PARTIAL IMPACT. The Birth of New Worlds.

Progress, Volume III, Issue 11, 1 September 1908, Page 368

PARTIAL IMPACT. The Birth of New Worlds.

Prof. Bickerton's Cosmic Theories. AN APPRECIATION BY A. C. GIFFORD.

Scientific discoveries may be divided into two main classes, according to the way in which they are received by the world. Some meet with an immediate welcome, others have to wait for years and perhaps sink into oblivion, until at last they are re-discovered and gain a tardy recognition. It is generally neither the truth nor the value of the discovery which determines into which of these

classes it shall fall; it is moie often a question of whether or not the world is ready and waiting for it. Fortunately, the majority of discoveries are made by workers who are carried forward on the crest of some advancing wave of human knowledge, and all these belong to the former class. A dozen men are on the watch gazing intently in the same direction, and it is more or less a matter of chance which eye catches the first gleam of light. The fortunate seaieher finds his discovery instantaneously we'eomed and corroborated by the otheis, who vie with one another in hastening to give him his due meed of praise. Examples of this class are not fai to seek. We might choose them from almost any period in the history of any science, but as the present is a particularly stirring time m the scientific woild, we could not wish for a more striking example than ib ready to our hands in the splendid series of

triumphs that are still being made by the brilliant band of workers who are establishing on a firmer basis the electron theory, a theory which promises to explain so many of the most puzzling enigmas of science, besides opening up to us two new worlds and presenting to the mind 's eye an indication of an infinite geometrical progiession of marve'lously perfect worlds within worlds. As we watch these pioneers opening up for us a new and magnificent realm of knowledge, it is a pleasure to note how generously each advance made by any one of them is appreciated by all the other workers.

Very different, indeed, is the fate met with by a discovery of the second class. It is made somewhere out of the direct line of progress at the time, or else is so far ahead that the distance hides it from all but the keen sight and clear scientific imagination of some so'itary genius Such a discovery, however beautiful in itself, is doomed to remain unrecognised as long as the world's attention is riveted elsewhere. If it is a new theory it is even harder for it to gain acceptance than if it is a new fact, and rightly so. But we must not forget that the march of knowledge is delayed whenever a truth is rejected. New theories have a way of upsetting so many preconceived ideas. When a theory is inconsistent with the statements of the text books, and is neither accepted nor even recognised by the leaders of scientific thought, the man in the street quite naturally assumes it to be unsound. But this is by no means necessarily the case. Text

books have erred repeatedly in the past, and we can hardly believe our present ones to be in fallible. Moreover, a truth discovered by one man must wait for recognition till some one else perceives it, which he cannot do until he diiects his attention towards it. Thus it happens that in almost every chapter of the history of human thought we read of truth waiting unhonoured till some reigning error shall have passed away. To this second class of discoveries Professor Bickerton's Cosmic Theory belongs. When first enunciated 30 years ago, it was not in the direct line of asti onomical progress. Astionomers then were moie intent on perfecting methods of observation and completing surveys of the heavens than in making comprehensive generalisations The new theory was, moreover, opposed to some of the accepted dicta of contempoiaiy scientific thought, especially to the theory of the dissipation of energy. The tidings, therefore, fell on deaf ears. It is easy to understand why this was so in 1878, but it is not so easy to explain why some of its main points are still unrecognised to-day, and why Professor Bickerton's name is not mentioned in the text-books of astronomy. In 1878 the facts on which the impact theory relied were few, though sufficiently striking. Now they are innumerable. During the last thirty years the advance in observational astronomy has been unprecedented; and every year the observations have verified the deductions which were originally made, the \erifications often extending to the minutest details. Thus it happens that though his name is not referred to, Bickerton's ideas aie creeping into the books For thirty years lie has waited, not too patiently, foi some recognition of his work, but it is highly probable that he will not have to wait very much longer; and all along he must ha\e had at least the satisfaction of knowing that he waited in excellent company Let us recall two or three names from the great scroll of those whose proffered gift of tiuth was for a time lejected. All will remember what a storm of opposition greeted Galileo when he pioceeded to make deductions from some of las most important discovenes, and how he was persecuted for affirming that the eaith moved.

