# Popular Science Monthly/Volume 78/June 1911/The Underlying Facts of Science

 THE UNDERLYING FACTS OF SCIENCE
By ALFRED SANG

PARIS

SCIENCE originated in the temple; for ages it remained as a mass of detached observations floating in mysticism. The civilization of Greece gave us the broad lines of many of the sciences, but the confinement of knowledge to monasteries, the enslavement of the human mind and the suppression of the wisdom of the ancients during the dark middle ages, deferred the rise of science until within comparatively recent times. From mysticism science has gradually drifted into agnosticism; mysticism cramped the work of the investigator; agnosticism lays no restraint whatever on his mental ambitions. The suspension of judgment on all matters unproven has helped in mighty measure to make theory the indispensable weapon of the scientist in attacking unsolved problems.

The Value of Theory

Theory, based on observation, is an accepted factor of inquiry, and the temporary acceptance of a theory serves as a scaffolding in the building up of knowledge; it is necessary to the work of correlating facts and to train the mind for the discovery of new facts. When we find our theories checked and kept within certain definite bounds, we can assume that we have found the measure of our ignorance and that the truth lies somewhere within the compass of these theories. If a theory is not a logical deduction from facts it should be called a hypothesis.

Nothing has created more prejudice, and thereby done more harm to theory as an instrument of progress, than the easy acceptance by the general public of all novel and sensational theories as proven facts if consecrated by the daily newspapers and the magazines. From the husk of the acorn an oak is postulated, although it may be rotten at the core and worthless. But we must theorize because we are built that way. As Tyndall once said:

Man is prone to idealization. He can not accept as final the phenomena of the sensible world, but looks behind that world into another which rules the sensible one.

The Limits of Conception

In scientific speculation, it is essential that we lose all sense of proportion, of time and of space. No dimension must appear impossible because it is infinitely large or infinitely small; no time must seem impossible on account of its infinite length or of its infinite shortness; the grains of sand of the ocean bed and the bubble capacity of a million tons of soap are crude and inadequate figures of comparison. e must remember that in extra-mathematical investigation we judge everything by human standards, but that in reality anything which can be expressed as a mathematical formula is as simple in nature and in operation as the facts of every-day life. If we do not get away from the habit of setting limits to every conception—limits based upon our own surroundings—we shall find our speculations conflicting with science at every turn.

The knowledge of principles clears the fog in which the speculative mind wanders in search of resting spaces, and the secret of clear conception lies in the ability of ridding oneself of pre-conceptions. If in attempting to conceive the speed of propagation of light we bring to mind the speed of a railway train or of a rifle bullet, we set a limit to our mental grasp, just as a student who can not assimilate an algebraical formula without an arithmetical parallel shuts himself out of the higher mathematics.

The greatest limitation from which our forefathers suffered was the rushing to conclusions from analogies, and the shallowness of the results can not be better illustrated than by quoting from a book called "The Art of Metals," published in the year 1640, and at one time considered an authority in matters metallurgical. Referring to blue copperas, or sulphate of copper, the learned author writes:

It is admirable to see its effect in Aqua-Fortis, (in which all Mettals like Salt dissolve and are turned into water) and an occular demonstration of th« possibility of the transmutations of Mettals one into another, for with Copperas dissolved in Aqua-Fortis, (without any other artifice) Iron, Lead and Tin become fine Copper, and Silver will lose of its value, and be turned into Copper also.

When discussing the principles of physical science we are confronted by a condition which continually vitiates clearness of exposition. Conceptions of energy and of matter are now becoming more and more convergent and we find ourselves in the dilemma of having at times to think of matter as energy and at the same time to describe energy in material terms. The world of science is becoming daily more accustomed to the convertibility of the terms energy and matter; but there is a natural tendency to incredulity, for, as some one recently stated:

In the estimation of material beings matter must necessarily assume a position of special importance; but nature may not perhaps regard it otherwise than as one of numerous forms of force, between which (as Newton wrote) it "delights in effecting transmutations."

There exists a public impression that the dreams of the old alchemists who, with the possible exception of an occasional Paracelsus, sought hap-hazard for the transmutation of the metals, has been vindicated by the disintegration theory of atoms and the discussion of the possible transmutation of one chemical element into another. This is doing altogether too much honor to the alchemists whose only object was personal enrichment; there is no credit due to them; the most extravagant theory may be realized under suitable conditions and in this mysterious universe any condition or concurrence of conditions seems to be possible.

Theories of Matter

For the belief that all matter may have a common origin, we must go back twenty-five centuries to Thales of Miletus and the hylozoistic school; it is another case of the premature leakage of subliminal wisdom. Sir Norman Lockyer can be said to have put the theory into tangible form by his work on stellar evolution which has developed the fact that the complexity of stellar matter is a function of its temperature. The higher the temperature of a star is, the fewer and the simpler are the elements present. Würtz wrote that "the diversity of matter results from primordial differences, perpetually existing in the very essence of these atoms and in the qualities which are the manifestation of them." Ascribing a common origin to all matter would tend to make the formation of new compounds from heterogeneous chemical elements appear more rational.

