A NOTED ASTRONOMER.

Hokitika Guardian, 5 August 1922, Page 4

A NOTED ASTRONOMER.

STUDIES OF THE' ECLIPSE. 1

EXPEDITION TO WALLAL.

WELLINGTON, July 31

Oil of the world’s leading astronomers, Dr William Wallace Campbell,

director of the Lick Observatory, arrived in Wellington yesterday on his .way to Wallal, West Australia. He is

the leader of the Lick Observatory Eclipse ExpFdWon' which has been organised in accordance with the policy of the observatory to study solar eclipses at all available opportunities. This is the seventh eclipse expedition in which Or Campbell has taken part Resides being president of the International Astronomical Union, he is chairman of the eclipse section of the AnieficaiV Astronomical Association and n member for America of the International Eclipse Committee. Dr Campbell stated that the party which will he stationed at Wallal will 1 comprise besides himself and Mrs Campbell’ (who will' be one of the observers), Dr J. H. Moore, Associate Astronomer of the hick Observatory, and Dr Trumpler, also of hick, wild' passed through Wellington a few weeks ago. They will he joined here by Dr C. E. Adams, Government Astronomer, and Mrs Adams, and later by Mr Husking, Astronomer at Melbourne University, and Professor Ross, of the University of West Australia. TherA will he three other parties at Wallal, one from Perth observatory, one from the University of Toronto, and a third from England. The Royal Greenwich observatory’s expedition is now at Christmas Island.

Wallal, which lies fairly in the centre i line of the track of totality, a belt roughly 130 miles in width and ex- ! tending from llarri in East Africa to a point north of New Zealand, is ; “placed on the map” by the event, (or lit is no mere than' a post and tek>I graph station in an almost deserted ! region though, fortunately, close to a | well-known’ runhold’evs' station. Trans- ! port and other facilities arc very scanty, but the Commonwealth OovI eminent lms made provision, which Dr Campbell describes as exceptionally liberal. From the moment the expedition sets foot in Australia, tlie members will he the guests of the Governincut; which is not only transporting the party to Perth and then bv sea I to Broome and back to Wallal, but is , sending a naval party to Wallal to j establish the camp and assist in erect- j ing the apparatus. [ The observation of a solar eclipse j is a remarkable undertaking. The J magnitude of the preliminary work can i be gauged from the number ol the per- j sonnel and front-the fact that as much j instrumental ef|iiipir.enl is used as can j conveniently be operated by those eon- ! Conibd. The eclipse, however, does not choose its occurrence to suit the convenience of man. The observatory is a purely temporary installation in which the instruments cannot have such j stability and refinement as are possible j in a peEnanent establishment as, in j this instance, it is often necessary in j order to secure the most favourable astronomical and weather conditions to j go to out of the way places to make j the observations and the totality of j the eclipse lasts only a little time. At j Wallal it will be 5 minutes It) seconds. I l)r Campbell explained that in order. to make the best use of the short time > available it bad been found advisable | not to attempt too much. Photo j grnphy is the most important part of j the work to be done, and during sev j oral days before the eclipse the mem- 1 hers will be put through full rehear- | sals until the actions necessary become almost as automatic as those of walking. Tn that way it is possible to eliminate nervousness and without any undue haste to carry out a surprising amount of work.

A special section of the work, Dr Campbell stated, had been allotted to Dr Adams and Mrs Adams. They would have charge of a 40ft telescope with a five-inch object glass, with which a series of photographs would he taken of the eclipse from just before until just after totality. The images of the sun and moon in these photographs would he about' four inches ill diameter, and their purpose would he to provide very exact data as to the precise time of the phases of the eclipse, and also as to the relative positions of the sun and moon. The photographs might he expected to provide the basis for exact measurements of the apparent diameters of the sun and moon. The time determinations would he compared with time signals sent by wireless from the Berth Observatory, and very accurate measurements should he possible, ns the moments at which the photographs are taken would he recorded h.v electrical means for comparison with the standard time.

Unusual public interest has been aroused in regard to the September eclipse because of the test which it is proposed to apply to the famous Einstein theory of relativity. Dr Camphell said lie did not care to commit himself to a definite statement as to the validity of the theory, which appeared to have Ih’ch remarkably confirmed hv the observations of the eclinse of 1919, hut the evidence, astronomical and otherwise had up to the present been strong, lv in favour of the Einstein theory as representing an actual fact of Nature, hilt many scientists, including those whose observations in 1919 had been so fruitful and apparently successful, felt that the importance of the matter required that confirmation should he sought. Professor Einstein argued that in accordance with his tlieofv rays oP light passing close to a larger mass, such as the sun, and thus tTlrmigh an intense “gravitational field,” should he deflected from their straight path by a definite amount. The stars by whose light the theory can alone he tested cannot be seen when near the sun under ordinary conditions, hut become photographically visible during total eclipses. Dr Campbell is confident that the photogfnphs to he taken at AA'allal on Septemlier 21st, when compared with those which Dr Triimplef recently made at Hawaii, will produce Hie most valuable evidence, hut whether the displacement of the star | images will conform exactly to the amounts predicted by Professor Einstein remains to he seen. This test is one of extreme delicacy. It is itn- j possible to photograph stars very close to the sun because they are hidden in the glare of the corona, and those further away are snhject to less displacfe-

nibiit. The astronomers moreover, have to tabe the conditions that offer themselves. They cannot arrange an eclipse to take place in the neighbourhood of the bright stars, and they cannot throw away satisfactory records and make a fresh sot of observations. Fortunately, a further opportunity *oi the .test- will occur in September, 1923. when a total eclipse will be dhservanl? in Mexico and Southern California. I'