SCIENCE UP TO DATE.

Lyttelton Times, Volume CXVII, Issue 17078, 29 January 1916, Page 6

SCIENCE UP TO DATE.

RECENT MISCELLANEOUS ADVANCES. (By JAMES COLLIER.) INTERCHANGING SIGHT AND HEARING. An English physician with a French name, Dr Fournier d'Albe, has invented an apparatus that makes it practicable for a blind' man to distinguish between light and darkness. He may even, with its aid, recognise at a distance the presence of opaque objects. What is the nature of the ingenious device that accomplishes this fresh scientific miracle? THE OPTOPHONE.

To begin with, it is little more than a telephone, but a telephone into whose circuit a cell of selenium has been introduced. Now, selenium, while it resists an electric current in the dark, facilitates its passage in daylight. Therefore the new instrument, which is called an optophone, has its cell of selenium, and blocks the light excepting a* admitted through. a narrow tube. Let this tube be directed towards the light; then the electric current passes, and the holder of the telephone hears a buzzing or whirring sound. On the other hand, when the tube is pointed at a dark object, the electric current is faint, and the sound heard in the receiver is scarcely audible. ~.',„ mi How does it affect the blind? The blind man slowly move 3 the optophone about, and is then enabled to detect here and there a human being. The instrument has still to bo so perfected as to enable other and inanimate objects to be perceivecr or detected. The chemical clement thus utilised was so called after the moon, and was discovered by the Swedish chemist, Berzelius, in 1817. A distinguished chemist at the university told us that the name of it was derived from "selena," the Greek word for the moon, and' Dr Smith Williams tells us that it comes from " selenus." Evidently, classical scholarship is not the strong point of chemists. _ That selenium conducts electricity only in the light was discovered so recently as the year 1873 by two telegraph operators at Valentia, Ireland, the last home station of the Atlantic cable. Wonderful things were bred out of that discovery. Take one or two instances. An electrical engineer started' and stopped' at will a nyed\namo only by waving his hand across a ray of light directed towards a selenium cell introduced into the electric circuit. The- same electrician fired a cannon by throwing a beam of light from a distance. Many more wonders are predicted in the near future or have been already invented'.

THE FLIGHT OF STARS. It is a "fixed idea" with us when we talk of the "fixed stars "■' and the Germans have but one word for these luminaries. There are no such bodies. We simply cannot perceive their motion because they are so far away. In fact all of them are in motion, and some are moving with a prodigious velocity They flee through space singly, in pairs, in groups, in clusters and swarms and streams of unimaginable dimensions. Some revolve at the terrific rate of 150 or 200 miles a second, or 540,000 miles an hour. At the otner extreme our sun, with Ins cortege or planets, moves 124 miles per second, or at the very respectable rate ot tti million miles a year. Between these extremes the average rate, according to the head of the Lick Observatory, in the United States, is about twentj miles a second. The figures are complicated by cross and counter ™ti°ns. The earth rotates at the rate of 10W miles an hour; it revolves round the sun and reels and plunges through, space at nineteen miles per second; and it is carried through space with the rest of the solar system at 124 miles per second. The result is a zig-zag spiral movement of the utmost complexity. AGE AND STEED. <

What is it that governs or most affects the speed of the stars? _Their aee, chiefly. In the words of \N . «• Campbell, 'of the Lick Observatory, "stellar velocities are functions of spectral types," that is, they vary with the age of the stars, and stellar velocities increase with increasing age. So, apparently, the Lick Observer believes, though he does not express his formula in a. dogmatic fashion. It is doubtful whether matter in its pre-stellar stage is subject to the law of gravitation. Then what law, in place of gravitation, do they obey? Some other law or force there must surely be. A comparatively recent discovery comes to the rescue. As all know, the nebula? in their earliest stage consist of finely divided particles of matter that are driven or pushed hither and thither in apparent defiance of the law of gravitation. By what force? By a new force that has but recently come to our knowledge. It is called the pressure of light, or radiation pressure, and it is a force of appreciable magnitude because it is derived from myriads of incandescent suns. As the nebulas develop, their finer particles arc aggregated—possibly through collision —and then ..the light-waves cannot act on them effectually. This leaves gravitation free play, and having, up to this stage, been governed by light, they now fall under the control of gravitation. Thus when the finer particles df the nebulnr stage are more or less integrated as to form a star, gravitation begins to affect them, and the pressure of light ceases to be exerted,' being overcome by the stronger force of gravitv. The star falls towards the gravitational centre —on this earth, in the solar system, or in the stellar universe, and it gathers speed as it falls.' But this, speed will not remain uniform. It will find its limits. The star will come into collision with another star. The substance of both will be reduced to powder, and the two will revert to their original nebular condition. And there will recommence the Sisyphean labour of beginning their development over again. PLURALITY OF WORLDS.

