OF CURRENT INTEREST

Taranaki Daily News, 19 January 1935, Page 11 (Supplement)

OF CURRENT INTEREST

THE EVENING STAR

(By

the Rev. B. Dudley, F.R.A.S.)

Gracing our early evening skies at the present time is the planet Venus. She is making her way round “from the back of the sun,” as it were, in whose light she has been lost, since she adorned our morning skies a few months ago. As Venus journeys about the sun in an orbit smaller than that of the earth, she thus appears now on one side of him and then on the other. On the first of the present month she set at about 8.20 p.m. Each evening she will set a little later until her greatest eastern elongation is reached. This occurs on June 30. Meanwhile she is becoming more and more brilliant. Venus is the second planet in order of distance from the sun, being 67.2 million miles from that luminary. Her diameter is 7600 miles, so that she compares in size with the earth. In density she is 5.21 times that of water, as against the earth whose density is 5.52 times that of water. Her synodic period in days is 583.92. The period of her axial rotation is not definitely known. Eclipses in 1935.

During 1935 there will be the maximum number possible in any one year. On January 5 there occurred a partial eclipse of the sun. But this was invisible on any land surface. The maximum magnitude of the eclipse was very small, being only 0.001. On the 20th inst. (to-morrow) there is scheduled a total eclipse of the moon, visible in New Zealand. Totality begins at about 3.33 a.m. and ends at about 4 a.m. There will be a partial eclipse of the sun on February 4, visible in North America, etc. This again will be of but slight magnitude, viz. 0.739. Other eclipses for the year are July 1, partial solar eclipse; July 16, total eclipse of the moon; July 30, partial eclipse of the sun; December 26, annular eclipse of the sun; all except the last named being invisible in New Zealand (and this will be partly visible only as a partial eclipse at sunrise). The above times are all New Zealand standard mean time. The Summer Time Act requires 30 minutes to be added as long as it is in operation.

Expected Comets. The year 1934 was noted for a paucity of comets. But the present year is likely to bring a plenitude. Three of these bodies, named respectively after Holmes, Schaumasse and Temple, will probably make their appearance close to the times predicted—Temple’s about September, and Schaumasse’s about November (for northern observers). Holmes’ comet is not so certain, since it has not been seen since 1906. But, says Dr. Crommelin, “the facts that it was discovered in London • . . . and that it will be very favourably placed from August to November were thought to justify its inclusion” in the list of promises. ‘Another five comets will be searched for at due dates. Crommelin also makes the remark: “The fact that a year has passed without a single unexpected comet being found suggests that the search for such bodies has not been very active?’ Many comets are entirely telescopic objects, and a close watch is necessary to detect them. Time Reckoning.

A note repeated in the Handbook of the British Astronomical Association for 1935 runs: “Before 1925 January 1, the astronomical day was considered to begin at .mean noon, that is, at the upper meridian passage of the mean sun. Mean time was therefore defined as the hour angle (measured positively westward) of the mean sun at Greenwich or at any other place for which local mean time was to be defined. From that date onward, the astronomical day has been considered to begin at midnight, thus agreeing xvith the civil day. .Thus 1924 December 31d 12h, by the old time reckoning was the same as 1925 January Id Oh by the new reckoning. All astronomical time records prior to that date must be understood as referring to time beginning at noon.” There is some danger of this change in time reckoning being forgotten with rather confusing results under certain circumstances. Hence the reminder. It will be seen that the arrangement has now been in vogue for a decade. And the general testimony is doubtless in its favour, notwithstanding the exception that was taken to it in some quarters when first adopted. The British Summer Time Act also has been in operation for 10 years, having been enacted in 1925 that “the time for all civil purposes is advanced by one hour during the period beginning at two o’clock, Greenwich mean time, in the morning of the day following the third Saturday in April, or,- if that day be Easter Day, the next following the second Saturday in April, and ending at two o’clock, Greenwich mean time, in the morning of the day next following the first Saturday in October.” Prior to this Act being passed, the beginning and end of Summer Time varied from year to year. The dates of beginning and ending of Summer Time, from its introduction in 1916, are given in the Nautical Almanac. Reminder may be given that Summer Time, whether in Great Britain or New Zealand, is intended for civil use only. For astronomical, meteorological or navigational uses it should be ignored, as also in recording observations. For this reason astronomical and certain other clocks are maintained at the normal or solar times. Size of Our Cosmic System,

It may interest some readers to ponder over the figures given by two first rate experts concerning the size of our galaxy. The galaxy consists of all the stars we can see with the naked eye, and many more visible only in the telescope, the entire scheme being bounded by the Milky Way which passes not only over our heads but beneath our feet. The whole is a spiral structure, the Milky Way being the coiling arms or whorls by which it is bounded. Beyond this—across gulfs of space that are quite inconceivable by us—are millions of other galaxies -visible as tiny specks on the photographic plates of the astronomer. Some of these are as large as our galaxy; but most of them are smaller. Our galaxy, the spiral in which we live, is, according to these experts, Dr. J. S, Plaskett and Dr. J. A, Pearce, of the following dimensions: Distance from the solar system to the centre of the spiral, 10,000 parsecs (or 32,000 light years); diameter of the spiral, 30,000 parsecs; rotational velocity of the spiral at the place of the solar system, 275 kilometers (about 170 miles) per second; period of rotation of the sun in its path round the centre of the spiral, 224 million years. Hungry intellects may find in these estimates (the fruit of most careful study) much food for thought.

The British Post Office carried more than 150,000,000 parcels last year, 67 tons of them being sent by air.