David Forbes Martyn was born on 27 June, 1906, at Cambuslang, Scotland, the son of Dr. Somerville Martyn. He was educated at Plymouth College and Allan Glen's School before entering the Royal College of Science in London. He graduated BSc, ARCSc, in 1926, obtained his PhD from that institution in 1929, and the DSc in 1936. The great depression was on its way when he graduated and research posts were very difficult to obtain.
The Australian Council for Scientific and Industrial Research (CSIR) had concentrated its work from its inception in fields of importance to the primary industries, since the export of wool, wheat and some other products of the land, earned virtually the whole of Australia's overseas income. It was surprising, therefore, that John Madsen, Professor of Electrical Engineering in the University of Sydney, was able to persuade CSIR to establish research in radio, through a Radio Research Board modelled on the British body with the same name, as the first departure from its original policy. His proposals were put forward in 1926. Following a conference and ministerial approval, the Australian Radio Research Board was established in 1927, and after the squabbles inevitable at that time, it set to work, with Madsen as Chairman, and a sum of £2,250 included in CSIR's estimates for 1927-29 for radio research. David Martyn was among the first four research officers appointed by the Board, with a salary of £450 p.a.
Before leaving Britain for Australia, Martyn worked on the stability of the triode oscillator, publishing three papers on this problem. He also developed a new method for measuring extremely small alternating currents. Upon arrival in Australia he submitted to the Radio Research Board two detailed proposals for his work. The first was that an attempt should be made to observe the reflection of very high frequency radio waves from the moon; the second was the suggestion that Appleton's frequency-change method of studying the ionosphere might be modified by transmitting continuous saw-tooth shaped frequency sweeps. The Board arranged for him to work in the Physics Department of the University of Melbourne, with Professor T.H. Laby, but after a year he joined other members of the Board's staff in Sydney. His second proposed project had been approved by the Board and was developed there. He soon discovered that it involved a subtle fallacy, and abandoned it to concentrate on echo-pulse sounding techniques. However, this abortive investigation proved important for the subsequent development of radar in the United Kingdom (see section on wartime activities).
In 1934 Martyn collaborated with V.A. Bailey in a theoretical explanation of the newly discovered 'Luxembourg Effect', where, under certain conditions, the modulation of one radio wave becomes imposed on that of another. They showed that this was due to a non-linear effect in the ionosphere. This explanation of the "interaction of radio waves" was quickly accepted and their paper on the subject is now classical.
In 1935 Martyn collaborated with A.L. Green in a paper which showed that the effective reflection point of radio waves in the ionosphere sometimes moved quite rapidly. This appears to be the first discovery of moving disturbances in the ionosphere, a topic on which a large literature now exists. In that same year he developed a theorem relating equivalent height and reflection coefficient at oblique incidence to that at vertical incidence. This is now known as "Martyn's Theorem" .
This work was concerned with various aspects of the propagation of radio waves via the ionosphere, an understanding of which is essential for the provision of a satisfactory country-wide broadcast system. In this he worked in close collaboration with the Postmaster General's research staff responsible for such broadcasting. The study involved fading and its causes and remedies, and included measurements of the polarization of the downcoming waves and how this might be utilized, in conjunction with a complex receiving antenna system, to improve reception.
He also widened the scope of his researches beyond the ionosphere to the study of all properties of the upper atmosphere above the stratosphere. Prior to that date the generally current view of the highest part of the atmosphere was that it consisted of hydrogen, and was very cold and still. There was however, evidence (from sound-ranging and meteor studies) that there might be a region at about 50 km that was slightly warmer than the stratosphere. In a now classical paper ('The temperatures and constituents of the upper atmosphere') communicated to the Royal Society of London by Lord Rutherford, the revolutionary views were put forward:
This paper, which was highly commended by Rutherford, aroused vigorous discussion when read at the Royal Society.
All the conclusions mentioned above have been substantially confirmed by later workers, notably by numerous post-War rocket and satellite flights. It is no exaggeration to say that this paper, of itself, transformed all subsequent thinking on almost all aspects of the high atmosphere.