The problem of the ultimate structure of matter has stirred the philosophers of all ages, Democritus and Leucippus were the real discoverers of the atomic theory, and Lucretius was its poet; but the times were not propitious for its use as a working hypothesis; it was not, therefore, until revived by Gassendi and adopted by Dalton, that it became acceptable to science. As long as the chemist was obliged to work with molar masses of matter, his work was unsystematic and in a great measure fruitless; the atomic theory put things in their place and gave the chemist definite molecular masses with which to work. The proof of the atom has been its results; we have not here a question of nature, nor a question of form to discuss; the atom is a fact in chemistry, even if it has no existence in any conceivable form. Molar masses are continuous aggregates of molecules; molecules are definite aggregates of atoms. The selective qualities of atoms, the phase-rule, etc., belong at present more to chemistry than to physics, and they will, therefore, be left out of the discussion. Molar activity is known by its comparatively slow mechanical effects; atomic and molecular activity are known as heat and other forces, and as we go down the scale of size we find the activity more intense. But if it is unnecessary for the purpose of this exposition to discuss atoms and atomic aggregates, it is very important to understand the rô1e of ions.

Positive and Negative Ions

An ion is a charged atom, an atom carrying a quantity of electricity, such, for instance, the dissociated atoms of an electrolyte. Ions can be compared to diminutive Leyden jars, and as it has been discovered that they all carry the same charge and that each atom has the same electrical capacity, the physicist has been enabled to count the actual number of ions in any gas by the electrical properties of the gas. If an ion is electro-positive, it is known as a cation; if electro-negative, as an anion—two old words due to Faraday, which are immediately related to the familiar terms of cathode and anode.

Whatever the essential difference between them may be, the two electrical states (+ and −) may be said to differ chirally only, or, to give a more distinct if rather crude mechanical analogy, one may imagine that two discs, each suspended by a thread in its center, are revolving at a high uniform speed; if they revolve in the same direction they will spring apart as soon as they come into contact, part of their motion of rotation being converted into motion of translation; if they revolve in opposite directions their motions will not interfere, in other words they will be "in mesh." Thus, according to this conception, each is the enantiomorph, or opposite form, of the other; positive and negative charges of ions are equal but opposite. This idea of opposite charges owing their difference to opposite directions of rotation is only a working hypothesis, but is worth keeping in mind.

Distinction between Energy and Force

Having adopted negative and positive ions as the basis of matter, we must now examine the distinction between force and energy before going any further into the sub-atomic world. Force is the action, the manifestation of energy, just as visibility is a physiological manifestation of light. Light, in the abstract, is energy; in the concrete, as something that we see, it is a force. It is propagated as energy and manifested as a force; force, therefore, always implies matter.

As we shall have opportunities to see later, all energies are almost certainly modes of motion. Matter, on the other hand, is perhaps best described as whatever can occupy space, but this description is not suited to all theories. If motion is an essential property of matter, matter might be best described as whatever possesses energy in virtue of its motion; but in this essay the nature of matter will be discussed, and not its structure.

The ether, in which energy is manifested, may be said to have owed its recognition to the impossibility of believing in action at a distance and through a void space. Sir William Crookes at one time suggested a fourth state of matter for the ether; before accepting this theory, however appropriate it may appear, it seems reasonable that all the possibilities within range of our understanding be exhausted; we can hardly expect to understand a fourth state until we have fathomed the relations between the three states which we already know, and also their intermediate forms which immediately precede their critical points of transformation. We may some day be forced to an acknowledgment of this fourth state, although we may never be able to conceive it. It would be somewhat surprising that the ether be in any form known as matter; much more surprising than that matter be, after all, but another manifestation of energy.

It is a common thing for writers to dwell upon extinct theories. History is very well in its place, but in this essay extinct and not-generally-accepted theories will be disregarded in favor of those of more recent growth, or such as may be suggested by the recent discoveries in physical science. On this account it will be necessary, in the first place, to review very briefly the present state of radiology, without a knowledge of which a proper understanding of modern theories would be difficult.

Credit must be given to the early work of Sir William Crookes on radiant matter for having prepared the way to recent discoveries in this branch of physical chemistry. Credit must also be given to Sir J. J. Thompson, for work on the electric properties of gases, without which many of the important facts of radiology would have remained either undiscovered or barren, to which have been added his many masterly discoveries in the electronic world.

The most studied radio-elements and the most interesting for the present discussion are uranium, actinium, radium and thorium. The distinctive property of the radio-elements is to disintegrate, forming other radio-elements and also a more stable element. The disintegration is not molecular; it is atomic; the atom breaks down, it is destroyed or converted into the atom of another element. Radium is apparently de-energized uranium; the spectrum of uranium is entirely distinct from that of radium and they may therefore be considered distinct chemical elements. The radiations and emanations of all radio-elements being, in a general way, the same, it is only necessary to describe in detail the disintegration of radium, which is the most interesting and complete of all.

The magnet will separate the radiation from radium into three distinct streams, just as a prism will break up white light into its physiological primaries. These three radiations are known, respectively, as ${\displaystyle \alpha \,\ \beta }$ and ${\displaystyle \gamma }$ radiations, and radiations possessing similar characteristics are given off by all known radio-elements. The ${\displaystyle \alpha }$ radiation, which appears to be composed of helium atoms, has secondary rays composed of particles, until recently considered negative electrons, but, according to Professor Soddy, by no means finally proved as such for all cases. These particles of the a radiation are probably of relatively large size and are beautifully exhibited by the scintillation of the zinc sulphide in the spinthariscope. The ${\displaystyle \beta }$ rays are extremely complex and interesting and their power of penetration is about ten times that of the ${\displaystyle \alpha }$ rays. The ${\displaystyle \gamma }$ rays, which are themselves about ten times more penetrating than the ${\displaystyle \beta }$ rays, but do not affect the photographic plate to an equal extent, seem to be produced by the explosive disturbance which takes place at the formation of the ${\displaystyle \beta }$ rays, just as X rays are produced by the impact of cathodic rays; in fact, these ${\displaystyle \gamma }$ rays are very similar in degree of penetration and in some other properties to the X rays. In addition to the ${\displaystyle \gamma }$ rays, the explosive disturbance referred to produces an emanation, a veritable spray of the radio-active element. The emanation is, according to present standards, a form of matter, whereas the radiations can not be positively defined as such if judged by the same standards. The emanation, which is therefore a spray of the radio-element, a vapor, renders any object bathed in it radio-active and the action does not cease until the dust deposited on it has decomposed into radiation and emanation. The most significant product of the disintegration of the radio-elements, however, is helium, which has been mentioned in connection with the a ray; it is a distinct element with a distinct spectrum, perfectly stable chemically and therefore quite unlike the other products of disintegration.

