Charles F. BRUSH
Kinetic Theory of Gravitation
"A Kinetic Theory of Gravitation"; Nature 86:130-132, March 23, 1911
Letter to the Editor (Sir Oliver Lodge); Nature (March 30, 1911)
"Gravitation"; Proc. Amer. Philos. Soc. 68: 55-68 (May 1929)
Nature 86: 130-132 (March 23, 1911)
A Kinetic Theory of Gravitation
Charles F. Brush
Ever since Sir Isaac Newton enunciated the law of universal gravitation, more than 200 years ago, philosophers have speculated on the nature of that mysterious agency which links every atom of mater in the universe with every other atom. Newton found himself unable to offer any adequate explanation.
Since Newton’s time several theories of gravitation have been proposed; but all, of which I am aware, are open to strong objections, and are not considered even promising by physicists.
Study of the nature of gravitation is beset with unusual difficulties, because gravitation is ever with us and about us; it is the one universal phenomenon, and we cannot escape from its influence -- cannot obtain any outside point of view.
Gravitation is often described as a feeble force: and so it is, from one point of view. It is difficult to measure, or even to detect, attraction between two small bodies. But when the bodies are pf planetary size the aggregate attraction of their molecules is enormous. It is easy to calculate that the attraction between the earth and the moon, which is just sufficient to retain the latter in its orbit, would, if replaced by a steel cable, require that the cable be about 500 miles in diameter in order to withstand the strain. Between the earth and sun, the cable would have to be nearly as large in diameter as the earth: and attraction between the components of double stars is millions of times greater than between the earth and sun (Lodge). So tremendous a phenomenon as gravitation, a phenomenon compared with which all others seem trivial, must have a mighty origin.
That gravitation is a phenomenon of the all-pervading aether is beyond reasonable doubt. This is so generally conceded that it need not be argued. But how does the gravitative influence originate? How is it transmitted and maintained? What is the mechanism of gravitation? It is the purpose of this paper to attempt an answer to these questions.
Let us consider what happens to a falling body. We know that it gathers kinetic energy from some source, as evidenced by its acceleration; that this energy may do external work or develop heat; that the amount of energy gathered is measured directly by the distance fallen through (within the limits of uniform gravitation), irrespective of the time or rate of falling. When the distance fallen through is of inter-planetary magnitude, and the attracting body large, the gathered energy is enormous, sufficient, if converted into heat, to vaporize the most refractory falling body.
We are here confronted with the question, Whence comes the energy acquired by a falling body? Certainly it was not inherent in the body before the fall, as evidenced by the fact that during unimpeded fall none of the physical or chemical attributes of the body, aside from the acquired motion, changes in the slightest degree.
We have been taught that before the fall the body was endowed with "potential energy of position" which is converted into kinetic energy during the fall. I think "energy of position" is an unfortunate term, because it is so very inadequate. To me it explains nothing. The case is not like that of a flexed spring, where there is internal molecular strain or displacement.
Let us imagine a pound-weight of iron, for instance, raised from the surface of the earth to a point near the moon in a line joining the centers of the two bodies, the point so chosen that the opposing attraction of the earth and the moon shall exactly balance each other, leaving orbital motion out of consideration.
On the surface of the earth the two-pound weight had some so-called "potential energy of position", because it was capable of falling into a pit; but in its new position near the moon, this potential energy not only has not been augmented, but has disappeared entirely; the pound-weight, left free to move, remains stationary; and yet we must have expended more energy in overcoming the attraction of the earth and lifting the weight to its new position. This amount of energy would be sufficient to impart to the weight a velocity more than 10 times greater than that of the swiftest cannon-ball, or, if converted into heat, would be many times more than sufficient to raise the iron weight to dazzling incandescence and then vaporize it. Now, in lifting the weight, this large amount of energy has disappeared utterly. We cannot believe that the whole or any part of it has been annihilated; it must, in some form, be resident somewhere. I think no one will contend that this energy is resident, in any form, in the cold, motionless pound-weight. I believe it was absorbed by, and is now resident in, the aether through which it falls. This is a fundamental idea to which I invite attention. Faraday glimpsed it long ago, and others have appreciated it more clearly since his time. But, so far as I am aware, no one has realized its significance.
This view of gravitation implies that the aether is endowed with very great intrinsic energy in some form. Many men of science now hold that the aether is so endowed, and that the amount of this intrinsic energy is enormous. Sir Oliver Lodge ("The Ether of Space") appears to regard this energy as potential in form, and estimates the intrinsic energy of a single cubic millimeter of the aether to be almost inconceivably vast. He says, "All potential energy exists in the ether". Sir J.J. Thomson says, "All kinetic energy is kinetic energy of the ether".
I conceive the aetherial energy involved in gravitation to be kinetic rather than potential, the latter involving strain or stress. Newton, and later Maxwell, assumed that bodies produce a stress in the aether about them of such nature as to account for gravitation, but they were unable to imagine any physical cause for the stress.
All the past theories of gravitation of which I am aware, except the corpuscular theory of La Sage, appear to regard gravitating matter as the seat of the gravitative influence, the surrounding aether, by induced stress or otherwise, acting simply as the medium of transmission. I cannot see that any of these theories account for the energy acquired by a falling body.