Towards the end of the War, Martyn recommenced his fundamental researches, at Mount Stromlo Observatory, Canberra, opening up the study of solar tidal effects in all regions of the ionosphere, and of lunar effects in the upper (F2) region. This work comprised, in the first place, a detailed statistical analysis of an enormous body of data in the form of equivalent heights of the ionospheric layers. The results were the magnitudes and phases of the tidal effects in the various layers which, for the first time, were accurately determined. These were later related by Martyn and others to the theories of tides caused by solar heating and lunar gravitation, the outcome being a greatly improved understanding of these effects.
Later Dr. Martyn demonstrated the great variety and importance of electrodynamic effects in the ionosphere. It had long been recognized that at low levels where the density and collision frequency were relatively high, the gas could be treated as a conducting fluid, whose passage across the field lines induces an electric field. However, at greater altitudes, where the ion gyro-frequencies are much greater than their collision frequencies with neutral molecules, the ions are firmly fastened to magnetic field lines and do not move with the neutral molecules. They are caused to move by electric fields which are induced at the lower levels and conducted up magnetic field lines. This bi-polar drift, in turn, causes a drag on neutral molecules and so creates winds at the high levels. This basic work has subsequently been confirmed and extended to the earth's magnetosphere. Dr. Martyn also pointed out that the magnetic equatorial anomaly (low F2 peak electron density) was almost certainly due to electrodynamic elevation of ionization at the magnetic equator, coupled with diffusion down the geomagnetic force lines to latitudes on either side. This explanation is currently accepted. Finally, these electrodynamic investigations were adapted to the extension of the earlier work on small-scale moving disturbances. There was an error in the initial work in the conclusion that ion drift around a local inhomogeneity would lead to accumulation of ionization in a particular region; in fact it leads to a wave motion. However, this work stimulated much further theoretical investigation, notably at the Cavendish Laboratory, a field of activity which is now very extensive.
In 1946 Martyn noted that bursts of solar radio waves were associated with sunspot activity. He concluded that such bursts almost certainly emanated from sunspot regions and that they would be circularly polarized. Accordingly he devised an experimental technique which immediately showed that certain radio radiations from active sunspots were circularly polarized. This discovery has opened up an entire field of research.
Because of close contact with solar astronomers, Martyn became aware of the structure of the corona and of its probable temperature (1,000,000°C). He thereupon worked out the thermal radio radiation likely to be received from the solar corona and chromosphere. In particular he calculated that the sun would show a base thermal radiation corresponding to l,000,000°C at metre wavelengths; at shorter wavelengths a lower temperature running down to the chromosphere temperature of 10,000°C; and that limb brightening should be observed at wave lengths of 60 cm downwards. All these predictions have been confirmed experimentally, and Martyn's work stands, not merely as the explanation of results already found, but as a prediction of what was eventually found experimentally. In his paper on this subject. Martyn referred to the 'Quiet Sun', a term chosen to indicate absence of spots on the solar surface. This term has now passed into international usage, as for instance the IQSY, the International Years of the Quiet Sun (1964 – 1965).
In 1882 Balfour Stewart suggested that the diurnal geomagnetic variations were due to electric currents in the upper atmosphere, produced by the dynamo action of solar tidal winds in a conducting region in the presence of a magnetic field. Subsequent calculations by Schuster, Chapman and Cowling had apparently shown that the conductivity of the ionosphere was inadequate to account for the necessary currents. In 1948 Martyn suggested that the necessary conductivity was present if account was taken of the Hall effect. In 1953 he worked this out in detail in collaboration with W.G. Baker, and established that the world-wide conductivity of the ionosphere was adequate to explain the diurnal geomagnetic variations, and also that it explained the electrojet at the magnetic equator, which he had already attributed to specially enhanced conductivity in that region.
In later works Martyn made the first clear study of the morphology of storm geomagnetic variations in the ionosphere, and suggested a theory of their occurrence which is still under active investigation.
In 1956 Martyn pointed out that current rocket estimates of air density in the high atmosphere were in conflict with those derived from observations of ionic diffusion at the 300 km level. He drew attention again to this matter in a talk before H.R.H. the Duke of Edinburgh in a symposium held by the Royal Society of Victoria on 3 December, 1956. In October, 1957, the first sputnik was launched; it came to earth in a time consistent with Martyn's calculations; upper atmosphere densities have since been revised by a factor of 14.
Martyn established the Upper Atmosphere Section of CSIRO, in 1957, at Camden, New South Wales.