The ancient 'and medieval populations can hardly have believed that any of the planets or other stars were inhabited. They did not believe that the starry orbs were fit scenes for the abode of life because these were too small to answer such a purpose. They were but ornaments of the universe, mere lamps of the sky, a standing illumination of our Earth. Then, when the telescope opened up new worlds to the sight and imagination, it began to be realised that those vast bodies might well be inhabited. Theology, of course, took sides against the tenet as endangering the machinery of the scheme of man's redemption. In the forties and fifties the question : Are the planets inhabited ? was still a live question! In late years the discovery of the alleged canals on Mars and the obvious similarity between the conditions of Venus and those of Eprth have prompted the inquiries: Shall we ever be able to communicate with the Mar-

tians? and, may there not be quasihuman inhabitants on Venus?

FLUID PLANETS. Thoroughly equipped astronomers have at last Ijaken up the subject and brought all possible new light to bear upon it. The greater planets, even half a century ago, were held to be not impossible abodes of life. AVe know better now. Those great globes, Jupiter and Saturn, Uranus and Neptune, cannot possibly harbour human inhabitants; if they are inhabited at all, it is by very different beings from ourselves. The structure of all these planets is so tenuous that they cannot be other than gaseous or, at the best, fluid. The equatorial portions of Jupiter may be molten liquids, because they rotate more rapidly than |its pales. Fluid, these, is the verdict equally of mathematicians and physicists. Hundreds of millions of years hence they may recapitulate the history of our Earth.

MERCURY. Other planets are differently conditioned. If Jupiter and Saturn, Uranus and Neptune are too big to liave cooled down sufficiently to receive a humanity of their own, Mercury is too small. It enjoys the unenviable privilege of living ever in the sun's arms and never being able to change its axis of rotation. It _ resembles the moon in always presenting one face to the sun. One half of the planet is thus unendurably hot, while the other remains as intolerably cold. A queer population it would be that could inhabit either eid'e.

MARS. Mars seemingly stands in, a more hopeful case. Who has not heard of the canals of Mars? M. Antoniadi, the highly capable student of the architecture of St Sophia at Constantinople, has been eclipsed by Percival Lowell, one of the few American privato gentlemen who devote themselves to the exact sciences, whose imagination has run away with his judgment. The Italian astronomer, Schiaparelli, was the first to 6ee, or to imagine that he saw, the now celebrated canals. Mr Lowell has gone much.further, and has discovered their straightness, uniform size, and tenuity, the duality of some, the oases, and a systematic network in relation with these. The American astronomers, Keeling and Bernard, have taken photographs that reveal curious markings, but no such structures as Mr Lowell found. A thorough examination of the whole subject lias been made by Mr E. W Maunder, superintendent of the solar department at the Royal Observatory, Greenwich. Mr Maunders experiments on human subjects (in a schoolroom) appear to have conclusively shown that Mr Lowell's constructions are optical illusions. In any case, the temperature of the surface of the planet is believed' to be so low that animal life at all resembling out own cannot possibly exist.

VENUS. The evening star is differently situated. Its atmosphere is dense, and, being so much nearer the sun than our earth, it receives almost twice the amount of light and heat that our earth receives. Plant and animal species could readily adapt themselves to these conditions. But that is not all that is demanded. Venus must have another point of resemblance: it should rotate like the earth, so as to expose its two faces alternately _to the sun. But this, apparently, is just what it does not do. The Italian astronomer, De Vico, considered that Venus does so rotate, but another Italian astronomer, Schiaparelli. claimed to have shown that it rotates as Mercury and the moon rotate; and other astronomers (not all) take the same view: In that case, on one side the temoerature will rise to hundreds ot degrees, and on the other it will fall correspondingly. Life is possible on neither side of the planet. It is for ever condemned to sterility. The lesson of the spectroscope has still to be learned; however. Schiaparelli was evidently in the wrong about the canals of Mars, and it is possible that he was in the wrong about Venus. Recent work with the spectroscope appears to prove that Venus rotates in the same manner as our earth it that is so, it may well be that it lias the same physical conditions as our own favoured planet.