That Avogadro discovered his great law, now one of the corner stones of chemistry, nearly 50 years before the world was ready to receive it is almost equally well known. Less familiar is the fact that when Jules Robert Mayer enunciated the principle of the conservation of energy his paper was contemptuously rejected by all the journals of physics. Similarly, when Waterston, jn 1845, submitted to the Eoyal Society a memoir embodying the kinetic theory of gases, it was withheld from publication because it contradicted the views then current amongst scientific men, and the discovery had to be remade by Clausius and developed by Clerk Maxwell As early as 1867 Niepce proved that salts of uianium impressed photographic plates in the dark, but the researches on radio-active substances did not start in earnest until Beequerel noticed the same thing in 1896.

Even Sir William Grookes, who in 1879 showed the mechanical effect of the Cathode Bays, had to wait twenty years before his theories with regard to them met with decisive confirmation.

Partial Impact. Now what is this theory of partial impact, the history of which is destined to take its place in the records of science along with these and countless similar instances of the irony of fate? The

easiest way to get a clear idea of it is to read the articles by Professor Biekerton himself which were published in three recent numbers of Progress They are written in his usual picturesque style, and breathe a splendid optimism. They give, moreover, very clearly, though of course in a condensed form, some of the main points in his theory , and show conclusively how wide and farleaching it is and how fertile in suggesting subjects for further research.

Let anyone lead through those three ai tides, and weigh carefully a'l the evidence adduced, and the piobabilities aie that if he has approached the subject with an unbiassed mind he -will consider the case fully pro\ed, with a wealth of evidence to spare. But let him next take up half-a-dozen of tho newest books on astronomy and turn in each to the chapter on temporary stais. He will find inadequate causes tor a stupendous phenomenon seiious y discussed, and impact possibly dismissed with scant courtesy as unable to account for the facts observed. This evidently needs some explanation. Let us, therefore, cull and examine a few such extracts. iiut in case any readers have not the original articles by them, let us first give, m as few words as possible, the kernel o± the theory, premising that such a statement can give no idea whate\er of the number, the importance and the beaut} of the deductions that spring from it. Col.isions of celestial bodies almost certainly occur. It would indeed be smpiising if they did not. The collisions are of infinite \ariety, for e\ery kind of celestial body may take part in them. A collision between two similar bodies may be of any degree of completenss.* from the merest graze to direct impact. The lattei must be exceedingly rare in comparison ruth paitial impact, for jt can occur only when the bodies have no original proper motions at all, or when their proper motions are entirety in the straight line joining their centres; which are both exceedmg'y improbable suppositions. In a'l other cases, when bodies of any kind are drawn together by gra-u-tation they describe conic sections round their common centre of gravity, and if they come near enough they graze one another. In the ease of a grazing impact of suns, the paits coming into collision coalesce, and have their motions of translation in great pait changed into molecular motion. The wounded suns generally go on, and form a pair of Variables. The coalesced parts form the third bodj . This is the real new star. It is as hot as if the whole suns had come into collision, but it has not the same gravitating power If it i& small enough in comparison to the suns it is unstable, and is soon dissipated into space. If larger, 'it forms a permanent planetary nebula. In any case, it is the scene of that wonderful phenomenon Selective Molecular escape, so well explained in the article in June. Grazing impacts and selective molecular escape seem able to account for the infinite variety of the forms of celestial bodies, and for their continual iejuvenescence. Just as a gas remains to us apparently the same whilst countless billions of impacts take place amongst its molecules, so our universe persists in spite of, or rather by means of, the impacts which gi\ c it perpetual youth. The sequence of e\ents that should follow impacts of a'l kinds has been worked out in considerable detail, and every year's work in the observatories of the world brings numbers of fresh verifications of these deductions. Let us now take a temporaiy stai as a test case and see how astronomers account for it A new star appears in the heavens In a day or two, sometimes in an hour or two, it increases in biightness till it is shining m space with ten thousand times the brilliancy of the sun. It gives a most characteristic spectrum as shown in our April number. In two or three weeks, or months, it sinks back into insignificance, and the final result is frequently a planetaiy nebula. Before it can be considered satisfactory, any theory of new stars must account for three things : 1. Their sudden lise. 2. Their sudden decline. ?>. The marvellous complexity and variability of the spectrum and the staitlmg changes in constitution which it implies. The theory we are discussing does all this per fectly, whilst no other theory so far suggested suciceeds at all satisfactorily. That an impact accounts for the first characteristic is evident, for the collision between two stars like our sun would last less than an hour. The sudden disappearance or decline affords a crucial test. When the third body is taken into account, there is no difficulty whatever. Without it every theory fails. The wonderful spectrum which has puzzled the astronomers of the world, and has disproved all other theories is not only explained, but was actually foretold by this one. Let us think for a moment what the spectrum will be like if a new star is formed by two suns giazing one another. By far the greater part of the heat produced by the collision is concentrated in the third body formed by the coalescence of the parts struck off from the colliding suns. This explosively hot body gives at first a continuous spectrum. But a tremendous outrush of gas from its surface