In early 1939, following political negotiations with Britain about the newly developed techniques of radar, Martyn was chosen to follow up with a more technical study. He found that the secret radar work being developed under Sir Robert Watson Watt was using pulse techniques. On the other hand, the Royal Aircraft Establishment (Farnborough), with Sir Edward Appleton's support, was pressing an alternative development using continuous frequency change, and there was serious argument whether a substantial part of the country's effort should not be diverted to this alternative, which appeared likely to be more efficient. The files on the matter were shown to Martyn, who recognized at once that the latter involved the fallacy which he had himself found earlier in the decade, but had not published. Watson Watt and Appleton accepted his reasoning immediately, and no further attempt was made to divert a part of Britain's defence effort into this channel. He returned to Australia in August, 1939, reporting en route to the Cabinet of the New Zealand Government upon these secret developments.
Shortly after reaching Australia, he reported to the wartime Cabinet. Very rapid agreement was reached that CSIR should set up a Division of Radiophysics, with Martyn as its Chief.
A Radiophysics Laboratory was established just before the outbreak of war in an enlarged part of the Standards Laboratory, situated in the grounds of the University of Sydney. Its earliest members, later to become group leaders, were J.H. Piddington (radar systems design), J.L. Pawsey (basic research), H.J. Brown (laboratory services). The initial efforts were directed towards adapting British equipment to use in Australia, but it was soon realized that this equipment was quite unsuitable for conditions here. The first new system designed was called Shore Defence Radar, for detecting and accurately locating surface vessels. This system was successfully integrated with the 9.2 inch and 6 inch coast defence guns, and although these played little part in the war, the day and night warning system was important as insurance. Its qualities were recognized by the British Army, and units were ordered to be sited in Malaya, Hong Kong and Burma. Fortunately the equipment had not been delivered when these areas fell to the Japanese.
An important aspect of the Shore Defence set was its provision of a basic design framework for the Air Warning Radar. The necessity for such equipment was realized immediately following Japan's entry into the war, and a unit was designed, built, and put into operation within a week. This particular set provided Sydney with its only air warning system for some nine months, although by that time Martyn had left Radiophysics.
A major difficulty in the use of radar by the armed forces was the development of adequate liaison between the designers and the users. Martyn recognized this difficulty and spent a great deal of time travelling to radar sites, lecturing to groups of officers and developing close contacts. Of these, the earliest and most fruitful was with Colonel (later Major-General) J.S. Whitelaw, who was largely responsible for the early introduction of radar into the armed services, and who became a close personal friend of Martyn.
In 1942, for reasons which are not now clear, Martyn was replaced by F.W.G. White as Chief of the Division of Radiophysics. This action affected Martyn profoundly. It left him with bitterness which became, at times, an obsession, and it coloured both personal and institutional relationships. It did not, however, reduce his desire to contribute, as fully as he could, to the war effort. He left the Division of Radiophysics in June, 1942, to direct an Operational Research Group for the armed services.
The group was restricted to weapon research in general, and radar in particular. It was not concerned with design and maintenance of radar, but with the scientific principles involved in its efficient operational use. The major activity of the group was an investigation of the effects of severe atmospheric refraction of radio waves and the consequent malfunctioning of radar sets. These studies led to a general improvement in the operational efficiency of radar, particularly along the northern coast of Australia.
In the 1930's, Australian physics had fallen into a backwater. Martyn and Pulley's paper ('The temperatures and constituents of the upper atmosphere') redirected world attention to physics in Australia. In particular, in 1936 Professor T.H. Laby, FRS, brought out to Australia Professor H.S.W. Massey, his former pupil, to study the implications of the new discoveries. Sir Harrie Massey, FRS, has since followed up these matters assiduously, and is now known internationally for his upper atmosphere and space research activities.
In 1950, because of his work on radio-emission from the sun, Martyn was recognized throughout the world as a leader in radio astronomy, and in consequence was elected at Zurich as President of the newly formed Radio Astronomy Commission of the International Union of Radio Science (URSI). He promptly invited URSI to hold its next General Assembly in Australia, although the necessary finance had not yet been obtained. Eventually this bold attempt achieved the necessary financial backing from the Commonwealth Treasury and Australian industry, and URSI held its next General Assembly in Australia, in 1952, the first time that any international scientific union met south of the Equator. This meeting showed the scientific world how far advanced Australia was, not only in ionospheric research, but also in radio astronomy.
