SOLAR ECLIPSE.

Hokitika Guardian, 7 February 1922, Page 3

SOLAR ECLIPSE.

i NEXT SEPTEMBER. IMPORTANCE TO AUSTRALIA. On September 21 the first shadow caused by a solar esclips© will begin to steal upon the west coast of Australia in the vicinity of Wallal, shortly before noon, and travelling across the continent will touch the Pacific at about 2 o’clock in the afternoon. The eclipse will be a total one—the first observable in Australia since colonisation. As Australia is tlie only important area of the earth coming within the region of the sun’s eclipse on this occasion, the event becomes of great scien tific importance to the Commonwealth. Observers from many parts of the world are to take up. their stations south of tlie Equator for purposes of observing the phenomena of eclipse. During the passage of the shadow across Australia observations will be taken at several points between the Indian Ocean and the Pacific* The period of complete eclipse will vary, of course, at different points, shortening as the earth turns eastward, to be lost in the night on the waste of ocean north of New Zealand. ; The duration of complete darkness at Wallal will be approximately 5 minutes 15 seconds, at Goondiwindi about 3 , minutes 13 seconds, and somewhere in the region of 3 minutes at Lismor© and 1 Casino, as the shadow flits from the face of Australia. It is for the purpose of , seizing such advantages as may be offer- i ed during thre c to four minutes that j scientists are eagerly looking forward to j September 21. Issues of tremendous j importance to science turn upon the re- ; suit of these observations. ; The shadow thrown from interposi- ; tion of the moon between the sun and . earth will be about 114 miles wide. ; Hence, along a strip of that width from j roughly, Wallal to Lismore, observers j will be right within the track, so to . speak, of one of the great happenings ! in Nature. But far north and south I the eclipse will he seen to varying degrees of partiality, according to distance on either side of t-.ie shadow. Th ( ,, extreme southward limit of the eclipse will he a long way south of Tasmania, i For purposes of general understanding it- may he said that Sydney will be in the dusk of a four-fifth eclipse. Mel- : bourno will only be privileged to enjoy a three-fifth eclipse, but will receive additional particulars from Sydney. The phenomena associated with the various phases of the eclipse—that- is from the first contact to final contact—will bo in progress for about a couple of hours. These periods are, of course, merely approximations.

Observers from the United Stntes and Canada will establish themselves at Wallnl with Western Australian astronomers. The South Australian Government will send an expedition to Coridllo Downs station, in Central Australia—a remote hut very suitable spot that can only be reached by weehs of travel with camels. New South Wales and Queensland will operate at Gondiwindi, in South-eastern Queensland. An expedition organised hv the New South Wales branch of the British Astronomical Society, under the leadership of Mr W. F. Gale, the president, will proceed to Stanhope. The expedition from the Greenwich Observatory, under .Mr Spencer Jones, will conduct its observations from Christmas Island. Although Christinas Island lies some distance north of the central line of eclipse, it will have a duration of approximate totality last 3m 425. There this phenomena will occur at local noon, and it is considered to he a distinct advantage that observations should he recorded from a point at which the sun is at its zenith. British observers will also he at one of the .Maidive Islands. They will encounter the shadow at about 9 o’clock in the morning. Christmas Island has one distinct disadvantage—a heavy rainfall. The reason of the pending eclipse having created so much interest all over the world is that from the observations to be taken important lbwill lie thrown upon the Einstein theory of relativity, which has in some degree rocked physical science to its foundations, and seriously disturbed philosophy. What may he termed a phase of tin; Einstein theory bears upon the action of gravity on light—on the attraction of light by a heavy gravitating body. Observations in -May, 1919, by an Eclipse Expedition to Brazil and Principe supported the deflection theory of Einstein. September’s eclipse will submit the theory to more rigid test. Hence the enormous intellectual interest associated with the phenomena of which Australia will he in the direct path. Photography will play an important part in the coming observations. Plates taken during the eclipse showing the stars will be superimposed on plates taken at other periods, and measurement will reveal the extent to which light from these stars is deflected. But it is not only the stellar bodies that are examined during an eclipse. Important observations of the earth’s magnetism and atmosphere phenomena are contemplated