SCALE OF UNIVERSE.

Auckland Star, Volume LXIV, Issue 113, 16 May 1933, Page 6

SCALE OF UNIVERSE.

OUR HOME IN SPACE. (By PvEV. B. DUDLEY, F.K.A.S.) ■Sir James Jeans' recent lecture, from which quotations were given the other day in the '"Star, may have awakened in the minds of some readers a desire, for further information on the immensity of the universe as made known to the. modern astronomer. Our sun, it has been discovered, is only one of main- millions of stars. To us it is a, blazing orb" merely because- we are near. From Areturtift or Canopus it would be quite impossible to distinguish it. In truth, although the sun dominates the system to which we belong, compared with other stars it is an insigniiicant object. It is 400 times less in diameter than Antilles. How mueh, therefore, in bulk!

The distances that separate suns from each other are enormous, the nearest neighbour to us being 20,000,000,000,000 miles away. And no one knows how far off is the remotest. The majesty and extent of the. heavens lias grown with our knowledge of the universe, Within the lust few years our conception of the vastness of the cosmic order has been profoundly modified. According to Hubble, tlio farthest nebulae are 140,000,000 light years away, the greatest distance yet known to astronomy; although still remoter objects are smspected, a suspicion which will doubtless be confirmed when the great 200 in mirror has been completed.

Among these mighty hosts we live and move, and have our being on a tiny ball occupying its own little corner of the ,sky—an infinitesimal pinpoint in tho universe. Away across the enormous gulf outside the bounds of the eolar system, which is itself but a minute speck in comparison, lies the milky way, a complete ring of stars forming the limits of the great, scheme known as the galactic system —the outer walls, Oβ it were, of our domain; but in reality the enfolding coils of a gigantic spiral. Beyond this system, across still greater gulfs of the infinite void, arc to bo found the extra-galactic nebulae that take no part in the rotating movement of the spiral in which we live. These, also arc spirals which work out their own individual careers. They constitute universes independent of ours, many of them being as vast. Two million such universes have been discovered. Our own galactic system is so wide that light, which shoots a distance of (170,000,000 miles an hour, would tiiko hundreds of tliouciamls of light years to cross it. "livery universe outside our system," wrote Dr. Harlow Shapley, "is to-day regarded as a, galactic system, with a diameter probably exceeding 300,000 light years." Still farther away in immensity, above or below us, according to the point we occupy on this little world of ours, lies the realm of the unexplored, the realm beyond tho reach of our mightiest telescopes, a region in which—for no other conclusion seems possible —"universe must follow universe in procession up lo infinity."

Jeans,, who is a past-master in the matter of drawing comparisons and eimiliee, that assist the. imagination, puts the case for us in this way: "We can construct an imaginary model of "the system of the great nebulae by taking about fiO tons of biscuits and spreading' them so as to fill a sphere, having a mile radius, thue spacing them at about 25 yards apart. The sphere represents the range of vision of the existing lOOin telescope; each biscuit represents a great nebula of some 4000 pars-ecs diameter. A few nebulae of exceptional size miiet be represented by articles rather larger than biscuits, while our system of stars would be represented by a flat cake 13in in diameter and 2iin in thiekneee." On this scale, Jeans estimates, the earth is far below the limits either of vision or of imagination. It is little, more than an election in one of the atoms of his model. To bring it up to the size of even the. smallest particles which are visible in the'most powerful microscopes we should have to multiply its dimensions , many millions of times. A parsec ie. a distance very much greater than the light year. The latter has come to be too small a measuring rod in modern astronomy. A light year is the distance light travels at the unimaginable velocity of 130,000 miles a second. It is equal to about 03,000 times the distance of the earth from the sun, or approximately 0.000,000.000,000,000 miles. The parsec is equal to 3.2(5 light years, and is about 200,000 times the distance of the earth from the- sun; that is to say, 200,000 multiplied by 03,000,000. It is the distance of a star with the "parallax of a second," a fact which its name, parsec, conveys to us. The fact that there is no known star within one parsec of the sun ehows the immensity of the scale on which, th-e universe is built.

We live, then, in a sense, in a roomier universe than our grandparents. Since the telescope first began to explore the heavens, man has been compelled to domesticate himself in a new cosmos. Creation was once, as a noted theologian writes, "a comparatively smug affair; the earth was its centre and man its raison d'etre." Our planet was thought of as the fixed point round which everything revolved. The sun was created to give light to man day by day, the moon and stars to shine upon him by night. "At a handy distance above him," continues the same writer, "was a paradise for the good, and beneath, within easy distance, an avernus for the wicked." The astronomer has combined with many theologians in overturning this conception. The scone they now contemplate is one in which our earth is found to be the insignificant satellite of a star nearly a million times bigger—a sun which, in turn, i* itself only a minute speck in the surrounding immensity.