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The End of Matter  (1906) 
by Henri Poincaré, translated from French by Wikisource
In French: La Fin de la Matière, first published in Athenæum (1906), reprinted in "La Science et l'hypothèse" (edition from 1917), Chap. 14.


The End of Matter.[1]

One of the most surprising discoveries made by the physicists in recent years, amounts in the claim that matter doesn't exist. We simultaneously add, that this discovery is not definitely established. The essential property of matter is its mass and its inertia. Mass remains constant everywhere and always, it even remains when a chemical transformation changes all observable properties of matter, and has apparently created an entirely new body. Thus if one is able to show, that matter carries mass like a foreign jewelry, that this mass (always considered as constant) can also suffer variations: then one surely has the right to say that there is no matter. But this is precisely what is announced.

The velocities observable up to now, are only small, because the celestial bodies, although much faster than automobiles, hardly make 60 or 100 kilometers per second; yet, light is ca. 3000 times faster, thus we aren't dealing with moving matter, but with a disturbance of equilibrium which propagates in a relatively unmovable substance, like a wave at the surface of the sea. All experiments conducted at these small velocities, have always confirmed the constancy of mass, and nobody has asked himself the question, whether this law is also valid at higher velocities.

The speed record of mercury (the fastest planet) was broken by those infinitely small bodies: I'm talking about the corpuscles by whose motions the cathode rays and the radium rays arise. It's known that these emanations were caused by a veritable bombardment of molecules. The projectiles ejected at this occasion, are charged with negative electricity; one can convince oneself of this fact by collecting this electricity with a suitable apparatus. In consequence of this charge, they will be deflected by a magnetic or an electric field, and by measuring these deflections one can determine their velocity and the ratio of their charge to their mass.

On one hand such measurement have taught us that their velocity is enormously great, by achieving approximately a tenth or a third of the speed of light, and thus being a thousand times greater than the velocity of the planets; on the other hand they have taught us that their charge with respect to their mass is considerable. Any moving corpuscle thus represents an electric current. Now, it's known that electric currents show a special kind of inertia, which is denoted as self-induction. Once created, a current has the endeavor to conserve itself; from that it comes that one notices a jumping of a spark, when one cuts the conductor (which is traversed by a current) and thus current is interrupted. The current endeavors to remain its intensity in the same way as a moving body endeavors to remain its velocity. Also our cathode-corpuscle will have a certain resistance with respect to the influences which can change its velocity: first by its actual inertia, second by its self-induction – the latter is the case because every change of its velocity would be connected with a simultaneous change of the corresponding current. The electrons – the name of the corpuscles – thus would have two kinds of inertia: the mechanical inertia and the electromagnetic inertia.

The works of the theoretician Abraham and the experimentalist Kaufmann were aimed to specify these two kinds of inertia more closely. For this purpose they had to made a hypothesis; they assumed that all negative electrons are identical with each other, that they all have the same essentially constant charge, and that the differences which exist among them are only caused by their different velocities. When the velocity is changing then their real, i.e. their mechanical mass, remains constant; this is so to speak the definition of the latter. However, the electromagnetic mass which causes the apparent mass, increases with velocity by a certain law. Therefore a certain relation must exist between the velocity and the ratio of mass to charge; as it was already said above, one can calculate both quantities by observing the deflections which were suffered by the rays under the influence of a magnet or an electric field; the study of these relations allows to separately determine the amount of both inertias. This result is totally surprising: the real mass is equal to zero. This conclusion is based, however, on the hypothesis mentioned before, but the agreement between the theoretical and the experimental curve is at least great enough, to make this hypothesis plausible.

