ASTRONOMICAL NOTES.

Press, Volume LXII, Issue 18888, 31 December 1926, Page 20

ASTRONOMICAL NOTES.

FOR JANUARY, 1927

SPECIALLY WRITTEN FOR THE PRESS.)

(By E. G. none, M.A., F.K.A.S.)

The earth will be in perihelion on .January 3rd, when its distance from the sun will he ahout !)1.440,000 miles, which is about 3,000,000 miles less than when the two bodies arc farthest apart.

The planet .Mercury rises on January Ist. at 3.1 D a.m. and on January loth at 3.0.j a.m.; it will he in superior conjunction with the sun on January 28th. It will rise well to the south of east and as its apparent magnitude is —U.;; en the earlier ill' the tivu above dates, it should he easily picked up during the first few days of the month. Venus sets on January Ist at 8.22

i. :■.... am! on januai.v l-'iih ai S.'-'O p.m. ; its apparent magnitude during the month will he -3.4. -Mars sets on the above dates at 0.38 a.in and 11.54 p.m. respectively: its distance from the earth will increase by about ■.V,000,000 miles during the month, and its apparent magnitude will fall from —0.4 to plus 0.4. Jupiter will set on January Ist at 10.8 p.m. and on January .15th at 9.20 p.m.; Saturn rises on these dates at 2.10 a.m. and 1.20 a.m. respectively. Duriii" next year there will be live eclipse.-,—three of tho sun and two of the moon: one of the solar n-liices will lie iiunnhi.. eiie Intnl. and

one'partial; both of the lunar oclipses will be total and visible in New £ealand.

There will "bo a transit of Mercury over the sun's disc on November 10th; the ingress of the planet will be visible in .New Zealand, but the sun v, ill havo set here before tho transit is completed. .During 1927 there will be sixteen ovulations of a planet by the moon as compared with those during the year just ended. Saturn will be occulted no less than twelve times, Venus twice, and Mars twice. The first of tho series occurs on January Ist, the earth, moon, and planet Saturn being in a line at 9.57 a.m.: in the latitude of Christchurch the phenomenon will, however, present itself as a closo graze. An occultation of Venus will occur on January sth at 3.30 a.m., but as the moon will be only eighteen hours old

then, it is unlikely that it will be seen. Saturn will bo again occulted on January 29th, soon after midnight, but the phenomenon will not be visible in New Zealand.

Sun Spots. A century has now elapsed since tSeliwabe began his observations of the sun, which eventually led to the discovery of a periodicity in tho waxing and waning of sun-spots; information has been gradually accumulated from which \vc have learnt that the outflow of heat from the sun's surface is greatest when tho number of spots reaches its maximum and least when the surface is quiescent and free from spots. It has also been found that there is a distinct connexion between sunspots and terrestrial magnetic phenomena. To these two direct in-

fluences of sun-spots on the earth, itwould seem that we must' now add a third.

Wo believe light to be propagated through the luminiferous ether in waves, which, like those seen in water, vary in length. There is a wave of certain length which, when it falls on the retina, excites the sensation of red light; others much shorter excite the sensation of violet light. Ther are, however, waves shorter than these violet waves, known as ultra-violet waves, wliith are at the present time engaging the attention of physicists, owing to their therapeutic effects. They are the part of solar radiation that causes sun-burn, has great beneficial power in the case of rickets and other diseases, and is now coining to he '•"- garded as an important influence on general health.

Dr. Edison Pettit, who has been working on this question for sonic time past iit the Mt. Wilson 'Observatory, lias reached the conclusion that the radiation of ultra-violet waves from the sun increases as the spots on the sun grow more numerous, and he infers that, when the eleven-year maximum of spots is reached within the next year or so, the sun will give off about two and a half times as much ultra-violet radiation as it did in 1922-23 when the spots were at ii minimum.