My own view of gravitation differs from these radically. I believe that kinetic energy of the aether is the fundamental cause of gravitation, and that a gravitating body plays a secondary role only in disturbing the normally uniform distribution of the aether’s energy, in manner I shall endeavor to explain later.
Let us assume, then, that the aether is endowed with very great kinetic energy normally uniform in distribution.
Kinetic energy implies motion of something possessed of inertia. Now, inertia is a fundamental attribute of the aether. The aether is highly elastic also, which, with its inertia, enables it to possess kinetic energy in wave form, as exemplified in radiation. By the term wave, I mean progressive motion locally periodic; doubtless the aether as a whole is stationary. Hence we may consider the kinetic energy of the aether as consisting in aether waves of some kind.
These waves, vast in aggregate energy, eternal in persistence, without finite source or destination, are imagined as being propagated in straight lines in every conceivable direction. The isotropic distribution of kinetic energy, essential to my theory of gravitation, was, for me, a difficult conception until I reflected that isotropic radiant energy is approximately realized in the interior of any furnace with uniformly heated walls.
Any kind of waves capable of exerting motive action on the atoms or molecules of matter will fulfill the requirements; but I shall first consider the transverse, electromagnetic waves of radiation, because these are the kind of aether waves we are familiar with.
Of course, intrinsic aether waves, if of the radiation kind, cannot be of any frequency at present known to us as radiation, because then all bodies would become heated. But we can easily imagine them of such extremely low frequency that the molecules or atoms of matter cannot respond to them -- cannot vibrate in unison with them -- molecular resonance cannot be established; hence no conversion of the aether’s energy directly into heat in the ordinary way can take place.
We are familiar with the dissipation or degeneration of the higher forms of energy into heat, and the continual degradation of heat to lower degree; that is to say, less violent molecular vibration and more general distribution. As is well known, it is only through this degradation or running down of natural energy that we are enabled to utilize some of it. Lord Kelvin called this function of energy "motivity" (we now call it entropy), and said the motivity of the universe tends to zero.
We know that ordinary radiation waves in the aether persist indefinitely and without change of frequency or direction until they encounter matter, when they are absorbed and converted into heat, only to be radiated again, usually in longer waves, to some cooler body. This degradation of wave frequency continues until we can no longer follow it. I beg to suggest that the ultimate destination of this wave energy is that vast reservoir of kinetic energy intrinsic to the aether. We may liken the waves of radiant energy, which we apprehend as light and heat, to wind ripples on the surface of water, which continually degenerate in wave frequency until they are absorbed into and become part of a mighty swell of the ocean.
Thus we may, perhaps, regard the aether’s intrinsic energy as energy in its lowest form -- Kelvin’s zero of "motivity". But unfortunately we may, and do, get some of this energy back in available form in many ways, as, for instance, when a falling body is arrested and develops heat; some of our wind ripples are then returned to us.
When two gigantic astronomical bodies collide under the influence of gravitation, as sometimes happens, we witness in far distant space the birth of a nebula. The inconceivably vast amount of heat developed by the collision converts both bodies into luminous vapor, which expands with incredible rapidity into the nebulous cloud. This heat energy must in course of time degenerate back into the aether whence it came, though billions of years may be required; and during all this time the energy has "motivity". We may picture the stupendous result of the collision as only a local splash in the aether’s mighty ocean of energy.
Having postulated that the aether is endowed with very great intrinsic kinetic energy in wave form of some kind, that the waves are propagated in straight lines in every conceivable direction, i.e., the wave energy is isotropic, and that this energy is distributed uniformly throughout the universe except in so far as the distribution is disturbed by the presence of matter, I shall endeavor to explain my conception of the mechanism of gravitation.
For illustration in terms of the known, let us imagine a closed space having uniformly luminous walls of such character that every point on their surface radiates light in all internal directions. The enclosed space may be of any shape, but for the sake of simplicity let it be spherical or cubical, and large, say as large as a lecture-room. The space will be filled with isotropic radiant energy uniformly distributed -- any cubic centimeter of space containing as much energy as any other.
Next let us picture a small opaque body suspended anywhere in our luminous sphere. The body may be of any shape we may imagine an atom or molecule to have; but, again for simplicity, let it be spherical -- say a small grain of shot, and let it be located near the center of the space.
The small body will absorb the light which falls upon it, and will cast a spherical shadow, the depth or intensity of which will vary inversely with the square of the distance from the center of the body; and the shadow will extend to the confines of the enclosure, however large the latter may be. We cannot perceive the shadow but we know it is there. It is true that the body will soon acquire the temperature of its surroundings, and radiate as much energy as it receives; but for the purpose of this illustration let us consider only the high-frequency light energy.
As is well known, the aether waves of light will exert a slight pressure on the body. But in the case supposed the pressure will be equal on all sides, and no effort toward translation can result.
Now let us introduce a second small body, similar to the first, and some distance from it. This will also cast a spherical shadow like the first. The first two shadows will intersect, and each body will lie within the shadow of the other. In other words, each body will be partially shielded by the other from the aether waves coming from that direction. Hence the light pressure will be less on that side of each body which faces toward the other than on the side which is turned away, and the bodies will be urged toward each other by the excess of light pressure on the side turned away. This excess of pressure will vary with the inverse square of the distance between the centers of the bodies so long as the ratio of distance to diameters remains large.
