THE LIFE AND WORK OF DENNIS GABOR; HIS CONTRIBUTIONS
TO CYBERNETICS, PHILOSOPHY AND THE SOCIAL SCIENCES
1900 – 1979
Professor T.E. Allibone CBE, FRS.
The Dennis Gabor Memorial Lecture Given to the
Cybernetics Society on the
23rd of April 1985
Today we celebrate Shakespeare's birthday so, thinking of Dennis Gabor, I open my remarks with Miranda's greeting to her father. "Oh, brave new world, that hath such people in it".
Part 1 The University Years
On a lovely Easter day in 1947 as Dennis Gabor sat waiting his turn to play a game of tennis, his subliminal ego suddenly presented him with the solution to a problem which had worried him for almost a year: out of that flash of genius a new branch of physics, Holography, has evolved and a new industry is rapidly developing. Gabor was ever grateful that he had lived long enough to witness and enjoy the rich harvest that matured from those seeds he sowed 38 years ago. Holography was born in Britain but the inventor was born in Hungary. Few scientists are inventors, and this gift frequently runs in families, indeed Gabor's father, uncle and brother were all inventors. His father's family came originally from Russia, his mother's from Spain, so music and dancing, joi de vivre and happiness were inborn. Jules Verne, and that greatest of all inventors, Thomas Edison, were his boyhood idols, and his father, a leading industrialist, brought engineering and science into the home. Thus it came about that engineering was Dennis's choice for study at the Politechnic University in Budapest and from there he went on to Berlin to do research under the great engineer Professor Matthias at the Technische Hochschule at Charlottenburg. In order to record electrical transients he built one of the first high-voltage cathode ray oscillographs, focussing the electron beam with a magnetic field produced by a short solenoid. This solenoid he shrouded in iron, his first great invention, and he incorporated in the oscillograph a circuit and device by which the electrical transient tripped the oscillograph and thus, so to speak, took its own photograph. It was these two inventions that attracted me to Berlin in 1928 to meet him; I was the first Englishman he had met and from that visit sprang a friendship that I have always treasured.
College years must alas come to an end and after completing his Doctorate he left university life to join the Siemens Company in Berlin and there he began to work on a new form of electric lamp. As it happened, leaving College at that moment of time proved to be very unfortunate for him, because before leaving, he had invented the magnetic lens system for his oscillograph, and now, in Prof. Matthias's laboratory there was born the first electron microscope using Gabor's ideas of lenses to focus the electron beam, and to his great regret, he was not there; the midwives to the electron microscope were the research students he had left behind in the university.
Gabor told a story, some years later, that as he sat in a cafe in Berlin with his fellow countryman, the physicist Leo Szilard, in 1930 they discussed the wave-nature of electrons and the magnetic lenses which could focus electron beams, and they reflected upon the concept of an electron microscope but they both agreed that it would serve no purpose; you could not put living matter into a vacuum, and everything would burn to a cinder under an electron beam having an energy of, say, 100 kV. But, he wrote, "Who would have dared to believe that the cinder would preserve not only the structure of microscopic bodies but even the shape of organic molecules'? He always regretted having left the university at this time and thus having lost the chance to be in on the evolution of the electron microscope. It remained his first love for the rest of his life.
The black shadow of March 1933 fell upon the Jews in Germany so Gabor left Berlin and returned to Hungary working on an invention concerning another new form of lamp. From Budapest in 1934 he wrote to me at the Metropolitan-Vickers Electrical Company to ask if my Company could offer him employment to develop his patent. We were only a part of the large AEI Company and we were mainly concerned with heavy engineering; my research director, then Mr Arthur Fleming, suggested that I should send the correspondence to Mr Hugh Warren, the director of research of the BTH Company, the other half of AEI mainly concerned with light engineering. Warren accepted my recommendation and so it came about that Dennis spent the next 14 years in Rugby inventing an incredible range of devices, many of which unfortunately were of such complexity that they did not come to fruition; indeed you might say they were born before their time. One of his colleagues of that period, Mr. Ivor Williams, speaks of the great agility of his mind and of the tenacity with which he held on to a difficult task in spite of repeated setbacks.
During the war he was classed as an alien and had to work in a hut outside the security fence, but a continuous stream of colleagues poured into the hut to derive inspiration from his fertile mind. Dr Dyson, another of his collaborators of those days, has described some of the war work done there, of a brilliant scheme for detecting aircraft by the heat rays emitted from their engines - alas this did not quite reach the production stage of manufacture. From the hut he was obliged to take a prescribed route out of the Works but he never left the laboratory with enough time to catch the works bus. Mr. Williams describes how Dennis ran down the drive, battered trilby in hand, coat tails flying out behind him, his legs reminiscent of the emblem of the Isle of Man, to the vigorous encouragement of his fellow passengers: but no driver would have dared to have gone off and left him.
