THE EARLY HISTORY OF RADIO ASTRONOMY

The organizers of this Conference have asked me to present a paper on the early history of radio astronomy, using personal experience where possible. Upon further inquiry, I found that this history should end around early 1950, which makes the task of using personal experience rather hard, as I started graduate studies in that year, The literature on the subject contains a wealth of material on the early days, however, and since the science is so young, the historian can still talk to many of the original investigators. Since most of the early history can be found in the introductions to textbooks and popular books, this paper will necessarily contain many items well known to the reader. Contrary to popular belief, radio astronomy did not start with Jansky’s discovery in 1932, but actually very shortly after Hertz produced and measured Maxwell’s electromagnetic waves in 1887. And believe it or not, it was Thomas Alva Edison himself who, in 1890, proposed an experiment involving a radio telescope weighing many megatons! Edison reasoned that since disturbances were seen on the sun in visual light, they might also radiate at radio wavelengths. Edison planned to put a loop of telephone wires around a huge field of iron ore in New Jersey! The ore was magnetite, which becomes magnetized by induction. The electromagnetic disturbances from the sun might magnetize the ore; this might cause an induction current in the telephone wires, which could then be listened to. The poles for the telephone wires actually arrived on the site, but there is no record of the actual experiment having taken place. Solar radiation would not have been detected, firstly because even this huge detector would not have been sufficiently sensitive, and secondly because radiation of wavelengths long enough to be picked up by this equipment would not have penetrated the ionosphere. Two of Hertz’s associates, Wilsing and Scheiner, tried to look for radio waves from the sun around 1896, and it may well be that Hertz himself was involved. In England, Sir Oliver Lodge made a serious effort to look for solar radio waves between 1894 and 1900. He placed a very crude detector “behind a blackboard or some other opaque substance,” thus shielding out any visible light. Interestingly enough, the electrical interference in the city of Liverpool, where these experiments were made, was already strong enough to make Lodge give up his early attempts. Shortly afterwards, in 1901, a Frenchman, C?Nordmann, made another attempt to detect solar radio waves but was equally unsuccessful. Nordmann applied reasoning that was well ahead of his time. He went to the top of a high glacier, to be away from man-made radio noise and as high above the atmosphere as he could get. He suggested that the radio emission from the sun might vary with the solar cycle, and as a consequence that the radio emission from the sun might well originate in sunspots. Unfortunately, he only conducted his experiment for one day (the glacier was perhaps too cold under his feet) and then gave up. If he had been more patient, and had waited for a solar maximum (1901 was a solar minimum), he might have succeeded. The reason for the long delay in further experimentation after these initial attempts may well be due to Planck, who announced his radiation theory in 1902. If this theory were correct, it followed that the radiation from the sun should be