Helium seems to be the state in which the unstable atom of the original uranium at last finds rest. It has been suggested that the helium may be merely occluded, but valid arguments have been brought to bear against the idea, and, if anything, radium would be a true compound of helium and of some other element. It has even been suggested that all chemical elements may be helium compounds. This is a return to Front's theory, but with helium in place of hydrogen. Contrary to general belief, helium is not exclusively a product of the radio-elements; Strutt has recently succeeded in obtaining a very fair percentage of it from New Hampshire beryl which did not exhibit any measurable radio-activity; it may, however, have done so in the past, the helium remaining occluded.

The speed of decomposition of the radio-elements, or rather of their salts—the bromides and chlorides being the most generally used—is so rapid that the use of chemical methods of analysis is almost hopeless. Radium is comparatively manageable, but actinium, which is said to be at least one thousand million times as active as radium, has a life period of less than eight seconds. It has been suggested that actinium is an intermediate product between uranium and radium.

The Disintegration of Matter

One of the latest developments of the theory of the disintegration of matter is a suspicion, which scientists hardly dare to voice, that there is a continual disintegration of all matter, stability being only relative and the new and perfectly inactive gases discovered in the atmosphere being among the most stable elements. It is just as natural for the atom to die as for it to be born; if we accept the latter, we can not deny the former. The atom of matter slowly expends its energy as does a watch-spring in doing the work of keeping time. Matter, according to this theory, is concentrated energy, the dissipation of which is almost too slow for us to detect. This theory has been taken advantage of to try to explain the sun's effulgent shell, and the question arises: when the unstable matter of the sun has completely disintegrated, will it become a globe like ours, dark and relatively cold, a mass of molten iron in the complex slag of which creatures not unlike ourselves shall dwell and dig for mineral treasures, subject to the changed conditions? Has our planet itself been through that state? Such a supposition is certainly no more extravagant than many we have heard, and the scarcity on the earth of radio-active substances and of the rare-earth elements which are such powerful emitters of the more useful light waves, does, in some measure, support such a theory.

However, in order to show the immense periods of time which are brought into question, we might borrow the following impressive example: one cubic centimeter of hydrogen contains approximately 525 octillions of atoms; if 10,000 of these were allowed to escape every second it would take about 17 quintillion (17,000,000,000,000,000,000) years to empty it. Upon a similar basis of expenditure of their contained energy by atoms of matter, it is evident that the detection of this expenditure would be very difficult. Before returning to the ether the electric atom or electron must be studied.

Corpuscles and Electrons

To understand what an electron is, we must imagine an ultimate particle—not a particle of matter, nor a particle of force, but just simply "a particle"—and let us give to this particle the old-time attribute of the atom; let us assume it to be indivisible. This, of course, is only a working hypothesis. This particle considered in the abstract we shall call a corpuscle. If we endow it with energy we shall call it an electron. Quite possibly the corpuscle can not exist except as an electron, or atom of negative electricity. However this may be, we must assume, in order to facilitate the discussion, that a corpuscle is only an electron when it is endowed with sufficient motion, which may be either vibrational or translatory, to manifest itself to us electrically. We shall assume that the abstract corpuscle exists, and that it only becomes electron when it is energized. Atomic action and the behavior of charged, or rather unbalanced, atoms, called ions, belong as much to chemistry as to physics, but corpuscular motion is purely physical as yet; it has no direct bearing that we know of on chemical reactions. As regards the nature and dimensions of corpuscles, J. J. Thomson has estimated them at one one-thousandth the mass of the hydrogen atom. As regards speed of translation, many radiations composed of electrons approximate the speed of light; this represents almost nineteen million times more activity than the one mile per minute ascribed by Clausius to the hydrogen atom which has already been taken as a standard of comparison. There are some very interesting theories to be derived from the study of electrons.

The Atom and its Metamorphoses

The present theory of the atom as derived from radiology is that it is composed of electrons moving rapidly in all directions and necessarily in constant collision; these electrons are assumed to be held together in each individual atom by a positive force. Differences in the number of electrons in an atom give rise to different elements. Imagine a glass globe of about the same diameter as the dome of St. Peter's, in Rome, with a quantity of grains of wheat shooting about inside in all directions, and acting and reacting by continual collision; the globe itself represents the force which keeps the electrons within the compass of the atom; the grains of wheat represent the electrons. We can, if we wish, assume that the electrons have orbital motions in relation to one another, as regular as those of the planets; it is only a difference in mass and in speed, and the mass being so enormously smaller, it is not surprising that the speed be so enormously higher, and, furthermore, there is no reason for thinking that the same laws which regulate a solar system may not regulate an atomic system. When the atom disintegrates it loses some of its electrons until a balanced system is reached, and it can then be assumed to be a stable atom, of a different element, however, provided the loss of electrons was not complete. If the theory of universal, or almost universal, disintegration and re-formation of atoms is correct, there is a constant outpouring of electrons from all atoms of matter, which even with a liberal allowance of units per second would hardly amount to an appreciable difference in atomic characteristics within historical periods of time, but which, premising a common era of formation for terrestrial elements, might explain the fractional discrepancies in atomic ratios; if such a theory were true, the elements as found in other worlds might have slightly different chemical constants.

