WHEN A STAR FALLS.

Hauraki Plains Gazette, Volume XXXVI, Issue 4825, 1 May 1925, Page 4

WHEN A STAR FALLS.

THE STOUT OF A METHOB. Shooting stars, or meteors, us they are technically termed, are among the most beautiful of the phenomena to be seen in our night skies (writes William Pick, B.Sc., F.R.A.S., FR. Met,S„ in the Newcastle Weekly Chronicle). What is seen as the shooting star is the jinal catastrophe in a long chain of events.

The whole of they universe is filled with tiny particles of matter revolving at planetary speeds, at speeds so high that the fastest train would ap : pear stationary in comparison.

Through some caujse or other such a particle is drawn into the earth’s atmosphere. Entering that atinosphere with prodigious speed, it forms in front of itself a small cap of highly compressed air. If a gas be rapidly compressed its temperature, rapidly rises. As the compression in front of the meteor is extremely high, the process cxremely Quick,- the temperature of the cap of air becomes intense, a temperature that has been estimated to be between '4OOO and 7000 degrees Fahrenheit. This intense heat quickly causes the solid matter to turn into vapour, and it is at this point that the shooting star becomes visible, for it iis believed that the. light'evolved is manufactured by .the collisions of the vapour particles with the air particles

in the cap. Very quickly the meteoi

is completely vapourised.and, the, collisions over, the light fails ; and as a visible shooting star the careejr of the meteor is ended. .

; ..It is al.l; : a wonderful illustration' of what, results can be obtained from .-very little, for • the meteor itself is generally only about one twenty-liftn of an inch in diameter. Of what, then, are these meteors competed ? Da they contain elements not known on earth ? Or, iw it the’case that in die nature of things their structure' cannot be determined ? All these questions can be answered because of the fact that occasionally the meteors are larger than the size already given, and that in consequence they..are not completely consumed, and thus fall on the eaith ready for the analysis of th.) chemist. Those that fall appear to classify themselves rnto three gio ups, to which groups the names Aerolites, siderites, and siderolites are given,, the aerolites being similar in composition to certain rocks, the sidei ites being composed roughly of an alloy ol 95 per cQiit. iron to 5 per cent, nicke., and the siderolites being intermediat: in composition, partly stony and partly metallic. To quote from A. .?■ Hinks’ “Astronomy” : “Im no case has there been any evidence of the presence of an element not found in. the crust of the. earth.” Another proof in support of the one-ness in make-up of ths widely scattered bodies of the universe I

A further interesting subject is the height of the shooting stars. Very seldom, indeed, is. the height of such a star above 100 miles, but occasionally they have been observed as high as 200. Denning, who is, perhapis, the best known English authority on these matters, gives the average height of first appearance as, roughly, 74 miles, and that of disappearance, as, roughly, 45 miles. Their average speed he gives as 27 miles a second, and the average length of visible train as 62 miles.

It is interesting to realise one lesson that the shooting stars teach. Inasmuch as they become visible owing to the compression of a cap of air in front of them, and as.- some have been noticed at a height of 200 miles, then our atmosphere must extend at least up to that height. Very atten-uated-it must be, it is true, but neverthe less even at that high altitude U must be of an appreciable density. The thickness of the belt of air girdling our earth is not, therefore, so little as we might be pardoned for thinking; at least 200 miles, it probably is very much greater, though exactly how much greater cannot yet be told, that being one of the mysteries still left for man to solve.