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Volume 27, 1894
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Art. LXIII.—Synoptic Statement of the Principles and Phenomena of Cosmic Impact: prepared for the Criticism of Scientific Men and Societies.

[Read before the Philosophical Institute of Canterbury, 7th November, 1894.]


The new photographic charts have demonstrated that there are over a hundred million bright stars in the Milky Way.


The companion of Sirius and the dark component of Algol prove the existence of dead suns. These are possibly very numerous. Sir Robert Ball thinks them more numerous than luminous ones: for other theoretical reasons I believe him to be right.


Stars have an independent velocity or proper motion of about ten miles a second upon an average. Recent spectroscopic observations seem to suggest a slightly higher velocity than this.


This motion is apparently without much order. It will alter the relative distance of stars, and may bring them near each other, and possibly into impact.


If they are brought near each other their mutual attraction will alter their velocity, and curve their courses into hyperbolic orbits. If they do not graze they will ultimately again attain their original proper motion.


When stars are very near each other their attraction will cause them to be distorted into an egg-shape.


The tendency to collision will therefore be increased by their mutual attraction in these two ways, for it will cause them (1) to curve their courses, (2) to be distorted when very near each other. The chances of collision will thereby be made one hundred times greater on an average. In the case of two such bodies as our sun the chances of collision would be one thousand times greater.

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All impacts brought about in this way by defiection will be of a grazing character; consequently nearly all stellar collisions will be of a grazing character.


The average velocity of stars at impact will be hundreds of miles a second, and in many cases thousands. The average “proper motion” will not appreciably affect the final velocity. Thus a proper motion of ten miles will only add one mile a second to a colliding velocity (velocity acquired by attraction) of one hundred miles a second.


A mere graze of the atmospheres of stars obviously will not cause them to coalesce, nor will a slight graze of the stars themselves. As a mean result, when more than a third of each of two equal bodies collide, coalescence will ensue, but this will depend on the original proper motion. Were ninetenths of 1830 Groombridge to collide with a similar star the remaining tenth would not be stopped in its course; it would pass on in space, the bulk of the two stars temporarily coalescing and then dissipating into space.


The effect of the collision will be to intensely heat the colliding parts.

Partial Impact.


The heating effect of a graze of two stars, of two starclusters, or of two nebulæ, or even of a star plunging through a star-cluster, will not appreciably extend to the parts not colliding. To emphasize this fact such impacts have been called “partial.”


“Partial impacts” generally result in the formation of three bodies. The fraction of each star, lying in the path of the other, which actually collides, and whose momentum will be nearly or quite destroyed, will be cut off from the rest of the star; they will coalesce and remain behind, whilst the two cut stars pass on in space.


Partial impacts of a third of two equal stars having considerable original proper motion would, make of the two impacting orbs three equal bodies: two of them would travel on in space in opposite directions; the third would merely revolve without any motion of translation. If there had been no proper motion the three bodies would have coalesced. If less than a third be cut off from each, the two bodies become three bodies orbitally connected.


The temperature produced by an impact depends on the velocity destroyed and on the chemical constitution of the colliding bodies. High velocities and heavy molecules both tend to produce high temperatures. Consequently the temperature depends upon the velocity destroyed and on the molecular constitution, and not upon the amount of the graze. Were one-tenth or one-hundredth grazed off the impacting

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stars, the temperature of the coalesced part would be the same.


Although the temperature will be the same, the gravitating power of the coalesced part will depend upon the mass and size of that part; it will increase as the mass increases, and diminish as the size increases, the mass remaining constant.


Heat is molecular motion. In a small graze of any given pair of stars the molecules will have the same velocity as in a large graze, but the gravitating force holding the bodies together will be different. In a large graze the body may be stable, the velocity not overcoming the attraction of gravitation; in a small graze the body will expand indefinitely in consequence of the small attractive power of the coalesced mass, and every expanding particle will have so high a velocity that it will in general become an independent wanderer in space. Consequently space will be spread with free molecules.

New Stars and Planetary Nebulæ.


The mass of gas produced by such an impact will obviously expand temporarily into a hollow shell of gas. Herschel tells us this is the condition of planetary nebulæ.


