SCIENTIFIC.

Otago Witness, Issue 1900, 20 April 1888, Page 36

SCIENTIFIC.

A NEW THEORY REGARDING THE UNIVERSE. It is a wonderful thought to consider that, although we human creatures can by no possible means convey ourselves outside the confines of the globe upon which our lives are passed, we have been able to learn so much about those other globes and appearances which are popularly spoken of as " the heavenly bodies." The knowledge has; it is true, been slowly acquired. A theory has been enunciated to last for a time, perhaps for centuries, when it is pushed put of place by some other theory, which perhaps in its turn may soon have to give place to a newer one. How natural was it for the ancient observers to suppose that ,the various orbs, which appear to execute so stately a march across the sky, together with those seemingly much larger bodies, the sun and moon, were travelling round the earth as a centre. Thiß — the Ptolemaic theory — was so plausible, and one so evidently in accordance with common sense, that it held its ground for 18 centuries. Thales, Pythagoras, and other« had previously taught a different lesson, and one more in accordance with modern ideas ; but their followers were few and their teachings were discredited because they seemed to be contrary to the ideas gleaned from popular observation. Seeing was believing, then, as it is now ; and when the stars were seen to move across the heavens, and the sun and moon to rise and set, it was only natural to assume that their movements were real, and that the earth was as still and immovable as it appeared to be. Then came Copernicus, who retaught the forgotten doctrine of " ' ' ' THE EABTH'S MOVEMENT ON ITS OWN

AXIS, and its annual journey round the sun 'as the centre of our system. Galileo corroborated this hypothesis by his telescopic observations ; and Newton crowned all by his grand conception of gravitation. In this way the now universally accepted theory of the solar system was founded. But the solar system, vast though it be — its most remote member, Neptune, is 2,745,998,000 miles from the sun ■ — really constitutes but a very small part of the great scheme of the universe. The nearest of the so-called fixed stars is ,'so distant from us that we have no means of measuring that distance, and when astronomers endeavour to give to others some idea of their remoteness, "they tell us 'that light, which j travels at the rate of 186,000 miles per second, would occupy so many centuries in bridging I the gulf which separates us from those remote bodies. We see, therefore, that any difficulty which we have in learning about the constitution of the planets which form members of our own system; is immensely increased when we' come to ask for information concerning the far more distant star's. In the one case we are dealing with things which are, so to speak, within reach of our hands ; and in the other case, with objects which are upon another continent. The only messengers which reach this earth from space are THE SO-OALLED SHOOTING STABS, or meteorites. Thsse are assumed to be dark bodies, which, travelling through space, become attracted by this earth, and are quickly drawn towards it by the jirresistible power of gravitation. Upon entering our atmosphere — which, it will be remembered, .extends about 200 miles, above the surface of the carth — the course of these meteorites is checked by the resistance which the air offers to their progress — a frictional resistance, which is accompanied , by the evolution of light and fervent heat. As a result, these swiftly moving bodies are vaporised; but the vapour formed quickly condenses into solid particles— -meteoric dust, which is deposited, slowly but surely, upon the earth. Such dust has been found on the pure snow of the Arctic regions, where dust of the ordinary kind is impossible. It has also been collected on the tops of elevated buildings, and has been dredged, up from the depth's of the Atlantic. ' , Besides this celestial dust, which is slowly adding to the bulk of the earth, there are many authentic records of the fall of meteoric stones of large size, many .of which have been preserved as curiosities in j our public museums. These shooting-stais : are familiar enough to us; perhaps some will say that they are too common to be regarded as phenomenal. But few persons are aware how plentiful these beautiful objects really are. We are indebted to Professor Newton, of America, for some statistics with regard to them. He made a series of careful calculations, with a view to discover a3 nearly as possible how many meteorites enter the atmosphere of this earth in a given time, and so become visible. As a result, he has found that the annual number is about 146,000,000,000. That is to say, in every '24 hours, no fewer than 400,000,000 meteorites are propelled towards and re- ' ceived by the earth. And this number, be it noted, does not include that vast number of shooting-stars which are Galled telescopic, for the reason that they are too small or tod - distant to be detected by the unaided eye. It is therefore easy to see that the earth in travelling along her orbit passes through, showers of these meteoric stones, and that' it is only by the protecting influence of our atmosphere that these stones do not represent deadly missiles to its inhabitants. Travelling at the enormous velocity of 30 miles a second, they would, were it not for that protection, be far MOKE EFFECTIVE PROJECTILES THAN THE

SWIFTEST OF CANNON BALLS. Upon a close investigation of the nature and composition of these meteoric stones, Mr Norman Lockyer has founded a new theory with regard to the constitution of the heavenly bodies. Like all theories, it will have to bear the test of time, either to be preserved, or to be discarded for something better. Still, until that something better makes its appearance, we must admit, upon considering this new hypothesis, that it contains nothing but what seems to be consistent with truth. Let us endeavour to explain in a very brief manner the salient points or this new doctrine. We know that meteors have a tendency to collect in swarms, and that these form closed, rings, which travel in elliptical orbits round the sun. On two nights in the year — one in August, and one in November— the earth's

orbit intersects these meteor-paths', and on • those nights shooting-stars are plentiful. , In 1866 Schiaparelli showed that , one of these swarm's of meteors had an orbit which was identical with' the path of a certain comet, an observation which led to the inference that a comet consists of a mass of meteors rendered luminons or incandescent ' by frequent and innumerable' collisions among themselves. This theory of the genesis of a comet is now widely accepted among astronomers. Mr Lockyer not only accepts this view, but he holds that all the heavenly bodies owe their origin to meteorite's. He tells us that all .. • . SELF-LUMINOUS BODIES IN THE' HEAVENS

