Some Fresh Ideas on an Old Subject.
Originally published in Pearson's Weekly (C. Arthur Pearson Ltd.) vol.1 #24 (03 Jan 1891).
The early astronomers, gazing at the sapphire skies of Chaldea and Arabia, counted 3,000 stars in each hemisphere, 6,000 in all, and down to the time of Galileo this was supposed to be the whole number. But Galileo's little eyeglass showed that the 6,000 were only the beginning, and hardly that, for behind them were other thousands that had been shining unseen from the dawn of creation without their existence having been suspected.
And this was not all. Galileo's glass revealed four stars where one had been counted before, but a somewhat larger and better instrument doubled the number again, and, as the improvement of telescopes went on, astronomers ceased to count, and contented themselves with estimates.
Twenty years ago the number was placed at twenty millions; ten years later this estimate had to be doubled; and the multiplication process did not stop even here, for photography has recently come to the aid of astronomy, and the camera has reproduced on the sensitive gelatine dry-plate swarms of points of light so faint and minute as to have hitherto escaped the keen vision of the most assiduous and patient searchers. Indeed, in the last seven years photography has pushed back the confines of the stellar universe so as to multiply the number of stars five hundred-fold, and substitute milliards for millions in astronomical computations.
The distances of these photographic stars are inconceivable, and the attempt to grasp the numerical-expression of them only staggers the mind. But the human mind is very ingenious. It may do in one way what it cannot do in another. And a cannon-ball illustration, which combines motion and time in the same phenomenon, enables us to form some idea of these tremendous stellar distances.
A modern bolt starts from the muzzle of a rifled gun at the rate of about one thousand miles an hour, which is the speed of the earth's axial rotation at the equator. Suppose one of these bolts was endowed with the power of maintaining its initial velocity, and of moving perpetually forward in a straight line, without being arrested by the attraction of any of the heavenly bodies near which it should pass. Suppose, further, that it were fired straight at Alpha Centauri, the chief brilliant in the southern constellation of the Centaur, and believed to be the nearest fixed star to the earth; and imagine that some daring and adventurous explorer should manage to mount it at the moment it emerged from the muzzle.
In ten days he passes close to and abreast of the moon, and is appalled at the solitude and desolation of that crater-pitted cinder. But our satellite is soon left behind, and in six and a half years the explorer reaches and crosses the orbit of Mars and enters a region infested with planetoids, air stones, and other cannon balls.
If fortunate enough to pass through these swarms without being beaten to pieces, in forty-eight years more he crosses the track of the giant planet of our system.
Sixty years more bring him to the orbit of Saturn, and still another period of a hundred and thirty years to that of Uranus.
It is growing dark and cold, and the adventurer experiences a feeling of horror on looking back at finding that the earth has disappeared, and the sun itself has shrunk to the size of his fist. Nevertheless he continues on his course, and, after another long and weary period of a hundred and forty-five years reaches the orbit of Neptune, the first-born and most distant of the solar family.
He is now on the frontier of the solar system; but he is four hundred and ten years old, allowing him to have been twenty-one when he started, and although he has travelled twenty-eight hundred million miles, or thirty times the distance of the earth from the sun, he is amazed and discouraged at finding that he has only taken a step in the prodigious journey.
The Centaur's chief brilliant is no larger and brighter, and, apparently, no nearer, than when he started. And no wonder--for, before him stretches an abyss eight thousand times as wide as the distance he traversed.
It would take that cannon bolt, plunging into the cold, dark depths, three millions of years to cross it and reach the point of destination. And yet, Alpha Centauri is our nearest neighbour of the fixed stars.
A ray of light moves with such inconceivable velocity that it might wrap itself eight times round the earth between two ticks of a clock; and yet it would take that ray of light fifty years to come from the North Star to the earth. When we look at that steadfast, unchanging sentinel of the pole at night, we see it in the light that left it half a century ago, and if the Omnipotent hand that formed it, and set it in its place, should suddenly destroy it, we would continue to behold it in its own light fifty years after it had ceased to exist.
The very foundations of knowledge dissipate before these vast inter-stellar spaces, for we have no assurance, while gazing at the lilac scintillations of the great Dog Star, that "King of Suns," as astronomers call it, that it did not pass out of existence before we were born.