Sir Oliver Lodge FRS DSc LLd
Those who read Mr Risilons article in last weeks Popular Wireless will have realised the importance of the controversy that is now agitating the scientific world of America. In this article Sir Oliver Ledge, the greatest scientist of our day, expresses his views on the new theory which Dr. Steinmetz, the chief engineer of the General Electric Co. of America, believes to have abolished the present belief in an etheric medium. In the following brilliant article Sir Oliver Lodge explains why it is impossible for Dr Steinmetz to lay down the law and to say 'There is no ether'.
The merest novice and beginner cannot fail to be interested in this fascinating subject, and if Sir Oliver Lodge's article is read with care the layman will easily comprehend - Editor
The Theory of Relativity ignores the Ether of Space, 'having no need of that hypothesis'. It treats of occurrences mathematically, from the point of view of the individual observer, and in terms of what he can observe. It is quite clear that we, as human beings, can observe only Matter. That is what our senses enable us to perceive, and everything else is an inference. Mind, for instance, makes no direct appeal to our senses, and though it is the instrument of Consciousness, it is a philosophic question how far Mind can be regarded as an object of Consciousness.
But we are directly aware that we are thinking beings, and therefore each individual concludes that he himself possesses a Mind; or if he thinks deeper he may conclude that he is a mind and possesses at body. By some means or other most people come to the conclusion that they consist of both Mind and Body, though how rightly to express the conjunction may be difficult even to a Metaphysician. We do not, however, directly perceive the minds of other people; we only perceive their bodies; but those bodies look something like our own; and the way they act suggests that they are similarly each associated with a Mind. That, however, is an inference, and there is a system of Philosophy in which it has been argued against the system known as Solipsism.
Does Magnetism Exist?
To common-sense, however, such a system seems absurd, and we most of us are quite willing to make the inference that other people have. minds like our own, whether we directly, perceive them or not. There are many other entities in like case - lots of things which make no appeal to the senses directly, but which are inferred from the behaviour of Matter. Life, like the life of a tree for instance, is of such a nature. We only infer that a tree is animated by something; which we call Life because of the way in which it grows and develops and fructifies and reproduces and decays. But many Biologists have doubted the existence of any separate vital principle, and endeavour to treat the organism as sufficiently explained by the laws of Physics and Chemistry, and by the interactions of molecules, the effects of which they observe.
We might go further and say that Electricity and Magnetism are in a similar position. How do we know that such a thing as Magnetism exists? Only by observing the behaviour of some kinds of matter - behaviour which seems inexplicable unless we assume that it is, as it were, animated by something that we call Magnetism, though we have no idea, at present, what it really is. It is hardly true to say that we have no idea: some of, us have ideas, but there is no certainty about them. And I suppose it would be possible to work out a theory of the Motions of Matter without mentioning the term Magnetism at all; for after all, by derivation; it only means the singular property of a certain stone which was found in Asia Minor (The Lodestone, which pointed in a certain direction when suspended, and which imparted its property to steel, is supposed to shave been first found near a place called Magnesia.)
The Aim of Relativity
But a gyrostatic compass points to the North, and the theory of its behaviour can be worked out without reference to anything magnetic. Indeed, there is nothing magnetic about it, only an elaborate spinning top. If we knew all about a compass needle it is probable that its theory could be worked out on somewhat similar lines. There is a hypothetical spin inside the atoms of the steel which may account for its behaviour, just as the spin of the gyroscope accounts for its behaviour, provided the spin of the earth is taken into account, too. So it may be with Magnetism. But no one has ever seen the magnetic spin, nor do we know for certain what it is that is spinning.
Again, we never actually see an electric current; What we observe is the motion of a compass needle which it detects (as in a galvanometer), or the bubbles which arise in a liquid which it has decomposed (as in an electrolytic cell), or the light which is emitted by a filament which it has heated (as in an ordinary glow-lamp). No one has seen an electric charge. All we perceive is the behaviour of bodies - the attraction of light things in its neighbourhood; and to say that that behaviour is due to an electric field, or that the pattern of iron filings is due to a magnetic field, is no better than saying that it is due to Electricity or to Magnetism. It might be difficult, but it would be possible, to work out a, theory of the Motions of Matter without introducing those terms. And if we forcibly limited ourselves to that which was really and directly observed, such a theory would be the inevitable result.
That is what the Theory of Relativity aims at - to specify exactly what is perceived, and to make no hypotheses beyond it. If an observer fails to detect any difference in the Velocity of Light through Space - whether he has reason to think he is moving towards the source or not - then let us proceed on the assumption that the Velocity of Light is absolutely the same relatively to every observer - granting the hypothesis, which is doubtful - for it is constant so far as the observer is concerned. If an observer is unable to detect any difference between his own motion and the motion of Matter near him, then let us assume that there is no difference, and that, everything is as relative as it appears to be. So says the doctrine of Relativity. In that way we get rid of the idea of Absolute Motion, that is, of the motion of bodies referred to something which is not Matter something omnipresent and fundamental, in which Matter, ever since Newton, has been hypothetically held to exist.
