History of physics in the University of Oxford

Physics at the University of Oxford

IN THE FIFTEENTH CENTURY the New Learning brought to medieval Oxford the study of Greek and access to Greek Science. William of Wayneflete founded Magdalen College (1457) and a lectureship in Natural Philosophy, but the creation of Professorships in Geometry, Astronomy and Natural Philosophy was left to 1620. More important was the migration of scholars some thirty years later from London to Oxford, where they met in the lodgings of John Wilkins (1614-1672), Warden of Wadham College. His father was an Oxford goldsmith, said to be "a very ingeniose man and had a very Mechanicall head. He was much for Trying of Experiments..." a remark equally applicable to his son. John had the ability "to bring people together to discuss and debate,... especially in the new fields of natural and experimental philosophy... he may truly be accounted as the progenitor of the Royal Society." Among his group was Robert Boyle (1627-1692); with his Assistant Robert Hooke (1635-1703), Boyle lodged in the High Street, on a site now marked by a plaque placed in 1965 to commemorate the tercentenary of the publication of the identification of the living cell.
    Also at Wadham College was Christopher Wren, who became Professor of Astronomy (1657) at Gresham's College in London, and later became famous as an architect. In 1659 Wilkins left to become Master of Trinity College, Cambridge, but he was present with others of the Oxford group at the foundation meeting of the Royal Society of London, 28 November 1660. Another was John Wallis (1616-1703), Savilian Professor of Geometry from 1649 until his death; his important contributions to mathematics were acknowledged by Isaac Newton. Elias Ashmole (1617-1692) was also present; in 1675 he began negotiations for the foundation in Oxford of a museum to house the famous botanical collection of the Tradescants, with additions of his own. This, the first public museum in the British Isles, was housed in the old Ashmolean Building, now the The Museum of the History of Science ( >6 Kbytes), but for 150 years the centre of scientific activities in Oxford.

Astronomy and Astrophysics
Edmond Halley (1656-1742) published his first papers as an undergraduate in Oxford before he was 20 years old; he then departed to make stellar and magnetic observations on the island of St Helena. His famous star catalogue contained the first telescopic observations of stars in the southern hemisphere. Two further years (1698-1699) in the Atlantic Ocean produced the first maps of the geomagnetic field and of the prevailing winds (both invaluable for navigation). With Hooke he attempted to solve the problem of planetary orbits; in 1684 he found that Newton had already shown the orbit must be an ellipse, but had lost the proof! Halley encouraged Newton to expand his studies of celestial mechanics into the Principia; at his own expense he looked after its publication (1687). Halley realised that the great comet of 1682 was identical with those of 1607 and 1531, moving in an elliptical orbit. Its return in 1758, as predicted by him, greatly influenced the acceptance of Newton's theory in Europe, leading to the mathematical investigations of Euler, Lagrange and Laplace. Halley became Savilian Professor of Geometry in 1704; his house, with its top floor room for observing still stands against the city wall in Oxford.
    James Bradley (1693-1762) held the Savilian Professorship of Astronomy from 1721 to 1742, when he succeeded Halley as Astronomer Royal. From his observations of Stellar Aberration (1725-28) he deduced a value of 2.95x108 ms-1 for the velocity of light; he also showed that the annual change in declination arose from the nutation of the earth's axis through the gravitational attraction of the moon.
    In Oxford there was still no Observatory building when Thomas Hornsby (1733-1810) became Savilian Professor in 1763. An eminently practical astronomer, of abounding energy, he obtained funds from the Trustees of John Radcliffe (1652-1714), the great benefactor of Oxford, to build the Radcliffe Observatory (picture - 7 KBytes) (completed 1793). This was equipped with some of the best instruments of that era, and Hornsby's observations of light ascension and declination were not surpassed in accuracy until 1925.
    Hornsby and his two successors, Robertson and Rigaud, were each both Radcliffe Observer and Savilian Professor of Astronomy. The election in 1839 of separate holders of these positions left the University without an Observatory of its own. In 1873-1875 a new building (picture - 28 KBytes) was erected in the Parks for Charles Prichard (1808-1893), Professor from 1870-1893. With a new refractor and a wedge photometer, his great work was on comparative stellar brightness. His successor Herbert Turner (1861-1930) was largely responsible for compilation of the Astrographical Catalogue, an international project housed, like the centre for seismology, in the Observatory. After some controversy, the Radcliffe Observatory moved to Pretoria in 1935, while the University Observatory, under Harry Plaskett (1893-1980), Savilian Professor 1932-1960, became a centre for Solar Physics, eventually with two powerful solar telescopes and spectrographic equipment. Numbers remained small (some 8-10), but increased considerably under the present professor, Donald Blackwell. The study of solar and laboratory astrophysics continues, supplemented by high energy astrophysics, stellar and galactic research at telescopes in many parts of the world, together with theoretical astrophysics.

