John Paul Wild

Australia

1923-2008

Obituary:

John Paul Wild was born on 17 May 1923 in Sheffield, England. Paul described three ambitions when he was seven years old: to be a train driver on a King Class locomotive, to be an opening batsman for Yorkshire and to become a Fellow of the Royal Society. As he later said 'I was happy I achieved one of these’.

Paul went to Cambridge in 1942 and for the first year did the Mathematical Tripos Part 1; he switched to Physics to avoid going into war service but left to join the navy in July 1943. He became Senior Radar officer on the Flagship HMS King George V and spent the next two and a half years in the Pacific. Sydney was the base for the Pacific fleet and it was during his many visits to Sydney that Paul met Elaine Hull and they married after he returned to England at the end of the war.

In 1947, Paul joined Joe Pawsey's group at the Radiophysics Laboratory of CSIR (later CSIRO) in Sydney. Paul built a spectrograph to study solar bursts and set up a very crude field station with just a couple of trailers and an antenna not far from Penrith at the foot of the Blue Mountains outside Sydney. He used this instrument to display a frequency versus time (dynamic spectra) and named three types of solar bursts – Types I, II and III, distinguished by the way the frequency drifted with time. The series of papers published in 1950 became the foundations for all future work on solar bursts. He deduced that the Type II bursts were associated with shock waves coming out through the solar atmosphere at 1000 km/sec and were associated, thirty hours later, with Aurora in the earth night sky. They associated Type III bursts with streams of electrons being ejected at a third the speed of light and taking only an hour to reach the earth. The mechanisms proved to be correct and the nomenclature for the phenomena became the international standard. The dynamic spectra showed a slanting band indicating systematic decrease in the burst frequency with time. Paul realised that the slanting bands were due to the source of radiation moving outwards through the solar atmosphere. After ten years of research, Paul’s collected papers gained him a Doctor of Science degree from Cambridge. Paul's Sydney group had become the pre-eminent group in world for solar radio astronomy.

In the course of this solar work, Paul began to suspect that there were spectral lines in the solar burst they were observing and became interested in the radio spectrum of hydrogen. He wrote up an internal report related to the potential for spectral lines in the solar bursts. But when 'Doc' Ewen and Ed Purcell at Harvard in the USA first detected the 1420 MHz (21 cm) hydrogen line transition in the interstellar medium in 1951, Paul went back to his report, generalized it to include the hyperfine structure of hydrogen, and 6 months later published the first detailed theoretical paper on the hydrogen lines – a classic in the field.

Sunspot minimum occurred in 1955 not many years after Paul's solar radio spectrograph commenced operation and in this period solar observations were only recorded occasionally when sunspots were visible. Paul used the resulting availability of equipment and manpower to study the ionospheric intensity scintillations. He was joined by Jim Roberts and they measured the dynamic spectra of scintillating sources for the first time. They realised that the observed scintillations must be produced by the focusing effect of large refracting elements in the ionosphere but this work received very little recognition at the time and it wasn't until 1975 when the full theory of scattering by a power law spectrum was worked out that the role of the refractive scintillations which had been seen by Wild and Roberts 20 years earlier became clear.

In 1957 Paul realised that the 21cm hydrogen line could be used to measure the Zeeman Effect and Bolton and Wild published a paper that started the search for Zeeman splitting of the 21 cm line.

All the results from Paul’s solar group had been inferred from the spectral observations and there was a growing desire to make moving pictures of the radio Sun. Paul devised a unique beam forming method using an annular structure with 96 antennas on a 3 km diameter circle, the "Radio Heliograph". This would behave like a filled dish of 3 km diameter. The fast image generation needed exceeded the computational capability of contemporary computers and Paul invented a new image processing technique called J2 synthesis which used the real time electronic summation of Bessel functions to solve the imaging problem. The Radioheliograph commenced operation in 1967. It could produce dual polarisation radio pictures of the Sun at a rate of one 2-D image per second. These moving images led to our understanding of the evolution of the type II and type III solar bursts.

Paul was one of the driving forces behind the foundation of the Astronomical Society of Australia and he chaired the inaugural meeting in November 1966. He was one of the first vice Presidents of ASA and was also the editor of the Society's new Australian astronomy journal (PASA) for its first two years.

Paul succeeded Taffy Bowen as Chief of the CSIRO Division of Radiophysics in 1971. While continuing his interest in solar research, he now looked around for opportunities to use the skills gained from radio astronomy to provide a balance of pure and applied research. His group developed an aircraft Microwave Landing System to replace the ILS (Instrument Landing System). This new system called "Interscan" was eventually selected as the international standard.

Paul Wild was appointed Chairman of CSIRO in July 1978. He realised that the Organisation must adapt to bring it closer to the industries and the community which it serves and provide the scientific and technological leadership in a changing world. Paul emphasised the need to maintain an appropriate balance between fundamental research and the strategic mission-orientated research. While Chairman of CSIRO (1978 to 1985) Paul never lost sight of his key principles – ‘whatever the changes, one characteristic must remain inviolate: a high standard of excellence and originality. Without excellence and originality, research achieves nothing.' During this period he was instrumental in securing funding for major national research facilities in Australia, including the oceanographic research vessel, the Australian Animal Health Laboratory and the Australia Telescope. The Australia Telescope, consisting of a compact array of six antennas at Narrabri in northern NSW, was built on the site of Paul’s Radioheliograph and the Observatory was named the 'Paul Wild Observatory'.

A longstanding interest of Paul’s was gravitational theory. In his later years Paul published a modified Newtonian theory of gravity which satisfies the demands of special relativity. The resulting theory is simpler than the general theory of relativity but still yields the Schwarzchild metric and makes equivalent predictions. Although this is acknowledged as a valid and complementary approach to the theory of general relativity it has had limited impact and the work was still incomplete when he died in 2008.

Paul stands as one of the founding fathers of Australian Radio astronomy, a towering figure in the solar arena and a great scientific leader on the broader scene. He spent his entire professional career in CSIRO, despite some very attractive offers from elsewhere, including NRAO and Cornell. He clearly had an exceptional intellect, wide knowledge and a continuing and unstoppable interest in 'the new'.

Paul served as Foreign Secretary of the Australian Academy of Science from 1973-77 and was President of the International Astronomical Union Commission on Radio Astronomy from 1967-70.

Paul gained many honours. These include the URSI Balthasar van der Pol Gold Medal and the US NAC Hendryk Arctowski Gold Medal in 1969; the Royal Astronomical Society Herschel Medal in 1974; the Royal Society of London Royal medal and AAS Hale Prize for Solar Astronomy in 1980. He gave the Jansky Lecture in 1973 and the Australian Academy of Science Pawsey Lecture, in 1978. He was a fellow of the Australian Academy of Science, the Australian Academy of Technological Science and Engineering, a fellow of the Royal Society, a foreign member of the American Philosophical Society and a fellow of the American Academy of Arts and Sciences. He was made a Commander of the Order of the British Empire (CBE) in 1978 and a Companion of the Order of Australia in 1986.

Contributed by R.D. Ekers and R H. Frater

Reference:
https://rahist.nrao.edu/wild_bio-memoir.shtml