The Extreme Relativist
The Theory of Relativity is professedly a pragmatical and observational mathematical theory, and hence it is claimed that it ought to be acceptable to Physicists. It dispenses with speculation, dispenses with hypotheses, and attends only to what can be observed and measured at least, that is its ideal, though whether it quite comes up to its ideal may be doubted. We will give it the benefit of the doubt, and assume, that a Theory of the Universe can be elaborated without reference to anything but Matter and its motion relative to other Matter.
An interesting example of this kind of Relativity is furnished by a letter in Nature for July 8th, 1922.
A correspondent there points out that of the two theories of the Atom, one (namely, Bohrs) requires the electrons to be revolving round a nucleus, while the other (namely, Langmuirs) requires them to be stationary. He proposes a Copernican reconciliation, letting them be stationary while the nucleus spins on its axis, saying that according to the Theory of Relativity that should do just as well; in other words, that it does not matter whether a group of electrons revolve round a nucleus, or whether the nucleus rotates inside a group of electrons. Just so, according to any extreme Relativist, it might be held that it makes no difference whether the whole system of stars revolves round the earth once a day, or whether the earth rotates diurnally on its axis.
Ignoring the Ether
Put in this way, the notion is repugnant to common-sense, and, we need not hesitate to say, is false. So, also, the reconciliation of atomic theories suggested in the ingenious letter to Nature is imaginary and devoid of efficacy. But according to strict Relativity it is not so easy to say why common sense comes to these conclusions. The fact is that the centrifugal acceleration required for radiation cannot be conferred on an electron by a relatively rotating nucleus. Nor, is it possible for the stars to move far quicker than the Velocity of Light as they would have to if they were to revolve round the earth.
For what, after all, is the Velocity of Light, and why should a thing be unable to move faster than that? If we wholly and finally ignore the Ether no explanation is forthcoming. We can only merely say that it is so. Relativists all agree that it is so - the equations demonstrate that - but by pure Relativity they cannot explain why.
Hence, those who have gone most deeply into the Theory of Relativity sooner or later perceive that there must be something substantial filling otherwise empty space; in other words, that the Ether is really and truly indispensable, however much for practical purposes it may be ignored. For though we can proceed a long way without mentioning or thinking of it, sooner or later it is bound to make its existence felt, not physically but mentally; because of certain physical effects or consequences which are inexplicable without it, and because its existence is necessary to clear and adequate conceptions. To put it in the most ordinary and elementary form - one cannot really think of waves without some substantial medium for their conveyance.
So Far and No Further
Let it be known, then, that the great apostles of Relativity have never denied the existence of Ether. They have dispensed with mentioning it as far as they can. It does not seem essential to their theory as far as that has been-worked out. It does not seem amenable to direct experiment; and they can write down their equations without attending to it. But to deny the existence of the Ether, or of Electricity, or Magnetism, or Life; or Mind, merely because we find it possible for many purposes to ignore them, is to stultify ourselves. And to accuse any of the great Relativists of denying the existence of an Ether is to attribute to a man of genius a stupidity which he is very far from exhibiting - still less of possessing.
How, then, is it possible for Dr Charles P Steinmetz to lay down the law and to say that 'there is no Ether', that 'there are no Ether Waves', that 'according to the Theory of Relativity there can be no such thing'; and that no carrier for Light or Electro-magnetic Waves is needed.
Plainly, because he has gone a certain distance into the Theory of Relativity, and has not emerged into the atmosphere beyond it. He is satisfied with the way in which it works out the motions of Matter as observed by the senses, and he considers that any inference beyond the immediate testimony of the senses is illegitimate.
Freer Play for the Mind
That, then, is where we part company. To limit ourselves to sense indications alone is to reduce ourselves to the level of animals. No one really does it; and some even of the animals may make inferences of a kind. Certainly it is our human privilege to discover, to infer, to generalise, and to predict. And I advise those who are every day using the Ether, for electrical and magnetic and optical purposes, not to confuse themselves with the gratuitous and rather stupid hypothesis that Matter is all that exists because Matter is all they perceive; but to allow their minds freer play, and to realise that many other things exist, too, for which we have no sense organ.
So, if they care for my advice, I will recommend them to use a nomenclature in accordance with common sense to give a name to the substance or medium in which all their phenomena are occurring; to realise that wherever there is an electric field, or a magnetic field, or a gravitational field, or a beam of light, there must be something going on in this medium - something which Physicists can hope to analyse and examine and reduce to law and order. I would urge them not to remain satisfied with an abstract statement about the existence of unexplained forces in absolutely empty, un-physical, and merely geometrical Space.
No Easy Task
A field of force in vacuo has to be accounted for: the mere statement that it exists is no theory. A theory of the Ether has not yet been worked out; it remains for the next generation of workers to do it. Perhaps some of those now living will lend a hand. It is no easy task. Meanwhile, we can remember always that the properties of the Ether are largely unknown, and remain to be discovered - which surely is a stimulus to us to pursue our researches. That which we know definitely about it so far is the rate at which it can transmit waves; and we know, also, a great many things which follow directly therefrom.
We know, further, that it has properties akin to elasticity and inertia, which are experienced respectively in Electricity and Magnetism; and again we know (through the genius of Clerk Maxwell) that the combination of these two properties gives rise to that special kind of disturbance which stimulates the eye, and is responsible for all that is experimented on in Wireless Telegraphy.