The old Clarendon Laboratory (1872-1939) and the Electrical Laboratory (1910-1945)
The duties (very much part-time) of a Readership in Experimental Philosophy, founded in the eighteenth century, were carried out mainly by the professors of Astronomy. From 1839 it became a full-time post, held by Robert Walker (1802-1865); his initiatives made physical science a university subject for study and examination in 1850, and promoted the building of the University Museum. In this he gave lectures and demonstrations, becoming Professor in 1860. His successor in 1865, R B Clifton (1836-1921) designed the original Clarendon Laboratory (12 KB): a "building of dark little rooms, winding corridors, and unexpected corners", it was the first purpose-built physics laboratory (1872) in the British Isles. Unfortunately Clifton believed that "the wish to do research betrays a certain restlessness of mind", though he gave space in the cellars to Charles Vernon Boys, driven from London to escape vibration, for the measurement of the constant of gravitation, G. When Clifton retired in 1915, the department was virtually defunct.
    John Sealy Townsend (1868-1957) was elected to a second chair as Wykeham Professor of Physics in 1900, and the Electrical Laboratory was built for him (1910). In 1902 he initiated the teaching of electricity and magnetism; well known for his work on gas discharges (including observation of the "Ramsauer effect"), from 1919 he also experimented on high frequency electromagnetic waves. In 1913 Henry Gwyn Jeffreys Moseley (1887-1915) arrived to work on x-ray spectroscopy; on display in the laboratory is his original diagram, the first arrangement of the elements of the periodic table in the correct order.
    F A Lindemann ("Prof") (1886-1957) became Professor of Experimental Philosophy in 1919, and immediately set out to obtain apparatus from the Admiralty and the RAF, and money to start research in the Clarendon Laboratory. By 1922 there were two Readers, Thomas Merton (1888-1969) and Alfred Egerton (1886-1959), and a Lecturer. With his father Lindemann developed (1919) a very sensitive photo-electric cell to detect light from stars, nebulae and comets; the current was measured by a new electrometer, designed with T C Keeley (born 1894). Thereafter Lindemann himself did no experimental work, but wrote papers on isotope separation, chemical kinetics and, many years later, on pure mathematics (including an important contribution to the theory of prime numbers).
    Derek Jackson (1906-1972) made the first experimental determination of a nuclear spin (that of caesium, in 1928), and then, with Heinrich Kuhn, developed the use of atomic beams to reduce broadening by the Doppler effect. As well as Kuhn, Kurt Mendelssohn, Franz Simon and Nicholas Kurti were brought from Germany in 1933-4 by Lindemann to establish a school of Low Temperature Physics, and work began on magnetic cooling by adiabatic demagnetisation. The film of liquid helium II was discovered by Bernard Rollin and Simon in 1938; details of its behaviour were unravelled by Mendelssohn and John Daunt.