immediately takes place, and the spectium is ciossecl by daik lines which aie soon followed b} bright ones. At first all the elements ha\e equal molecular velocities, and therefoie very different temperatures As the temperature becomes equalised, the velocities tend to become inversely pioportional to the square roots of the atomic weights. Thus the nucleus becomes surrounded by rapidly expanding concentric shells of gas, hydrogen leading possibly at the rate of 1000 miles a second, liehum coming next at half the speed, and the other elements following in order. The velocities of all the lighter elements at least wil be much above the critical velocity, and will, therefore, hardly be reduced by gravitation. As the gases are rushing outwards in all directions, the lines of the spectrum will be widened to bands, the hydrogen hands being twice as broad as those of helium, and nearly five times as broad as those of sodium; and since the nucleus shines through the parts of the shells that are coming towards us, every bright baud will be accompanied by a shadow band on the violet side. As the intensity of the light of the third body ■wanes, the wounded stars may begin to assert themselves., and the blazing will then give bright lines displaced according to their rates o± motion. If the third body is small enough it will be completely dissipated into space, leaving a variable star, which, in course of time, will separate into a pair oP variables; the variability, of course continually diminishing. If the third body is larger, the heavier elements in it will be unabl( to get aw r a\ and the new star will fade into a planetary nebula and meteoric swarm giving a faint continuous spectrum Needless to say, this is the sequence observed in temporary stars. As possible causes of such a phenomenon as this, Flammanon suggests sun spots on a vaster scale, eruptions from the interior furnace, an encounter wdth a celestial body breaking up a continent on a crusted sun or tremendous 'tieteoiic streams meeting in space. The total inadequacy of all but the last of these is apparent, and if the last weie on a sufficiently stupendous scale, how could the light possibly fade so fast? Tn Professor Newcomb 's book, ' ' The Stars, ' ' he discusses at length the spectrum of Nova Aurigae, and shows how utterly inexplicable the phenomena are from his point of view. He does not considei the third body, or everything would be as clear as day. He seems to favour the idea tl.at some foreign body has made an opening in the shell of a star and allowed the interior gases to burst forth, but adds- "What magnitude the outburst might assume it is impossible to say, and cautious thinkers will decline to accept this or any other solution until we have had more experience on the subject. ' ' We may well decline to accept this solution, but why should we reject another if it gives a complete explanation of the facts? Tn the "Story of the Heavens," Sir Eobert Bale, whilst discussing Nova Cygni says: "We know no cause which would account for such a phenomenon nioie simply than a gigantic collision." "Tw r o or three days (or less) for the lise, two or three weeks for the fall. Yet even two oi three weeks was a short time in which to extinguish so mighty a conflagration. It is comparatively easy to suggest an explanation of the sudden outbreak; it is not equally easy to understand how it can have been subdued in a few weeks. A good sized iron easting in one of our foundries takes nearly as much time to cool as sufficed to abate the ce T estial fires in Nova Cygni." Of course it didn 't cool It was dissipated into space. In "The Earth's Beginning," Sir Eobert Ball discusses Nova Persei without mentioning the possibility of the third body. He points out that the heat developed by a collision might be much more than sufficient to raise the masses of the two colliding bodies to a state of incandescence, and then adds : "A collision affords the simplest explanation of the sudden outbreak of the star, any. also accounts for the remarkable spectrum which the star exhibits." A collision as Ball pictures it certainly does account for the sudden outbreak, but it completelj fails to account for the rapid disappearance, and without the third body it would certainly not account for the peculiarities of the spectrum. In Bryant s ' ' History of Astronomy, ' ' 1907, he says : ' ' The original idea that the appearance of these "temporary stars" must be attributed to a collision between two moie or less solid bodies, or one solid body and a fairly con densed nebula, is gradually being abandoned since of the several successive different phases shown in the spectrum of a Nova until it reaches the stage of a faint star again, theie is not one that necessarily denotes instability."