A partial impact of stars will therefore generally produce in less than an hour an intensely heated body that will expand enormously without, for a time, much diminution of heat. It will consequently become very bright indeed, and will continue to expand with diminishing intensity until it becomes a planetary nebula, and will then disappear by dissipating completely into space.


That is, a new star has been born that increases in intensity until the general parallelism of motion of the molecules causes a lessening number of impacts between the molecules. As molecules only radiate immediately after encounters, the luminosity will diminish, and will go on diminishing until it disappears. In special cases the planetary nebula may be fairly permanent. In other cases a permanent star may appear in the centre of the nebula.


The molecules on the far side of the nebula (or third body formed by the two colliding stars) will be retreating from us; those on the near side will be advancing towards us. The spectrum of such a body will consequently be crossed by broad bright bands with a maximum in the centre and gradually dying imperceptibly away. If this body has any motion in space, as it probably will have when the two colliding stars are unequal, the line of maximum intensity, though in the centre of the band, may be displaced from its true position.

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Molecular Selective Escape.


Immediately after the impact the temperature of different kinds of molecules will be very different from one another. Were the two colliding spheres composed of oxygen, they would be sixteen times as hot as if they were similar spheres of hydrogen. The temperature at impact will be proportional to the atomic weight. In a sphere of mixed elements these inequalities of temperature would quickly equalize themselves. When this was the case the hydrogen would be moving four times as fast as the oxygen. The velocities would vary inversely as the square root of the atomic weights.


This difference of velocity will tend to sort the molecules into layers like those of a lily bulb. The hydrogen on the outside will be followed by lithium and other elements in the order of their atomic weights.


If there are elements lighter than hydrogen, as spectroscopic observations of the corona suggest, these will, of course, precede hydrogen. In my lectures and papers on this subject I have called this action “molecular selective escape.”


Space will be thickly spread with free molecules of the lightest elements. This fact is important: it is one of the counteracting agencies that prevent the theory of the dissipation of energy being of cosmic application.


A telescopic view of a new planetary nebula produced by a partial impact, if seen through a prism, should give a series of discs of diameters diminishing with increase of atomic weight in its component elements.


This fact, taken in conjunction with the broadening of the lines into bands, will enable us to calculate the distance of such a body. It is possible, however, that the parallelism of the motion of the foremost molecules may prevent encounters; hence this layer of gas may not be luminous.

Formation of Star-Clusters and Meteoric Swarms.


The hydrogen will rob the heavy molecules of their energy: hence in any considerable graze the heavy metals might not indefinitely expand. They would lose their velocity by radiation and by doing work against gravitation, and they would be attracted back again, and may form a star in the centre of the nebula. Some nebulæ have such stars.


In a partial impact the coalesced part will not have all its motion converted into heat. The momentum on the two sides will not be exactly balanced. The body will consequently tend to spin. It is generic of partial impact that it tends to cause rotation in all the bodies produced, and also that the rotation is all in the same direction.

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It is a peculiarity of oxygen that it tends to render its compounds with metals less volatile than are the metals themselves. Almost all oxides are less volatile than the metals forming them. Consequently, when metallic atoms and oxygen come together, they produce molecules that tend to coalesce. Thus nuclei form in a nebula and it becomes dusty. If the nebula be rotating this dust tends to move in orbits, and it would be constantly picking up other dust and molecules. Thus a rotating metallic nebula, in which molecular selective escape has dissipated the light molecules, tends to aggregate, not necessarily into a single body, but oftener into a number of bodies orbitally connected. If the mass be large it will become a star-cluster, if small a meteoric swarm.


In star-clusters impacts should be frequent. These groups should be photographically observed to notice any sudden increase of intensity. Then the pair of impacting stars should be watched for nebulæ and for variability.



Meteoric swarms when near the sun would be distorted, and the constituent fragments would impact with extraordinary frequency. They would therefore become very brilliant, and show as comets. The friction would produce an enormous development of electricity.


It is certain that the material of a tail of a comet does not belong to the comet itself. It is the dust of space lit up in some way like motes in air illuminated by a search-light. The phenomenon of the tail is almost certainly electrical. In a paper “On a New Relation between Heat and Electricity” I have discussed agencies that may explain the phenomenon.


Such a swarm, when close to the sun, would have its near part drawn in advance of, and its distant part left in the rear of, the general swarm. Its weak attractive power would cause it to separate into a train.

