THE STARRY HEAVENS.

Thames Star, Volume LVII, Issue 14725, 2 August 1921, Page 8

THE STARRY HEAVENS.

A DEEP STUDY. '

MATHEMATICAL ASTRONOMY

Lecturing on astronomy at Dunedin Professor White stated that in primitive times man had leisure to study the stars, but as the demands of civilisation became more complex .this oldest of sciences drifted somewhat into the background. The daily recurring pherioma of the heavens, so familiar to us, seen every day and night of our lives, were viewed with indifference and it required the appearance of a comet and the threatened destruction of the earth to arouse any interest. Mathematical astronomy was rightly regarded as a very difficult branch of science, which only a few could understand, but the subject had a popular side as well and that side repaid any study that was devoted to it. It was not known who first mapped out the constellations or who first gave them tneir peculiar and picturesque names. They bore the |same names to-day tV*t they had 4000 or 5000 years ago. The "Chaldeans, Babylonians and Adrians had left some authentic rocm'.s regarding the constellations, and some of the more conspicuous stars, and by their association of the simultaneous appearance of these stars with certain natural events it wap easy to understand that they should consider the stars ' as the controlling forces in bringing . about these physical-changes that indeed the stars ruled the earth. The Egyptians studied the stars more systematically and their reappearances were used to fix the beginning of the year and to determine their religious and civil festivals. The Pyramids of . Egypt had been the subject of much speculation,, and one curious circumstance to which he would like to call attention was that in the Great Pyramid there was a pasage directed at an anglo towards the Pole Star and another passage on the south side directed to the Pleiades at its culmination - at midnight at the vernal equinox. But it was to the Greeks that we were indebted rfor the fundamental principle's of scientific astronomy. They were great mathematicians and they applied this knowledge to the study of \ the earth as well as to the motion of the heavenly bodies. Hyparclus and Ptolemy were both great astronomers, but so long r as the Ptolemaic system Held sway no further I advance than that made by the Greeks was possible. MEASURING .THE UNIVERSE. Coming to weighing and measuring of the earth Professor White described the l .various methods by which this had been done so as .to attain results that' would be scientifically accurate, and outlined the various considerations such as shape, volume, density, etc, that had to be taken into account. Proceeding, he, described how the distances between the various heavenly bodies were measured and measured with an extraordinary degree of accuracy. He first of all explained what was meant by parallactic angle, or the apparent changes of placo which a body underwent by being viewed from different points. From this point he went on by means of diagrams to detail how it had been ascertained that the moon was a little less than 240,000 miles distant from the earth, and that it had a diameter of 2160 miles. The mass of the earth was 80 times greater than that of the moon, and the density of the latter three-fifths that of the earth. Speaking of the sun, he stated that, although to, our eyes it did not appear any larger than the moon, yet in reality its disc was 400 times greater than that of the moon, he acual difference being due to the fact that it was 400 times further away. The stin was 866,000 miles in diameter, and we could place 100 of our globes side by side across its' diameter, but even this comparison failed to give an adequate idea of its actual size. The volume of one sphere compared with another was repesented by the cube of their diameter- Measured in this way, the moon would be represented by the figure 8, the earth by 512, and the sun by 1,305,000. The mass of. the sun was to tho mass of the earth as 330,000 to one, and was indeed much greater than that of . all the planets put together. Calculated by parallax the distance of the sun from the earth was 92,908,000 miles and other jnethods of calculation had given appioximately the same result showing in the words of Professor Newcombe, "the striking correctness of the astonomical views of the earth." Dealing with the movements of the planets the lecturer stated that the student was at once struck by the fact that ">the whole movement of the solar system was essentially a problem of mechanics and higher mathematics, and that certain well-defined lines of calculation gave results that would inevitably verify themselves.