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The Century Magazine, July 1929, Vol. 118, No. 3, Pgs. 311-315

The Twilight Of Science

Is The Universe Running Down

Bertrand Russell

It is a curious fact that just when the man in the street has begun to believe thoroughly in science, the man in the laboratory has begun to lose his faith. When I was young, no physicist entertained the slightest doubt that the laws of physics give us real information about the motions of bodies, and that the physical world does really consist of the sort of entities that appear in the physicist's equations. The philosophers, it is true, throw doubt upon this view, and have done so ever since the time of Berkeley; but since their criticism never attached itself to any point in the detailed procedure of science, it could be ignored by scientists and was in fact ignored. Nowadays matters are quite different; the revolutionary ideas of the philosophy of physics have come from the physicists themselves and are the outcome of careful experiments. The new philosophy of physics is humble and stammering where the old philosophy was proud and dictatorial. It is, I suppose, natural to every man to fill the vacuum left by the disappearance of belief in physical laws as best he may, and to use for this purpose any odds and ends of unfounded belief which had previously no room to expand. When the robustness of the Catholic faith decayed at the time of the Renaissance, it tended to be replaced by astrology and necromancy, and in like manner we must expect the decay of the scientific faith to lead to a recrudescence of pre-scientific superstitions.

Whoever wishes to know how and why, scientific faith is decaying cannot do better than read Eddington's ton's Gifford lecturer, entitled "The Nature of the Physical World." He will learn there that physics is divided into three departments. The first contains all the classical physics, such as the conservation of energy and momentum, and the Jaw of gravitation. All these according to Professor Eddington boil down to nothing but conventions as to measurement true, the laws they state are universal, but so is the law that there are three feet in a yard, which, according to him, is just as informative concerning the course of nature. The second department of physics is concerned with large aggregates, and the laws of chance. Here we, do not attempt to prove that such and such an event is impossible, but only that it is wildly improbable. The third department of physics, which is the most modern, is the quantum theory, and this is the most disturbing of all since it seems to show that the law of causality, in which science has hitherto implicitly believed, cannot be applied to the doings of individual electrons. I shall say a few words about each of these three matters in turn.

To begin with classical physics. Newton's law of gravitation, as every one knows, was somewhat modified by Einstein, and the modification was experimentally confirmed. But if Eddington's view is right, this experimental, confirmation does not have the signification that one would naturally attribute to it. After considering three possible views as to what the law of gravitation assert about the motion of the earth round the sun, Eddington plumps for a fourth, to the effect that " the earth goes anyhow it likes," that is to say, that the law of gravitation tells us absolutely nothing about the way the earth moves. He admits that this view is paradoxical, but he says: "The key to the paradox is that we ourselves, our conventions, the kind of thing that attracts our interest, are much more concerned than we realize in any account we give of how the objects of the physical world are behaving. And so an object which, viewed through our frame of conventions, may seem to be behaving in a very special and remarkable way may, viewed according to another set of conventions, be doing nothing to excite particular comment. " I must confess that I find this view a very difficult one; respect for Eddington prevents me from. saying that it is, untrue, but there are various points in his argument which I have difficulty in following. Of course all the practical consequences which we deduce from the abstract theory, as for example that we shall perceive daylight at certain times and not at certain other times, lie outside the scheme of official physics, which never reach our sensations at all. I cannot but suspect, however, that official physics is just a little bit too official in Eddington's hands, and that it would not be impossible to allow it a little more significance than it has in his interpretation. However that may be, it is an important sign of the times that one of the leading exponents of scientific theory should advance so modest an opinion.

I come now to the statistical part of physics which is concerned with the study of large aggregates. Large aggregates behave almost exactly as they were supposed to do before the quantum theory was invented, so that in regard to them the older physics is very nearly right. There is, however, one supremely important law which is only statistical; this is the second law of thermodynamics. It states, roughly speaking, that the world is growing continuously more disorderly. Eddington illustrates it by what happens when you shuffle a pack of cards. The pack of cards comes from the makers with the cards arranged in their proper order; after you have shuffled them, this order is lost, and it is in the highest degree improbable that it will ever be restored by subsequent shuffling. It is this sort of thing that makes the difference between past and future. In the rest of theoretical physics we are dealing with processes that are reversible; that is to say, where the laws of physics show that it is possible for amaterial system to pass from state A at one time to state B at another, the opposite transition will be equally possible according to these same laws; but where the second law of thermodynamics comes in, this is not the case. Professor Eddington enunciates the law as follows: "Whenever anything happens that cannot be undone, it is always reducible to the introduction of a random element analogous to that introduced by ,shuffling." This law, unlike most of the laws of physics, is concerned only with probabilities. To take our previous illustration: it is of course possible that, if you shuffle a pack of cards long enough, the cards may happen to get into the right order by chance. This is very unlikely, but it is far less unlikely than the orderly arrangement of many millions of molecules by chance. Professor Eddington gives the following illustration: suppose a vessel divided into two equal parts by a partition, and suppose that in one part there is air, while in the other there is a vacuum; then a door in the partition is opened and the air spreads itself evenly throughout the whole vessel. It might happen by chance that at some future time the molecules, the air in the course of their random movements would all find themselves again in the partitions in which they originally were. This is not impossible; it is only improbable, but it is v" improbable. "'If I let my fingers wander idly over the keys of a typewriter it might happen that my screed made an intelligible sentence. If an army of monkeys were strumming on typewriters they might write all the books in the British Museum. The chance of their doing so is decidedly more favorable than the chance of the molecules returning to one half of the vessel."

