physicsworld.com Comment: Robert P Crease Critical Point The Treiman effect

Robert P Crease discusses an day of each semester, hanging it in his office in case of sartorial emergency.) often-overlooked feature of the Yet Treiman was not warm and fuzzy. He discovery process was cool and clearheaded – reserved with- out being remote, dedicated without being distant. Treiman knew that a researcher The art of discovery comes in two versions. CERN Collaboration, CMS usually gropes about with a complex of One is the formal textbook version often assumptions, intuitions and speculations promoted by my philosophical colleagues. that form a kind of mental map. Any dis- The other is messy reality. The latter, how- covery you then make is also significant in ever, has few phenomenological traits that that it brings new trust in this map, even might help us construct a theory about when you find elements must be changed. discovery in general. A rare instance is Research is like filling in a crossword puz- something I call the Treiman effect, named zle: finding that a certain word fits solidly after the late Princeton University theorist and securely confirms not only that word Sam Treiman. but also the validity (or invalidity) of the I met Treiman just once – and that other pencilled-in words that had inspired was only briefly at a conference – yet the you to come up with it in the first place. encounter was enough to make me admire Treiman took an unconventional route the way he was not content with the usual into physics. He had originally studied formal and tidied-up pictures of scientific chemical engineering for two years at discovery. I’ve also spoken with many of his Northwestern University, attracted there former students, who remember his deep Multiplicity The route to a discovery, such as the in 1942 by the subject’s “nice mixture of and intuitive grasp of scientific practice. Higgs boson, has more than one consequence. science and practical usefulness appro- One of them, my colleague Alfred Gold- priate to a time of war”. After a spell in haber, recalls that whenever Treiman fin- they came from (singly ionized) helium, but the US Navy, where he learned to repair ished discussing some extraordinary new noted that – contrary to Bohr’s proposal – radio equipment, Treiman moved to the discovery, he would often say, almost as a the frequencies were not 4 but 4.0016 times University of Chicago, acquiring bachelor, catchphrase, “So…we are invited to jump their values for hydrogen. When Bohr Master’s and PhD degrees in physics. He to two conclusions at the same time.” One realized that he had not accounted for the then landed a job at Princeton, where he conclusion would be about the discovery increase in effective or “reduced” mass of was to spend virtually his entire academic itself. The other would be that the route the electron when it revolves around the career – first in an experimental cosmic- to the discovery has more than one conse- helium instead of the hydrogen nucleus, he ray physics group, then in particle-physics quence, and finding those consequences recalculated the frequency ratio and found theory. Treiman’s background in engineer- reinforces one’s confidence in them all. it should indeed be 4.0016. This agreed ing and experimental physics surely played As an example, Goldhaber cites Niels with experiment to five significant figures. a role in his clear-eyed assessments of the Bohr’s famous trilogy of papers of 1913– “Game, set, match!” Goldhaber says. research process. 1914, in which he proposed the then seem- Bohr had not only discovered that the ingly far-fetched idea that electrons in an Pickering series was indeed produced by The critical point atom can exist only in specific, discrete ionized helium, but had also greatly rein- It is easy to oversimplify the discovery pro- orbits. Bohr’s idea resolved at a stroke the forced scientific confidence in his then- cess – to portray it as moving progressively mechanical problems that plagued Ernest radical assumptions about atomic struc- from a solid base of what we know, guesses Rutherford’s “planetary” atomic model ture. This episode overwhelmed the scep- about what we don’t, tests of those guesses and, moreover, accounted for the spectral ticism of many scientists regarding Bohr’s and new knowledge added to the original lines of hydrogen that had been quantified audacious proposal. “It showed that you base. The Treiman effect, however, directs by the Swiss physicist Johann Jakob Balmer weren’t dealing with a single discovery,” our attention to a deeper process at work (see June pp34–38). But Bohr went further, says Goldhaber, “but with a complex of in which each new result affects our assess- arguing that lines in the spectra of the Sun things that snapped together as neatly as a ment of the path we have been taking all that had been seen by the Harvard astrono- car door slamming into place.” along. This is as true of the Higgs boson mer Edward Pickering with four times the discovery as of the Bohr atom; the Higgs frequencies of the Balmer lines must be A physicist’s physicist discovery does not simply give us another from helium. (Twice the nuclear charge Treiman, who died in 1999 at the age of particle, but reinforces our trust that we gives four times the frequency.) 74, specialized in quantum field theory, in were on the right track in the first place. Other scientists, however, argued that which he mentored many of the finest US The Treiman effect shows us that, in often Pickering’s lines came from hydrogen, but theoretical physicists, including the Nobel strange ways, our research programmes with denominators in Balmer’s formula laureate Steven Weinberg. Often called a continually feed back on all of what we that were four times smaller, and hence “physicists’ physicist”, Treiman was famous thought we already knew. frequencies that were four times bigger. for his beautifully organized and fluently Bohr faced a different challenge from the delivered lectures. He would give these as Robert P Crease is a professor in the Department of British astronomer and spectroscopist if prepared for manual labour, with shirt Philosophy, Stony Brook University, and historian Alfred Fowler. Fowler studied the Picker- sleeves rolled up to his elbows. (He did have at the Brookhaven National Laboratory, US, ing lines in his laboratory and verified that a jacket, but would wear it only on the first e-mail [email protected]

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