Becquerel's blunder

Social Research, Spring, 2005 by Lawrence Badash

INTRODUCTION

THE DISCOVERY BY WILHELM CONRAD RONTGEN OF X-RAYS IN LATE 1895 was the most globally astonishing scientific event prior to the atomic bombing of Hiroshima and Nagasaki in 1945. * Some 50 books and pamphlets and 1,000 papers on X-rays were published in 1896 alone, remarkable testimony to the impact of these penetrating rays. (1)

By contrast, Henri Becquerel, who discovered radioactivity just a few months later, wrote seven papers on the subject in 1896, only two the following year, and then left this seemingly exhausted topic. Others added several papers in this period, but amidst the plethora of various radiations being studied at that time, the radiations from uranium did not seem extraordinary (Badash, 1965a). Especially, uranium rays could not produce the sharp images of bones through the flesh of a living hand that made X-rays so intensely fascinating. Not until Gerhard C. Schmidt and Marie Curie in 1898 independently reported that thorium exhibited the same properties as uranium was interest in radioactivity resurrected, drawing Becquerel and many others back to his discovery.

Over the next century, X-rays were used in increasingly sophisticated medical imaging devices, applied to test the integrity of welds and other structures, told us more about the nature of atoms (the importance of atomic number) through Henry Moseley's examination of their spectra, and led to the revolution in molecular biology through X-ray crystallography. Again by contrast, radioactivity seemingly was left in the dust. Aside from radium's sometimes successful medical application in the treatment of cancer and other diseases, it appeared to have limited import: a pre-World War I use in luminous paint for such showbiz items as poker chips, cocktails, and nightclub dancers' costumes, and its wartime employment in luminous watches and gun sights (Badash, 1978). During the decades before World War II, however, physicists and chemists determined that there was a nucleus to the atom and that nuclear reactions could be induced, and they gained an understanding of the components of the nucleus. The discovery of nuclear fission in late 1938, coupled with the fears of war, led to projects in several countries that ultimately produced both nuclear weapons and nuclear reactors. Then, for nearly half a century, the bomb dominated international relations among the developed countries, in particular the superpowers: the United States and the Soviet Union.

The discoveries by Rontgen and Becquerel thus were both extremely important to society, but that of radioactivity had a far more significant impact on science and the world. It is therefore worthwhile to look more closely at what constitutes discovery and what Becquerel thought he was doing.

BACKGROUND TO THE DISCOVERY

For some time, those who study nature have recognized that the truths of science are written with a lower-case t, not a capital T. In practice this means that our understanding of Nature is not permanent; it is influenced by the ideas and apparatus at our disposal. More insightful thoughts, new data, and more powerful tools have changed the paradigm.

This suggests that a large percentage of past scientific ideas have been modified, and that many current beliefs will be changed in the future. Scientific error thus is common, if not almost the norm. Why then are we fascinated by scientific mistakes if they are so plentiful? It is not because we wish to gloat with the wisdom of hindsight. Rather, these examples provide us with insights. We learn what were the contemporary beliefs and practices that influenced a new interpretation of Nature, and we see, gratifyingly, that scientific research is a very human enterprise: scientists can fixate possessively on an idea that brought them a measure of fame and ignore other viewpoints that are equally reasonable. We may also speculate whether the mistake hindered the development of science or actually inspired increased activity. For a successful theory should not merely explain existing data but suggest new research to be performed. Success need not be congruent with a later consensus of truth.

The discovery of radioactivity by Antoine Henri Becquerel early in 1896 provides a useful example to explore scientific error. This essay's title, calling his work a blunder, is meant to be provocative and alliterative, far more than to convey an accurate depiction of his competence. In fact, Becquerel was a highly talented and innovative physicist, even if his vision was limited. A professor of physics at the National Museum of Natural History in Paris, and at age 43 already a member of the prestigious Academie des Sciences, Becquerel was moved in January 1896 to see if X-rays were emitted from luminescent crystals. X-rays had been discovered in Wurzburg, Germany, just a month or two earlier by Rontgen, and were then the most newsworthy topic among scientists.

It is true, of course, that humans were long familiar with the passage of visible light through glass and some liquids, but X-rays were novel not only because they were invisible to the eye, but particularly because they traversed fairly thick pieces of opaque material. Their true nature, whether particle or radiation, remained unclear for several years. But that did not stop feverish investigation. In Paris, for example, the physicians Oudin and Barthelemy, tempted by the diagnostic potential of X-rays, quickly began work with a Crookes tube (a variety of vacuum tube) furnished to them by the physicist Gaston Seguy. Soon, a report of their work and a photograph of the bones of a hand were sent to the Academy of Sciences, where they were communicated at the meeting on January 20, 1896, by the prominent professor of mathematical physics at the Sorbonne, Henri Poincare. (2)