THE SIZE OF THE UNIVERSE.

New Zealand Graphic, Volume X, Issue 13, 1 April 1893, Page 305

THE SIZE OF THE UNIVERSE.

To us, puny dwellers thereon, the earth is a mighty object. Yet few have any really adequate idea of its size. The greatest travellers, whose lives have been spent in wandering to and fro over the earth, have seen only a very small part of its surface. Climb a lofty church steeple, and look at the landscape visible from it, and note that to see the whole earth 900,000 such landscapes must be viewed. But 500 earths like ours, placed side by side, could be enclosed by Saturn's outermost ring, and it would take 1200 globes of the size of the earth, rolled into one, to form a single globe as large as J upiter. The sun itself, if hollow, would hold 300,000 earth-globes, and to view its surface an eye capable of taking in hourly 10,000 square miles would requite 55,000 years. It is easy to say that the sun’s distance from the earth is, in round numbers, 92,000,000 miles, but it is quite another matter to have even the roughest notion of what such a distance means. Illustration has been piled on illustration to make it a little more comprehensible. The oddest is that used by Professor Mendenhall, who says if we could imagine an infant with an arm long enough to reach the sun, and burn himself, he would die of old age ere he could feel the pain, as, according to Helmholtz and others, a nervous shock is communicated only at the rate of about 100 feet a second, or 1637 miles a day, and would need more than 150 years for the journey. Neptune, the outermost member of the solar system yet known, is 30 times farther from the sun than the earth is, or 2,780,000,000 miles, and the tremendous line of his orbit, which circumscribes our small group of heavenly bodies, is so long that, though journeying at the rate of three miles a second, it takes him 165 years to complete one circuit. Passing beyond the bounds of the solar system, the members and dimensions of which are known with some approach to exactness, its size sinks into insignificance——its entire extent becomes a mere atom in comparison with the immensity of star studded space. Exact measurements fail us; approximations, often rough and uncertain, must take their place ; but, with a wide margin for error, enough is known to stagger the imagination. It is a tremendous leap from the outermost bounds of the solar system to the nearest fixed star, which is 200,000 times remoter than the sun, or 20,000,000,000,000 miles. Light itself, flashing with the inconceivable velocity of about 185,000 miles a second, takes three years to come to us thence. But most of the stars visible to the naked eye on a clear night send us their light from distances we cannot yet measure.

Billions of miles and light-years are but meaningless words. It is, however, possible to bring star distances roughly within our grasp by reducing them to scale with a sufficiently small unit. Taking the distance from the earth to the sun as the unit, and supposing it reduced to one inch, then, on this scale, the stupendous distance which light traverses in a year will be represented by one mile, and the distance of the nearest fixed star by three miles ; and so with other known star distances a mile to a light-year. The brightest stars are not always the nearest, else the problem would be much simplified. Sirius is one million times as far from us as the sun, and yet the sun, which is to us as bright as 20,000,000,000 stars each equal to Sirius, if removed to the distance of that magnificent star, would send us only about one-fiftieth part of the light Sirius now sends us. There are stars visible to us so inconceivably remote that the light by which we now see them left there a thousand years ago.

On a clear night 3,000 stars may be seen in England without a telescope. Argelander chartered 324,188 stars in the northern hemisphere, all visible in a telescope of 3in. aperture. Each increase in the power of the telescope multiplies the numbers visible, while the sensitive photographic plate shows the existence of stars that are probably beyond the reach of the most powerful telescope that can be made.

There are in the Milky Way at least 20 000,000 stars. Each is probably attended by 50 planets—a thousand million heavenly bodies in this one cluster, of which we are supposed to occupy an insignificant corner. But there are, beyond this, known to us some 3,000 star clusters, each representing a Milky Way like our own. If 2,000 of these are as large as our Milky Way, the number of stars mounts up to 40,000,000,000 or, 2,000,000,000,000 heavenly bodies. To view these at the rate of one a minute would require 3,840,000 years.