Now here again, is not the whole trouble in interpreting the spectrum caused through omitting to notice that the third body is the new star, and that the two original ones take quite a minor part in producing the spectrum. Miss Agnes M. Clerke, in "Problems in Astrophysics, ' discusses at length the phenomena observed in all the new stars of recent times. Every page contains striking confirmation of the predictions made long ago from a consideration of the sequence of events that should follow a partial impact. She describes very fully the spectrum of Nova Aurigae (1892). which really affords a most convincing proof of the grazing impact theory. It is Incredible that all its peculiarities, which astonished the astronomers of the world, could have been foreto'd without a clear conception of what was really taking place. Bnt she tries to account for the spectrum without considering the two essentials, the third body and selective molecular escape, and says, "The collision theory collapsed under the weight of the facts it had to carry. ' ' The very next year Nova Normae appeared; its spectrum was virtually a replica of that of Nova Aurigae. Miss Clerke says: "There was then nothing casual about its production. The spectral displacements and the augmented refrangibility of the darJc lines belonged to the essence of the phenomenon. The appearance of Nova Normae then disposed of what was left of the encountering star theory." In reality it piled proof on proof. ' ' Nova Carinae, 1895, disclosed precisely the same arrangement of coupled lines, the dark set above the bright. ' ' And so it has gone on ever since. A grazing impact followed by selective molecular escape is the on'y hypothesis that explains the observed facts, and this all-powerful double key to the mystery is the very one she does not try. In discussing Nova Persei, which afforded the most complete confirmation of all, as it was discovered at an earlier stage, she says: "The sodium band actua'ly moved upwards; the emitting molecules quickened their vibrations through some unknown kind of influence." But why is the influence unknown? The light sodium molecules must necessarily have their velocities increased by the heat they take from the heavier elements during the equalisation of temperature that follows the collision. But not having the "open sesame " Miss Clerke misses the solution, and sums up as follows: "On the whole the most promising theory of their occurrence is that stars in the Milky Way occasionally get entangled in the diffused nebulosities with which that region abounds, and blaze through the resistance offered to their motion, "just as meteors kind'e to brief splendour in shooting athwart our cloud of "circumfluous air." Fancy a star heated in this manner till it glows with ten thousand times the brilliancy of the sun cooling in a month or two. If this is the most promising theory, what shall we say of the otiieis? One of the latest and most interesting speculations on the origin of the universe is that given by Airhenius in "Worlds in the Making." It approaches neaier to Bickerton's theory than any previous one. In the preface Arrhenius writes: "My guiding principle in this exposition of cosmogonic pioblems has been the conviction that the unrveise in its essence has always been what it is now " This is the same idea as Biekerton's "Immortality of the Cosmos." Arrhenius adopts the collision of suns as the true explanation of new and variable stars, and on the assumption that dark suns are 100 times as numerous a 'uminous ones, calculates the probable interval up to the next collision of our sun as something like a thousand billion years. He discusses at length the probable sequence ot events in such a collision, and tries to account for the observed facts. But his leasoning in several particulars fai's to bring conviction, as he does not consider the formation of the third body, and does not definitely accept selective molecular escape. His explanation of the sudden disappearance of the star amounts almost to saying that it is hidden by its own dust. His words are : ' ' But what has meanwhile become of the new star? Spectrum analysis tells us that it has been converted into a stellar nebula 'ike other new stars. The continuous light of the central body has more and more been weakened by the surrounding masses of dust. ' ' In accounting then, for the phenomena of temporary stars, Professor Bickerton 's theory appears more successful than any other. We might, with similar resu'ts, compare his method of treating variable stars, double stars, planetary nebulae, spiral nebulae or, in fact, any of the detai's of the scenery of the heavens, but space forbids. Let us, therefore, confine our attention to one more pomt — the structure of our own Galaxy. Professor Biekerton appears to have been the first to suggest, as he did a quarter of a century ago, that our visible universe owes its form to the interaction of two great cosmic sys-

