OUR NEIGHBOUR MOON

Taranaki Daily News, 26 April 1930, Page 17 (Supplement)

OUR NEIGHBOUR MOON

LITTLE WORLD NEAR US.

(By Rev.

B. Dudley, F.R.A.S.)

Apart from the sun, which of necessity takes a large place in the physical economy of daily life, the moon is the most interesting of the heavenly bodies. But for the fact that wo actually see it with our own eyes, wo should never, with all our modern scientific knowledge, have imagined anything like it. The mo-on presents one of the problems of the solar system, and remains, although so near, a riddle to the astronomer. If she is queen of tho night, it is her “glory to conceal a thing.” She both helps* us in coming t-o conclusions about the universe and baffles us in our attempts to read the story of her own origin and history. Though so familiar an object, she is one of the marvels of tho cosmos.

Our satellite is but one of many. In tho solar system, to say nothing of other possible systems, .there aro no less than twenty-seven moons. The planet Neptune, remotest of the solar worlds, owns one; Mars has two, Uranus four, Jupiter nine and Saturn ten. Venus and Mercury, on the other hand, arc devoid of satellites. This article is concerned entirely with the ono that looks into our windows “oft in the stilly night.” This remarkable little world is in the unique position of being the nearest of the heavenly bodies to the earth, and in spite of the mysteries connected therewith, we know more about her than about., any other object in the skies. The mean distance cf our satellite from the earth is 237,000 miles. As, however, the earth docs not occupy a position exactly concentric to her" orbit, her distance from us varies i considerably. Sometimes she is only 221,000 milel from the centre of the earth, while at her maximum distance she is as far as 253,'000 miles away. Speaking broadly, we may state her distance to be 2-40,000 miles. -

In comparison, the moon is a small body, being but 2,160 miles in diameter. It would require fifty moons rolled intoono to make a body as large as the earth. While there are moons in the solar system larger than ours, these bodies are, as an Irish astronomer once put it, “very largely smaller.” Titan, one of Saturn’s satellites, for example, is considerably over 3,000 miles in diameter; as large, that is, as the planet Mercury. Phoebe, another of Saturn’s attendants, is almost the twin of our moon in size. Other moons are small bodies but 500 miles or less .in diameter. The weight' of objects on - tlic lunar surface is much less than here, being in the proportion of one to six.?" Tht weight of a body depends entirely upon the gravitational pull which it receives. The force of gravity at . the earth’s surface is six times as great as that at the surface of the moon. A man weighing twelve stone would, if-suddenly transferred t-o the lunar surface,.' weigh no mere, than 28 pounds, and find himself (other things being equal) so wonderfully agile that a day’s march would be as easy as eating a meal, while his powers of endurance would be enormously increased. Were he to visit planet after planet in turn his weight would regularly alter according to tho force of gravity at each planet’s surface.

From tho spectacular point of view, the special attractions of the moon mo its mountains, craters, walled plains, clefts and rills. Among those the most distinctive features are tiie so-called craters. These are numbered by thousands,' and it' is ’ doubtful whether .they are correctly named. A crater is, as we understand it, formed by volcanic action, but it is by no means ■certain that the lunar craters were so originated, although many astronomers still think they were, According ,to some experts this crater-like scenery is the result of meteoric bombardment, enormous meteoric masses having made such impacts upon the lunar surface as to give rise to the pitted, appearance that is. so well known to observers with -the: telescope. The question is at present in an unsettled state, and must be left in abeyance in the hope that tne future may yield more light on the subject. So far as is known, there is neither atmosphere nor water in the moon. The “seas” are' only called so accommodatively. If there is any such thing as an atmosphere to the moon, it can be only a fraction of that of the earth' in density—say, one eight-thousandth, as Pickering estimates. ' Some of these facts-themselves answer the question whether there can 'be life on the satellite. No air, no water; these are conditions that forbid the opinion that tho moon is the abode of life such as we understand it. The suggestion has. ..-been made that perhaps traces of atmosphere might be found at tho bottoms of the lunar clefts already mentioned, and that 'this could support feeble forms of life. But a discussion pf the subject must at present be ended with the confession that we do not know, ■

It is held by some astronomers that tlie attraction of the sun upon the moon is such that in time the larger body will disturb the present apparent harmony of the earth-moon system, and ultimately bring the moon back to the earth whence it -originated, the two bodies finally being one again as before they were separated. Professor Pickering, the exponent of this theory, says that in his opinion our satellite had its origin in the Pacific. This ocean, as is well known, is roughly circular, and apart from Australia contains no large land masses. Our planet, Pickering boldly suggests, long ages before the moon’s birth, was already covered with a slight crust, “in tearing away that portion which was by and by to become the moon the remaining area of the crust was rent in twain by the shock. In that way were formed the two great continental masses of the old and new worlds. These masses floated apart across the fiery ocean, and at last settled in tho positions they now occupy.” Thus the Professor accounts for the remarkable parallelism existing between the opposite shores of the Atlantic.