IN STARRY SKIES

Evening Post, Volume CXII, Issue 145, 16 December 1926, Page 28

IN STARRY SKIES

PEERING INTO SPACE

THE MESSAGES OF LIGHT

(By "Omega Ccntauri.")

The most wonderful thing in the whole range of modern, science is the fact that man has been able to extend his explorations far beyond the limits of the Earth; in fact, to inconceivable distances in every direction around it. The livo senses are the channels through' which all his information comes, and of the five, four are severely limited iii range. Tasite, touch, and smell require- actual material contact of some kind between tho observer and the tiling perceived, whilst hearing, wliieli occupies a somewhat wider field, is dependent on tho presence of the air. Tho range of usefulness of this sense has indeed been enormously extended in recent times through tho development of wireless telephony, but in this case the original aerial sound waves are transfprmed before transmission into something entirely different, and have to bo changed back into waves of the air beforo they can be received by the human car./ No sound whatever has therefore reached üb, up to the present time, from beyond tho limits of tho Earth'a. atmosphere. Wo cannot, except in imagination, hear tho music of the spheres. Sight, however, is a nobler and far more potent sense, approaching in some, ways Iho divine. 'No distance, however fjreat, appears to present to its use an . insuperablo obstacle. Even without ; any artificial optical aid wo can see j thousands of stars, mostly at such vast distances from us that light, the swift- ! cst traveller known to science, takes I hundreds of years on tho way. "We ! talk of peering into the distance, but j u-o are not the active agents in tho transaction. We simply havo to be receptive. Our role is to receive and interpret messages which come to us uncalled. The messages are incessantly streaming through us and past us, most of them utterly unheeded. But we are furnished yripi a truly marvellous optical instrument, the eye. ,In its small compass it contains the germ and the original of. every scientific instrument that lias beei. developed for use in. atitronoiny. Ita lens, ;liko the object glass of a telescope or camera, gathers the light and brings it into a focus-. Tho retina, provides the sensitive film some of whoso duties have now been taken over by .the photographic plate. . The distinct impressions which the brain, forms of colours thrown on the retinb, gives a first hint Of the analysis of light, which has been omployod so successfully in the spectroscope. The power of judging distance through the joint, action of two eyes, suggests the modern use of the interferometer. Whatever other tools are used, the eye is the ultimate receiving apparatus. But reception is not the ultimate aim. There is something beyond and above the eye. Astronomical, instruments may-gather' the light, focus it nt certain points, and magnify tho images which arc thrown on the retina. Spectroscopes may .analyse the light and break it up into all its components. The messages thus brought are received asi mere sense impressions. The power of deciphering and interpreting these messages is the glory of man's intellect, and proves the presence in humanity of some spark of the divine. Jt was' not easy for man to pass from seeing to knowing, and progress has been very slow: throughout long ages. The first steps wore the most difficult of all.' A dog can see the stars as clearly as-we do, but they mean almost infinitely less to him than to us. He can gaze on them unmoved. He never pictures this great round world flying endlessly through unbounded space with orderly motion, though terrific speed. The brightest star to him is of less importance than a motor lamp, and he never dreams of the planetary worlds that perchance it draws along with it on a never-ending journey through space. It is easy for us now to realise that the earth, which seems so big, is' a small and comparatively unimportant planet in the solar system, that it is relatively so insignificant tl it it is quite invisible from all other members of the galaxy. But this is simply the result of accumulated knowledge which has been handed down to us. 'If we had never read, and never been told, one single fact about the heavens, how much should we know now? How little wo could discover with our own unaided brain. When we reached mature old age would a star mean much .more to us than it does now to" the average thinking dog? He certainly understands many things at least as well as we do, perhaps indeed much better. Could wo without assistance have learnt any more of astronomy than ha has done? We feel superior to Mm, as. he barks at the moon, rejoices in the sun, and gazes at the Milky Way without, emotion. But should we regard these objects any more intelligently if with a man's full senses and measuring power we had passed through life absolutely cut off from all sources of inherited information? How long would it take us to discover the precession oi! the equinoxes, or the diameter of Antares? Considerations such as these should make us marvel at and honour those great men who discovered man's place in the universe. What an astounding fact it was to realise for the first time that the earth is a great globe hung upon nothing; that tho sun far exceeds the earth in size and in importance, and that the twinkling stars are suns, many o£ them at least as great and glorious as tho mighty ruler of o^ir own system. We have already glanced at the history of a few of the great thinkers of the past, men who by their inspired -labour!! widened and ennobled | man's outlook on the universe. Times J are different now. Who can compare with Democritus, Pythagoras, Hipparchus, Copernicus, Tycho, Kepler, Galileo, Newton, or Herschel? And yet progress was never so rapid as it is to-day. The present ago is marked chiefly by two things—the enormous increaso of artificial instrumental aids to the power of perception, by the senses, of messages which come from afar, and secondly the development of team work. The former enables us to receive clearly innumerable messages whose very existence would otherwise have remained utterly unknown, the latter leads to an unprecedentedly rapid increase of knowledge combined with a difficulty in attributing each advance to its real originator. A dozen men may bo thinking out the same problem at the very same moment, and the final solution may contain contributions from all of them. Before considering recent developments of science which havo changed man's outlook on the universe, it will be well to glance at the instruments which make a modern observa-, tory so different from that of Tycho. The eye, though supreme amongst the senses, has definite limitations. Botli tho eye and tho ear arc receivers of vibrations. The latter is tuned to respond to the comparatively wide oscillations of the air, the former to thos>c of a much more mysterious ether. The ear responds to some eleven octaves corresponding to sounds of different pitci., the eye sees less than, a single octave. Tho waves oi! sound require some material, either gaseous liquid or solid, to transmit them. Tho waves of light pass through what' is often considered to bo empty apace, and travel with the astounding speed of over 186,0.00 miles

