The evolution of scientific thought from Newton to Einstein

by A. D'Abro

The novel point of Einstein’s theory consists in proving that this attitude is untenable. Assuming the various planets to rotate with the same speed when their axes are at relative rest, each different observer must henceforth abide by the rotations of his own planet and not by those of the other planets when relative motion is present. Only thus can the special principle of relativity be maintained. In particular, if we assume one rotating planet to be transferred to a distant star, then returned near the rotating earth as in the example of the two twins, it would be found that, owing to the solidarity between the optical clocks and the rotations of the planets, the wandering planet would have revolved less often during its trip than would have been the case with the earth. So we see that the slowing down we have mentioned is absolutely general, and must indeed be so if the special principle of relativity is to endure.

Furthermore, we see that the great difference between classical science and relativity consists, not in having substituted an optical clock for the earth’s rotation, since both these determinations of time would be identical, but in having proved that the earth’s rotation or the earth’s optical clock is valid only as a measure of time for an earth observer or for one at rest with respect to him.

Having established the solidarity of the evolution of all physical phenomena at rest in the same Galilean frame as an inevitable consequence of the relativity of Galilean motion, we must now enquire whether this general solidarity should be assumed to extend to vital phenomena and to our consciousness of the flight of time. Of course we cannot deny that aging is accompanied by a physiological alteration of our bodies; hence, on this ground alone, there can be no doubt that physiological aging will proceed in terms of the general solidarity of all physical phenomena. But there exists another aspect of the passage of time, and that is our consciousness of its stream.

Our awareness of the flight of time is probably the most fundamental fact of consciousness; and it remains an ever-mysterious enigma. If we credit it to certain physiological processes occurring in the brain, it must of course accompany the general evolution of physical processes; but if we wish to regard this flight of time as a vital or spiritual phenomenon different in its essence from anything physical, there can be no a priori reason for assuming that it would accompany the general physical processes. Of course our awareness of the flight of time is an extremely vague feeling; nevertheless, so long as we retain a conscious state, we have no difficulty in differentiating a duration of twelve hours from one of one second.

If, then, in the example of the two twins, we assume that the length of the trip and the velocity of the travelling twin have been so selected that when the twins meet again, the clock of the traveller marks an advance of only one second, whereas that of his stationary brother marks an advance of ten years, our differentiation between physiological time and our consciousness of the time-flow would lead to the following result: The travelling twin would not have aged, physiologically speaking, but he would be fully aware, in his inner consciousness, that a stretch of time far in excess of one second had elapsed during his trip. However, we cannot fail to observe that if such were the case, if there existed two crates of aging for the same man, one physiological and the other corresponding to a psychological sensing of the flow of time, the special principle of relativity, and with it Einstein’s theory, would have to be abandoned.

The reason for this last statement is easy to understand: If the two species of time-flow varied independently, the rate of evolution of all processes would appear to vary according to the frame in which we might be situated—a tortoise would appear to crawl or to be galloping madly through space. Theoretically, therefore, it would be possible to detect a difference as between Galilean frames, hence to discover absolute velocity through the ether or through space. And this would be contrary to the principle of relativity.

When one places in the balance the mass of empirical evidence which lends support to the special principle of relativity, and the total lack of evidence of any sort or kind which would encourage the belief that the time sensed and lived is different from the time of physics and of physiological aging, one cannot be surprised at the total lack of interest the mathematicians of relativity must take in such vague hypotheses of certain philosophers.

Moreover, there is yet another aspect of the question. The fundamental reason for all the criticisms we have mentioned, is that deep down at the bottom of his heart the critic wishes to preserve, in spite of all, his hereditary belief in the absoluteness of time. Even when convinced that as a result of Einstein’s physical discoveries any such belief is incompatible with the evolution of things physical, he endeavours to assert that absolute time must continue to endure when the sensing of the flow of time and our consciousness of being alive are contemplated. In this way he proceeds to draw a distinction between time actually lived and time as measured by our optical clock. But the critic overlooks the fact that this belief in an absolute time which he refuses to abandon is in no wise a rational necessity, any more than is the hypothesis of the plurality of times. Experiment alone can yield us a clue; and granting that physical experiment may not be capable of throwing light on the spiritual, nevertheless, if we are to be eternally ignorant of things spiritual, there is surely no reason to state a priori that they must be governed by absolute time or that time itself should have any meaning so far as they are concerned. Thus the trouble with the critic who wishes to understand the significance of Einstein’s discoveries is that in spite of himself he remains obsessed by this unwarranted belief in the absoluteness of time. This conviction is undoubtedly hard to eradicate, and only prolonged introspection can gradually rid us of an obsession which is so thoroughly ingrained in the species. Then, and only then, will the so-called paradox of the two twins cease to be a paradox.

For all these reasons, if we accept Einstein’s premises there is no alternative but to recognise that the duration marked out by an optical clock in a Galilean system will give us the same measures of duration as will any other isolated periodic physical phenomenon; and that our aging, our awareness of the flow of time, and the time we are conscious of living accompany the oscillations of the optical clock. In short, therefore, if the optical clock in our Galilean system indicates that one year has elapsed, we must have aged by one year. We shall have gone to sleep and we shall have risen from bed on 365 different occasions, and we shall have had enough time to perform all those duties which usually occupy the space of one year.

Under these circumstances, to what does the example of the two twins finally reduce? Simply to this: The departure of our twin brother and his return to earth constitute two definite events. The duration separating two events being robbed of any definite value by the theory of relativity, there is no cause to be surprised that this duration should manifest different magnitudes to different observers.