As recently suggested by the author,[1] if the atom is continually losing electrons and, therefore, atomic weight, until, a certain critical point being reached, a readjustment takes place resulting in transmutation to a lower element, it may be supposed that the atomic weights of the elements may vary in different worlds of space. The more or less uniform weights found on this planet would be due to the fact that the period of formation was practically identical in all cases. The slight divergences between the theoretical and actual atomic weights in the periodic system would be due to the electron contents having fallen below the contents at the last points of readjustment. The list of the chemical elements arranged in decreasing order of their atomic weights would represent the steps of the degradation from the highest elements having, possibly, atomic weights exceeding 250. It was further suggested that the atomic weights of the elements in meteorites be determined to check the truth of the theory of transmutation by disintegration; as far as known this has not yet been attempted.

It would seem to be rather idle to discuss the possible reasons for the diversity of elements in each chemical group on the assumption that they all originated at one time for each individual body in space from extremely dense elements, themselves concentrates of the one primal element. At most, it is proper to state the theory as follows. As the nucleus of a nebula condenses and cools into a solid mass, the structure of the matter at the center becomes extremely dense and the atomic weights are high; these weights taper off to the surface, which is then of a somewhat irregular and slag-like nature like the crust of the earth and brings to mind many parallel cases in metallurgy. Many scientists hold that the earth has solidified more or less in the shape of a modified tetrahedron; if this be true, it encourages the view of a fairly homogeneous core which may be composed of elements even heavier than radium, thorium and uranium. The radioactive properties of these elements may account for the internal heat of the earth. The view that the bulk of this globe of ours is of similar composition to the crust is not only unjustifiable, but highly improbable; the slag of a steel-making process is a good indication of what there is not underneath. The theory of a core composed of elements having high atomic weights will go far to explain the high average density of the earth as compared with that of the crust.

The Electrical Nature of Gravitation

A discovery of inestimable value is due to Kaufmann; he found that the mass of the ${\displaystyle \alpha }$ particle varied with the velocity. This discovery all but consecrated the old theory that mass, that gravitation, is a form of energy, a mode of motion. There can not be a manifestation of energy when the motion is uniform. No motion of energy can be evidenced without acceleration followed by arrest and a reversal of motion, or what is known as "periodic acceleration," pulsation or vibration. We can not measure a uniform motion in a particle moving with the speed of light, but we can measure its acceleration. All forces pulsate; they are all propagated as waves, which set up vibratory motions in matter and thus make their presence evident.

In support of this statement about the nature of mass, which is of such fundamental importance, the words of Professor Rutherford may be quoted:

If a charge of electricity in motion exactly simulates the properties of mechanical mass, it is possible that the mass of.matter in general may be electrical in origin and may result from the movement of the electrons constituting the molecules of matter.

It is to be noticed that Professor Rutherford refers to the electrons as charges of electricity. His words give a full, if concise, definition of the electrical theory of matter which is accepted by the mass of physicists and of which Sir Oliver Lodge is the able historian. When Davy suggested that matter and electricity were kindred phenomena he could hardly have suspected how near he was to the truth as it is seen to-day. The materialists and energists are now on the high-road to reconciliation, and we are permitted to feel that an explanation may soon be forthcoming for the well-known relation between specific heat and atomic weight, and for that existing between spectral phenomena and atomic weight.

The matter of gravitation can not be put aside without a few additional remarks. Lord Kelvin, by calculation, has ascribed to the ether a weight of one-thousand-billionth of a gram per cubic meter. This is not very much, and can give little encouragement to Lothar Meyer's suggestion that the slight divergences between theoretical and actual atomic weights in the periodic system may be due to the imprisonment of a quantity of the ether within matter; as just suggested, these differences are more likely due to electronic losses.

If the new theory of mass is accepted we must postulate a quantity of energy in the ether in keeping with its weight. We shall know more about this when these quantities have been calculated by different indirect methods and the results compared. We shall have occasion, a little later, to discuss the temperature of space between which and its internal energy and mass some relation may exist. Heat is usually considered to be due to atomic agitation; we are now assuming mass to be due, possibly, to corpuscular agitation, which already produces, as we know, light and other electro-magnetic phenomena. The day may come when, able to control the internal forces of the atom and effect transmutations, man may set about destroying matter, as such, altogether, for use in his industries at so much per kilowatt-hour. To the peculiar forms of insanity which induce some men to sell eternal salvation and others to capitalize the future, will be added the new feature of utilitarianism of annihilating the earth in order to improve it as a place of habitation.

