Beyond the Atmosphere: Early Years of Space Science

[184] Clearly the discovery of the earth's radiation belt and the subsequent description developed for the magnetosphere constituted a major scientific achievement. It is natural, then, to ask what the significance of the achievement might be. Was magnetospheric physics really a new field of research, as some claimed? Did Van Allen's discovery set in motion a scientific revolution, or was the unveiling of the magnetosphere simply normal science? The attempt to answer these questions provides a good illustration of the difficulties in Kuhn's concepts of paradigm, normal science, and scientific revolution.
[185] As to whether magnetospheric physics was a new field of research, certainly before the discovery of the radiation belt no one was consciously working on investigating the magnetosphere, since the existence of such a region was unknown. Following Van Allen's experiments, scores of researchers began to investigate the magnetosphere. One could then legitimately argue that here was indeed a new field of research, not being pursued before, now being pressed vigorously. But this seems too shallow a conclusion. For research on the earth's magnetic field, the auroras, sun-earth relationships, and cosmic rays had been of long standing when Explorer 1 went aloft. From this, magnetospheric physics appears more as simply one aspect of those other fields-a remarkable and hitherto unforeseen aspect, to be sure, but integrally related.
Did, then, the unveiling of the magnetosphere constitute a scientific revolution in the related scientific fields? Certainly the magnetospheric paradigm that emerged from the first half-dozen years of satellite and space-probe research was new and unpredicted. One is tempted, then, to argue that the emergence of this entirely new paradigm was evidence of a scientific revolution. But again the quick answer may be too superficial. True, the trapped radiations and the magnetosphere as it was revealed were unpredicted. But that is not the criterion of a scientific revolution. One must ask instead whether the radiation belt and the magnetosphere were unpredictable from the existing paradigm in the sense of being fundamentally inconsistent with it. The answer to this question may well be no. In fact, the work of Stormer and others, based wholly on the existing paradigm, had provided an adequate basis for predicting the existence of trapped radiations in the earth's magnetic field. In this light the new magnetospheric paradigm appears as a straightforward extension of the previously existing paradigm, requiring no changes in fundamental principles or concepts. From this perspective, then, the magnetospheric research of the early 1960s was normal science-exciting, productive, important, yet normal science. But magnetospheric physicists are likely to consider the above perspective too broad. Norman Ness, one of the key figures in magnetospheric research, regards the progress made in the half-dozen years following the discovery of the radiation belts as revolutionary. In this assessment Ness considers the emergence of a new magnetospheric paradigm and the fact that no one predicted it as of primary significance.29
One major implication of the research on the earth's magnetosphere-which was immediately recognized-was that the way in which the interplanetary medium affects a planet depends strongly on whether the planet has a magnetic field. In a period when the idea of comparative planetology was being emphasized by the availability of spacecraft to carry scientific investigations to the different planets, scientists previously interested in sun-earth relations were beginning to talk about sun-planetary relations. It had already appeared as though the moon produced a detectable wake in [186] the solar wind, although later measurements by Explorer 35 would show that the lunar wake extends only a few lunar radii downstream, instead of to the vicinity of the earth as originally supposed.30 The moon presented the case of a planetary body with very little magnetic field and no atmosphere. Solar wind particles might be expected, then, to strike the lunar surface directly. In the case of Venus, which also has little magnetic field but which has an atmosphere perhaps 100 times that of Earth, the solar wind would impinge on the top of the atmosphere but would not be able to reach the planet's surface. Mars would present the case of a planet with little magnetic field and an atmosphere about one percent that of Earth. Jupiter, on the other hand, with its very strong magnetic field would have a huge magnetosphere. If radio bursts that were observed to come from Jupiter were from trapped particles, the Jupiter radiation belt would prove much more intense than Earth's. At the end of 1964 these were principally ideas for future research. Knowledge of Earth's magnetosphere invested that future research with considerable promise.