Dr. Pettit's method of observation is very simplo in theory if not in practice; it depends on the fact that the ultra-violet radiation passes through a thin layer of silver, but not of gold, while a similar layer of gold transmits visible green light. Glass being opaque to the ultra-violet waves, two quartz lenses are used, one being silvered and the other gilded; by means-of these lenses an image of the sun is thrown on a vacuum thermopile, which gives an electric current when the radiation falls, on it. This current is measured and from it can be determined the intensity of the ultra-violet or the green radiation, according to the lens ployed, and as the intensity of the green light remains relatively constant, _it can bo used as a standard with which to compare the ultra-violet radiation. Dr. Pettit's discovery should go far to rehabilitate sun-spots in popular esteem. They have, quite undeservedly, been regarded in the past as exercising a baneful influence on things terrestrial; they are associated in men's minds with tho cataclysmic in Nature, and one writer of liigh repute in his own sphere, the late Mr Stanley Jevons, has gone so far as to attribute to them the commercial crises which periodically convulse our social and economic life. These crises have their root in bad harvests and bad harvests are intimately connected with sun-spots! Unfortunately for this theory the worst financial crisis of the last century came in the same year as one of the finest harvests ever known on the planet, and when also the sun's disc was cxceptionallj afflicted with spots.

The Week. "I wis!) " savs William Clissold, "the a-ncient people who invented the week had invented it longer and larger " This Taiscs the interesting question of the origin of the week, and we mav as well say that wo do not know either at what date the adoption of this division of time became general or what primitive race evolved the happy idea of a day of rest after six days of work. It is not a natural unit of time like the year and the month, but so far as our records go tho week of seven days lias always been in usein the East except in Egypt, where at one time a week of ten days was in voizue. , . The students of chronology have always recognised the contemporary existence of two weeks—the planetary and the Jewish—which in combination have produced our seven-day cycle. The origin of the constellations is lost in obscuritv, but it is likely that the race which evolved these arbitrary divisions of the sky may also have been the one which observed the times of the apparent rotation o£ the planets round the earth, and so arranged them in an order which, later, had so great an astrological importance, and was—according to some authorities—the mode by which the present names and

.■sequence of the days of the week were derived.

The planets iu their astrological order arc Saturn, Jupiter, Mars, the sun. Venus, Mercury, aud the moou and the twenty-four hours of the day (which division of the day wc owe, by tho way, to the Egyptians) were dedicated successively to these planets. I lie day wa.-; consecrated to the planet of the first hour—thus, if tlie first hour wa.s dedicated to Saturn, the second would be dedicated to Jupiter, and so on, but the day would be .Saturn's day. Tho eighth, "fifteenth; and twentysecond hours belonged to Saturn; tho twenty-fourth hour of .Saturn's day would be dedicated to .Mars, and so tho first hour of the next clay would belong to tho sun, and tho day would he the,sun's day. Similarly, the next day would be the .Moon's clay—theu would come .Mars' day, then .Mercury's day would be the moon's day—then Anglo-Saxon progenitors have observed the planetary explanation of the order of the days of tho week by naming them iu honour of their, gods, Tew, Woden, Thor, and Friga, but it is brought out clearly by the French names, .Mardi, .Mercredi, Jeudi, and Yendredi.

The planetary week probably camo into genera) use only a century or two before our era,' the point of contact between it and the Jewish week being the Sabbath, identified with Saturn's clay, on which, being an unlucky day, it was best not to be active. 'Eventually the Sabbatical week of the Jewish Christian and the planetary week of the Gentile Christian were fused iu the seven-day round which] retaining the old names for the days, renewed itself with the celebration of every Sunday as the Lord's Day. It is an interesting point that tho "week" as_a division of time spread through North Europe not under Christian btit under pre-Christian Itoman influence.

Mr Clissold wished for a longer week; had he been living in France at the time of the Revolution he would have had ample experience of a ten-day week —nine days of work and one of rest. The National Convention having introduced a new mode of weights and measures based on the decimal system tried its hand at reforming the calendar. On September 22nd, 1791, a day which, by a fortunate coincidence, was that of the institution of the Republic, and also of the autumnal cquiuox, bepan the now era. The year would have been divided into ten parts, in conformity with the decimal idea, but this was found impracticable; the mouth was, however, fixed at thirty days and divided into three portions of ten days each, called decades, the tenth day of each decade being set apart for rest. As these twelve months of thirty days each only accounted for 360 days of the year, the five remaining days wero set. apart for national festivals, and were not counted as days of the mouth; each leap-year saw an additional festival on a grander scale than the others. This scheme lasted till January Ist, ISO 6, but there is little evidence available, as to its social and economic effects. As a specimen of calendar reform it is not to be commended.