Chemical Theory of the Ether

Returning to the ether, we find ourselves in better position to discuss its probable nature, and the first theory to be examined, while perhaps the least satisfactory, merits respectful consideration as coming from such an authority as the late Professor Mendeleef, who gave its full development to the periodic system of Newlands, with its strong argument for a common origin of all the chemical elements. Mendeleef's theory is known as the chemical theory of the ether. He suggests that space is filled with chemically inert gases such as argon, krypton, neon and xenon; thus, no chemical reactions would be possible in space, although it is filled with what is actually matter. This is a return to the Cartesian theory of matter filling all space, and implies an atomic structure of the ether. From a purely structural point of view, Mendeleef's theory is not incompatible with the theory of an ether entirely made up of corpuscles, but on account of the larger size of atoms it would be more definitely granular, and therefore less continuous. Cauchy has attempted to calculate the probable dimensions of ether particles and claimed one ten-thousandth of a wave-length as a result. This is not an encouraging figure for the chemical theory, as it is very much smaller than any of the atoms known to us, and it is worth while on that account to examine some of the physical conditions of the medium in space.

This medium is, according to the figures of reliable investigators, under considerable pressure, and Professor Poynting tells us that interstellar space is at a temperature of about 10° abs., or several degrees warmer than the lowest which Sir James Dewar has been able to obtain by artificial means. This would be, of course, an average temperature, because variations must exist in different parts of space. The high pressure combined with low temperature is not in itself suggestive of the presence of known gases.

There is no indication that a fall of temperature lessens chemical activity—in certain cases it has been found to increase it—nor that it in any way accelerates the disintegration of atoms, and there is no reason, therefore, to believe that gaseous activity would be reduced in space by the absolute, or almost absolute, withdrawal of heat. This statement may appear to contradict a previous statement that heat was the result of molecular agitation, but it does not, for gaseous activity, which causes expansion, is an intrinsic activity entirely independent of, though influenced in degree by, the superadded activity imparted to masses or aggregates of gaseous atoms or molecules by heat waves passing through them. Furthermore, no extrapolation of results actually obtained warrants us in suspecting that molecular aggregates can not exist at zero absolute; thus we may well believe that chemical affinity, while influenced by temperature, is in no way dependent on it, but is an intrinsic property of the atoms themselves. Gaseous matter in space is not necessarily "frozen to death."

It has just been stated that there was no indication that a fall in temperature hastened atomic disintegration; the reverse may be true. Jean Becquerel has recently shown that at the temperature of liquid air the transparency of matter increases and the spectral absorption bands become finer. It is well known that the very opposite is the case with a rise in temperature above normal. In this we may see a vindication of the theory that heat is due to molecular agitation, or, to speak more correctly, is manifested as molecular agitation, which interferes with translucent properties.

Phenomena of Inteestellar Space

If the ether is a mass of elementary gas or gases, in what relation will it stand to the energies which it transmits? If the ether is gaseous, i. e., material, all our accumulated knowledge of matter is at variance with the accepted facts of astrophysics. If this gaseous ether is the ultimate condition of matter, the luminiferous medium, all our accumulated knowledge of the ether is opposed to many accepted facts of science. The acceptance of a material ether necessitates too much work of reconciliation and the distortion of established facts to suit its requirements. We turn, therefore, to sub-material theories.

The ether transmits but does not manifest heat, light and other forms of energy. Light is not manifested in space—at least not to any appreciable extent; the variations in our distance from the sun do not produce color phenomena of the order of those which a variation in the depth of atmosphere through which we view the sun produces. Heat stands in the same relation to the ether as sound does to gases of suitable density; it is not manifested in a non-material ether; it is transmitted, and that part of space through which it passes is unaffected. If a molecular mass, our globe and its atmosphere, for instance, be interposed, the light and heat will be manifested, dissipated and finally absorbed by atoms or atomic aggregates, the periods of whose vibrations coincide with theirs. If not manifested they can not be dissipated, but will travel forever in a right line.

But if this is correct, how is it that interstellar space possesses any temperature at all? Why is it not at zero absolute? Heat, as already stated, is known to us by its manifestation; it is manifested in matter and ultimate corpuscles can only transmit it without retaining it. Heat and light may be identical in nature, but they are distinct in their action; it has recently been shown that the change of period in the movement of electrons which absorb light is quite independent of temperature, thus confirming the theory that heat does not affect the corpuscle as it does the atom, and that therefore space, if it were corpuscular (sub-atomic) in composition, could not possess temperature.

Assuming that Poynting's calculation of the temperature of space is right, or even adopting that of 1.5° Centigrade absolute, as was more recently calculated by Schaeberle, we shall either have to accept a material theory of the ether, like Mendeleef's, or else suppose that molecular dusts—solid, liquid or more likely gaseous—are present in space, as material impurities in a sub-material medium. Such a supposition, recently made by the author,[2] is not only possible, but is highly probable. If, as is far from unlikely, this dust is found here and there in masses more dense through which our planet glides, we do not have any further to seek for another explanation of the aurora borealis and kindred phenomena, which would be caused by the electrification of this dust when near the earth. These auroras occur at irregular times, whereas the theory of Arrhenius, which attributes them to cathodic rays emanating from the sun, would lead us to expect a continuous or periodic performance. By adopting Villard's theory of the telluric origin of the cathodic radiations of the phenomenon, we can introduce the cosmic dust as a rarefied gas in which it is displayed. Zodiacal light will be due to dusts burning when contacting with our atmosphere, just as on a large scale and detachedly, meteorites will illuminate the sky. Night brightness, as for instance the "extraordinary lightness of whole nights in the year 1831, during which small print might be read in the latitude of Italy and the north of Germany," mentioned by von Humboldt, might have been due to a very dusty condition of space following solar activity. Abney has claimed that the region of space which we are traversing contains benzene vapor, ethyl hydride and other alcohol derivatives; these would assuredly burn when in frictional contact with the atmosphere. The more recent suggestion of a permanent corona around the earth which becomes visible under certain conditions as sky lightning does not stand analysis, but such a corona will exist as the earth passes through dusty regions in space.

