TOTAL ECLIPSE OF SUN

Otago Daily Times, Issue 18446, 6 January 1922, Page 3

TOTAL ECLIPSE OF SUN

VISIBLE IN AUSTRALIA IN SEPTEMBER. BRITISH OBSERVERS- FOB CHRISTMAS ISLAND. The first total eclipse of the 'sun visible in Australia, since the earliest settlement in--the continent will take -place on September 21, 1922. The South Australian G,overnment Astonomer (Mr Dodwell) poipts to the important field for investigations, and the beauty and rarity of the phenomenon. The total eclipse gives a possibility for testing Einstein’s general theory of relativity, which has revolutionised the ideas of scientific men regarding the nature of space and time. One aspect deals with the action of - gravity on a beafn of light, and shows that rays of light are attracted in common with material bodies towards a heavy gravitating body, and that to a definite degree which may be predicted. This prediction can he tested during the total eclipse of the sun, and then only. Mr Dodwell points out .that Wallal, on the West Australian .coast, has the clearest skies and lowest rainfall, as well as' the longest duration of totality, but the possibility of a thin veil of cirrus cloud, which not infrequenty occurs, must not be overlooked. This would prevent photographic observations "of stars near the sun at the time of the eclipse. .Christmas Islandhas been provisionally selected by the British expedition for observation purposes, but it has only a short duration of totality, and a, heavy and variable rainfall. A map prepared by Mr Dodwell show6_ the line oi totality passing through Oordillo Downs, in South Australia, and the Lord Mayor Of Adelaide has urged, in view of the weatherconditions in the far north, that an effort should be made to'induce the British expedition to visit the South Australian station instead of Christmas Island. The Greenwich party going to Christmas Island will consist of Mr H-_ Spencer Jones, chief - assistant, and Mr P. H. Melotte, the discoverer of the eighth satellite of Jupiter. They will leave England early m February for Singapore,. whence they and their equipment will be conveyed to the island by a steamer belonging to the Christmas Island Phosphate Company, which is giving valuable help to the project. Participation in the expedition has rendered it necessary for Mr Melotte to resign the joint honorary secretaryship of the British .Astronomical Association after eight years’ service. A joint Dutch and German expedition, the personnel of which will include . Pr<> fessor Voute, of Batavia University, and Professor Freundlich, of Germany, will also go to -Christmas Island, and it is possible that Professor Einstein will himself be present to observe the eclipse. . It is hoped to confirm the results obtained by the British expeditions at Pimerpo _ and Sobral during the eclipse of May,. 1919, when Einstein’s prediction as to tee value of- the deflection of a may of light pasang through a: gravitational field was verified by measurements of the position of stars in the immediate neighbourhood o£ the sun during totality. . . . ; As an eclipse expedition is necessarily in the nature of a gamble, owing ,to the uncertainty of weather conditions during, the few minutes of totality, it has been , arranged that -the Greenwich expedition, which will have erected its instruments, by May, shall carry out an extensive programme of photometric work. Based on the Harvard standard sequence of stars at the North Pole comparisons will be made of areas in South Declinations 30deg. and 45deg., with areas in North declination 15deg. Magnitudes of stars in the latter zone have already been determined, at Greenwich in direct comparison with those in the North Polar area, and the photographs to bo taken at Ohnstmas will- enable work on these lines in the northern and southern hemispheres to bo linked up by southern observatories. The equipment to be taken by the British party will include the 13in astrographio telescope used in the making of the Greenwich sections of the international photographic chart of the sky. , The path of totality will begin in Abyssinia, pass over the centre of Italian Somaliland, and across the Maldivo Islands, where Mr J. Evershed, the director of the Kodai-, kanal Observatory (India), will bo stationed. At the Maldives the duration of totality will be 4mip lOseo with the sun -34 deg. above tho horizon. At Christmas Island the duration will only bo 3min 42sec, but the sun will be 78dog above the horizon. The maximum duration, nearly 6miru, occurs over the Indian Ocean, where'no obtorving station exists. After leaving Christmas Island the path of totality crosses Australia in latitudes which, except in Queensland and in a comer of Now South Wales, are to tlio north of the inhabited regions of the continent, and ends near Norfolk Island in the Pacific. No_ part or phase of this eclipse will be visible in the United Kingdom. This year will be singularly barren of eclipses. There will only be two. in all; both of the sun.- In addition to tho total eclipse there will be one ; on March "28, which will be visible as an annular eclipse in portions of Brazil. West and North Africa (including Egypt), and Arabia. In the British Isles it will be seen aa 'a small partial eclipse, about one-fifth of the gun’s disc being obscured. As the eclipse beginsat Greenwich at 1.19 p.m. 'and ends at 3.8 p.m. it will be readily observable, bat will bo ,of little interest. f ■■ ' ' »