Physics in my Generation
From the postscript to The Restless Univers
On July 16, 1945, the first experimental bomb exploded near Los Alamos, New Mexico. This was certainly one of the greatest triumphs of theoretical physics if measured not by the subtlety of ideas but by the effort made in money, scientific collaboration and industrial organization. No preliminary experiment was possible, the tremendous risk was taken in the confidence that the theoretical calculations based on laboratory experiments were accurate. Therefore it is no wonder that the physicists who watched the terrific phenomenon of the first nuclear explosion felt proud and relieved from a heavy responsibility. They had done a great service to their country and to the community of allied nations.
But when, a few weeks later, two "atomic bombs" were dropped over Japan and destroyed the crowded cities of Hiroshima and Nagasaki, they discovered that a more fundamental responsibility was on their shoulders. The world had become pretty callous against the horrors of the war. Hitler's seed had grown. His was the idea of total war, and his bombs smashed Rotterdam and Coventry. But he found keen pupils. In the end the bombers of both sides succeeded in a systematic devastation of Central Europe. A great part of its historic and artistic treasures, the inheritance of thousands of years went up in flames. An architectural jewel like Dresden was destroyed in one of the last days of the European war, and 100,000 civilians, men, women and children, are said to have perished with it. I do not doubt that those responsible for this act can rightfully claim tactical and strategical necessity; and the world in general found sufficient justifications, ranging from blind hatred and the wish of retribution to the quasi-humane idea that to shorten the war all means are good enough. Ethical standards had fallen sharply, indeed. Still the two atomic bombs dropped on Japan made a stir, and when details of the human tragedy became known there was something like an awakening of conscience in many parts of the world.
This is not the place to express my personal judgment of the statesmen who decided to use this brutal application of power. Cases of precedence are plentiful-there is not much difference in the responsibility for killing 20,000 in one night or 50,000 in one minute. But being a scientist I am concerned with the question of how far science and scientists share the responsibility.
The motives of those who took part in the development of nuclear explosives were certainly above reproach. Many of them were just drafted to this work as their war service, others joined it, driven by the apprehension that the Germans might produce the bomb first. Yet there was no organization of scientists which could form a general opinion. Single men became little cog-wheels in the tremendous machine, which was directed by political and military authorities. The leading physicists became scientific advisers of these authorities and experienced the new sensation of power and influence. They enjoyed their work and its tremendous success and forgot for the time being to think hard about its consequences. It is true that a group of scientists warned the U.S. Government not to use the bomb against cities, but to demonstrate its existence and power in a less murderous way, for instance on the top of Fujiyama mountain. They predicted very accurately the disastrous political consequences which an attack on a city would have. But their advice was neglected.
The principal discrepancy between public opinion in the United States and the conviction of the scientists is concerned with secrecy. The scientists are convinced that there is no secret in science. There may be technical tricks which can be kept secret for a limited period. But the laws of nature are open to anybody who is trained in using the scientific method of research.
Therefore it was futile to keep the atomic bomb project from being known to the Russian allies, and the maintenance of this secret has with necessity transformed them from old friends into enemies. They felt menaced by a tremendous new weapon; they started to develop it themselves, and they obtained it in a shorter time than was ever expected. On the other hand this phantom of secrecy had disastrous effects on the development of nuclear physics in America. Many physicists have been subjected to suspicion and even to accusation of disloyalty. The whole of science has been hampered by the classification of discoveries into secret and open ones, and by the supervision of publication. There is no doubt that certain security measures, mainly in regard to technical questions, are unavoidable. But the subordination of fundamental research to political and military authorities is detrimental. The scientists themselves have learned by now that the period of unrestricted individualism in research has come to an end. They know that even the most abstract and remote ideas may one day become of great practical importance like EINSTEIN's law of equivalence of mass and energy. They have begun to organize themselves and to discuss the problem of their responsibility to human society. It would be left to these organizations to find a way to harmonise the security of the nations with the freedom of research and publication without which science must stagnate.