The Clarendon Laboratory, from 1939
In a new building, occupied in September 1939, the majority of the research staff remained; most of them started war-time work on devices for centimetre waves and the far infrared. Reflex klystrons for 32 mm and 12.5 mm were developed, together with magnetrons and methods for determining receiver sensitivity, but the most important item was the transmit-receive tube suggested by Arthur Cooke (1912-1987), used in all radar equipment. Later in 1940 the remaining staff were recruited for the British atomic bomb project, but they transferred to the USA in 1943.
    In 1945 the new building had still to be equipped for its planned specialised areas, such as low temperature physics on a much enlarged scale. Studies of liquid helium and superconductors were resumed; the melting curve of helium was extended up to 40 K, and other thermal and electrical properties up to 300 K. The effects of defects caused by irradiation were observed through the reduction in the thermal conductivity, and "internal friction" was studied by ultrasonic measurements.
    Microwave spectroscopy began with the inversion spectrum of ammonia gas, and the discovery in 1945 of ferromagnetic resonance by James Griffiths was followed by the new field of electron paramagnetic resonance (EPR). In diamagnetically diluted crystals, values of the nuclear spins were established for isotopes (some radioactive) of the 3d, 4d, 5d, 4f and 5f groups. Paramagnetic relaxation measurements determined the hyperfine splitting in undiluted crystals, and NMR studies (including those on solid hydrogen) at low temperatures showed that in insulators thermal relaxation depended on paramagnetic impurities.
    The first successful nuclear alignment experiment (1951) employed a novel method suggested from EPR measurements of anisotropic hyperfine structure. Experiments to achieve nuclear cooling reached microkelvin temperatures in 1956, and nuclear orientation techniques have since been extended to include ion implantation, and on-line methods for short-lived isotopes. The High Magnetic Field Laboratory was created, from which an important commercial off-shoot is the Oxford Instrument Company, started by M F (now Sir Martin) Wood.
    In October 1956 Sir Francis Simon, elected to succeed Lindemann (Lord Cherwell), died before taking up office and Brebis Bleaney became Dr Lee's Professor (1957-1976). Solid state and atomic spectroscopy were extended, with an atomic beam apparatus including novel resonance methods to determine nuclear moments directly. Later, laser methods brought fresh activity in atomic spectroscopy, including non-linear effects, Doppler-free spectroscopy, and the study of weak interactions, and in solid state physics. Research activities have continued to expand under E W J (Bill) Mitchell, Professor 1977-1987. His successor (1988) is R A Cowley.

Atmospheric Physics
Study of the upper atmosphere began in 1920 when G M B Dobson (1889-1976) came to the Clarendon Laboratory as Lecturer in Meteorology (Reader 1927, Professor 1945). With Lindemann he deduced from meteor trails that the temperature of the upper atmosphere begins to rise above a height of 50 km, in contrast with the steady fall then expected. Realising that the source of energy for the warm layer is absorption of ultraviolet solar radiation by ozone, Dobson embarked on the study of atmospheric ozone that he was to pursue "with unrelenting vigour for the rest of his life". The ozone density was determined from the absorption of the solar spectrum in the region near 300 nm, using a special spectrograph of great simplicity (the original is now in the Science Museum, London). Extensive observations in 1925 established the seasonal variation of ozone (maximum in spring, minimum in autumn), and the close correlation with meteorological conditions in the upper troposphere and low stratosphere. Later, Dobson designed a sensitive, direct-reading photo-electric instrument, the prototype of the modern ozone spectrophotometer. Since the International Geophysical Year, 1956, for which 44 Dobson spectrometers were calibrated in Oxford, the ozone network has been a world-wide organisation.
    During World War II, Dobson and Alan Brewer, with a frost-point hygrometer, showed that the stratosphere (contrary to expectation) is very dry. Research on cloud physics continued under Brewer (Lecturer 1948, Reader 1956-1962). John Houghton, first Lecturer and then Reader, studied atmospheric radiation and ozone measurement, but in the main work turned to remote sounding from satellites. Nimbus 4 (1970), with the Oxford Selective Chopper Radiometer, produced global temperature maps in the laboratory the following day. Later satellites (Nimbus 5, 1972; 6, 1976; 7, 1978) provided extensions to the atmospheres of Venus, and then to Mars and Jupiter. In 1983, John Houghton (Professor 1976) became Director General of the Meteorological Office, and he was succeeded as Reader by F W Taylor. The following year the Robert Hooke Institute was formed for cooperative research with the Meteorological Office, and the title of the Department is now Atmospheric, Oceanic and Planetary Physics.