Consequently, these negative electrons have no actual mass; if they still appear to be equipped with inertia, then this due to the fact that their velocity cannot be changed without a simultaneous disturbance of the luminiferous aether. Their apparent inertia is only borrowed, it doesn't belong to them, but to the aether. Yet, matter doesn't entirely consists of negative electrons; one can rather assume that there also exists real matter which possesses a certain inertia. There are rays also due to rain of projectiles, yet those projectiles carry positive charges with them: the canal-rays of Goldstein and the rays of radium belong to them; do those positive electrons also have no mass? This cannot be said, because they are much heavier than the negative electrons and are moving much slower. Here, two hypotheses are possible: either the electrons are heavier because they have a particular mechanical inertia besides the electromagnetic inertia from the aether, thus they would form the actual matter; or they are without mass as well, and only appear to be heavier because they are much smaller. I intentionally say "much smaller", even hough this may appear paradoxical; by this assumption, the corpuscles would only represent holes in the aether, and only the aether alone would actually exist and be endowed with inertia.

So far, the existence of matter wouldn't be endangered a lot; we still can decide ourselves for the first hypothesis, we even can assume that there also exist other atoms besides the positive and negative electrons. However, this last refuge was also taken away from us by the recent investigations of Lorentz. We are carried by Earth in its extremely fast motion; should the optical and electrical phenomena not at all be influenced by this translation? For a long time, one has believed in such an influence, one has assumed that it would be possible to demonstrate (depending on the orientation of the apparatus with respect to Earth's motion) differences in the observations. This expectation was in vain, even the most precise measurements never demonstrated anything like that. So by that, the experiments justified a conviction common to all physicists: if it were possible to demonstrate any influence, then one would be in the position, not only to determine the relative motion of Earth around the sun, but even its absolute motion in the aether. For many persons it will be hard to believe, that something different than relative motion can ever be demonstrated by experiment; they rather stick to the conclusion that matter has no mass.

Thus we weren't too much surprised by the negative results; although they contradicted the predominant theories, they satisfied a certain deeper instinct, which is older and stronger than all theories. There remained nothing left than to change the theories, so that they can be brought into agreement with this fact again. For this purpose, Fitzgerald made a surprising hypothesis: according to him, alls bodies shall suffer a contraction of about a hundred-millionth in the direction of Earth's motion. A perfect sphere consequently changes into an oblate ellipsoid, and if one sets it into rotation, than it is deformed so that the minor axis of the ellipsoid always remains parallel to the direction of Earth's velocity. Since the measuring instruments are deformed in the same ways as the observed objects, the deformation cannot be observed, unless one could determine the time which is required by light to traverse the object along its length.

This hypotheses accounts for the observed facts. But one cannot be satisfied by that; sometimes one will make observations which are still more precise: will the results be positive? will they give us the means to determine the absolute motion of Earth? Lorentz doesn't believe this; he thinks that such a determination is impossible also in the future; the agreeing instinct of all physicists, the failure of all experiments up to now, sufficiently justifies his view. Thus let us consider this impossibility as a general law of nature, let us take it as a postulate. Which consequences follow from that? This question was further investigated by Lorentz; he found that all atoms as well as all positive and negative electrons have an inertia, which (for all of them) varies with velocity by the same laws. Any material atom would therefore be composed by small and heavy positive electrons, and when the observable matter doesn't appear to us as electric, then this is caused by the fact that both kinds of electrons are present in approximately the same amount. They all have no measures, and their inertia is borrowed from the aether. In this system there is no actual matter, there are only holes in the aether.

According to Langevin, matter is liquefied aether that has changed its properties; when matter is moving, then it is not the liquefied mass that travels in the aether, but the liquefaction still affects new parts of the aether; and the aether that is located behind moving matter (and which was liquefied before) has returned to its earlier rigid state. Therefore, moving matter doesn't remain identical with itself.

This was the state of facts until recently; but now Kaufmann arrives with new experiments. The negative electron, whose velocity is extraordinarily great, must also suffer the contraction assumed by Fitzgerald, and by that the relation between velocity and mass would be modified; however, this wasn't confirmed by the recent experiments; thus the whole building seems to break down, and matter seems to keep its justification to exist. Besides, it is only about very small quantities in these experiments, and therefore a definite decision would still be too early today.

  1. See the book by Gustave Le Bon: l’Evolution de la Matière.