The above are some of the phenomena that may ensue in the coalesced mass.

Variable Stars.


The two stars that grazed would have a part cut out of each: this would expose the probably hot interior. Each star would entangle a portion of the other. This would increase the temperature and luminosity of the cut part of each.


The stars after collision would recover their sphericity chiefly by the molten interior welling up. This by momentum would overfill the space, and there would be a rhythmic tidal action, the molten lake overfilling and then sinking.


The retardation of the sheared stars by the entangled material would cause them to spin. This would act chiefly

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on the outer layers; the inside would tend to retain the original rotation of the star.


Thus in the sheared stars there are three tendencies struggling with one another—(1) the original rotation, (2) the new rotation, (3) the tidal action.


But the new rotation would be a large component. We have therefore a star which rotates and shows us alternately its hot and cool sides. The old rotation and the tidal motion produce other fluctuations of intensity, and also inequalities of the rate of motion.


Evidently such a body as described would be a variable star, and for a time such stars would be in pairs.


Many variable stars are in pairs. It is so striking a phenomenon that the probability is one hundred sextillions to one against its being the result of chance.


Conduction, convection, tidal motion, and the contending rotations will tend to bring about equality of temperature. This condition of variability will consequently be a temporary one. The star will ultimately become of uniform luminosity. These are all of them known peculiarities of variable stars.


Convection is due to difference of density. This difference may result from differences of temperature, or of chemical composition, or of both. The lake of fire in the sheared star will consist of heavier molecules than the remaining surface, and it will also be at a higher temperature. These two will tend to neutralize each other; so that equality of temperature due to convection will not be brought about quickly.


Therefore, although such variable stars will doubtlessly become unïform, it is surprising what a number of agencies there are tending to retain this inequality of temperature. On theoretical grounds it appears that this condition of unequal heating may, as an extreme case, last thousands of years.

Double Stars.


The work of cutting the stars will be infinitesimal in relation to their available energy before collision. It will not cause any appreciable lessening of the velocity of the escaping stars. But the middle body will exert a powerful attraction. It will exercise a retarding influence, preventing the retreat of the two bodies, equal to that of three times the mass either body loses. Hence, when two bodies lose a third each by impact, they do not as a rule become free from the new central body.


If, however, the original proper motion were large, and the graze small, the two stars would escape each other. If the original motion were small, and the graze on an average

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more than a tenth, then the two stars would become orbitally connected.


Such a pair, when thus connected, would form a permanent double star. It is the opinion of Proctor and other astronomers that impacting stars becoming orbitally connected could not make double stars, as they think such stars would impact again. But they overlook the fact that the nebula that retarded their escape and formed an important factor after the first impact, will have dissipated before they return.


Hence the eccentricity will lessen greatly, and, as a rule, instead of impacting again they will be scores of millions of miles away at perihelion. In fact, they will have about the eccentricity that double stars are known to have.


There is a possibility of a second impact when the graze has been a very small fraction, or if one of the stars were multiple. But the period of the subsequent recurrence of impacts, after the first recurrence, would lessen in point of time. On calculating the dates of the apparently recurrent star, “The Pilgrim,” viz., 945, 1264, and 1572, this is proved to be the case. The dark bodies producing these impacts must be of absolutely stupendous dimensions. The dark bodies producing Nova Aurigæ were probably 8,000 and 4,000 times the mass of the sun respectively.


Double stars should be more often variable than single stars. Struvé has proved that they are hundreds of thousands of times more variable than ordinary stars.


We should expect them also to be more frequently coloured. This, too, is most strikingly the case.


We should look for them to be associated with nebulæ. Herschel says the association of nebulæ and double stars is most truly remarkable.


They should be highly eccentric. This is also well known to be the case.


A large number of agencies tend to render the orbit less eccentric. These are fully discussed in my papers of 1880.



If stars come into partial impact, the tendency to form definite nebulæ, other than planetary or cometic, seems to be entirely destroyed by the outrush of the high-velocity gas. This is not the case with the impact of nebulæ.


Impact may take place between nebulæ, between starclusters, between meteoric swarms, and between any two similar or dissimilar celestial bodies. The graze may be little or large; the original bodies may have had a small or great proper motion; and all these peculiarities will tend to vary the results.