The release of nuclear energy is an event comparable to the first fire kindled by prehistoric man-though there is no modern Prometheus but teams of clever yet less heroic fellows, useless as inspiration for epic poetry. Many believe that the new discoveries may lead either to immense progress or to equal catastrophe, io paradise or to hell. I, however, think that this earth will remain what it always was; a mixture of heaven and hell, a battlefield of angels and devils. Let us have a look around: what are the prospects of this battle, and what can we do to help the good cause? To begin with the devil's part, there is the hydrogen bomb. We have seen that, though almost all matter is unstable in principle, we are protected against nuclear catastrophe by the low temperatures on earth, which even in our hottest furnaces are quite insufficient to initiate nuclear fusion. But the discovery of fission has destroyed this security. The temperature in an exploding uranium bomb is presumably high enough to start the fusion of hydrogen with the help of the "carbon cycle " , which is the source of stellar energy, or a similar catalytic process. Thus an explosive ofmany thousand times higher efficiency than the fission bomb could be made from a material available in abundance. Of course, work has started with the usual argumentation: ifwe do not do it, the other fellow (meaning the Russian) will. If it succeeds there will be a new instrument of wholesale destruction, but no peaceful application of the new forces seems to be possible. No way is known to slow down fusion in order to use it as a fuel. A perfectly hellish prospect.
Fission however has many and far-reaching applications of a peaceful kind. It can be used as fuel, since the reaction velocity can be controlled. Each pile produces an enormous amount of heat which at present is wasted in most cases. Power stations using uranium or thorium as fuel are possible, as the difficulties connected with the pernicious radiation could certainly be overcome. The question is however an economic one. The raw material is rare, and if the same amount of energy which is at present made from coal would be produced by nuclear reactors, the whole uranium ore at present or in future available would be used up in less than half a century. Hence it is improbable that the new fuel will be able to compete with coal and oil. Under certain conditions, however, this may be the case, namely where the advantage of the small bulk and weight of nuclear fuel, as compared with that of coal or oil, is decisive. There is a possibility of increasing the efficiency of fission by 'breeding', i.e. by directing the process in a pile in such a way that a great proportion of the nuclei present is transformed into fissionable isotopes. This would mean an extension of the raw material over a much longer period.
Apart from the still problematic application of nuclear reactions for power production, there are numerous others which have already led to great progress'and which are more promising. There is first the generation of new isotopes in the pile. Our knowledge of the stability of nuclei and of the laws of their interaction has been immensely increased. Some of the radio-active products can be used in medicine for therapeutical purposes, replacing for instance radium in the fight against cancer. The most important application is the so-called 'tracer method' which is revolutionizing chemistry and biology. Already in the first period of radio-activity v. Hevesy had the idea to trace the fate of atoms in chemical or biological processes by adding to them a small amount of a radio-active isotope. This discloses its presence by radiation, and as the methods of detection of radiation are extremely sensitive, one can thus determine much smaller amounts of an element than with the balance. It is even possible to investigate the distribution of atoms in living tissue. The actual application of this idea was formerly restricted to the few atomic types for which naturally radio-active isotopes were known. Isotopes are now available for almost all elements of the periodic system. The work on this line, though hardly begun, has already led to important results, and will lead to still more.
But what are these important results compared with the spectre lurking in the background, the possibility of atomic warfare on a great scale? In combination with other infernal contraptions, like rockets to deliver bombs at large distances, chemical, biological and radioactive poisons, such a war must mean a degree of human suffering and degradation which is beyond the power of imagination. No country would be immune, but those with highly developed industry would suffer most. It is very doubtful whether our technological civilization would survive such a catastrophe. One may be inclined to regard this as no great loss, but as a just punishment for its shortcomings and sins: the lack of productive genius in art and literature, the neglect of the moral teachings of religion and philosophy, the slowness to abandon outdated political conceptions, like national sovereignty. Yet we are all involved in this tragedy, and the instinct of self-preservation, the love of our children, makes us think about a way of salvation.