The aether waves concerned in gravitation cannot, however, be like the light wave I have just used for illustration, because light waves heat bodies on which they fall; and their pressure is almost wholly superficial, it does not reach molecules much below the surface, and hence bears little relation to mass.
But let us substitute for the short and feeble waves of light powerful waves, still of the radiant kind, but of such great length and slow frequency that, as before explained, they do not excite the molecular vibrations which we appreciate as heat, and hence are not absorbed by matter; they pass freely through all bodies, bathing the interior molecules as effectively as those on the surface.
Under these conditions each molecule or atom or unit of a gravitating body will have its own spherical shadow or field of influence, and the gravitative force acting on the body will vary directly with the sum of its units, i.e., with its mass.
The spherical shadow which I have pictured as the field of influence of each atom or material unit implies that the atom has caused, principally in its immediate neighborhood, a diminution of the aether’s energy. Let us further imagine this subtracted energy resident in the atom as kinetic energy of translation in many paths, almost infinitesimally short and in every direction, but without collisions, because neighboring atoms follow very nearly parallel paths. We may then picture the collective atoms or molecules of matter buffeted in every direction by the aether waves in which they are entangled, like a suspended precipitate in turbulent water.
Each atom or molecule may be regarded as a center of activity due to its kinetic energy of translation, with continual absorption and restitution of the aether’s energy, normally equal in amount. The manner in which this molecular activity maintains, in effect, the supposed spherical shadow, requires explanation, which I shall attempt in a future paper.
Of the several components into which the composite motion of each atom can be resolved, that one lying in the direction of an attracting body will be the greatest, because the waves from that direction, being partially intercepted by the attracting body, are weakest, and the atom will be pushed in that direction by the superior waves behind it than it restores to the weaker waves in front, and will thus acquire additional kinetic energy of translation in the line of fall, measured directly by the number of waves involved, i.e., by the distance moved. Conversely, if the atom be forced away from the attracting body, restitution of energy will exceed absorption, and the energy expended in moving the atom against attraction will be transferred to the aether.
It will be seen that gravitation is a push toward the attracting body, and not a pull. It is clear, also, that the velocity which a falling body can acquire tends asymptotically to a limit, which is the velocity of the aether waves which push it -- the velocity of light, if transverse waves are involved
I have already intimated that any kind of aether waves capable of imparting motion (not internal vibration) to the atoms of matter will fulfill the requirements of my theory, but have thus far discussed only transverse waves.
Let us now consider longitudinal waves -- waves of compression and rarefaction, like sound waves in air and in elastic liquids and solids. The "spherical shadow" conception which I have employed in connection with transverse waves applies equally well here.
So far as I am aware, longitudinal waves in the aether are unknown, but that such waves have not been observed is not convincing argument that they do not exist.
Assuming, then, that some, or perhaps much, of the intrinsic energy of the aether is embodied in longitudinal waves, we have only to find some motive action of such waves on atoms to account for gravitation. Adequate motive connection may perhaps be effected by the locally alternating flow and ebb -- acceleration and retardation of the aether in which the atoms are enmeshed, incident to its wave motion. We have ample reason for believing that does obtain a grip of some sort on the atoms of an accelerating (falling) body and a retarding (rising) body, from which it follows that accelerating and retarding aether, as in a wave of compression, must grip a comparatively stationary atom.
Certain facts of astronomy apparently require that gravitational attraction between bodies, however distant from each other, must, in effect, be instantaneous; that is to say, the line of apparent attraction between them is a straight line adjoining their centers. I believe my theory meets this condition, but shall reserve discussion of the point for a future paper.
I feel much diffidence in presenting the foregoing rough draft of a theory of gravitation, but I cannot avoid the belief that it contains some germs of truth, perhaps the real key to the great mystery, though, if this be true, I have no doubt used the key clumsily and imperfectly.
If the aether theory of gravitation is, in the main, the true one, it offers some hope of experimental verification. Provided the waves are of one principal frequency, or even of several, we may find something, doubtless of molecular magnitude only, which will oscillate in unison with them so that resonance can occasionally be established and a cumulative effect be obtained sufficient to manifest itself as heat.
In searching for some natural phenomenon of this nature, I thought of the thermal condition of the upper atmosphere as a possible case. The mean molecular velocity of a gas at some temperature, in connection with the mean free path of its molecules at some particular pressure or pressures, may possibly afford the necessary conditions for fortuitous resonance, with development of some slight amount of heat by the increased violence of inter-molecular collisions. I have done much experimental work on these lines during the past year, but, notwithstanding refinement of method and manipulation, the results have thus far been unsatisfactory. The work is till in progress, however, and investigation of other phenomena is contemplated.