At this time, discussions between CSIRO and the Department of the Interior resulted in an understanding that the Mount Stromlo Observatory would no longer pursue radio astronomical studies, to avoid duplication of effort with the Radiophysics Division of CSIRO. In consequence, Martyn reverted to ionospheric research, and after four years as President of URSI's Radio Astronomy Commission, was elected to a four year term as President of the Ionospheric Commission of URSI.
Martyn spent much effort in preliminary organization of Australia's activities in the International Geophysical Year, and in securing funds for this notable enterprise.
In 1959 the Australian Broadcasting Commission inaugurated an annual series of ABC lectures, which 'A prominent member of the Australian community would be invited to present the results of his work and thinking on one of society's major problems.' Dr. Martyn was invited to give the first of these lectures. He chose as his topic 'Society in the Space Age', a series of four lectures which has been published and recently re-printed by the ABC.
Mention has already been made of Martyn's Presidencies within URSI. In 1962 he was invited by the United Nations (following agreement between the US and USSR) to be Chairman of that body's Scientific and Technical Sub-Committee of the Committee on the Peaceful Uses of Outer Space. (This Committee is attended by the leading space scientists of 28 nations.) The Committee is also enjoined to achieve its objectives by unanimous consent. It has provided unanimously agreed reports on such matters as contamination of outer space, and has also set up an international research rocket range in South India. It is unique to have Australia chairing a UN Committee for a decade. This is due both to Dr Martyn's scientific eminence, and to his tact and impartiality in dealing with countries from the so-called West, East, and unaligned regions.
Dr Martyn was also elected for a four year term to the Executive Committee of the International Council of Scientific Unions (ICSU), the body controlling the activities of all international scientific unions and the joint activities of groups of unions. It is known that he was nominated by several countries for the Presidency of ICSU; however, he refused these nominations, stating that at the present time he considered that the President of ICSU should reside closer to the current centre of gravity of international scientific activities.
Dr Martyn was editor (for the Southern Hemisphere) of the international journal Planetary and Space Science; he was also on the Board of Editors of Space Science Reviews, and a member of the Board of Trustees of the International Astronautical Federation.
During the last three years of his life, Martyn became increasingly concerned with problems of conservation of the biosphere as the milieu of all life of which there is knowledge. The importance of action to preserve what remained of 'natural' environment for wild flora and fauna, and to counter man's senseless and increasing contamination of the atmosphere, the waterways and even the sea, was brought home to him through international discussion of the contaminants which space-vehicles could carry to other planets and the moon. As he became aware of the nature and scale of man's spoilation and destruction of his own environment, and encountered apathy and distrust in officials of government and industry towards measures of control, he began to feel that little or nothing could be done to avert ultimate disaster. This was not characteristic of Martyn, for he was ever a fighter for any cause in which he became deeply involved, and it clearly contributed to the despondent mood which overcame him in the end.
The high esteem in which Martyn was held in the international field is reflected in the numerous letters and telegrams received by his widow. The Minister for External Affairs stressed how highly his Department valued its association with Martyn, which began on his election as Chairman of the Scientific and Technical Sub-Committee of the U N Committee in 1962. He added that Martyn did a great deal to advance Australia's standing in the United Nations, and that many officers of his Department remembered him with affection and with gratitude for the help and advice he gave them. The Minister for Education and Science wrote of his high opinion of Martyn and his feeling of a personal sense of loss. The Secretary-General of the United Nations wrote to the Australian Permanent Representative of the United Nations of Martyn's pursuit of the goal of international co-operation with devotion and scholarship, and added that his contribution within the United Nations and several international scientific organizations will long be remembered.
Martyn was elected a Fellow of the Royal Society of London in 1950, the first such election of a physicist in Australia for twenty years. He was awarded the Lyle Medal of the Australian National Research Council, and the Sidey Medal of the Royal Society of New Zealand, both in 1947. In 1950 he received the Burfitt Medal of the Royal Society of NSW, and in 1954 the Charles Chree Medal of the Physical Society of London.
