Figures that Stagger Imagina"
-tion: Dr. Chatley's Lecture Dr. H. Chatley in addressing thd Quest Society at the: first. meeting of the' session on October spoke on the subject of stella distances, He explained how the istence of the Moon was found, by, simultaneous observations from different points on the Earth and how the strength of the sunlight reflected from the Moon enabled an approximate estimate of thd distance of the Sun to be made, He spoke of the known propor= tionate distanecsgof the planets from the Sun aid described how simultaneous observations of Mats, Venus and Eros, when nearest the Earth, from different places on the Earth enabled the Sun's dis~ tance to be computed. The apparent immobility of the stars in spite of the Barth's huge annual swing of 200 million miles indicates their immense distance and he described how eventually the distances of the nearest stars were found by, observation of tae small annual di placements. The method of parative "parallaxes" for near and distant stars and the method of deducing the orbits of double stars was then described and. reference was made to the velocities in the Tine of sight derived from the spectroscope which when compared with the cross motions indicated roughly the distances of stars.
Until 1913 the only other available method of extending these reits was by assuming that alt tars resembled the Sun in, light and dimensions. The nearest ones ('ive light years away or say 30 million million miles) do roughly combat ed to the Sun, but there is a lot of variation in individuals, Since 1013 new methods based on the study of the spectra of the stars have enabled fair estimates as te temperature, size nnd luminosity, to be made from which, together with the observed magnitudes, the dist, has also mn found possible actually to men= sure the diameters of few stars, The regular variation in the light of certain pul stars called Cepheids has also to be made of the distances of very, distant groups and nebulae,
Text read from the printed page and cleaned; old type leaves the occasional error.