Nature (March 30, 1911)
Letters to the Editor: Sir Oliver Lodge
Re: A Kinetic Theory of Gravitation
The subject of Mr. Brush’s article in Nature of March 23 (p. 129) is certainly of profound interest, and will continue to be so until the problem as to the nature of gravitation is solved. Meanwhile, a few questions raised are comparatively simple. Anyone asked, Where lies the energy of a raised weight? Must surely reply, "In the aether", i.e., in the medium, whatever it is, that is driving the weight down towards the earth. A critic who either doubts or asserts this will not be confused -- as Mr. Brush suggests he will be -- by the suggestion that the weight might be raised up so high as to reach the neutral point between the earth and moon -- a suggestion which carries with it the tacit questions, "Where is the energy now?" and "What has become of the work done?" -- for this case is no more troublesome than the case of a weight raised and hung on a hook. Something -- some opposition force -- sustains the weight, i.e., opposes the pull of the earth, and it matters little whether the opponent be a shelf beneath it or the moon above it. The important thing to understand is the nature of the downward propelling force -- indeed, of both the upward and the downward force -- in either case.
The question whether the energy of a raised weight is potential or kinetic is of little or no importance. The energy is certainly potential, according to our definition of potential. So is the energy of a strained spring: for there also the atoms are separated against their mutual (cohesive) attraction, and there again the energy really resides in the aether. But that all energy may turn out to be ultimately kinetic -- when we come to understand what elastive stress fundamentally is -- that proposition is not negatived in the least.
Mr. Brush proposes a shadow theory of gravitation, a modification of Le Sages’s theory except that the pressure is supposed due to the non-syntonic impact of waves traveling in all direction, instead of to a bombardment of utterly minute particles flying at random. There is nothing new in a shadow theory, and all such theories are faced with the difficulty of plausibly explaining the absence of noticeable screening -- a difficulty which is bound to reduce them to acquiescence in an approximation.
The contribution which Mr. Brush makes to the discussion is the suggestion that the supposed gravitational aether-waves are the result of accumulated thermal radiation from all past and present suns, the wave-lengths having automatically increased during their long storage.
To this view several objections might be urged -- one of them being that in that case the constant of gravitation would be secularly increasing; another, that it should be greater in a hot enclosure, say the interior of a sun, than elsewhere; but a more salient objection is raised by the inquiry as to which is cause and which is effect. How did the bodies get hot and so radiate? Was not their heat perhaps due to their having clashed together with gravitational energy itself derived from the aether?
The fact is that every question concerning origin involves us always with insuperable puzzles, and that is just the main difficulty about gravitation. An atom of matter, by its very existence, sets up a fixed stress in the aether, varying directly as the mass and inverse as the distance -- that is only another way of stating the law of gravitation; we are trying to understand the nature and cause of that stress. It appears to be one of the fundamental properties of matter, and until we can understand what is meant by the generation or destruction of an atom -- i.e., of an electron if that is the fundamental unit -- we are hardly likely to understand its gravitational influence more than any other of its fundamental properties -- including, perhaps, existence itself.
Let this not be understood as a negative prediction or estimate of impossibility -- such predictions are always absurd; it may be that when the structure of an electron is understood, we shall see that an "even-powered" stress in the surrounding aether is necessarily involved. What I do feel instinctively is that this is the direction for discovery, and what is needed is something internal and intrinsic, and that all attempts to explain gravitation as due to the action of some external agency, whether flying particles or impinging waves, are doomed to failure; for all these speculations regard the atom as a foreign substance -- a sort of "grit" in the aether -- driven hither and thither by forces alien to itself. When, some day, we understand the real relation between matter and aether, I venture predict that we shall perceive something more satisfying than that.
University of Birmingham
March 25, 1911
Proc. Amer. Philos. Soc. 68: 55-68 (May 1929)
Charles F. Brush
At the Minneapolis meeting of the American Association for the Advancement of Science in December 1910, I had the honor to outline "A Kinetic Theory of Gravitation" (Ref. 1). This was followed by a "Discussion" of the theory in 1914 (Ref. 2) A second "Discussion" came in 1921 (Ref. 3) A third "Discussion" in appeared in 1926 (Ref 4).
The later paper contains a concise synopsis of the theory and very convincing argument supporting my contention of 1910, that the energy acquired by falling bodies is derived from the ether.
This Kinetic Theory of Gravitation postulates that the ether is endowed with vast intrinsic energy in the form of waves propagated continually in every conceivable direction, so that the wave energy is isotropic. The belief expressed is that all energy is primarily energy of the ether.
The very high-frequency ether waves, which embody most of the ether’s intrinsic energy, pass freely through matter without obstruction except that concerned in gravitation, and a very small heating effect (which will be explained later). The ether waves exert motive action on atoms or particles of matte whereby the latter are buffered about in all directions with some absorption of ethereal energy. Thus a lump of matter casts a spherical energy shadow into space, the depth of shadow diminishing with the square of the distance from its origin. The energy shadows of two or more bodies interblend, so that energy density between them is less than elsewhere, and they are pushed toward each other by the superior wave energy from directions beyond them. The 1926 paper (Ref. 4) explains this at length.
To aid in forming a mental picture of the relation of the very high-frequency ether waves postulated as the cause of gravitation, to other well-known classes of ether waves, I have prepared the chart of ether-wave frequencies shown in Figure 1.
Each horizontal line in the scale of frequencies represents double the frequency of the line below it, or half the frequency of the line above it. Thus the scale of frequency increases upward by octaves as in music.