There are an immense number of illustrations of the same kind of thing. For example, if you drop one drop of ink into a glass of clear water, it will gradually diffuse itself throughout the glass. It might happen by chance that it would afterwards collect itself again into a drop, but we should certainly regard it as a miracle if it happened. When a hot body and a cold body are put in contact, we all know that the hot body cools and the cold body gets warm until the two reach the same temperature, but this also is only a law of probability. It might happen that a kettle filled with water put on the fire would freeze instead of boil; this also is not shown to be impossible by any of the laws of physics, it is only shown to be highly improbable by the second law of thermodynamics. This law states, speaking generally, that the universe tends toward democracy, and that when it has achieved that state, it will be incapable of doing anything more. It seems that the world was created at some not infinitely remote date, and was then far more full of. inequalities than it is now; but from the moment of creation it has been continually running down, and will ultimately stop for all practical purposes, unless it is again wound up. Professor Eddington for some reason does not like the idea that it can be wound up again, but prefers to think that the world drama is only to be performed once, in spite of the fact that it must end in eons of boredom, in the course of which the whole audience will gradually go to sleep. Quantum theory, which is concerned with individual atoms and electrons, is still in a state of rapid development, and is probably far from its final form. In the hands of Heisenberg, Schrodinger and Co., it has become more disturbing and more revolutionary than the theory of relativity ever was. Professor Eddington expounds its recent developments in a manner which conveys more of it to the non-mathematical reader than I should have supposed possible. It is profoundly disturbing to the prejudices which have governed physics since the time of Newton. The most painful thing about it from this point of view is that, as mentioned above, it throws doubt upon the universality of causality; the view at present is that atoms have a certain amount of free-will, so that their behavior even in theory, is not wholly subject to law. Moreover, some things which we thought definite, at least in theory, have quite ceased to be so. There is what Eddington calls the "principle of indeterminancy"; this states that "a particle may have position or it may have velocity, but it cannot in any exact sense have both," that is to say, if you know where you are, you cannot tell how fast you are moving, and if you know how fast you are moving, you cannot tell where you are. This cuts at the root of traditional physics, in which position and velocity were fundamental. You can only see an electron when it emits light, and it only emits light when it jumps, so that to see where it was, you have to make it go elsewhere. This breakdown of physical determinism is utilized by Eddington in his concluding chapters to rehabilitate free-will.

Professor Eddington proceeds to base optimistic and pleasant conclusions upon the scientific nescience which he has expounded in previous pages. This optimism based upon the time- honored principle that any. thing which cannot be proved untrue may be assumed to be true a principle whose falsehood is proved by the fortunes of bookmakers. If we discard this principle, it is difficult to see what ground for cheerfulness modern physics provides. It tells us that the universe is running down, and if Eddington is right, it tells us practically nothing else, since all the. rest is merely the rules of the game. From a pragmatic or political point of view probably the most important thing about such a theory of physics is that it will destroy, if it becomes widespread, that faith in science which has been the only constructive creed of modern times, and the source of virtually all change both for good and for evil. The eighteenth and nineteenth centuries had a philosophy of natural law based upon Newton. The law was supposed to imply a Lawgiver, though as time went on this inference was less emphasized; but in any case the universe was orderly and predictable. By learning nature's laws we could hope to manipulate nature, and thus science became the source of power, This is still the outlook of most energetic practical men, but it Is no longer the outlook of men of science. The world according to them is a more higgledy-piggledy and haphazard affair than it was thought to be. And they know much less about it than was thought to be known by, their predecessors in the eighteenth and nineteenth centuries. Perhaps the scientific skepticism of which Eddington is an exponent may lead in the end to the collapse of the scientific era, just as the theological skepticism of the Renaissance has led gradually to the collapse of the theological era. I suppose that machines will survive the collapse of science, just as parsons have survived the collapse of theology, but in the one case as in the other they will cease to be viewed with reverence and awe. Perhaps this is not to be regretted.