How the Twentieth Century Started Ahead of Time

The Centennial Encounter of a Physicist

by PHILIP MORRISON

NRICO FERMI is said to have evaded some query about a new particle with this rebuff: “Young man, if I could Eremember the names of all those particles I would have become a botanist.” (It is true that the first really new particle, the neutrino, was first understood—and, in fact, was given its Italian name—by Fermi himself.)

4 SUMMER 1995 BEAM LINE 5 X-ray photograph of a snail shell taken by SLAC physicist Hobey DeStaebler at the Stanford Physics Department in 1962 (×2.4).

If I could have recalled dates well, level that he was then a very foun- I might have become a historian! tain of opportunity to do good for Many physicists share my inner need physics students anywhere. This for such approximation, and so it is time it was the Oklahoma City Uni- not really remarkable that twentieth- versity that would provide me an century physics itself began a few audience for a rousing popular talk years early, on New Year’s Day of on something new in physics. I can- 1896. On that day Professor Wilhelm not really recall my topic; pretty sure- Roentgen mailed from his universi- ly it was about quasars or supernovae ty at Würzberg the preprints of his or the microwave background, some- forty-ninth paper. (His first forty- thing out of current astrophysics, eight are less well known.) He in- presented for the interested but cluded an X-ray photo of his own unspecialized student of physics. hand, a piece of bone-hard evidence The details were elided by Zach; for the new penetrating radiation. So we always worked on mutual trust. much the books tell us. There would be an evening public My own encounter with the dawn lecture on the Oklahoma City cam- of twentieth century physics was per- pus to which I had acceded cheerfully sonal, but of course second-hand. long before. But a luncheon meeting Even so veteran a member of the APS earlier in that day was my first en- as myself doesn’t go all the way back counter with my hosts. It was to Gibbs and Helmholtz. But the marked by experiences unique in all anecdote makes vivid connection my years of such little formalities. with Roentgen on this present oc- The luncheon setting was not at casion, the hundredth anniversary of all novel; a lot of people sat at table his recognition of X rays. in some club or hotel dining room, The story unfolds in an unex- whom I faced from my place at a long pected location in space-time, Okla- table among a dozen or so who were homa City, Oklahoma, about 1976. singled out for introduction. What I found myself in Oklahoma was novel was my luncheon partner, through the formidable persuasive who was sitting beside me. He was a powers of Jerrold Zacharias, physi- spry and articulate elder, and I soon cist and impresario at MIT. Zach had learned that this day was—at least already drawn me to MIT years for official purposes—his own hun- before. He was so energetic and ef- dredth birthday. Not only was he a fective as an organizer and standard- man of unrivaled seniority, but he setter for science education at every was the focus of the whole event, my

6 SUMMER 1995 X-ray photograph of two spring- blooming daffodils taken by Hobey DeStaebler (×0.5).

The interior of Roentgen's laboratory at Würzburg. lecture and all. A pillar of Oklahoma “This morn- City life, he was a generous bene- ing’s newspaper factor to the City University, and the brought a report owner, if I remember well, both of that a German the city’s main newspaper and of its professor has dis- chief TV station. Plainly he was ruler covered an ex- on this day of all days. traordinary new I was there, a visitor from MIT,to form of radia- speak about physics on campus at his tion, one so pen- express request for a good lecture. He etrating that for instance he is able had very sound reason; the now- to photograph the bones within the powerful centenarian had been a living hand, or a coin hidden inside physics student while an undergrad- the pages of a thick book. The sto- uate, and he still loved and admired ry is not very complete, but it says the subject. He had drifted away into enough about how it was done that a long career in journalism to reach I think we could duplicate the results an elevated level of achievement, but with apparatus we have right here in he still wanted to talk physics when our college laboratory. he could. At some point I came to ask “It would be wonderful to do that, him about his days as a student of and perhaps we might even be the physics so long ago, and he unfolded first in all America to repeat his re- this wonderful narrative. sult, since we are getting started in He was then a student at Colorado the first hours of the morning. Let’s College in Colorado Springs. One get going; first we’ll collect what we morning in January 1896 he came to need and then set it up. the physics lecture room as usual. “If we all work together we can But the lecturer was filled with un- easily do the job by lunchtime. Will common excitement. (Here I can you join me?” only paraphrase what I recall from The delighted class set about the my hundred-year-old companion .) task. The needed materials were all “Gentlemen,” began the lecturer, soon found on the lab shelves: the big “something so unusual has happened sparky induction coil, the Crookes that I want to seek your help. If you tube, the fluorescent screens, the consent, we will not simply go ahead darkroom materials, the filters of with the planned lecture. Instead we black paper....Soon it all came to- will all work together in the lab to gether. And it worked! By lunch- an amazing new purpose. time my host recalled running over

