FALSE NIGHT

Southland Times, Issue 21219, 21 October 1930, Page 9

FALSE NIGHT

THE MOON’S SHADOW.

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

Various accompanying l phenomena connected with total solar eclipses are not without interest and significance to students of nature. The false night no less than the real and normal cannot, even though so brief, be produced without giving rise, to certain far reaching effects. For one thing, it. is never sudden; some warning is given of its approach. Viewed from the top of the high hill, observers tell us, the onsweeping shadow of the moon, coming with a swiftness greater than that of a cannon shot, is something more than awe-inspir-ing. An eye-witness describes this feature of an eclipse as follows: “Then, with

frightful velocity, the actual shadow of the moon is seen approaching, a tangible darkness ■ advancing almost like a wall,

swift as imagination, silent as doom. The immensity of nature never comes so near , as then, and strong must he the nerves not to quiver as this blue-black shadow rushes upon the. spectator with incredible speed. A vast palpable presence seems overwhelming the world.” A hill-top view of this shadow is advantageous because from such eminence one looks down upon it and can see it as a whole and in relation to the entire landscape, the actual speed being 1830 miles per hour, or 30J miles per minute. As a matter of fact it is only observers who are stationed on high ground with some..miles of open low land spread out beneath their vision who can see it at all, so easy is it. to miss its advent altogether unless a sharp look-out is kept as it comes up, flits over them and passes on-

ward. The effect of eclipses upon birds and beasts must here be mentioned. By their distressed cries, birds in particular indicate knowledge that something abnormal is ■ taking place. Where they do not immediately go to roost, they show, by their behaviour, much discomfort and suspicion. The animal and vegetable world make preparation as for night. Flowers begin, or threaten, to close as the aspect of nature assumes “an unearthly cadaverous hue.” Bats emerge stealthily; sensitive flowers close their petals, and a sense of hushed expectancy deepens with the darkness. The assembled crowd is awed into absolute silence almost invariably. “Trivial chatter and senseless joking ceases,” states a reporter, “sometimes the shadow engulfs the observer smoothly, sometimes apparently with jerks; but all the world might well be dead and cold and turned to ashes. Often the very air seems to hold its breath for sympathy.” During an eclipse in North East Germany foresters record that the birds which had begun their morning chorus prior to the first phases suddenly became silent and showed signs of disquiet when darkness overtook the scene. Herds of deer ran about in alarm, as did the small four footed game; while in Berlin a noted scientist, arranged for an observation to be made by bird-dealers of the conduct of their feathered stock. The results were found to vary considerably. In some cases

the birds showed a sudden sleepiness, even though they had sung before the eclipse took place. In other cases great uneasiness , and fright were observed. Parrots showed far more susceptibility I han canaries, becoming totally silent during the eclipse, and only returning very slowly to their usual state.

The darkness of an eclipse is never complete, which fact is due to atmospheric, refraction. The light of the sun though cut. off from those limited parts of the earth’s surface included within the line of totality, illuminates the tipper atmosphere and is scattered thence into the* shadowed portions, so that the darkness is never as dense as that of true night. It is, however, subject to much variation. Ferrer, referring to the eclipse of the year 1806, states that during totality “without doubt the light was greater than that of the full moon.” That, however, is exceptional. Certain colour effects are noticeable during an eclipse. In this respect the sky usually undergoes remarkable changes. For example, Halley, in his account of the eclipse of 1715, says: “When the eclipse was about 10 digits (that is when five-sixths of the solar diameter was immersed) the face and colour of the sky began to change from a perfect serene azure blue to a more dusky livid colour, intermingled with a tinge of purple, and grew darker and darker till the total immersion of the sun.” This colouration was a feature well marked in the last total eclipse of the sun visible from New Zealand. It is the usual practice of expeditionary parties to apportion among the various members thereof the task of giving special attention to the various principal phenomena of eclipse. Such specialization has been provided for in connection with the observations to take place at Niuafou on the 22nd of the month.

Mention should be made of the fall in temperature that invariably accompanies a total eclipse of the sun. The air becomes decidedly cold, dew frequently forms, and the chill is sometimes confessed by those who feel it. to.be “mental as well as physical.” The editor of an astronomical Journal, “The Chaldacan,” in giving advice and hints to would be observers of the eclipse in England on June 29, 1927, said: “Wrap up well; really well. It will, be bitterly cold”—Counsel based on frequent experience.

The “shadow bands” often alluded to in astronomical books manifest usually a few minutes before total obscuration takes place, and may be seen, as one witness puts it, “dancing across the landscape in singular wavy lines of light and shade.” They are most in evidence when seen on the front of a high wall or stuccoed house which happened to be in their track. The bands vary in width and in their distance apart at different eclipses, just as they differ also in the speed with which they pass along. There is no perfectly satisfactory explan-

ation of this phenomenon; but. in all probability, the effect is due to irregularities in lhe atmospheric refraction of the slender beam of light coming from the sun.

Other accompaniments of solar eclipses are equaly interesting, but space does not permit their being dealt with here.