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If two nebulæ come into a slight grazing impact there will result a double nebula, which will show a spindle at the centre. As they are parting company they may have temporarily a dumb-bell appearance; but, as the two sides of the coalesced nebula are moving in opposite directions, a spiral begins to form at the centre. As the ends travel on in space the spiral would increase, and ultimately a double spiral would result.


One or both of the original nebulæ may be entangled in the spiral.


If the impact be considerable, the two nebulæ do not escape each other, and an annular nebula results. It would have gauze-like masses of nebulæ at the poles of the ring, produced by the outrush of gas during the impact.


There are nebulæ corresponding to every one of these conditions: nebulæ coming into impact—some in impact with the spindle showing between them; there are also spindle nebulæ left alone; others with an incipient spiral visible at the centre; others where the spiral is more distinctly visible; and others where the double spiral is fully developed.


Finally there are annular nebulæ with the gauze-like caps referred to above. Thus at one and the same time the evolution of nebulæ at any of its stages may be watched, and not unlikely older drawings may show the less advanced stages of the same nebulæ.

The Obigin of the Galactic Universe.


If two universes such as the Magellanic Clouds come into grazing impact, an annular universe will result, the poles of which will be covered with nebulous matter owing to the outrush of gas during the millions of years of the impact.


This principle of outrush needs some explanation. As two globular masses close in upon each other, the motion will lie chiefly in a plane which might be called the orbital plane. It is obvious that the pressure of the heated gas resulting from the impact, as the bodies close the gas in, can find no escape in this orbital plane, but can only escape upwards and downwards.


Stars will pass into such caps of nebula as originally covered the galactic poles, and will there be entrapped, and will attract nebulous matter. They will thus become nebulous stars; or they may be volatilized altogether and become globular nebulæ. Such a distribution of nebulæ exactly corresponds with our universe.


Where globular nebulæ are thick we should expect double, spindle, and spiral nebulæ. These nebulæ are actually found amongst the nebulæ at the polar caps of the Milky Way. Again, where stars are thick we should expect planetary

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nebulæ, double, temporary, and variable stars, and star-clusters—all the result of the impact of stars. These, as the theory requires, are almost entirely found within the Milky Way.


If the universe were formed by such a graze as we describe we should expect a greater density of stars in those parts of space where their motion chiefly directs the two original universes. Proctor speaks of two such clustering masses as striking features of our universe.


If the universe were the result of impact there would be much community of motion in adjacent stars. This is a remarkable peculiarity of the stars in the Galactic Ring. A large number of further coincidences are debated in my papers “On the Visible Universe.”

The Solar System.


Nebulæ must tend to entrap bodies passing through them. Such bodies would frequently become orbitally connected with the nebula. Then, when the nebula, with these bodies, became a sun, it would produce a system with planets in all azimuths, in the same way as the comets that our solar system has entrapped are in all azimuths.


Were a sun to impact with such a body or with a dense star-cluster, and were the graze considerable, all the planets would be whirled roughly into one plane, and the central mass would become a bun-shaped nebula.


It is not improbable that our sun was formed by an incipient star-cluster impacting with a nebulous sun, and that the present solar system constitutes a large part of the whole impacting mass. In other words, it is probable that there was not a large ratio of the original bodies dissipated into space during the impact, but it is probable that the impact was a large-ratio collision.


It is to be supposed that in every impact much matter will leave the system. Some of the gas extruded by the pressure acting along the axis will be lost, with much of the hydrogen. The attraction, therefore, on the return of the planets may be so much lessened by these losses that the orbits may be converted into an approximation to a circle. The nebula would expand enormously; all the matter of it that might pass outside aphelion distance would not aid in attracting the planet back. Perihelion distance would thus be increased by this agency.


Of course, at first the rotation on their axes of the new-constituted planets would be in all possible directions. Thus, the axes may be in the ecliptic, or the motion may be retrograde. The order observed in the rotation of the inner planets will be established afterwards, the outer planets largely escaping these agencies.

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Gaseous adhesion and many other agencies are at work to cause apsides to rotate. Consequently the larger nebular planets would gradually pick up all matter within the limits of their orbits, thus giving the rough order to the distance of the planets that is commonly known as Bode's law.


