STAR DUST.

Auckland Star, Volume LVI, Issue 115, 18 May 1925, Page 8

STAR DUST.

TWELVE THOUSAND TONS A TEAK. (By W. J. C\ MURRAY, M.8.A.A.) It is estimated that over 12,000 tons of star dust fall annually on the earth. This dust may have originated from a comet, or be the fragments of two great stars which crashed in their orbits ages ago, or the result of some other celestial catastrophe. Usually it reaches the earth's surface as fine dust, but it first encounters our atmosphere in the form of a meteor, or, more familiarly, a "shooting star." These "shooting stars" are small masses, usually of iron or stone, either following in the orbit of a comet long since dispersed or circulating in interplanetary space. They impinge on our atmosphere with a terrific velocity, become incandescent through friction with the air, and in a few seconds are either consumed or they explode with great force, and the ashes fall to the earth as star dust.

In view of the tremendous number of meteors that hourly plunge into the earth's atmosphere, 12,000 tons annually is a very moderate estimate.

The average number of meteors visible hourly in the whole night sky from a fixed position varies between 30 and 60. But as only those within a few hundred miles are visible to an observer, the computed total is not fewer than several millions daily.

Shooting stars vary much in sizs, but assuming the average weight to be a quarter of an ounce, then the fall of star dust is close upon 100 tons every twenty-four hours. This fall is continuous throughout the year. It is at a minimum now, and reaches a maximum in autumn. Yet it would take a thousand million years tefore sufficient material had fallen to overlay the earth to a depth of one inch.

Occasionally meteors are so large, that they reach the earth's surtace before they are entirely consumed.

If their fiery flight has been seen by one or two competent observers, the place where they lie buried can be determined and their composition discovered. Limestone and magnesia, iron, and sometimes nickel are found, but so far no element not known on earth has been discovered.

The fine dust which collects on our shelves and cornices contains a small percentage of star dust. But among the largest "pieces of star dust" that have yet been recorded is that which fell in' Greenland and was conveyed by Commander Peary to Xew York. It ■neighed 36$ tons.

"America has made the world what it is." says a. Chicago ■ senator. Yet Trotsky in his latest book blames Great Britain for it.—"Punch.''