Theoretical Physics
Theoretical physics, of course, has strong links with mathematics, and many of the earlier Professors were primarily applied mathematicians. A E H Love (1863-1940) held the Sedleian Professorship of Natural Philosophy from 1898 to 1940. His work on the elasticity of solids had applications to the earth's crust, particularly his distortional surface waves, in which the disturbance is horizontal and normal to the direction of propagation; "Love waves" become of great important in seismology. In another two dimensional application on the surface of the earth, he was a devoted player of croquet.
    Sydney Chapman (1888-1970) held the Sedleian chair from 1946 to 1953. In Oxford, as President of the Organising Committee, he was a tireless publicist for the International Geophysical Year (1956); he was also a great cyclist. Later, he held Professorships simultaneously in Alaska and Boulder, Colorado.
    A E H Milne (1896-1950) was the first Rouse-Ball Professor of Mathematics (1928-1950). His early research on radiative transfer through an ionised medium was followed by estimates of the pressure and temperature in stellar atmospheres, and construction of a temperature scale for the spectral sequence of stars. From 1932 his main interest was the creation of a theory of "kinematic relativity", an alternative to the theory of general relativity that did not meet with wide acceptance. His successor, Charles Coulson (1910-1974), devoted himself to Theoretical Chemistry, transferring in 1972 to a new chair in this subject, but Roger Penrose (Rouse-Ball Professor since 1973) returned to the field of astrophysics.
    Love gave his lectures in the Electrical Laboratory, and Milne held joint seminars with Plaskett in the Observatory, where all his research students were housed, but their professorships were primarily mathematical and there was no interaction with the interests of the Clarendon Laboratory. This situation was remedied in 1945; the Electrical and Clarendon Laboratories were joined under Lindemann, and the Wykeham chair became a Professorship of Theoretical Physics, held by Maurice Pryce from 1946 to 1955. Pryce realised that the field of electron paramagnetic resonance was an excellent subject for theoretical students. He himself, with Anatole Abragam, Kenneth Stevens, Roger Elliott, Brian Judd and Mary O'Brien, worked closely with the experimentalists, so the subject advanced at great speed. In other fields John Ward, John Ziman, Stanley Rushbrooke and Cyril Domb were also there for a few years, with Roger Blin-Stoyle until 1962.
    Victor Weisskopf was Visiting Professor 1955-56; Dirk ter Haar came as Reader, and Willis Lamb as Professor (1957-1962), followed by Sir Rudolph Peirls (1963-1979), and now Sir Roger Elliott. With R H (Dick) Dalitz as a Royal Society Professor since 1963, the department covers astrophysics, elementary particle, nuclear and solid state theory.