' ABB COMPOSED OF METEOEITES, or masses of "vapour produced by heat brought about by condensation of meteorswarms due to gravity;" and that J'the" existing distinction between starsj comets, and nebulae rests upon no physical basis." But how, it will be asked, does Mr Lockyer seek to prove the truth of this new hypothesis ? The answer to this reasonable inquiry is, that he depends upon the cvi- ! dence of the spectroscope. ' Let us, for the benefit of those who have not had an opportunity of following up .the more recently trodden paths of scientific'research, give a few words to this marvellous instrument.

THE SPECTKOSCOPE ' is the .outcome of the labours , of many minds. Two hundred years ago, the great Newton made the first contribution towards it by admitting a beam of sunlight through 1 a round hole in the shutter of a darkened room and causing 'that beam to pierce a prism of glass. The prism • split up the white light into its constituent coloured rays. Many years afterwards, Professor Wollaston ' substituted a slit for the round hole in the shutter, and found that- this alteration led to a strange result. The coloured ribbon of light was no longer continuous, as with Newton, but wa3 cut across by many dark lines. Fraunhofer, a German opticiar, mapped these lines to the number of several hundred, and they have since been called by his name. No one knew what they meant until the year 1835, when Bunsen and KirchhcfE discovered the secret. Theae two investigators were' examining the light given by different metals ■ when volatilised in the intense heat of the electric arc. They made this examination by means of the spectroscope, an instrument consisting of a prism placed in a tube, with an adjustable slit at one end, and a magnifying glass at the other end.' JThis instrument, it will be seen, is simply a convenient modification of the darkened room with a slit in its shutter.) They noticed that each metal gave certain distinctive bright lines, aud that these bright lines were identical in position with certain I dark lines on the solar spectrum. ' They next found that the dark lines were due to the vapours of the burning metals, and that the "corresponding bright lines were only seen when the glowing metals themselves were examined. • ' Such is, briefly, the history of the spectroscope, an instrument which has added enormously to our knowledge during the i past 40 years. The dark lines in the solar [ spectrum tell us that a large number of the I metals known to us on this earth are in a state of active combustion in the sun. We are also able, with the spectroscope, . to examine the light given by stars, comets, " and nebnlse, and to gain by the nature of their spectra some idea as to their composition. The spectroscope, in short, offers us a means of ' - ANALYSING THE LIGHT given by a body so remote from us that light' ; takes centuries of time before it can reach this earth. ' And it should be noted that by. this wonderful method of spectrum analysis we cannot only identify the nature of the glowing matter in these far-off regions of space, but we can also get an approximate idea of the temperature at which it glows. Some of these distant bodies — nublae, for instance — represent a heat which can be compared with that of the familiar' Bunsen burner; other bodies are associated with the heat given by the oxyhydrogeh flame ; others, again, with the far higher temperature of the electric arc ; while the brightest stars of heaven — Sirius, for • example — glow with a heat unattainable by any means at the disposal of man. We have already pointed out that the only substance which reaches this earth from j outside space is the meteorite. It is something ponderable, which cannot only be handled, but can be subjected to chemical | analysis, and to the still more searching eye , of the spectroscope, Mr Lockyer founds his i new theory upon the constitution 'of the j meteoric stone. Volatilising these meteorites at various temperatures, and examining their spectra, he finds that there is a wonderful agreement in character between the spectra so obtained and the spectra of the various classes of heavenly bodies just mentioned. We will quote his own words with reference 'to the application of this method to solar observation. He says : — " The solar, spectrum can be very fairly reproduced — in some parts of the spectrum almost line for line — by taking a composite photograph of the arc spectrum of several stony meteorites, chosen .j at random, .between iron meteoric poles." It is impossible to describe fully in a popular j manner the innumerable and patient experi- j ments, extending over a period of 14 years, which have guided Mr Lockyer to the conclusions at which he has arrived. To understand the force of his arguments, one ■ must have something more than a casual know- J ledge of the wonderful instrument which has assisted him in his labours. To summarise the matter : He seeks to prove that the. whole of the heavenly bodies are due to the übiquitous meteorite — sparsely clustered — their luminosity being due to glowing gases let loose by their collisions among themselves — and we have the nebulae. Drawn within the attractive influence of the sun, such clusters become comets. A further development is seen in a certain class of stars, where gravity has caused a nearer approach of the constituent meteorites. And at length we reach the highest stage of all, where the meteorites are volatilised, and the star is a mass of incandescent vapour at a temperature beyond our ken. The spectroscope therefore teaches us of what stuff the stars are made, and the physical reason for the % fact that "one stair differeth from another in glory."—" Chambers' Journal." '