in a second. The waves of sound are comparatively long. In ordinary conversation the waves caused by a woman's voice are from two to four feet long, those by a man's from eight to twelve feet. Tho waves of light are so short that we can form no clear per coption of their length. They are measured in units, each of which is only one ten thousand millionth part of a metre. The longest waves which affect the eye have a length of 7000 odd of these units. Tho shortest arc nearly 4000 units long. The former give tho sensation to associate with deep red, tho lattor with violet. If we speak, or drop a pin, in a small fraction of a second, every parliclo of air in the room will have been disturbed. The air in a concert hall convoys the vibrations duo to every note sounded by voice or instrument to the drum of every car. If a cracker is fired in the open air tho sound spreads .all around, but its intensity diminishes rapidly as it proceeds. At tho same moment a spherical wave of light starts

from the spot, spreading in all directions at a speed nearly a million times as great. The apparent brightness varies inversely as the square of the distance. The light from the sun reaches the earth in about eight minutes. Froni the nearest star it;takes nearly three hundred thousand times as long. Its brightness is thus reduced to one ninety thousand millionth part of what it would be if th« ptar were but as far as the sun is from us. Other stars in the galaxy may be &C distances ten thousand times as great as that of Alpha C'ontauri, our nearest stellar neighbour. This increase of distance diminishes the apparent brilliancy another hundred million times. No wonder then that the need is felt, of increasing the amount of light which enters the eye from objects so remote. Hence the marvellous advance which has been made in the power of the telescope. But all the increase of light thus secured would be wasted if the braiD could not interpret what is seen. For the ability to do this we .ire indebted to the achievements of the heroes of ' the past. They have taught us that things are hot what they seem. The sun and stars do not rise and set.. It is our earth which' spins on its axis. The planets are not wandering stars, but bodies of the same order as the earth, though in several cases immensely larger and more massive. The-transitory streaks of light, which wo so often see on a dark night, are not shooting stars, but small fragments of matter raised to. a white heat by friction as they rush into the atmosphere at a speed of a score or two miles per second. The stars themselves are not subsidiary lights added to the sun and moon to illumine this earth, but are immense suns, njany of them enormously greater than the orb of day.

Such factg as these, the great discoveries of the past, are commonplace bits of universal knowledge to-day. But the mind is perpetually craving for fuller information. The practical man responds by providing greater and greater facilities for increasing the power of the eye. The first requisite which man felt the need ,of was greater lightgathering power. The pupil of the eye is very small, and distant stars appear extremely faint. The power of collecting light and directing it to the eye is provided by the telescope. The eye is soon tired, the longer we gaze at any object the less perfectly we see it. A method was needed by which we could store up tho energy ,at a faint illumination and record the effect of it in some permanent way. This is now done by the camera and the photographic film. All the light from a distant brilliant object i» usually blended together. .Newton showed how to analyse this light and break it up into different colours. The spectroscope can now do this successfully even with light of a faint star, if this light has been gathered and condensed by a giant telescope. These great achievements would, however have given little intellectual satisfaction had not Fraunhofer, Kirchoff, Bunseij, Huggins, and many others taught us to decipher the hidden messages carried by' the waves of light.