terns that are now and have been for ages, undergoing whirling impact. This has at last been con firmed by observation, in the double drift of two majestic streams of stara, described by Sir David Grill betore the British Association. It is only during the last few years that Bickerton's ideas, and even some of his phrases have been finding their way into astronomical works. New comb, in "The Stars," 1902, gives a whole chapter to the stiuctnre of the universe and yet the most likely form, the spiral, he entirely omits to consider. But this idea appears without any reference to its originator in two or three books published last year. In his "Astronomical Essays" Gore gives an entire chapter to "The New Cosmogony," by which he means the "P'anetesimal Hypothesis" of Chamberlain and Moulton The essential part of this theory is that suns and systems are evolved from spiral nebulae. A spiral nebula, he says, may possibly have been formed by the "grazing collision" of two solid masses, or by the near approact of two bright stars. Thus the importance of the spiral in stellar evolution is becoming recognised more and more. In discussing any theory of eosmical evolution to-day the question naturally occurs to the mind: "How will it be affected by the acceptance of the electron theory, which is causing us to modify our ideas on ao many fundamental points? Will the electron theory supersede the theory of impact ? Probably quite the reverse. It will doubtless enlarge and extend it in some directions, but by directing attention to it, will be more likely to lead to its earlier recognition. The electron theory shows us that we have in the matter about us an epitome of the visible universe. A small portion of the atmosphere or of any comparatively rare gas, affords a model of our great galaxy, whilst a tiny solid organism may be a miniature copy of the great nebula in Andromeda, which is probably a universe much mightier and more wonderful than ours. Mooem researches are all tending to show the unity, infinity and immortality of the cosmos. Fournier d'Albe in his delightful book, "Two New Worlds," gives very good reasons for such a belief. In "The New Knowledge," published last year, Professor R. K. Duncan says: "The heavy elementc of matter are undergoing a steady and inevitable decomposition with the continuous production of infcer-elemental energy. Now, if the lightei elements were at the same time undergo ing the reverse process, were, in fact, synthesizing themselves into the heavy elements with the absorption of energy so that as much energy was collected up by them in their growth as was "wasted" by the decomposition of the heavy elements in their decay, the universe of matter would keep its available energy constant; it wou'd constitute a conservative system, having neither beginning nor end. ' ' Thus we find in the infra world an exact parallel to selective molecular escape and the aggregating power of a high potential in ours, and the one leads to the permanence of matter as the other to the stability of the cosmos. We have, then, m the impact theory as developed by P'ofessor Biekerton a remarkably complete ex-p)an;-tjon of the manifo'd processes at work in the visible universe. During the thirty years it has been seeking recognition it has had none of its ded\icl.ons contradicted On the contrary, it has been able to predict the sequence of most complex phenomena many years before they were ■confirmed by observation. Surely such a theory is worthy of serious consideration. It is so fertile in suggesting new directions for reseaich that had it been accepted as a working hypothesis a quarter of a century ago there can be no doubt that it wou'd have proved a most important factor in accelerating astronomical progress.