If the sun, out of those vast cavities in the photosphere which are called sun-spots, belches forth this cosmic dust, undoubtedly gaseous in at least its early constitution, and the earth gravitates through it, the electro-meteorological disturbances which are observed one week or 80 after the appearance of spots would be, in a general way, fairly well accounted for. It is significant that the growth of the red flames which has been estimated about 200 miles a second corresponds to a period of about six days to bridge the distance between the sun and the earth's orbit. It is to be expected that this planet be influenced by a material bridge between it and the sun. Sun-spots are regarded by many astronomers as a falling-in of a portion of the photosphere, but the reasons for this belief are not conclusive, and it is legitimate to believe in a movement in the opposite direction due to an explosive force within the effulgent crust which, as in the case of volcanoes, occasionally relieves the tension beneath that crust or in its cavities. Our periods of greatest heat often follow sun-spot activity—not that sun-spots are hotter than the rest of the sun's surface, but the matter which is sent forth intercepts and stores heat before it can pass beyond the limits of our orbit to be absorbed by extraneous systems.

A last consideration which makes the chemical theory of the ether untenable is the fact that if space were filled with gases, the temperature near heated bodies like the sun would be very great, and powerful currents would be set up which would be detected by optical if not by other means. A material ether would possess some degree of viscosity and would necessarily interfere with the progress of bodies, and this negative acceleration would create heat of friction, dissipated but undestroyed. This leads us to the consideration of the physical requisites of an ether in which matter, as we know it, must "fit," before we examine any of the other theories which have been offered within recent years.

Failure of Material Conceptions of the Ether

All the experience which has been acquired through telescope, microscope and spectroscope, with and without the aid of the camera, leads to the belief that the all-pervading medium must be uniform and homogeneous. While this may be taken for granted, it by no means implies that the medium must be continuous; in other words, each of its components does not necessarily have to stand in any physical relation to its neighbors, for this would imply a force of affinity or of cohesion which one may be unwilling to grant, as it yields a purely material conception and carries one back to the chemical theory, which has been laid to one side for the present.

Some of the most eminent physicists have adopted the view that the universal medium must be solid; this belief is based on the manner of propagation of light and other high-frequency energies, which take place without appreciable dispersion in space. But, on the other hand, in all theories but one, this medium is expected to be of a nature which will offer little or no resistance to bodies moving through it. At first sight it is hard to reconcile this requirement with the nature of a perfect elastic solid such as we picture to ourselves. It has been suggested that the medium must be somewhat like pitch which shows no track of a body which has passed through it, and we are asked to conceive our planet—not to mention our humble selves—moving at a rate of eighteen miles per second through it, and, what is still more incredible. that this takes place without practically any friction. The truth of the matter is that whether we call it a perfect gas, an incompressible fluid, a jelly, or a solid possessing perfect elasticity, we are tying ourselves down to a material ether, and the acceptance of any one of these conceptions ends in a reductio ad absurdum.

As for dispersion, if it be assumed that light is given forth from the entire surface of the sun equally in all directions, the lateral pressure of dispersion at each spherical zone, and at any distance—if it exists—would be equal, and there would be perfect equilibrium between adjacent cones of light; the bases of these cones are equipotential surfaces and no lateral dispersion could be rationally admitted. When, however, the light waves strike an object such as the earth, a shadow is formed. Leaving out the refraction in our mantling atmosphere to which we owe our twilights, the shadow which the earth casts is practically absolute for at least the distance from the earth to the moon (240,000 miles); and it is therefore evident that the medium itself is of such a nature that it will transmit transversal vibrations without any appreciable dispersion. If dispersion in space were serious the light of the stars would be shown as a haze and not as individual points,

The theory of a solid or, to speak more accurately, a rigid ether does not, as we shall see later, appear to be a necessity, and it presents the great weakness of compelling us to rack our common-sense to try and explain the passage of bodies through it, from the lightest comet to the most massive star. Rigidity of rotation was first proposed by McCullagh and its nature will be considered more fully when the subject of vortex-atoms is reached, but, however plausible it may be for material atoms—and it is eminently so—it seems to be a superfluous hypothesis for a non-atomic ether. Rigidity and elasticity of rotation can be compared to the gyroscope which resists deflection and yields elastically, although it is not itself elastic, nor immersed in a medium which could be considered elastic when the gyroscope is at rest. This is an elasticity of motion, not of matter; it must, however, be remembered that, as Lord Kelvin has pointed out, elasticity itself may be but another mode of motion. With elasticity of rotation, one might have practically a fluid ether possessing high elasticity with its oscillatory power, instead of the viscosity of ordinary fluids, with its dispersive quality.

Perfect elasticity by no means implies a solid or semi-solid state; an atomic structure presents elasticity of volume, but equilibrium in a homogeneous, non-continuous medium, regardless of the spaces which may exist between the component incompressible corpuscles, will supply rigidity and elasticity of shape. Pressure in space does not imply elasticity. If elasticity is a rotational effect and pressure one of bombardment, they are not necessarily interdependent. The fact that there may be pressure in space brings one back to the consideration of a gaseous ether, but can not pressure exist in a corpuscular medium, and may not the pressure be a manifestation of the innumerable energies which continually pulsate through space? If all forces—including chemical forces—were suddenly removed from a certain point in space, there could be no activity and therefore no pressure. Pressure is the result of activity, of bombardment, and space is truly "alive" with activity, for, as Clerk Maxwell said, energy transmitted must exist for a time in the medium. No wonder, therefore, that it is under pressure, which Sir Oliver Lodge estimates as equivalent to 1037 ergs per cubic centimeter.