Starting at the bottom of the scale with a frequency of one ether wave per second, the second line four waves per second, the third line eight waves per second, and so on to the tenth doubling where we get a frequency of 1,024 waves per second as shown. Continuing the doubling process another ten times we get a frequency of 1,024 time 1,024, or 1,024 to the second power, and so on up the scale to the third, fourth, and fifth, etc., powers of 1,024. Thus it is seen that the indicated wave frequency increases with great rapidity as we ascend the scale. At the 20th octave it is more than a million per second; at the 40th octave more than a million million waves per second.
I am indebted to a chart shown a the British Exposition in 1925; to a chart by G.L. Clark in 1927, and to a chart by W.E. Deming in 1929 for much of the material shown in my chart. But I have arranged it somewhat differently, emphasizing ether-wave frequency rather than wavelength.
Frequency is converted into wavelength by dividing the velocity of light per second by frequency of the waves per second. Thus the frequency 1 at the bottom of the chart means one wave per second, and its wavelength is the distance it would travel in one second, before another wave started after it. This is the velocity of light, about 186,000 miles, or about 300,000 kilometers. All ether waves travel at the same velocity.
A wave train of this very low frequency and very great wavelength could easily be launched into the ether by revolving a closed coil of wire on its own diameter as an axis, in a magnetic field, at the rate of one revolution per second. If we should increase its revolutions to ten per second, we would get a frequency of ten, and a wavelength of 18,600 miles. Such mechanically generated electric ether waves may be increased in frequency without much difficulty as far up as shown in the chart.
Next above we have Hertzian waves, covering about 28 octaves, generated by the condensor and sparkgap method. The upper half of of this long range of ether waves contains the waves used in radio transmissions and music.
Next above the Hertzian waves, of higher and higher frequency and shorter and shorter wavelength, we find the infrared and heat waves covering about 9 octaves. These waves embody most of the heat received from the sun, and nearly all the heat radiated from hot bodies below redness.
Then we cone to the exceedingly interesting and intensively studied light waves or rays. These cover barely one octave of the scale, and their mean frequency is about 500 million million waves per second. It seems unfortunate that the human eye is sensitive to such a short range of ether vibrations only, while the human ear can perceive about 11 octaves of sound, or air vibrations. Perhaps some animals or insects have a wider range of vision than humans.
Above the light waves we find about 5 octaves of ultraviolet waves. The sun’s radiation includes the last three classes of waves, though some of the ultraviolet is absorbed by our atmosphere and does not reach the earth. The ultraviolet rays or waves promote chemical action and are chiefly responsible for the ordinary photographic image.
Next in the growing range of frequency we have the well-known x-rays, so extensively used in x-ray photography for therapeutic and industrial purposes. These cover a long range of octaves in our chart, and overlap the upper part of the ultraviolet range and the lower part of the gamma range. X-rays, particularly those of the highest frequencies, pass rather freely through large thicknesses of light substances such as wood, fabric, animal tissue and metals of low atomic weight and density; but metals of large density and high atomic weight absorb and obstruct them greatly. Thus a quarter inch of lead almost completely stops x-rays of the highest frequency. The ability of x-rays to pass deeply into or through matter, is called "penetrating power".
Above the x-rays in our chart are the gamma rays of radium, so extensively used in therapy. These have a much greater penetrating power than the highest-frequency x-rays.
All the above described classes of ether waves have been demonstrated experimentally, and doubtless all exist to some extent, permanently in the ether of space. Particularly is this true of the heat waves, as I pointed out in my 1927 paper (Proc. Am. Phil. Soc. LXVI, 1927). In that paper I showed, conclusively I think, that a lump of matter far out in inter-stellar space could not possibly fall to absolute zero by temperature radiation of all its heat, as commonly supposed, but would soon acquire and then maintain the "temperature of space" which I estimated to be something like 50* to 100* above absolute zero.
Above the gamma rays there are about 6 octaves which have not been explored experimentally. Then we come to the cosmic rays, so ably demonstrated and studied by Dr. Millikan. These cover considerably less than one octave, and their mean frequency is about 5,000 million million million waves per second. This is 10 million times greater frequency than light waves possess; and yet there can be no doubt that cosmic rays are ether waves like all the rest. As might be expected, cosmic waves, on account of their very much higher frequency (shorter wave length), have far greater penetrating power than the highest-frequency x-rays; in fact, about 300 times greater, as they pass through 6 feet of lead.
Starting considerably above cosmic rays in the chart, I have drawn a long bracket with indeterminate ends. Somewhere in this region lie the isotropic ether waves of gravitation, probably having considerable range of frequency. The enormous frequency of these waves enables them to pass freely through all kinds of matter without obstruction except that concerned in gravitation.
Probably most of the vast intrinsic energy of the ether lies in the region of the gravitation waves.
Until about a year and a half ago, we had no experimental evidence of the gravitation waves other than gravitation itself. But gravitation is a most impressive demonstration of the ether waves which cause it, and of the very great energy embodied in them. As illustrating both pints, I call attention to Lord Kelvin’s graphic word-picture of collision of two large astronomical bodies under the influence of their mutual gravitational attraction, which I have quoted in my 1914 paper ((Ref. 2) and my 1926 paper (Ref. 4) As another illustration of the enormous differential ether-wave push of astronomical bodies toward each other, let us consider the case of the earth and moon. The urge toward each other is commonly called gravitational attraction, which is only another way of looking at it. If this attraction were absent, and the moon were held in her orbit by a weightless steel cable, the cable would need to be about 500 miles in diameter to stand the strain. Between the earth and sun, the cable must be about 6,000 miles in diameter. And the attraction (push toward each other) of the components of some double stars must be thousands of times greater than this.