In 1951, as part of the celebrations of the fiftieth anniversay of Federation, the Australian National University organized a seminar on Science in Australia. Sir Edward Mellanby, Secretary of the Medical Research Council in UK, and Dr J.B. Conant, President of Harvard, with prominent Australian representatives of industry and science, took part in a comprehensive discussion of the state and role of science in the Commonwealth. The seminar emphasized the need for an Australian society of scientists of distinction; to serve as the body adhering to the international unions, and represent Australian science generally, both nationally and internationally; to bring the scattered scientific efforts of the Commonwealth together; to conduct seminars and conferences; to offer advice to the Government on questions concerning the welfare of science in Australia; and generally to promote and disseminate scientific knowledge. Martyn took part in the discussion, and subsequently he and Oliphant considered how an Australian Academy of Science, the constitution and objectives of which should be based on those of the corresponding body in Britain, the Royal Society of London, might be brought into existence. They considered the factors which had rendered abortive several previous attempts to found a society of this kind, and concluded that interstate jealousies and personal difficulties were responsible. They decided that as the twelve Fellows of the Royal Society resident in Australia had been elected by an outside, disinterested institution, there would be less objection to an attempt by them to establish a new society at high level. Eleven agreed to co-operate. One, who was elderly and an invalid, disillusioned by previous experience, said that he did not wish to be associated with yet another failure.
The Australian National Research Council, with wide membership, was the adhering body to the international scientific unions at that time. It was necessary to obtain its agreement to hand over these responsibilities to the proposed Academy. In the delicate negotiations which ensued, Martyn displayed remarkable statesmanship. He was never impatient, and showed great understanding of the feelings and attitudes of the officers and members of ANRC. It was largely Martyn's persistent advocacy which persuaded that body to co-operate and hand over all its responsibilities to the Academy.
So that it was more representative of science generally, the Fellows of the Royal Society invited 25 distinguished Australian scientists to join with them as Foundation Fellows of the Academy. In this task Martyn showed sound judgment, and worked to ensure that these men were as widely distributed, geographically, as the standards adopted would allow. The enlarged group then drew up and adopted statutes and rules. With the help of Mr. Norman Cowper (later Sir Norman), who had agreed to serve as honorary solicitor to the group, Martyn cast these into acceptable forms, spending much time and great effort to ensure that they correctly interpreted the wishes of the membership and the needs of the law. On the basis of these documents, and with the willing co-operation of the Royal Society of London and of the Prime Minister, application was made for a Royal Charter. This was granted in the record time of three weeks, so that Queen Elizabeth II was able to present it to the Interim President and officers, at Government House, Canberra on 16 February, 1954. Thus, largely owing to the continued effort of D.F. Martyn, the Australian Academy of Science came into being. He was the first Secretary (Physical Sciences). The Commonwealth Government agreed to provide an annual subvention, following an interview which the Prime Minister granted to the President and Sir David Rivett, on the basis of estimates for which Martyn was largely responsible.
Martyn was elected President of the Academy in 1969 in succession to Sir Macfarlane Burnet, and held that office when he died. Meanwhile, he had continued to serve the Academy on various committees, and always played a prominent part in the Annual General Meetings. He was truly committed to maintenance of the standards of the Fellowship, and to the part the Academy could play to promote Australian science, at home and in its international relations.
The standards which Martyn expected in scientific research were high and when work which he regarded as wrong was submitted for any purpose, or published, his judgement could be harsh. But he gave full acknowledgement of good work, and pressed strongly the claims for election to the Academy, or for the award of a prize, by men of science whose work he approved. If he had a model of a scientist of distinction, it was Sydney Chapman, whose opinion he valued above all.
Martyn never gathered round him a large group of collaborators. In essence he was a theoretician, preferring to work quietly and alone on problems which interested him, and at his own pace. Yet, it is clear from his notable success in international scientific bodies that he was a gifted chairman of meetings, who could be tactful, yet firm. This attribute was particularly apparent in the foundation of the Australian Academy of Science. There were occasions when obstruction, and the desire to reduce standards for Fellowship, threatened collapse of the proposal to establish an Academy. It was then that Martyn's persistence, powers of persuasion and great tact, prevented disaster, without relaxing in any way the high objectives of the founding group.
Martyn was a trout fisherman of great skill, and a connoisseur of food and wine. On social occasions he was a man of charm and good conversation. He will be missed greatly by all who won his warm friendship. In 1944 he married Margot Adams of Sydney. They had no children.
This memoir was originally published in Records of the Australian Academy of Science, vol.2, no.2, 1971. It was written by:
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