Nuclear Physics
Minor experiments in nuclear physics were carried out in the old Clarendon Laboratory, where there was a high tension apparatus for 400 kV (at the back of the lecture room!). In the new laboratory a purpose-built high tension room contained Cockcroft-Walton sets for 400 keV and later 1000 keV; these provided valuable data for collision cross sections of the various hydrogen isotopes. An electron-synchrotron (125 MeV) produced high energy bremstrahlung for studies of nuclear photo-reactions. Hans von Halban (1908-1964) led a group in nuclear physics and nuclear orientation from 1946 to 1955/6.
    That year the personal chair occupied by Simon from 1945 until he became Dr Lee's Professor was assigned to nuclear physics, and held (with changes of title) by Denys Wilkinson from 1957 to 1976. Research made use of accelerators at Harwell and at Aldermaston, but in 1959 proposals for a large new nuclear physics laboratory at Oxford University were put forward, for research in nuclear structure and in elementary particle physics in roughly equal proportions. In 1960 an interim move to a disused school building released much-needed space in the Clarendon Laboratory. The building proposals were accepted, but that year the then Minister for Science wanted the whole project transferred to Harwell; this was yet another obstacle that would have deterred any but a determined and strong-minded professor, exceptionally adroit at arguing his case. Work began in 1962 on a new building, containing a negative-ion accelerator, injecting into a tandem van de Graaff for experiments on nuclear structure; elementary particle physics made use of international facilities, including the Rutherford Laboratory and CERN. Research under Professors Ken Allen and Donald Perkins has included neutrino experiments on nucleon structure; lepton studies of neutral currents; and low-energy studies of nuclear structure and nuclear magnetism. After the departure of Wilkinson in 1976, his professorship reverted to the Clarendon Laboratory, and is held by Patrick Sandars.

Research Laboratory for Archaeology and the History of Art
This may seem a surprising subject, but its roots and most of the staff stem from physics. It was conceived by Cherwell in 1950; with the Professor of Archaeology, Christopher Hawkes, he persuaded the University to create a Laboratory (1955) with two Senior Research Officers, E T (Teddy) Hall (now Professor) and Stuart Young, the latter soon succeeded by Martin Aitken (now Professor). Their work specialised in the non-destructive analysis by optical and x-ray fluorescence spectrometry of antiquities (not all turn out to be authentic); magnetic prospecting, and dating of fired clay objects by thermoluminescence and thermoremanent magnetism. Detection of buried remains (kilns, hearths, ovens) by the proton magnetometer was clearly a great advance over digging! More recently, separation of carbon-14 ions in an accelerator has reduced the sample size required for radiocarbon dating by three orders of magnitude (making possible work on the Turin Shroud). The journal Archaeometry, started by the Laboratory in 1958, soon achieved an international circulation.

The Undergraduate and Graduate Schools of Physics
Undergraduate numbers were small - from 2 in 1918, they increased rapidly to some 25 per year between the wars. During 1939-1945, the presence of a number of senior staff (still without official University positions) made it possible to teach 30 to 50 per year for a shortened two-year Finals course, and about 50 Airforce cadets per year in the Electrical Laboratory. Afterwards, undergraduate numbers grew steadily from some 50 per year to 80-90, with a sudden leap to 150 per year in 1957 at the end of National Service. Thus for many years Oxford has had much the largest physics school in Britain, with numbers now approaching 200 per year.
    An important innovation in 1946 was course work for graduates (now some 200 in total) to induce further study, particularly theoretical. Post-doctoral Fellows were invaluable both for research and for teaching. Initially they found jobs in Britain scarce, and many went to the USA or Canada, but the position improved in the 1960s with the foundation of new British universities, to the staffing of which Oxford made a substantial contribution.

Acknowledgements
For assistance in writing this article, I have been indebted to many of my colleagues; in particular, to Professors N Kurti, D E Blackwell and M J Aitken, and Drs M G Adam, R Berman, M A Grace and C D Walshaw, for help with both figures and text.

Bibliography
There is no general history of physics in Oxford, but some aspects are covered by the following articles.

Aitken M J 1978 "Archaeological Involvements of Physics", in Phys. Rep. C 40 277-351
Bleaney B, Cooke A H, Kurti N and Stevens K W H 1986 "F A Lindemann, Viscount Cherwell (1886-1957)" in Phys. Bull. 37 261-3
Dobson G M B 1968 "Forty Years' Research on Atmospheric Ozone at Oxford: a History" in Appl Opt. 7 387-405
Hartley Sir H (ed.) 1962 The Royal Society: Its Origins and Founders (London: Royal Society)
Hughes D W 1985 "Edmond Halley, Scientist" in J. Brit. Astron. Assoc. 95 193-204