BEAM LINE 7 Roentgen out walking later in life.

to the Colorado and the physics of the twentieth cen- College chapel to tury had begun, for good and for ill. borrow a large What a story! Yet it was to be Bible in whose capped that very evening. Of course pages they could I could not fail to re-tell the phys- hide a silver coin. ics student’s birthday story as a pref- The excitement ace to my lecture. It went well, al- was unforgettable. though certainly it was a digression. Of course they were not to be the After my talk, a young man came up first in America to run the experi- to speak to me. He was no under- ment. For the morning papers had graduate; he introduced himself as carried the story very widely. Col- a physics postdoc at work for a year orado had an irremediable handicap: or two in Oklahoma. His home was its longitude. So far west, they were Germany, where he had taken his late in starting, behind the many doctor’s degree. What he told me was physics labs of the Eastern time zone a family story that he had first heard a couple of hours as the earth turns. in his childhood, often told and re- Many had had a similar idea, and told in his presence. It was his elderly some of the Easterners would surely uncle, a physician, who was the sto- be first. I have no real data on exact ryteller. times or even dates, but I do know That man had been a medical stu- that Penn, Princeton, Columbia, Cor- dent in Würzberg in 1896. He took nell, Harvard, Dartmouth, and oth- physics from Roentgen. One day the ers recall very prompt repetitions Professor told his physics class of his of Roentgen’s wonderful result. recent work and demonstrated it This result came as though a seed briefly. Now, it is an ancient custom crystal had been dropped into a sat- in the German universities for stu- urated solution! The new physics dents to indicate high pleasure and crystallized out everywhere at once; approval by remaining seated in place the requisite apparatus was already while beating their shoes smartly on there in all serious labs around the the floor. In the usual lecture theater world. On the 20th of January, Henri there the seats rise up in rows step Poincaré, who had received a New after step, to allow all to view the lec- Year preprint from Roentgen himself, ture table. The floor structure is thus showed the marvelous photos to the hollow and resonant, and the noise session of the Paris Academy. Henri of the footbeats is grand. The stu- Becquerel was there, an expert on dents that day approved mightily of fluorescence like his father before Roentgen’s miracle, and continued him, and by March 2 Becquerel had their racket, so Uncle reported, for found, largely by happy accident, that one full hour without stopping. a uranium compound emitted some Twentieth-century physics was made such active radiation spontaneous- welcome for the first time. ly, without requiring exposure to It is curious that the best-known light or any other energizing input. finding of twentieth century physics Radioactivity had been discovered, was made in the same well-seeded

8 SUMMER 1995 context on the brink of WWII in Jan- uary 1939. The celebrated Berlin ex- perimenter Lise Meitner, newly ex- iled in Sweden, spent Christmas Day in a park near Stockholm with a vis- itor from Copenhagen, her younger nephew, physicist Robert Frisch. The two talked over the amazing new re- port from Meitner’s old lab that demonstrated that uranium upon ir- radiation by neutrons yielded ra- dioactive products that included not only the expected elements close to uranium in atomic weight, but one that was only about half as heavy. At one point in the conversation they

both came to an explanation and photo soon mutually understood that ura- AP nium had fissioned into two heavy ces that every serious nuclear phys- This X ray image, taken in North fragments, and that the fragments ics lab then held, as forty-three years Providence, Rhode Island, Thursday, must fly apart with unprecedented before every lab working with elec- Feb. 16, 1995, shows a diamond ring energy, to be detectable by the heav- trical discharges through gases al- that was swallowed by a robber to fool police. ily ionized tracks they left in matter. ready had its Crookes vacuum tube Within two weeks Frisch had seen and high voltage source on the shelf. on the oscilloscope screen the un- History had repeated itself. The mistakable strong spikes of ioniza- first time the stunning discovery was tion they had expected. rather light-hearted, in those shad- Their news came out even before ow photos through closed books and publication, by word of mouth direct bony hands, but the second time it from Niels Bohr, who had sailed off was fateful. By the spring of 1940 six to a conference in Washington held governments, all of them already at in the last week of January. With- or close to war, had each formed its in days eager phone calls back to own initial organization to seek home labs by the physicists who had large-scale energy from uranium. heard Bohr had induced the produc- For the last few years we have tion of those very spikes in many come to share reason for hope that places (I saw them myself then at the hundredth anniversary of fis- Berkeley); within weeks they were sion, when it arrives, will indeed be certainly familiar all over the world. commemorated mainly among the You had mainly to scrounge a small physicists, and not everywhere to amount of uranium compound in the universal public dismay instead of chemistry storeroom. The fission prolonged applause. spikes were easy to find with the little ion chambers, oscilloscopes of modest gain, and weak neutron sour-

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