Obviously, the ether waves of gravitation, and the other classes of waves we have discussed, must be permanent attributes of the ether; they cannot escape from either boundless or bounded space. They must fill all space; and we may therefore regard gravitation as a property of space, because wherever there are two or more particles or bodies of mater, however small or large, however near or distant, they are urged toward each other by the ever-present isotropic ether waves of gravitation.
Very high up in the chart I have tentatively drawn the line marked "Quanta waves or rays", indicating a frequency of 6.54 x 1027.
Experimental Evidence of the Ether Waves of Gravitation:
A year ago I had the honor of presenting a paper under the title "Correlation of Continual Generation of Heat in Some Substances, & Impairment of Their Gravitational Acceleration" (Proc. Am. Phil. Soc. LXVI, No. 2, 1928).
This division of papers is a continuation of last year’s paper; and to save the reader the bother of looking up that paper and its several references, I shall quote very freely from it and prior papers.
The third "Discussion" (1926; Ref. 4) contains in its title "Some Experimental Evidence Supporting Theory; Continual Generation of Heat in Some Igneous Rocks & Minerals".
"Heat is often defined as an agitation of atoms and molecules of matter, and measured by the total kinetic energy of such agitation. The agitation consists partly in internal vibrations of the elastic atoms and molecules and spinning about their various axes, and partly in very rapid transitory motion among themselves. Thus they are supposed to dart about in every conceivable direction, constantly colliding with each other and rebounding or glancing in new directions. The kinetic energy of this translatory motion constitutes sensible heat (not total heat) and is the measure of temperature. Anything (such as absorbed radiation) which stimulates the internal vibration of atoms or molecules likewise increases their translatory velocities by the increased violence of rebound after collision, and thus increases their temperature; and vice versa.
"All the above is known to be true of gases and vapors (kinetic theory of gases) and is generally believed to be true of liquids and solids.
"The ‘mean free path’ and the ‘mean velocity’ between collisions of the molecules of many gases under stated conditions have been computed. But it has also been shown mathematically that the higher and lower velocities, and the longer and shorter paths, differ greatly from the means, and may in each respect vary 20 or more times in amount. Doubtles this is true also of liquids and solids.
"From the fortuitously wide variation I velocities and free paths of the billions of vibrating atoms or molecules in their heterogenous movement, it follows that collision frequencies must also vary greatly, but have a wide range of frequencies as do the well-known x-rays.
"With the foregoing in mind it is easily conceivable that some kinds of matter may have atoms or simple molecules or complex molecules of occasional vibration frequency corresponding with some gravitation wave frequency, whereby fortuitous resonance can, for brief instants, be established at various points. This would result in a slight increase of vibrational activity and a cumulative rise of general temperature.
"A body of such matter, with some thermal insulation, would become and remain permanently warmer than a neighboring body similarly circumstanced, but not endowed, or less endowed with the permissive heat-generating quality".
A carefully designed calorimeter is illustrated and described in the paper (1926), and details of many experiments given. These resulted in the discovery that some rocks and minerals did generate an easily observable amount of heat.
In April 1927, I presented another paper on "Persistent Generation of Heat in Some Rocks & Minerals" (Proc. Am. Phil. Soc. LXVI). This is a continuation of the 1926 paper. It describes a new and different calorimeter, built in the spring of 1926, and since known as the "Ice Calorimeter". It has been in almost continuous use down to the present time (April 1928) and has proved very satisfactory. With this calorimeter it has been found that some of the natural heat-generating materials, and some of the artificial silicates hereafter described, have retained their heat-generating activity unimpaired; and none of these substances is more than minutely radioactive. Quoting from the 1927 paper:
"It is notable that all the materials which appear to be endowed with persistent heat generating activity are complex silicates".
There follows a description of the preparation, in the wet way, of many complex silicates, and their preliminary testing for heat generation. A silicate of the protoxide of nickel and cobalt showed very large activity, larger than either silicate alone: and this now appears to be permanent. Nickel and cobalt are almost identical in atomic weight, and differ but one unit in atomic number. Quoting again from the 1927 paper:
"In the absence, at present, of other explanation, it is thought that persistent heat generation in some rocks and minerals is due to isotropic ether waves of great penetration; very great indeed, if the generation goes on in the interior of the sun and planets as it does at the surface of the earth". Quoting now from the 1928 paper (Ref. 6):
"It is now believed that the class of isotropic ether waves postulated as the cause of persistent generation of heat in some substances, is the same class, perhaps of very wide range of frequency, postulated as the cause of gravitation.
"Conversion into heat of some of the energy of the gravitation ether waves, however little, might be expected to impair to some extent the falling velocity of a heat generating substance; and all such substances thus far tested have clearly shown impairment.
"I have yet found no exception to this remarkable phenomenon, though I have already tested many natural and artificial minerals. Substances which have shown no generation of heat in the calorimeter show no impairment of their falling velocity when compared with lead. Substances exhibiting small, moderate or large generation of heat have shown comparatively small, moderate or large impairment of the gravitational acceleration.
