind of flattering. Of course, as a writer and academic, I feel an obligation to get the sources right before I go quoting things in a book. and “make” there is kind of an odd word. So I did a bit of Googling and found a piece of the source online. With a bit more context, the quote becomes a little more ambivalent:
I am not much impressed by the neutrino theory. In an ordinary way I might say that I do not believe in neutrinos . But I have to reflect that a physicist may be an artist, and you never know where you are with artists. My old-fashioned kind of disbelief in neutrinos is scarcely enough. Dare I say that experimental physicists will not have sufficient ingenuity to make neutrinos? Whatever I may think, I am not going to be lured into a wager against the skill of experimenters under the impression that it is a wager against the truth of a theory. If they succeed in making neutrinos, perhaps even in developing industrial applications of them, I suppose I shall have to believe – though I may feel that they have not been playing quite fair.
The question is raised whether the experimenter really provides such an effective control on the imagination of the theorist as is usually supposed. Certainly he is an incorruptible watch-dog who will not allow anything to pass which is not observationally true. But there are two ways of doing that – as Procrustes realized. One is to expose the falsity of an assertion. The other is to alter things a bit so as to make the assertion true. And it is admitted that our experiments do alter things.
The extra sentences made me wonder again about what he was really saying. This almost sounds like he’s accusing experimentalists of being willing to resort to fraud– of ginning up something that would look and act close to what a neutrino is supposed to be, so as to deceive more righteous skeptics. That made me much less charitably inclined toward Eddington’s quote.
That is, however, a pretty bold accusation to make. But, of course, the fragment from Google Books left out the bits to either side of that, so I couldn’t make out what he was really up to. Which is maddening, and seemed to demand yet another trip to the library stacks.
Happily, a little more time with Google turned up the full text (as a Word document, of all things, that I’ve been cutting and pasting the above out of). And adding yet more context makes the whole thing less awful– the “artist” reference is a callback to an earlier analogy about the distinction between “finding” and “creating” reality, most clearly in this paragraph from a bit earlier:
Substance (if it had been possible to retain it as a physical conception) might have offered some resistance to the observer’s interference; but form plays into his hands. Suppose an artist puts forward the fantastic theory that the form of a human head exists in a rough-shaped block of marble. All our rational instinct is roused against such an anthropomorphic speculation. It is inconceivable that Nature should have placed such a form inside the block. But the artist proceeds to verify his theory experimentally – with quite rudimentary apparatus too. Merely using a chisel to separate the form for our inspection, he triumphantly proves his theory. Was it in this way that Rutherford rendered concrete the nucleus which his scientific imagination had created?
Seen in that light, the original bit is… well, somewhere between the first two extremes. It’s not quite as complimentary to experimentalists as I originally thought, but not quite as insulting as I thought on the second reading. I’m not hugely enamored of the general line of argument– it strikes me, frankly, as the sort of thing that sounds really deep at first but ends up not meaning much of anything, and at worst shades toward providing aid and comfort to New Age piffle about creating the universe via consciousness collapsing quantum fields and that sort of thing. But at least it doesn’t completely ruin the first quote for use as a transition to talking about Reines and Cowan and the direct detection of neutrinos (warning: PDF).
I suppose I should just be grateful that it didn’t turn out to be entirely apocryphal, as far too many really good lines do. I’ve already written too many “there’s little to no evidence that ____ actually said this, but it’s a great line…” asides.
I didn’t get an accusation of fraud from that, on first reading. I understood “alter things” to mean, experimenting and observing has the potential to change things, either in a Heisenberg uncertainty kind of way, or something more mundane, such as a loose optical cable –> faster-than-light neutrino kind of way. And in that sense, he’s wary of discarding a theory that doesn’t agree with experiment (or, conversely, of accepting a theory because it *does* agree with experiment). And that can be criticized for what it is, but I don’t think it’s an accusation of fraud.
The sort of line that Eddington takes here is familiar as a place on a multi-dimensional spectrum that includes various kinds of realism-to-anti-realism and invention-to-discovery in History and Philosophy of Physics. I find it hard to say that any one place is “right”. Even now we could say that neutrinos aren’t quite as real as electrons, in the sense that we can’t, as Ian Hacking would say, “spray” neutrinos with quite the same commonplace practical engineering application as we can spray electrons, atoms, and molecules (not counting spraying significant fluxes of neutrinos through the earth’s crust as especially commonplace or practical).
I can imagine a quantum field theory in which there are still electrons but the phenomena that are currently accounted for by neutrinos are accounted for by a different theoretical construction — although I’m not holding my breath, for such a change would presumably either remove or change the nature of the Higgs field and necessitate other large-scale changes to the SM — whereas accounting for the phenomena that are currently accounted for by electrons in a significantly different way would presumably wipe almost all of the SM into the history books.
Thanks for your musings on the History of Physics. I find myself comfortable a little more towards the invention end of invention-discovery than you appear to be.
It’s possible Eddington is just not being very clear here, but I think I have an idea of what he’s saying.
He says he’s not impressed by neutrino theory. But he also says he would accept the existence of neutrinos if experimenters made them. I think he’s drawing a distinction between theory and reality. Reality does whatever it does, and theories are just models we come up with to explain reality. When reality and theory are in accord, we say that the theory is correct.
So he may not like neutrino theory for whatever reason, but he’d be willing to admit that reality contains some particle that looks an awful lot like what the theory says neutrinos should look like. He doesn’t have to accept a theory, but he must accept reality.
I believe a similar thing happened with atoms early on. There came a point when the evidence was strongly in favor of the existence of atoms, but many chemists continued to believe otherwise, thinking they were just a convenient fiction that made the math work out. You could use the concept of atoms, but they didn’t correspond to anything true in reality. Maybe Eddington believed neutrinos would end up in the same boat.
I read it as a talk about the limits of experiments.
1. While unquestionably essential to all our progress they cannot tell us what objectively exists, only what works as a model. Different models that lead to the same experimental facts cannot be told apart.
2. Experiments only estimate relative utility of theories, they cannot give us an absolute measure of their quality. The fact that neutrino theory is the best explanation we currently have doesn’t mean neutrinos really exist or even that their theory is anywhere close to the hypothetical final theory.
3. Experimenters tend to be biased in favor of known explanations. For example are the bumps in LHC spectra really confirming the Higgs boson theory or are they viewed that way only because people expected to see Higgs boson in their data? In the later case it’s the experimenters who are *making* the Higgs real. I wouldn’t bet against the Higgs existence now but at the same time I am not entirely comfortable with the claimed discovery precisely because it was a Higgs fishing expedition from the start.
“The other is to alter things a bit so as to make the assertion true. And it is admitted that our experiments do alter things.”
I kind of read that as something like this. If you tell someone they’re going to see a zebra at the zoo, and then you show them a horse with stripes painted on it, they’ll probably believe it’s a zebra. Or maybe more to a point, they may think that all a zebra really is is a horse with stripes painted on it.
Kind of like how, around the turn of the 20th century, the concept of the ether kept becoming more and more complex as various experiments put more limitations on the properties the ether must have The experiments that were done altered the idea of the ether, until at some point Einstein came along and pointed out that we could just do away with the whole concept entirely.
I think Eddington may have been going after a similar bent. That no matter what a neutrino was in theory, if someone went out and found a neutrino, the theory would change so that it matched.