Before leaving the subject of pressure in space, it may be well to look further into the matter of ethereal activity. The activity of the ether might very well be of a higher order than that of the energies or forces known to us. When we consider that as far as we can discover the hottest stars have the simplest spectra, it may well be suggested that gravitation, electricity and light may represent falls of potential and not rises from the inherent activity of the ether, which, calculated to secure the necessary rigidity in the theory of vortical motion, is of stupendous magnitude. This degradation of the energy of the universe of ether into the energies known to us is in the same line of development as the degradation of matter, and the laws regulating the conceivable may logically govern the inconceivable.

No material conception of the ether is therefore to be considered excepting one which, at first sight, appears perfectly paradoxical, of an elastic solid of a density of 1012 (Lodge), as rigid perhaps as steel, and, in that case, fifty thousand times less dense than hydrogen (Michelson).

The Creation of Atoms

If, as already stated, energy, as we know it, is originated in matter—though not by it—and transmitted through a medium the ultimate particles of which are very much smaller than and different in nature from the atoms of matter, the disturbance at the source of origin must be transmitted by a number of corpuscles of that medium and propagated as a bundle of vibrations several corpuscles in diameter. This bundle of lines of force may be called a tube of force; this tube of force may be of any shape whatsoever, depending on the shape of the source of origin and the nature of its disturbance.

Plateau has shown that a liquid cylinder of excessive length and with a free surface first assumes an undulating contour, and then breaks up into separate vibrating drops. The resistance of the medium apparently puts the stream into vibration which causes a separation into equal drops by periodic strains which finally overcome the surface tension. The researches of Bjerknes confirmed Plateau's experiment and he found that the distance required for the breaking into drops depended, as might be expected, on the relative densities of the liquid and of the medium. Savart had shown that this natural tendency of liquid columns to break into drops can be induced by a musical note which synchronizes with the period of the drops.

We can now build what is possibly a wild theory, by means of that dangerous tool of philosophy: analogy. Let us imagine a bundle of energy not having a free surface but forming part of a general spherical disturbance, striking an object having an aperture which does not absorb or reflect the energy and therefore acts as a diaphragm; suppose that a cylindrical pencil is thus formed and propagated beyond the obstacle; this tube of force will have free surfaces; the analogy with the behavior of liquids dictates that after a while the tube will resolve itself into spherical drops and these drops we shall call atoms. We have thus created atoms from corpuscles and the energy traversing them; we have given an origin to what Crookes has called an "atomic fog," which is, according to the nebular hypothesis, the basis of the material universe. The "atomizing" of a liquid and the shredding of lead (lead-wool) by an air blast are identical in principle.

But the hypothetical diaphragm can be used to produce quite a different atom from the spherical drops which have just been created, provided the vibration be brought about before the energy, corpuscles, electrons, or whatever we wish to consider them, are ejected beyond the diaphragm. If a box with a hole (diaphragm) in it is filled with smoke and the side opposite to the hole is given a short tap causing the smoke to vibrate, a ring of smoke, a vortex ring, will be emitted, with the appearance and general properties of which we are well acquainted. A continuous motion of the smoke will not produce a ring; it will produce a stream, with a skin resistance like the stream of smoke in a chimney; to produce a vortex ring, a pulsation is required which will emit small disks of smoke which can be thinned at the center to the point of rupture by the resistance on the edges of the hole. If, therefore, a tube of force pulsates or is caused to pulsate by an elastic or pulsating resistance or otherwise, when it strikes the diaphragm in the obstacle, a vortex atom will be produced in place of a spherical atom. We have thus created the vortex atom as first proposed by Helmholtz and developed by Lord Kelvin into a theory which has stood the most careful mathematical scrutiny.

That an obstacle in the path of a stream of energy will alter that energy is evident. The conversion of cathodic rays into X-rays shows what impact may do. The clash of two similar or dissimilar streams of energy might create spherical or vortical atoms and the relative speeds and the angle of impact would influence their period of vibration.

The radiation from disintegrating matter on this planet may go far out into space to re-create atoms for use in some other system. The sun, while emitting an enormous amount of energy, may be gathering an equal amount and be a vast atom-factory. Vico with his "metaphysical points" and Boscovich with his theory of centers of force for atoms were the forerunners of the theory that matter is energy objectified, a theory so startling that it would be unwise, not to say positively indecent, for modern science to accept it offhand without at least a show of suspicion. Anaxagoras saw in the energy of atoms the evidences of mental power; even the most sceptic must refrain from criticizing or judging the statement that the energy of the atom is entitled to be called intelligent in the broad sense. It is quite significant that protoplasm molecules are very rich in atoms, each molecule of human hœmoglobin containing not less than 1897.

The Vortex Atom

But we must now return to the vortex atom. It is a gratuitous supposition, all too widely accepted, that atoms must necessarily be round. Secchi favored a round revolving atom. Lord Kelvin and many others found that the vortex atom more completely satisfies the requirements of observed facts, but that the vortex atoms may vary in their shape and proportionate dimensions. It may be best to give Professor Tait's definition of Kelvin's vortex atom, instead of attempting to fashion a new one. "The rotating part of an inert perfect fluid, whose motion is absolutely continuous, which fills all space, but which is, when not rotating, absolutely unperceived by our senses." By "perfect fluid" is meant one which is frictionless, clearly an impossibility for matter in the liquid state.