In Rugby he had no chance to return to electron optics; we in the other laboratories of the AEI Company, in Manchester and in Aldermaston, were fully engaged on developing and manufacturing the electron microscope, but Gabor kept in touch with all the work, fretting and fretting as to how to improve its resolution sufficiently to be able to see the very atoms in a crystalline lattice.
Meanwhile Scherzer had shown in 1942 that in electron lenses, neither spherical nor chromatic aberrations could be eliminated and a resolution below a few Angstrom units appeared to be impossible. This was the challenge Gabor accepted: he wrote "I had not been working in electron optics for 3 years but I must have been unconsciously digesting Hamiltonian methods and now effortlessly, I have solved the electron trajectories. It appears that lens correction is impossible in the absence of space-charge"; and in 1946 he showed how a zonally corrected lens might be made with a central wire supplying this space-charge. He wrote the first book on the Electron Microscope during the war and in the last chapter he said he was still searching hopefully to "see" single atoms. In his own brief autobiography, which he wrote in 1957, he said: -
"I realised in 1927 that I ought to have stuck to my original line when electron optics was just discovered but I hoped it was not yet too late to make a come-back by improving the electron microscope beyond the limits set by aberration".
He admired Zernicke's use of a coherent background of waves to show up aberrations in optical lenses and he had been to see Bragg's apparatus in Cambridge, for structure analysis by interference of one beam with a coherent background of waves. Suddenly, - the story is well known, - as he was awaiting his turn to play a game of tennis with his wife in Rugby during the Easter holidays of 1947 the solution presented itself to him in a flash; his sub-conscious had been working on the problem, maybe for many months, and it delivered the answer on a platter: -
"Why not take an electron microscope picture of an object, one which contains the whole information, including the phase, a coherent background must be supplied by the same electron beam, which will therefore produce interference fringes: photograph these, and then illuminate this photograph with light and focus it onto a photographic plate".
He called the electron diffraction pattern a 'hologram' because it contained the whole information, amplitude and phase, and the magnification obtained would be the ratio of the optical to the electron wavelengths. With his very skilled assistant, Mr. Ivor Williams, he decided to try out his ideas optically, to produce an optical hologram and then reconstruct the object optically. The experiments were very tricky, indeed difficult. Monochromatic light coming through a small pinhole was weak and exposures were long, but a hologram was recorded, and when this was illuminated with the reference wave alone, the reconstruction was a good representation of the original. Gabor's full mathematical analysis of the subject written in 1948 has stood the test of time and contains all the necessary information on which holography is based.
In 1947 the AEI Company, set up a new research laboratory in the village of Aldermaston (a laboratory not to be confused with a later Government laboratory in the same village working on atomic bombs, a laboratory from which scientists and Cabinet Ministers walked away). I was in charge of this AEI laboratory; we were working on the basic science of the electron microscope, so Gabor's proposals were immediately taken up with his guidance and support: Electron holograms and optically reconstructed images were made, but only with some degree of success: I will not tell the story of this work here. We wanted him to join us on a part-time basis but the BTH Company would not allow this, and at the end of 1948 he left BTH to become a Reader in Electronics at ImperialCollege, London. During the next few years the Aldermaston group worked very hard on electron holography but the time was not yet ripe, we had started 26 years too early, and for 15 years Gabor almost lost interest in holography.
Years later in America, the Laser was born and with this extremely fine beam of light very many scientists produced wonderful optical holograms, fully vindicating Gabor's invention and masterly theoretical exposition. By 1971 the world could see what a fantastic future lay ahead for holography and the Nobel Prize for physics recognised the brilliance of that inspiration on the tennis court 24 years earlier. Dennis concluded the address he gave before H.M. The King of Sweden with these words:-
"I am one of the lucky physicists who have been able to see one of their own ideas grow to a sizable chapter of physics; this has been achieved by an army of young talented research workers, and I want to express my heartfelt thanks to them for having helped me by their work to this greatest of all scientific honours".
Holography has indeed become a sizable chapter of physics. When the CityUniversity presented him with an Honorary Degree, the Orator on that occasion. Professor Walter Miller remarked that Guildhall had seen many great and varied events, and over the centuries many distinguished men had been honoured there; but there, in Guildhall, for the first time, a Nobel Prizeman received a degree, a most appropriate place in which to honour so great a scientist. Professor Miller said that a list of Professor Gabor's contributions and publications read like a syllabus for a degree course in Physics and in Engineering; and a very good course it would be!