"In making the above indicated comparisons of falling velocities I have largely used the method and apparatus described and illustrated in my 1923 paper on "Some New Experiments in Gravitation" (Proc. Am. Phil. Soc. LXII, No. 3; See also the 1924 paper of the same title: Proc. Am. Phil. Soc. LXIII, No. 1)
"Two aluminum containers are used, alike in size, shape, weight and smoothness of surface, and dropped simultaneously, side by side, through exactly the same distance (about 122 cm).
"Each container, at he end of its journey, breaks an electric circuit. But the breaks of both containers are in series in the same circuit, so that the break which occurs first produces a bright spark while the belated break gives no spark because its circuit is already open
"When the containers are equally loaded with the same metal, there is no visible spark at either break, or a very feeble spark at one or the other indifferently. But when they are equally loaded with certain different metals, one container persistently produces a bright spark, though containers are always reversed in position for each trial. From this it seems clear that the container giving the spark falls a little faster than the other. This sparking condition is clearly manifested when the faster container reaches the end of its free path as little as 0.0125 mm. ((0.0005 inch) in advance of its neighbor.
"The 1923 paper also describes how approximate quantitative measurements are made. These are very tedious, especially when falling velocity differences are large.
"To facilitate estimation of the larger falling velocity differences I am perfecting a photographic method of observation. After falling about 110 cm the small lower ends of the containers are photographed in silhouette against a white background having many horizontal lines, and illuminated by a very bright electric spark".
Then follows several pages of text, with figures and pates, describing the apparatus admits operation, too lengthy to quote here. Resuming quotation from last year’s paper (1928):
"The camera lens is located about 37 cm in front of the white surface, and the photographic plate about an equal distance behind the lens; so that the image is about equal in size to parts photographed.
"The plate holder moves vertically in guides, and rests on a pin in one of eight equally spaced holes 1.6 cm apart in the backboard of the camera. This backboard has a horizontal opening 1.4 cm wide, which limits the exposed portion of the plate to a strip of this width. Thus eight pictures of the falling container tips are made on one plate. The containers are reversed in right and left position after each exposure.
"Plate III shows a series of photographs. Each container weighted approximately 30.6 grams. One was marked with a white spot on its top for identification. This one, lettered S on the plate, was filled with silicate of nickel and cobalt, which weighed 13.6 grams, or about 30.8 % of the total weight of the loaded container. The unmarked container was loaded with lead sawdust, held tightly in the lower end by a short closely fitting cork above it, until it very closely equaled the marked container in weight.
"Each of the eight photographs on the plate, when magnified, clearly shows the S container (Silicate) slower than its companion. Six more similar plates have been made with the same loaded containers, and all show the same effect. It will be noticed that the amount of retardation of the S container varies considerably in the eight exposures of Plate III. This was principally due to small lateral air currents in the room which acted unequally on the two containers when one shielded the other; as was demonstrated with another plate by purposefully increasing the lateral air currents. I shall eliminate lateral air currents in future work.
"Of course I tried exchange of loads in the containers, but without observably affecting the result; the container holding the silicate was always slow.
"The observed retardation o the silicate container must be due to impaired gravitational acceleration of the silicate as compared with the lead sawdust in the other container; and as the silicate constitutes only 30.8% of the total mass undergoing acceleration, we must multiply the observed retardation by 3.25 to find the full impairment of the silicate alone.
"In the apparatus as set up, the centers of the container tips are about 1.6 cm in front of the lined background; hence tips and lines cannot both be sharply in focus of the camera lens. In Plate III the focal plane of the camera was about half way between the tips and the lines. Sharpness of lowest part of the curve of the tips was greatly enhanced by permanently covering all of the camera lens except a horizontal strip 2 mm wide across its center.
"The comparison lines in Plate III are spaced one mm apart between centers. I am installing another white background with very much finer lines spaced only half a mm apart, and far better adapted to micrometer measurement of container tip differences of level.
"The Bureau of Standards, with a calorimeter of its own design, is working with some of the heat-generating substances for the purpose of checking my findings."
Since writing the 1928 paper I have continued work on the fascinating subject of "Correlation of continual generation of heat in some substances and impairment of their gravitational acceleration". These phenomena appear to be related as cause and effect. I have gathered considerable new evidence, all affirmative, so that I now feel justified in dismissing doubt.
In the quest for more evidence, however, I have reversed the order of procedure; i.e., instead of hunting more or less at random, for new substances exhibiting generation of heat in the calorimeters, which is a very slow and tedious process, I have first tested many new substances for impaired gravitational acceleration, which is comparatively rapid and easy. In these tests I have made more than 50 new plates, and feel well rewarded for the labor.
In my former experiments it had appeared that silicates of the iron group of metals exhibited much greater impairment of acceleration than silicates and compounds of the metals of lower atomic weight. So I chose silicates and other compounds of metals of still higher atomic weight, viz., Barium, Lead and Bismuth as most promising materials to work with.
In all the artificial silicates there was some sodium silicate. Lead silicate gave a moderate effect, but after ignition none. Bismuth silicate behaved in the same way. Lead acetate gave a moderate effect.
