Michael Fowler UVa Physics
(Note: this first part overlaps, and is partly derived from, Fred Brown’s essay.)
Beginning in 1896, at the first dawn of modern physics, Llewellyn Hoxton was an undergraduate at the University of Virginia, studying physics under Professor Francis H. Smith. At that time, the Rouss Physical Laboratory was nearing completion at the south end of the Lawn, the new Rotunda still under construction at the upper end. The Rouss was one of the buildings replacing the burned down northern extension of the old Rotunda. Hoxton and his brother Archie lived in the home of Professor Echols on East Lawn.
Hoxton went on to do graduate work at Johns Hopkins, and returned to Virginia in 1906 as an adjunct professor (equivalent to the modern assistant professor). The following year Professor Francis Smith retired, and since young Hoxton was the only physics professor he was de facto chair. (There were some instructors.)
Hoxton proved to be a brilliant teacher, he created memorable lecture demonstrations, students even brought their dates to the Saturday lectures.
The Physics Department continues to honor him with an annual Hoxton Memorial Lecture. President Colgate Darden said of Professor Hoxton: “I remember with greatest pleasure my student days under him. He was one of the greatest teachers I have ever known, loved by all of us who studied under him.”
In Hoxton’s student days, Professor Smith had taught a rather limited physics sequence, even by the standards of the time. The only areas Smith covered were Newtonian mechanics and acoustical phenomena. Hoxton dramatically expanded the syllabus, introducing not only electricity and magnetism, but also X-rays and electrons, recent discoveries that were causing great excitement. In what little spare time he had, he completed his thesis and gained the Ph. D. from Hopkins in 1916.
In the half-century 1896 – 1948, the UVa Physics Department was transformed from a pretty good, but essentially undergraduate, teaching operation to a modern productive Physics Department, with well-funded research groups.
How did that come about? After all, relatively little of note had happened in UVa Physics during the preceding century. What changed?
Luckily, we have a participant eyewitness account covering almost the whole period of change!
That is, Llewellyn Hoxton’s 1948 Report to President Colgate Darden.
This is—allegedly—just a Departmental Annual Progress Report, but it’s Hoxton’s final year—out of 43—as Chair of Physics, and President Darden is new on the job, so, fortunately for us, Hoxton seizes the opportunity to give a very frank appraisal of how the Department and the University have done so far, and what he thinks is needed for the Department to develop successfully.
Hoxton begins by making clear what he considers essential in a university:
no institution can … even be called a university, unless productive scholarship is well known to thrive within its walls. Productive scholarship is here understood to include not only the publishing of scholarly research, but the training of persons, graduate students chiefly, to carry on the torch.
Applying this standard, Hoxton found (see his report) an antipathy to “productive scholarship” among many of the faculty from the 1850’s on. To quote him: (parenthetical remarks are mine, MF)
… there was a fruitful period for the advancement of knowledge in this School from 1838 to 1853 (mainly William Barton Rogers). Then followed a long period of sterility with a brief flare-up from 1897 to 1905 (largely Humphries’ self-funded efforts). After that followed a period of slow, almost stationary, growth until 1928.
Not much of a progress report!
There are many reasons why the sciences at UVa were struggling in the early 1920’s (and before). In particular (and in contrast to its competitors, Harvard, Yale and Hopkins), the University was publicly funded, but too few Virginia legislators were enthusiastic about paying for Jefferson’s vision of a purely secular (they would say godless) state institution with the teaching mainly by foreign professors. And, few foreign professors with the right qualifications found the salaries and conditions at Virginia appealing.
In 1927, then, UVa Physics looked doomed to almost stationary growth for decades. But then everything changed.
The funding problem eased dramatically in 1928, when the General Education Board (GEB), unsolicited, initiated an eight-year grant with (first year) $25,000 for UVa Physics, Chemistry and Biology. The GEB fund was launched in 1902 by John D. Rockefeller, with an initial capital of one million dollars (later increased to $140M), and targeted among other things science research infrastructure in the American South. A (GEB) committee visited UVa, assessed it as promising, and OK’d the grant. At almost the same time, the duPont Corporation gave significant money for graduate student support, and finally even the state was shamed into increasing the annual appropriation. But none of this largesse would have gotten us to the Manhattan Project without a further lucky break.
At this moment, we back up in time just slightly to bring another thread into the story.
In 1914, Dr. Carroll Sparrow joined the faculty. Dr. Sparrow was brilliant but disorganized—an inspiration to his graduate students, a nightmare for most undergraduates.
Probably Dr. Sparrow’s greatest contribution to physics was in 1923, when he challenged graduate student Jesse Beams to measure the rapidity of the photoelectric effect—when light falls on certain metals, electrons are emitted. The question was: is there a measurable delay time between when the light hits the metal and when the electrons begin to shoot out?
This was a very interesting question, because the well-established classical electrical theories of Faraday and Maxwell suggested there would be a measurable delay for dim light, but the new quantum theory of Einstein predicted no delay at all. By 1928, after receiving his Ph.D., Beams (now with E. O. Lawrence at Yale) continued to work on the problem and they established that if there was a delay, it was shorter than three nanoseconds, a far shorter time than that predicted by the old physics for the low light intensity they were using. This famous experiment (which deserved a Nobel Prize, at least in my opinion) is still quoted in some standard textbooks on quantum physics.