The most pronounced features of the vortex atom as compared with other conceptions which have been offered are its elasticity and its permanent character; its mathematical study is of unusual difficulty, but the properties which it must necessarily possess coincide in a remarkable degree with the observed properties of atoms. The vortex ring, one made of smoke, for instance, can not be cut; it will move away from the edge of the knife; it can, however, be deformed and will vibrate in various ways. It can revolve axially or in any other direction. It is even conceivable that vortex atoms be linked so that a great variety of arrangements would be possible, corresponding to stereochemical groupings.

One more point must be touched upon. Is the ether stagnant or in motion? At first it may appear as rather a waste of energy to attempt to discover if the ether is in motion, but Professor Larmor has shown mathematically that the absence of any optical influence of the earth's motion on light from the sun and stars suggests that the ether moves along with the earth. From another source comes the idea that the earth, being a magnet, drags the ether with it. In what a complicated turmoil the universe of ether would have to be if this conclusion were applied to all bodies in space! This dilemma brings us to the one theory which seems to clear up the most stirring mysteries of astrophysical science.

Reynolds's Theory of the Universe

The theory of the universe, which may perhaps be called the "dark horse," is due to the late Professor Osborne Reynolds, a thinker and mathematican of no mean caliber. The theory is thoroughly discussed and elaborated in his "Sub-mechanics of the Universe," which he very appropriately calls an "inversion of ideas." Instead of considering atoms as comparatively massive particles in a vacuum, a gas or a fluid, he considers them as negative inequalities or comparative vacua immersed in the perfectly rigid plenum which the phenomena of the universe require. The atoms in the ether might, therefore, be compared mentally to the pockets or bubbles of liquid in a colloidal emulsion. It is, of course, unthinkable that atoms be perfect vacua, that matter be the expression of nothingness; what is meant is that the ether is perfect fullness and that atoms are infinitesimal spheres of activity containing less ether; mass being a function of activity, there is no connection between quantity of ether and weight. It was with Reynolds's theory in mind that the statement was made that matter and the forces which make it known to our senses might possibly represent degradations of the inherent energy of the ether. The degradation of an element means at once loss of electrons and loss of mass; hence, perhaps increase of ether content or increase of inactive corpuscles, or even, which would amount to the same thing, loss of energy to corpuscles outside the atom. All this does not, however, solve the difficulty, it merely inverts the ratios of mass; to complete the system, a theory of the propagation or conduction of matter, in place of its transportation or convection, is necessary.

The Conduction of Matter

In the early days, astronomers found difficulty in ridding themselves of the geocentric idea, and in the same way it must be a difficult thing for the physicist to abandon the idea of positive matter; this conservatism is the fly-wheel of progress. Much harder still should it be to introduce the notion that matter is propagated like waves, like moving pictures on the cinematograph screen which truly live and give rise to emotions, although made up of nothing more tangible than lights and shadows. What a reversal of mental habits to conceive that the centers of force alone move and the component electrons change continually as the waves progress through the compact universe of ethereal corpuscles!

That such a propagation should take place without friction is possible, if friction is purely intermolecular and not an atomic operation like non-radiant heat. Heat, as already stated, is due to molecular agitation and all matter possessing heat above absolute zero is undergoing that particular form of molecular agitation; if the period of agitation is greatly increased by heating an article or greatly reduced by immersing it in liquid air, the effect on the hand at normal temperature will be much the same, physically, in either case; it is as if it were applied to a revolving emery wheel. The difference of period between the agitation of the molecules of the hand and that of the substance, whether positive or negative, will result in damage, the organic molecules being unable to respond without destructive decomposition to the periodicity with which they are put in contact.

If atoms can not vibrate in the order of heat or friction waves, any more than the optic nerve can vibrate in the order of sound waves, there can be no friction in the propagation of matter as postulated. Even if friction were interatomic, there would not necessarily be friction between atoms and sub-atoms. If there is any loss from the passage of atoms through space, it can not be as heat, unless the ether be atomic or molecular; it must be more in the nature of optical diffusion and the continual degradation of matter may be the effect of its propagation through space. Electrons may be strewn in the wake of each heavenly body to be swept up by comets in their courses and effect their growth, or gathered some day into nebular clouds from which new worlds will originate to take the place of those which wasted away in ages past.

The theory of the propagation or conduction of matter is equal mathematically to the ether moving with the earth. There is no actual relative displacement of the constituent corpuscles and it was therefore to be expected that, in the light of Reynolds's theory. Professor Michelson's elaborate experiment would fail to show aberration due to motion through the ether.

Man is a mass of prejudice; he is limited to one set of standards. From the first development of his organism from a zoophite, his senses have evolved in relation to matter alone, and it is only within recent times that he has commenced his evolution towards the understanding of submaterial truths. It may be untold ages before he may strike the endless path leading to the answer of the one and only problem in which he is interested and towards which he strives by the study of nature: the mystery of his self-consciousness.

The helplessness of the human mind in presence of the underlying facts of science is the deepest argument for a faith in some inconceivable universal mind of which our own is, at the very best, but an imperfect reflection.

1. Nature, February 18, 1909, p. 459.
2. Science, Nov. 20, 1908, p. 728.