The barium compounds were found very interesting, and were more fully investigated. Barium hydroxide, Ba(OH)2, 8H2O gave rather large effect, but required lining of the container on account of its powerful corrosive action on metallic aluminum. BaO (anhydrous; effect moderate. BaO, 8H2O, effect small but certain. BaCl2, 2H2O, effect small. BaBr2, 2H2O, effect very small if any. BaSO4; effect very moderate. Ba3(PO4)2; effect small. Ba(SCN)2, 2H2O; effect very small if any.
The Barium Aluminates were the most interesting of all the compounds examined. Three grades were prepared: (BaO)2Al2O3, BaO, Al2O3 and BaO(Al2O3)2. All, after air drying to constant weight, lost several % of hydroscopic moisture when dried at 100o C. and several more % of combined water when gently ignited. After ignition they were but very slightly hygroscopic. The BaO, Al2O3, dried at 100o C., gave largest effect; but after ignition the effect was somewhat reduced.
Plate I shows the impairment of gravitational acceleration in the BaO, Al2O3, not ignited, as compare with lead in the usual way. The upper two of the usual eight photographic strips are omitted, in order to permit enlargement of the remaining six strips about 50%. The black lines on the white background against which the lower tips of the two falling containers are photographed, are spaced exactly half a millimeter apart between centers, and are as fine as it was found practicable to make them. As before explained, neither the lines nor the tips of the rapidly falling containers are sharply in focus of the camera lens. The tip of the container holding the Barium Aluminate is marked S (slow) on the plate; and the containers were reversed in position after each dropping as indicated. As easily seen on the plate, the S container is unevenly slow in the six photographs, and even very slightly fast in the first. This unevenness is attributable to variation in the exceedingly slight friction of the containers in their guiding tubes during the first millimeter of their fall. The containers are perfectly free after that.
For accurate measurement of falling velocity differences of the containers in all plates, I have used a binocular microscope of low magnifying power, having a very large stage provided with a high-precision micrometer specially designed and built for this purpose.
In finding the average impairment of gravitational acceleration of the S container in the six photographs of Plate I, all were measured with the micrometer, the five affirmative values were added together, the slight negative value o the first one subtracted from the sum, and the remainder divided by six. This gave the mean slowness of the S container -- 0.099 mm, say one tenth of a millimeter. This is one part in 11,000 of the distance fallen (110 cm). But the Barium Aluminate constituted only 40.3 % of the total weight of the loaded container. Hence, impairment of falling velocity of the barium Aluminate alone, as compared with equal weight of lead in the other container, was one part in 4450. When a companion plate was made with the container loads exchanged (as customary in all tests), slowness of the Barium Aluminate was found closely the same.
Of the several compounds described and tested for impairment of falling velocity, only two have been tested in the ice calorimeter for continual generation of heat. Barium Sulphate, the first of these, was chosen because of its undoubted stability, although it had shown but very moderate impairment of falling velocity. It exhibited very moderate but steady and satisfactory generation of heat during a long run in the calorimeter. The second calorimeter test was made with barium Aluminate like that used for Plate I; but after preparation it was only air dried at room temperature, to avoid any unstability that might arise from hot air-drying, or ignition. The specimen was prepared about two months ago, and has been in the calorimeter during the last six weeks, where it continues to show rather large and steady generation of heat. It appears to be quite stable.
More than a year ago the Bureau of Standards very kindly offered to repeat some of my experiments on "continued generation of heat in some substances". A special ice calorimeter, quite different from mine, was designed and built for the purpose. After much time spent in perfecting and calibrating the calorimeter, a specimen of the air-dried Sandusky clay describe din some of my earlier papers, was tested during the last few months; and I have very recently received official announcement that this substance does continually generate a measurable amount of heat. The Bureau is about to commence testing the comparatively active Nickel-Cobalt Silicate described in my last two papers.
Correlation of continual generation of heat in some substances and impairment of their gravitational acceleration, is regarded as very strong evidence in support of the kinetic theory of gravitation; and we seem now well on the way of finding out something definite about the nature of gravitation, which has been by far the greatest of all outstanding physical problems.
Dictionary of American Biography, Suppl. 1,2; p. 29
Science (March 10, 1911)
Nature 86 (2160): 130-132 (March 23, 1911); ibid., 86 (2161) (March 30, 1911); Letter, Sir Oliver Lodge
Proc. Royal Soc. (Series A) 93 (1917); ibid., 95 (with Sir Robert A. Hadfield & S.A> Main)
Proc. Amer. Philos. Soc. 50 (3), 1926; ibid., 53 (213), Jan.-May, 1914; ibid., 54 (May-July, 1921; ibid., 60 (2): 43-61 (1921); ibid., 62 (3): 75-89 (Sept. 29, 1923); ibid., 63 (1): 57-61 (1924); ibid., 66 (3): 251-166 (1927); ibid., 67 (2): 105-117 (1928); ibid., 68: 55-68 (May 1929)
Amer. J. Sci. 88: 118-128 (Jan.-May 1914)
J. Franklin Inst. 206 (1232): 143-150 (Aug. 1928)
Phys. Rev. 9 (2), 1917
#1,698,669 (Jan. 8, 1929), Piezo-electric crystals
# 1,823,864 (Sept., 1915)