In a rotary nebula I have shown that much matter will tend to become meteoric. The absorption by a planet of every meteorite will tend to cause the planet to rotate in the common direction of the nebula, and will cause the axis to tend to become upright on the axial plane. This action will tell most with planets near the centre of the series, such as Jupiter and Saturn, because they will be largely gaseous and in the thick of the meteoric matter. The outer planets will necessarily be almost beyond the region of such influence, while the near ones will have but slight entrapping atmospheres, as explained hereafter.


All this exactly accords with the actual inclinations of the axes of the respective planets.


It is probable that the orbits of the planets were originally much smaller; but much of the potential energy of dimension would, as they shrank, be converted into energy of rotation, and this, by tidal action, into increased distance from the sun. The same may also be true of the moons.


As the volume of the nebula diminished its temperature would increase. An increased temperature would produce molecular exchanges between the planets and the nebula, and this would most affect the nearer bodies. Thus the near planets would lose all their light atoms by their escape into the surrounding nebula; whilst, on the other hand, the low velocity of the heavy molecules of the nebula would allow these molecules to be picked up by the planets.


Hence the near or inner planets would be small and dense, as we find them in our solar system, and the outer planets large and less dense, as in reality they are.


The heat of the contracting nebula will tend to increase the temperature of the planets, which would consequently expand. This would lessen their hold upon their light matter in two ways: (1) by the lessened attraction produced by expansion, and (2) by the increased velocity of the molecules themselves. The near planets would consequently be composed almost wholly of the heavy metals. The smaller and hotter any planets were the greater would be their chance of being without atmosphere. The absence of this and the small volume of the planets would lessen their trapping action. Consequently they would not be so upright in their orbital planes as the middle planets.


The distant planets, being almost out of the nebula, would not collect an appreciable quantity of matter; hence

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the original axes of rotation may be at any angle, or even retrograde, as, in fact, they are.


As the nebula shrank within the orbits of the planets, the planets would again pick up light molecules that would form an atmosphere; but the temperature of the planets would not allow of much hydrogen being picked up unless it were in combination.


The resistance and contraction of the central nebula would clear space of all meteoric dust unless such were orbitally connected with a planet. The asteroids are probably parts of an exploded planet. The impact of a rapidly-moving body plunging into a planet could easily blow it to pieces. It has been suggested that, if so, such bodies would pass through the common point of their explosion. This idea is an error.


The trapping of their moons by the planets would probably occur when the planets were nebulous, and before the central nebula had attained to any great density. Hence they would lie roughly on the planet's equatorial plane.


Whilst a body of the mass of the earth could pick up an atmosphere, the smaller attractive power of the moon would not allow this at the temperature it would be at when its nebula contracted within its orbit. The moon would probably be much nearer the earth at first, but the stopping of its rotation by tidal action would increase the distance.


Many other agencies that would convert the system under discussion into one similar to our own are treated of in my paper on “Causes tending to lessen the Eccentricity of Planetary Orbits.”

Mathematical Conditions of the Formation of Nebulæ.


It can be shown, if two gaseous suns impact completely, having no original proper motion, that were the whole of the motion converted into heat, and this heat into the potential energy of expansion, then the new sun would have a diameter the sum of the diameters of the original suns. It can also be shown that such a condition is one of stable equilibrium.


Consequently the complete impact of two gaseous suns not possessing much original motion, and brought together by gravitation, does not make a nebula of them; but as soon as the paroxysm of the encounter is over they are of the same temperature as before, having used up all their energy in increasing to the sum of their original diameters. This is a remarkable and unexpected result.


Were there great original proper motion, they might become a nebula by complete impact; but were the original velocity of the two bodies very high, and the impact of very great-energy, then an indefinitely-diffused nebula would result. Such a nebula, if hot, would be unstable, and would indefinitely

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  • expand. Croll's theory to account for an increase in the age of the sun's heat is therefore untenable.

The Cosmos possibly Immortal.


If our universe be proved, from its configuration and character, to have been formed of two previously-existing universes, as appears probable from 59 et seqq., then the entire cosmos may be made up of an infinity of universes.


