MOON IN FRONT OF SUN

Taranaki Daily News, 18 October 1930, Page 1 (Supplement)

MOON IN FRONT OF SUN

ECLIPSE IN NEW ZEALAND

(By

Rev. B. Dudley,

F.R.A.S.)

He who would write on astronomical subjects at the present time must perforce use black ink: he must dip his pqn in shadows, and think’ much of darkening skies. On Wednesday morning, through the eyes of our own and American astronomers, who will view the phenomenon from the lonely island of Niuafou, we are to see the sun completely blacked out. With our own eyes the event will be seen in its partial phase only. In a very ancient city, we read, there were “six score thousand persons that could not discern between their right hand and their left.” For a few seconds, at least, there will be such, assembled on Niuafou Island who will be there because, in a temporary seizure they “prefer darkness father than light.” But why all this lavish preparation? Why all this keen interest on the part of scientists? Why the long voyage

undertaken by American astronomers who have joined our own New Zealand observers at a suitable spot on the line of totality? In the first place, let it be remembered that it is but rarely that

a solar eclipse occurs at any one part of the world and that the width of the zone from which such eclipse is visible can never be more than 169 miles; while

it is generally much less. . For instance, prior to the total eclipse in the British Isles in, June, 1927, there had not been one. seen therefrom since May, 1721. , And, further, a total observation is a very different, and

much more important event .than a partial ecjipse. Indeed, from a scientific standpoint, a partial observation may be described as almost negligible. Totality, on the other hand, is extremely important, even though it last but a few seconds. They are precious moments.

A total solar eclipse is, caused by the passage of the dark body pf the moon between us and our great luminary. As the apparent size of the sun is practically the same as that of the moon, the total phase of an eclipse cannot last many seconds. And the value of the eclipse for the scientist lies in just those seconds when nothing of the sun can be seen but what reaches out beyond his . disc—the solar, environs, shall we call them ? While the moon temporarily cuts off the dazzling light of the sun, it enables astronomers to see the great hydrogen flames, known as ’ These are huge upheavaß that break out upon the sun’s surface, and are connected with' the more familiar sun-spots. A remarkable example of these appears on the solar % surface at the present time in a group of very considerable size. By means, of the spectroscope, used as an auxiliary to the telescope, these prominences can now be seen and studied independently of an eclipse. But this does not mean that the day of direct vision study past. One of the main objects of the scientific observer in such eclipses as that of next Wednesday is to see the solar corona. This phenomenon cannot be witnessed at any other tune than, during a total eclipse; and in a perfect understanding of these coronal streamers may be found the key that will unlock many mysteries that baffle scientificmen.

The corona,e take the form of a soft effulgent or pearly white, light, a kind of halo or nimbus surrounding the sun. These do not stretch out from the solar, surface to a uniform distance, however, but vary iu a strange and remarkable manner. Sometimes they have a brushlike .appearance; sometimes there are great streamers reaching out for several million miles from the sun. They are probably connected with the prominences already referred to, arid are affected by the maximum and minimum periods of sun-spots. ’At all events, the general form of the corona appears to undergo a distinct change in such a way as to suggest the connection. The spectroscope shows that the light of the corona.is due in part to reflected sunlight. It seems to indicate also that incandescent gases are present, one of these having been named “coronium,” because it.is an element unknown elsewhere. ■■ It is quite obvious that the particles that form the corona are exceedingly fine and widely separated. Comets sometimes pass through and among them without being affected in the slightest degree by the passage. It is to solve, if possible, the question of the nature of this appendage to th© sun, as much as anything, that makes the astronomer so eager to take advantage of an opportunity such as is now being afforded. Every total solar eclipse seems to be fruitful in some way, if not in giving new information, at least in the direction of confirming earlier findings, possibly '-in correcting past mistakes. A recent eclipse, it will be remembered, was of special value in testing Einstein’s doctrine of relativity. These events are admittedly among the grandest and most awe-inspiring sights that can be witnessed. It is not matter for surprise that in earlier times eclipsed excited public dread. It wot/ld not be necessary for a total blacking-out of the sun to coincide many times with the outbreak of a pestilence or the death of a monarch to create in ' the minds of superstitious races th© conviction that such sudden darkenings of th© sky were sure portents of disaster. Seen from New Zealand, about twofifths of the sun’s disc will be on Wednesday morning eclipsed. The event will began at 8.33, Wellington (summer) time, and terminate at 10.33, the entire stages thus occupying two hours. The central phase takes place at 9.3'1, and it will certainly be well worth observing. In Taranaki this will occur.: earlier; namely, at about 9.20. Shortly before that time the dark edge of the moon will bo seen to “nibble at the sun,’’ as she gradually steals in front of him, making her maximum bite out of his disc at the hour named.

Observers should be provided with a proper sun-screen such as is used by astronomers who view the sun telescopically. In lieu of this, a piece of deeply-smoked glass, or the darker portion of a' photographic film may be employed. If a pair of field glasses or a telescope is used, it should no’t on any account be turned to the sun without adequate protection in the manner just described. Damage to vision and even loss of sight may result from looking at the sun instrumentally unless the eye is so shielded. The observer should try the screen for himself in advance of the eclipse. Blindness is an exorbitant price to pay for a moment’s rashness.

Students of nature, who welcome every advance in knowledge of the universe, will eagerly await th© published result© of the observations taken on Wednesday morning.