Holography now blossoms all over the world; in Munich, the Institute for Medical Optics considers that "optics has been given new foundations" and in gratitude it has created a 'Gabor Laboratorium' for holography and Munich now boasts a Gaborstrasse. In America where he had held a high appointment at the laboratories of the Columbia Broadcasting System holography enters into many new developments that have not yet seen the light of day and there is hardly an issue of one of many scientific journals that does not record some new conquest.
In ImperialCollege he held a Readership, and later a Professorship relieved from any teaching or administrative duties: it has been written that he was not an administrator by temperament: how fortunate for the world, he had more time for his scientific genius to flower. In Rugby he married Marjorie Butler, also of Rugby, and they enjoyed a union of great and lasting happiness that they shared with innumerable friends who will always remember their generous warm-hearted hospitality both here and in their lovely home in Italy. They lived near to the College and this, as he once wrote, saved an hour or two of travelling every day thus giving him more time to think. He also was clean-shaven and claimed that many ideas came to him during the early morning routine of shaving so he warned the young men with beards that they might be losing great opportunities!
This change to academic life gave Gabor the greatest satisfaction: he wrote, "at last I was my own master and could work with young research students on problems of my own". His scientific output, some in collaboration with students, and some theoretical work done on his own, was considerable; 40 papers during his 10-year tenure of the readership and another 40 after his appointment to the Chair of Applied Physics in 1958 up to retirement in 1967. Clearly I can only refer to a few of these. The tasks he set his students to do were formidable; they were almost all based on inventions. As he explained in his Professorial Inaugural Lecture in 1958: -
"It was man's ability to invent which has made human society what it is. The first step of the inventor is to visualise, by an act of imagination, a thing or a state that does not yet exist and which appears to him in some way desirable. He can start rationally arguing backwards and forwards, until a way is found from one to the other".
This had been exactly what he had done when he invented holography; holography could have been invented 50 years earlier, it involved no optics discovered in the 20th century. It merely needed inventing. Unlike the nuclear physicist for example, he was not a discoverer of new phenomena, but an inventor of things and processes. His new laboratory was superbly equipped for vacuum work and he had some excellent research students. Every one of his patents was thought out in the greatest detail before an experiment began, indeed before the problem was presented to his research pupils. Then all they had to do was to follow very detailed instructions and as they went along he watched progress with the eye of a lynx, he would repair to his typewriter and hand out further instructions based on what he had seen of the experimental work, even several times a day: if new jigs or apparatus appeared to be wanted, he would draw these and have them made. One of these students wrote to me to say, "However, we did not feel suppressed or overpowered, we had the opportunity of exercising initiative" and indeed this is where Gabor excelled; great as he was, he could, and would, listen to the less experienced, younger, person, and with great kindness, steer him along the right path of progress: "a very kind man but a hard task-master", said one student, "he demanded the utmost from himself and could not see how others could not do likewise".
One of the first big projects he gave to some PhD students was the flat T.V. tube. The concept was an old American vision of the family looking at the T.V., a thin flat "picture" just above the mantelpiece. So Gabor invented a flat T.V. "Bring 3 beams downwards sweeping them from left to right, deflect them 180 degrees upwards, and then turn them 90 degrees forwards to strike a screen of lines of 3 colours", indeed an easier concept for 3-colour T.V. than was then being developed by various companies. The electro-optical problems were great, and there were naturally many unexpected difficulties. One T.V. company had been consulted and had considered the difficulties to be too great to be worth tackling. By 1958 Gabor admitted that his students could not wholly complete this development, but he persisted with more students until 1968 by which time the patent had run out. Thirty-five years after he had invented the flat T.V. tube the Sinclair flat T.V. tube is appearing on the market, a little different from Gabor's original concept but based on the same principles.
One of his many research students was writing up his thesis and asked him how long it ought to be; Gabor replied "Well that all depends: Fermi, the great Italian nuclear physicist, wrote his on the back of a postcard but in your case I should make it a little longer".
He was appointed to a Personal Chair of Applied Electron Physics in 1958 and in the first part of his inaugural address he reviewed the work of his students over the 11 years; then in Part 2, which he called "Inventions and Civilisation" he speculated on the part which sophisticated electronic machines might be expected to play. He had always thought deeply about philosophical matters, thoughts that may well have been provoked by Aldous Huxley’s “Brave New World” published before Gabor came to England. Even during the war he had composed a kind of Hippocratic Oath for scientists, a 10-point advice as to how scientists should equip themselves to play a full part in society: as he wrote, "We represent the greatest body of men schooled in thinking in a field in which lies cannot exist, where no amount of shouting will make an incorrect mathematical solution right. We may be masters of all kinds of engineering yet be ignorant in regard to the engineering of human consent".