There are the two political colossi, U.S.A. and U.S.S.R., both pretending to aim at nothing but peace, but both rearming with all their power to defend their ideology and way of life, and between them is a weak and divided Europe, trying to steer a middle course. Both sides are greedily devouring the latest achievements of scientific technology for their armed forces. Both have some kind of theory for .their way of life in which they believe with an amazing fanaticism. Yet the foundations of these theories are rather doubtful. They use the same words for different or even opposite ideas, as for instance "democracy", which in the West means a system of parliamentary representation freely and secretly elected, but in the East means something quite different and hard to formulate (a complicated economic and political pyramid of bureaucracy which aims at representing, and working for, "the people") . In other ways the American theory is much vaguer than the Russian, and that seems to have a historical reason. America has grown by expansion in a practical vacuum; the pioneers of the West had to overcome terrific natural obstacles, but negligible human resistance. The Russia of today had to conquer not only natural but human difficulties: she had to break up the rotten system of the Czars and to assimilate backward Asiatic tribes; now she has set herself the task of bringing her brand of modernization to the ancient civilizations of the Far East. For this purpose it is indispensable to have a well-defined doctrine full of slogans, which appeals to the needs and instincts of the poverty-stricken masses. Thus one understands the power which Marx's philosophy has gained in the East. What can we scientists do in this conflict? We can join the spiritual, religious, philosophical forces, which reject war on ethical grounds. We can even attack the ideological foundations of the conflict itself. For science is not only the basis of technology but also the material for a sound philosophy. And the development of modern physics has enriched our thinking by a new principle of fundamental importance, the idea of complementarity. The fact that in an exact science like physics there are found mutually exclusive and complementary situations which cannot be described by the same concepts but need two kinds of expressions, can be applied to other fields of human activity and thought. Some such applications to biology and psychology were suggested by Niels Bohr. In philosophy there is the ancient and central problem of free will. Any act of willing can be regarded on the one side as a spontaneous process in the conscious mind, on the other as a product of motives depending on past or present impressions from the outside world. If one assumes that the latter are subject to deterministic laws of nature, one has a conflict between the feeling of freedom of action and the necessity of a natural process. But if one regards this as an example of complementarity the apparent contradiction turns out to be nothing but an epistemological error. This is a healthy way of thinking, which properly applied may remove many violent disputes not only in philosophy but in all ways of life: for instance in politics.
Marxian philosophy, which is a hundred years old, knows of course nothing of this new principle. However, a prominent Russian scientist has recently attempted to interpret it from the standpoint of 'dialectic materialism', which teaches that all thinking consists of a thesis opposed by an antithesis; after some struggle, they are combined in a synthesis. In this Marxian dogma, so he claims, you have the prediction of what has happened in physics, for instance in optics: Newton's thesis that light consists was opposed by Huygens' antithesis that it consists of waves, until both were united in the synthesis of quantum mechanics. That is all very well and indisputable, though a little trivial. But why not go further and apply it to the two competing ideologies: Liberalism (or Capitalism) and Communism, as thesis and anti-thesis ? Then one would expect a synthesis of some kind, instead of the Marxian doctrine of the complete and permanent victory of communism. It can hardly be expected that the ideas of Marx, developed about 100 years ago, can throw much light on the development of modern science. The opposite is more likely: that the new philosophical ideas developed by science during these 100 years may help towards a deeper understanding of social and political relations. Indeed, we find two systems of thought which deal with the same structure, the state, in completely different, apparently contradictory ways. One starts from the freedom of the individual as the basic conception, the other from the collective interest of the community.
This distinction corresponds roughly to the two aspects of the problem of willing which we have just mentioned: the subjective feeling of freedom on the one hand, the causal chain of motives on the other. Thus the West idealises political and economical liberalism, the East collective life regulated by an all-powerful state. But as it seems likely that the contradiction in the problem of free will can be solved by applying the idea of complementarity, the same will hold for the contradiction of political ideologies. Thus the intellectual gulf between West and East may be bridged, and that is the service which natural philosophy can offer in the present crisis. The world which is so ready to use the gifts of science for mass destruction would do well to listen to this message of reconciliation and co-operation.
M. BORN, Physics in my Generation (London - New York: Pergamon Press, 1956), pp. 226-232.