Meteoric swarms prove space to be dusty with wandering dark bodies, and “molecular selective escape” proves it also to be spread with countless myriads of molecules of light gas. It is probably due to the dust of space that we see no distant universes other than the Magellanic Clouds.


If this be the case, radiation must all be caught by the dust of space, and, unless some agency be found to take this heat away, the dust must be gradually increasing in temperature.


Bodies not in closed orbits when moving at high velocities take but a short time to pass over great distances; they take longer and longer periods as the velocity is reduced. Hence hydrogen gas, when it has travelled into positions comparatively free from the influence of matter, will be generally moving slowly. But slowly-moving gas is cold: hence hydrogen gas may be at a lower temperature than any other matter in space.


Whenever by their mutual motions hydrogen strikes cosmic dust, it will acquire the temperature of the latter: that is, it will increase its molecular velocity. It will thus have a new start of motion.


It is evident that unless it strikes something the molecule can only lose this motion by radiation and by doing work. When it has done work, it will be further from matter, or in a position of higher potential, and Crookes's experiments prove that molecules do not radiate in free path except immediately after encounters.


Moving matter not in orbits will tend to move slowest where there is least matter—that is, where gravitation potential is highest—because in these places it has done most work against gravitation. Where bodies moving indiscriminately move slowest they obviously tend to aggregate: in other words the hydrogen of space tends to accumulate in the sparsest portions of space.


Thus radiant energy falls upon the dust of space and heats it. This heat gives motion to hydrogen, and the hydrogen then tends to use its new energy to pass to positions of high potential, thus converting low-temperature heat—that is, dissipated energy—into potential energy of gravitation—that is, into the highest form of available energy.

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This action will tend to go on until attraction is equal in different parts of space. Thus we should have, if there were no counteracting influence, in one part of space bodies in mass, in another part diffused hydrogen.


But long before this equality of distribution can ensue another action is set up. The mass of hydrogen-will become a retarding trap to indiscriminately-moving bodies.


Free bodies moving indiscriminately will tend to pass through a group of masses similar to our universe, through which 1830 Groombridge is passing now. But they will tend to be trapped in any mass of hydrogen they encounter. Thus the place that was most void of matter now begins to have more than a regular distribution of matter. A new universe of the first order has begun to form.


The Magellanic Clouds are probably universes of the first order. Our universe was probably formed from the impact of two other universes, and hence has a greater definiteness of configuration.


Mutual gravitation between the entrapped bodies would tend to concentrate the diffused mass. The new universe would be taking form.


When three bodies pass near each other, one at least has its velocity increased. In this way it is possible to account for the enormous velocity of 1830 Groombridge, although this high velocity might also be due to the attraction of our universe, or of a near dead sun, the truth of which latter idea could be ascertained by observations of its regularity of speed. Whenever the velocity is great enough to enable the body to escape the attraction of the universe, the body is lost to it, and the other two bodies would be moving more slowly. If this should occur only once in a thousand cases—seeing that when it does occur the body escapes—given time enough, much of the energy of any individual system must thus be used up in allowing the escape of bodies.


If it could be shown that the impact of two similar universes would result in the formation of one which, in a similar stage, was of larger mass than one of the originals, then impact would be, on the whole, an aggregating agency, and the permanent equilibrium of the cosmos would be disturbed.


This is probably not the case, for during the impact of the universes themselves much matter would escape, and at every impact of individual bodies within the new universe light molecules would be set wandering that would ultimately leave the system. When the new universe has become more dense, during the approach of any three bodies one would occasionally be sent out of the system. There are other agencies that, together with these, render it possible for two

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similar universes, by coalescing, to become one, which, when contracted to the size of either of its components, may retain no more matter than one of the original universes.


We have in these phenomena a complex series of agencies tending to overcome the dissipation of energy and the aggregation of matter. Impact developes heat, separates bodies, and, diffuses gas. Radiation falls on the matter of space and heats it: this energy is taken up by the hydrogen to increase its velocity. As the hydrogen loses this new velocity it is carried to positions of higher potential. It will tend to linger in the empty parts of space, and it then becomes a trap for wandering bodies. These wandering bodies are separated from systems by the mutual interaction of three bodies.


Thus, in opposition to the theory of the dissipation of energy, there is seen to be the possibility of an immortal cosmos, in which we have neither evidence of a beginning nor promise of an end.