Beams put limits on the very short time by using a rapidly rotating mirror, as Foucault had done to measure the speed of light decades earlier. To spin the mirror quickly enough, he attached it to a “spinning top” recently invented by Belgians Henriot and Huguenard: a cone-shaped rotor in a cone-shaped stator, driven and supported by jets of compressed air. H&H had reached 660,000 rpm, a factor 10 improvement on fastest rotating systems at the time.
Here are two direct quotes from Hoxton’s 1948 Report:
Beams from 1929 and both Beams and Snoddy separately and as a team have directed essentially all of the research done in this laboratory, and have made the University well known at home and abroad. It is a matter of particular pride to us at Virginia that our additions to knowledge are the fruits basically of homegrown ideas and not from ideas developed in other institutions such as Chicago, Hopkins and the like and then transplanted here.
Before 1906 only two Ph.D.’s in Physics were granted in the history of the University. From 1906 to 1921 there were none. Since then there have been fifty-seven of whom 7 were graduated before 1929. About half of these Ph.D.’s have gone to colleges and Universities, at least six of whom are department heads. About one quarter have gone into the research laboratories of the government or of the foundations, while a few of these have gone to medical research laboratories. Finally a quarter are in industrial laboratories, two having set up independent establishments of their own.
In the fall of 1928, Beams returned to Virginia (from Yale) as an associate professor. (The generous job offer made possible by the Rockefeller money.) His main interest at the time was in centrifuges, possibly because as a youth on his family farm in Kansas he had operated the cream separator, and now perhaps the spinning top could lead to a faster centrifuge. Furthermore, it was by then apparent that the centrifuge was becoming an important tool in chemistry and especially biochemistry, measuring sizes of large molecules by observing their behavior in large centrifugal fields.
At that time, Theodor Svedberg in Sweden developed what he called an ultracentrifuge, with centrifugal fields tens of thousands times more intense than gravity, and by studying sedimentation (falling and settling through fluid) rates, he proved, for example, that hemoglobin was composed of very large well-defined molecules, having atomic mass of order 67,000.
This was a completely unexpected result—almost nobody believed molecules could be that big.
Unfortunately, Svedberg’s beautiful ultracentrifuge, lavishly financed by the Swedish government, was too expensive to reproduce anywhere else. Beams decided in 1930 that perhaps the spinning top he used for rotating mirrors could be the basis of an affordable ultracentrifuge. It needed to be somehow encased and stabilized. Working with the shop mechanic Arthur Weed, they constructed one, and wrote it up in a 1931 article in Science (1931 Jul 10;74): “A Simple Ultracentrifuge”. By early 1931, they had reached 500,000 rpm. In early 1932, Beams added a Pyrex rod so that light absorption and index of refraction could be observed as functions of radial distance.
In 1933, Beams’ graduate student Edward Greydon Pickles decided to join Beams’ ultracentrifuge project, to study large molecule sedimentation, and hopefully to get to smaller molecules eventually. A main problem was that frictional heating of the rotor (its outer surface moving at close to the speed of sound) caused convection currents in the sedimentation chamber, stirring up and cancelling the sedimentation. This heating could be eliminated by having the rotor spin in a vacuum, but it was driven by a compressed air turbine.
Pickels’ solved this problem by a redesign of the apparatus: two separate chambers, one for the turbine, one for the rotor, with the rotor spinning in vacuum to eliminate frictional heating and therefore convection currents. The two chambers were on the same axis, joined by a thin steel central wire carrying the power and passing through an oil seal between them.
In 1935, Beams and Pickels achieved the first sedimentation of hemoglobin with affordable equipment (i.e. not Svedberg’s!). And, in letter to Weaver (at the Rockefeller Foundation) Beams gave credit to Pickels. Weaver realized that Beams-Pickles could be a “ridiculously cheap and simple substitute for the Svedberg technique”.
This Beams-Pickels vacuum ultracentrifuge was affordable, and, later, thousands were manufactured. After gaining his doctorate, Pickles moved to the Rockefeller Institute, continuing to work with others on the biophysical ultracentrifuge. Further improvements made possible the separation and characterization of viruses, leading ultimately to vaccines, such as the Salk vaccine for polio. Pickels went on to produce ultracentrifuges commercially, his company was called SPINCO, later bought by Beckman.
A quite different use of the centrifuge was in the separation of isotopes. The natural ratio of isotopic abundance, such as Cl35:Cl37, is the same everywhere, so natural physical and chemical processes don’t change it—except for really intense gravitational fields at low temperatures. Using an ultracentrifuge to change this ratio can give traceable chlorine. Beams and others successfully separated chlorine isotopes (using CCl4) in 1936 and later.
The importance of isotope separation increases exponentially in wartime 1942 with the first successful chain reaction (Fermi at Chicago), and suddenly Beams was funded to separate uranium isotopes for the Manhattan Project. The Rouss Building, containing Beams’ latest centrifuge, was placed under armed guard. In the end Beam’s method was not used for those first bombs—an immense diffusion plant was used instead. Beams’ project was classified, so was essentially shut down as the war ended. However, about ten years later the Atomic Energy Commission discovered that some German scientists were now working on uranium centrifuges in the USSR, and one, Gernot Zippe was invited and came to Virginia, to work with Lowry from August 1958 to June 1960, repeating the Russian experiments. As a result, the AEC added two centrifuge groups, at Oak Ridge and in California. This is now the standard method of separating uranium isotopes, referred to as enriching uranium.
To be continued…