LAMPS OF THE FIRMAMENT.

Shannon News, 22 June 1928, Page 3

LAMPS OF THE FIRMAMENT.

THE PLANETS AND THEIR PLACES. * \NCIENT STAR-GAZING AND MODERN ASTRONOMY. The old yet ever-new subject of astronomy was given a lucid exposition by Professor D. M. Y. Sommarville, of Victoria College, before a large audience in the Century Hall, Levin, on Friday evening. The title of the lecture was "The Solar System," and the Professor's remarks were illustrated by a series of appropriate lantern views. Mr W. G. Bis r hop, president of the Levin branch of the W.E.A., under whose auspices the lecture was given, occupied the chair, and he suitably introduced the lecturer.

PRIMITIVE IDEAS OF THE HEAVENS.

At the outset,. Professor Sommerville stated that astronomy was such a wide study that he could only hope to touch a small part of it in one evening. The apparent movements of the stars acioss the sky, as .noticed by the lay man, were in the main due to the changing position of the earth in its course round the sun; while the twinkling of the stars was due to the action of the earth's atmosphere. There were stars that moved about the heavens, and they were the planets —a name meaning wandering stars. They were known "to the early Phoenicians, who were great star-grazers, but in whose system the sun and the moon were included among the planets. The ancients recognised live planets: Jupiter as the largest and Venus as the brightest; Saturn (which could be seen late at night at present crossing the northern sky); Mars, the red star; and Mercury, which they discovered despite its 'smalln.ess and its proximity to the sun. AJI these bodies occupied very important positions in ancient mythology and astrology, and their names were given to the days of the week. The ideas then held as to the motions of the planets were very crude as compared with those accepted now, for it was thought that they described separate circles, or epicycles, within their orbits, and that they revolved around the earth. As Saturn was the slowest moving planet, the ancient astronomers supposed it to be the furthest away. Next in prder they placed Jupiter, and then Mars; the sun came next, then Venus, then Mercury, and finally the moon. Those observers had no means of determining the distances of the various bodies.

NAMING THE DAYS OF THE WEEK

Saturn . was put in charge of the first hour of the first day of the week, and the other hours were governed by the remaining planets, in their order. On the next day the sun controlled the first hour; the third day commenced with the moon, the fourth with Mars, the fifth, sixth and seventh with Mercury, Jupiter and Venus respectively—and so' the days obtained their names. This system was continued into modern times by the Italian, French and Spanish races, with the exception that they had abandoned the names of Saturn and the .sun for days of the week which were named instead afe the Sabbath (after the Jewish observance) .and the Lord's day. The English still named two of the days after the sun and the moon, but in the others had replaced the titles of the Latin sjods with those of Saxon deities. RISE OF MODERN IDEAS.

The idea of the planets revolving around the earth existed until the time of Copernicus, who, in face oi much opposition, affirmed the principle held to-day, that they travelled arouno the sun. Copernicus, however, retain ed the old idea of epicycles, or smal. circles turning upon larger circles. Kepler effected a change by sweeping all the circles away and stating that the planets followed an elliptica. path. ' He laid clown his famous laws which included a simple law of varia tion of speed and a simple relation be twoen the times of revolution of th planets. From the basis provided bj Kepler, Newton was able to deduct his great law of gravitation—that tin sun attracts the planets with a force inversely proportional to the square of the distance. LOGIC OF SPACE. Professor Sommerville went onto refer to the curious order"or ratio oi distances from which it was assumor ■ hut a planet should have existed be nvc-en Mars and Jupiter, and where eventually the asteriods or minor plan ets were found to be. He showed tha ■che/e was an arithmetical progression in the intervening distances, roughly doubling the space from one planet to another, if the planetoids were counted as one body. The reason for this apparent ratio was not yet known. Towards the end of the 18th century the first new discovery of a planet in historical times was made, when Hersehell located Uranus. A search for a planet to fill the gap above referred to resulted in an Italian astronomer named Piazzi finding one of the minor planets. A year later a search for the same planetoid caused another to be discovered as well, and the idea arose that these might be fragments of a large planet that had burst. Other pieces were, looked for, and five such planetoids were found in a few. years. The largest member of this group as now known had a diameter of about 400 miles, and there were others so small that they could not yet be measured —they perhaps ranged to a diameter of 20 miles. The first was discovered on the first day of the 19th century, and others during a few years after that; then there was an interval till the middle of the century, after which more had been discovered every year. > Over 1000 had now been listed; last year 90 were located. Finding names for them was a difficult business, and many of them only had numbers. .With regard to Uranus, variations of orbit were noted, and astronomers were led to think that something must

be pulling it out of its course. The Englishman, Adams and the Frenchman Le Verrier set to work to calculate what should be the path of the unknown planet, and eventually it was identified, having appeared on the date predicted. This was the planet Neptune, the outermost body, so far as was knoWn, of the solar system. SOME INTERESTING OBSERVATIONS. The lantern views were then shown, and the Professor expounded many- of the mysteries of the heavens. In was learned, for instance, that the year of Mercury is only 90 days, whereas that of Neptune is 160 years. Venus at its brightest can only be seen as a crescent through the telescope, owing to the relation of its orbit to the sun. Mars has cold polar regions, with a cap of snow or ice, which diminishes in the Martian summer and increases in the winter. There would appear to be a thin atmosphere, with little moisture content, and altogether it is rather a desolate kind of planet, which has passed its prime. The existence of an atmosphere is assumed as the re- V suit of photos taken with ultra-violet • and infra-red rays respectively. It is ' within the bounds of reason to suppose that there may be a race of in- i; telligent creatures living on Mars. In- ';, dications are given of the existence of vegetation, by colour changes. Low- ". ell, the American astronomer, observed •: the curious markings on the planet, and ; promulgated the idea that they were canals, probably constructed by eng-' ineers to bring water from the polar caps for irrigation purposes. If Mars is inhabited, the people should be more advanced intellectually than those of the because Mars is an older' planet. A picture was shown giving' H. G. Wells's fanciful conception of the Martians as octopus-like creatures. Mars has two moons, which are smaller than our moon; and they were only discovered 40 or 50 years ago. One of these moons revolves around the planet in about seven hours,, and the other in about 30 hours. Jupiter has. nine staellites, as far as is known, and Saturn is credited with 10. The ring of Saturn could not be a solid structure, as in such case it would collapse. It can be seen through in and is therefore believed to be composed of stones or very small satellites. In relation to the sizes of Jupiter and Saturn, their satellites are not very big; some of the larger ones of Jupiter may be twice, the size of our moon. Compared with the rest of the i solar system, the earth and the moon are like a double planet rather than a—planet and satellite. Views were shown of comets, and their movements explained. Some are known to consist of gaseons material, but others are thought to be merely collections of dust or stones. k The lecture was followed with much interest, and at the conclusion Professor Sommerville was accorded _ a hearty vote of thanks, on the. motion of Mr R. J. Foss. The thanks of the meeting were also expressed ty the Chairman to Mr Blackburn for having, operated the lantern; and the branch is indebted to Mr'J. A. Smith, Power Board engineer, and Mr Lunn, of Messrs Lunn and Henley, for assistance with the lighting arrangements.