ASTRONOMICAL NOTES

Press, Volume LXXI, Issue 21387, 1 February 1935, Page 17

ASTRONOMICAL NOTES

FEBRUARY, 1935 {fMfiii.LT warm* job the tbess.) [By ®- HOGG " UA ' F.R.A.S.] Th£ planet Mercury sets on Febi a t 8.40 p.m.: it is approaching *?7 sun and will be in conjunction jt on February 17. It may be in the eastern sky at the end of g)£ month. Venus sets on February 2at 8- 49 P m - and 011 Febru ary 15 at U2 pjn. Mars rises on February 1 ,j 10.47 p.m. and on February 15 at jj pjn.; Jupiter rises oil these dates jt 11.52 p m. and 11.5 p.m. respectively, gaturn seis on February 1 at 8.43 F pjn-i wi!l be in con j unc tion with sun on February 20, and a contime will elapse before it will be visible in the eastern sky. There will be a partial eclipse of the on February 4; it will be invisible jsKeu' Zealand. The area over which it can be seen corresponds roughly yitb North America and Greenland.

Greenland's Westerly Drift Scane years ugo the late Dr. Vtgener, reviving an hypothesis due" ta Daly, succeeded by his skilful advocacy in interesting the whole scientific world in the theory of drifting continents, which supposes that our jjtnd areas are not rigidly attached to tije earth but float on the surface of an underlying semi-liquid stratum, so tljat, under the action of lunar attrac-' tKB and other sources, they move relatively to each other and may in the course of ages undergo great displacements. The theory appeared to ejfer a solution of many difficult problems connected with the occurence of ice-ages in semi-tropical jaods and the distribution of flsid animals over the earth's surface." The land-mass whose displacement Itemed to have the best observational basis was Greenland,. and the recent publication of a new measurement of U»e longitude of Sabine Island, on the cast coast of Greenland, is interesting from its bearing on Wegener's hypo-v thesis. The longitude of Sabine Island wa first determined by Admiral Sabine is 1823: it was measured again fcy the astronomers of the Germania expedition and in 1906 by a Danish expedition under J. P. Koch. A comparison of the results so obtained led Wegener to postulate that Greenland is drifting in a westerly direction at the rate of about 30 metres a year. Heccntiy the Norwegian Government organised an expedition under ..Hans S. Felstrup to make a new determination of trie longitude of Sabine llsJand. using all the most modern ap;piiances and facilities available. The * results of Felstrup's work have now '-been published, with a critical exP*- : -ation of all previous records, rup is of opinion that there has "a real displacement of Sabine , jMjrad to the west between 1870 and 53332, the amount of which, after allowing for all known sources of error, he estimates to be 250 metres. This drift in the sense required by Wegener's theory is at the rate of 13.2 feet a year or a mile in 400 years. If this rate represents the average movement for a long period of time, it follows that, assuming the mean distance of Greenland from north-western Europe lo be 2000 miles, some .800,000 years have been required to effect the pretest separation of the two masses—a figure which is in approximate aereement with estimates of the date ot the last glacial epoch, subsequent to which Wegener concluded that the separation had taken place. Another Longitude Variation With the advent of wireless telegraphy and improved technique in time-measurement, the determination el the difference of longitude of

title, "Southern Stars," to take the place of the cyclostyled monthly notices which have appeared almost since the inception of the society. Congratulations are offered to the society on its courage in making this new venture and to the editor of "Southern Stars," Mr I. L. Thomsen, for the attractive form he has -given to the journal and the excellence of the matter he has placed before his readers. The numbers already issued clearly indicate with what zeal the members of the different observing sections are working. A large mass of valuable information is being accumulated on such matters as star colours, variable stars, meteors, sun-spots, the Zodiacal light, etc., and, as "Southern Stars" is transmitted to many of the leading observatories, this information reaches a considerable body of workers for whom it has a special interest and value. The circulation of the new journal will assist much in giving New Zealand its proper place on the astronomical map and also in drawing attention to the importance of the Dominion as an observing centre. The inter-change of "Southern Stars" with the journals of Home and foreign observatories will lead to the building up of an astronomical library at Wellington, the headquarters of the society, which will be of great use to all engaged in active research, enabling them to check results and also learn in what new directions their subject is expanding. All interested in astronomy will wish Mr Thoinsen and his collaborators every success in the future. Dr. W. de Sitter The death of Dr. Willem de Sitter at the comparatively early age of 62 has removed from the ranks _of astronomers one of its most gifted students and has deprived his country, Holland, of one of its most famous men of-science. Though Dr. de Sitter is most' widely known as the propounder of the "de Sitter Universe," his most valuable work has been his contribution to the theory of the motion of the four major satellites of the planet Jupiter and his reorganisation of the Leyden Observatory. The years 1897-99 de Sitter spent at the Cape Town Observatory, whither he had been invited by his Majesty s astronomer, Sir David Gill, to assist in. the discussion of the heliometer observations .of the Jovian satellites, a subject which gave full scope to his great mathematical attainments and to his interest in the practical side of astronomy. He spent many years studying this extremely difficult system, and it was not until 1929 that he became satisfied with the results obtained and published his definitive values of the masses and orbital elements of the satellites in question. In 1918 he became director of the Leyden Observatory, one of the oldest in Europe. (It celebrated the tercentenary of its foundation in 1933.) De Sitter applied himself to its reorganisation with energy and far-sighted-ness and rapidly succeeded in giving it a foremost place among such institutions —a fact which was fittingly recognised by his appointment as president of the International Astronomical Union for the period 1925-^B.

Cosmical Problems When the scientific world had given a general acceptance to the relativistic theories of Einstein and to his amended law of gravitation, it was only natural to apply the new knowledge and methods to the solution of the problem of ascertaining how our cosmos has attained its present state. We know that each moment it is changing;; in all stars matter is passing into radiation and, as we have no sufficient reason to believe that the reverse process—the passage of radiation into matter—is taking place anywhere in space, we can only look forward to a very distant date when all the matter which can pass into radiation has done so, while such matter as remains has fallen to a temperature at which life as we know it cannot be maintained. The de Sitter Universe It is no part of the duty of science to explain how the matter of which the galaxies and their constituent stars and nebulae came into existence but, given such matter, we can speculate as to its original form and the steps by which it has passed. These speculations have led to the presentation of a series of "universes"; at one end of the chain is the Einstein Universe, at the other is the de Sitter Universe, while the others occupy in-