Total solar eclipse

“ On July, 16th of 2186, it is expected a total solar eclipse will pass over Venezuela, lasting 7 minutes, 29 seconds, becoming the longest eclipse since 4000 B.C., and it will be until the year 6000 A.D., at least. ”

“ It is not easy to explain or define in words the circumstances which control the duration of a Solar eclipse, whereas in the case of a lunar eclipse the obscuration is the same in degree at all parts of the Earth where the Moon is visible. In the case of a Solar eclipse it may be total, perhaps, in Africa, may be of six digits only in Spain, and of two only in England. ”

“ The table of parallax makes this quantity vary between 66′ 6′′ and 56′ 21′′, the apparent diameter varying from 32′ to 36′ at full moon, while he believed to have found from his observations of eclipses that the diameter appears less at new moon (25′ 36′′ to 28′ 48′′) , owing to the limb being "extenuated" by the solar rays. He therefore denied the possibility of a total solar eclipse, to some extent also misled by the accounts of the luminosity seen round the sun at the eclipses of 1560, 1567, and 1598. ”

“ The most extended streamers are very little brighter than the sky, and must be photographed with long exposures.
The first application of the spectroscope to the phenomenon was made during the total solar eclipse of August 18, 1868, by P. J. C. Janssen and other observers in India. By them was made the capital discovery that the red solar prominences give a spectrum of bright lines, and are therefore immense masses of incandescent gases, chiefly hydrogen and the vapours of calcium and helium. ”

“ If it is an eclipse of the Moon, it will be total from its 13th until its 36th recurrence. There will be then about 13 partial eclipses, each of which will be smaller than the last, when they will fail entirely, the conjunction taking place [27] so far from the node that the Moon does not touch the Earth’s shadow. The whole interval of time over which a series of lunar eclipses thus extend will be about 48 periods, or 865 years. When a series of solar eclipses begins, the penumbra of the first will just graze the earth not far from one of the poles. ”

“ This may be due, in part, to the fact that investigations, which in the past could only be carried on at times of total eclipse, can now be studied throughout the year, and, in part, to the very large number of observations which have already been made. Eclipse expeditions, also are very expensive, and often end in total failure, owing to clouds. Photography has multiplied the results many times in recent years, but for the solution of many problems in solar physics, as complete records as possible for a long time are necessary. ”

“ In a distant future, we no longer can be witnesses of total solar eclipses since the Moon, even in its closest-to-the-Earth position, it won’t be able to block the Sun completely, and there will be only annular or partial eclipses. ”

“ In a partial eclipse, the moon, instead of passing directly between us and the sun, slips by, as it were, a little on one side, thus cutting off from our sight only a portion of his surface. An annular eclipse, on the other hand, takes place when the moon is indeed centrally interposed, but falls short of the apparent size required for the entire concealment of the solar disc, which consequently remains visible as a bright ring or annulus, even when the obscuration is at its height. In a total eclipse, on the contrary, the sun completely disappears behind the dark body of the moon. ”

“ If we add to this that at midnight the whole of the sky, except a round spot some four or five times the diameter of the moon, would be occupied by this cis-lunar matter under direct solar illumination, instead of that illumination from behind which such matter would receive during total eclipse, we see that the darkness of our midnight sky speaks as decisively against this theory as does the brightness of the long rays seen during total eclipse. ”

“ Under the most favourable circumstances the breadth of the track of totality across the Earth cannot be more than 170 miles, and it may be anything less than that down to zero where the eclipse will cease to be total at all, and will become annular. The question whether a given eclipse shall exhibit itself on its central line as a total or an annular one depends, as has been already explained, on the varying distances of the Earth and the Moon from the Sun in different [35] parts of their respective orbits. ”

“ Every solar eclipse has therefore a definite "life" of its own upon the earth, lasting about 1150 years, or 64 saros returns, and working its way little by little across our globe from north to south, or from south to north, as the case may be. Let us take an imaginary example. A partial eclipse occurs, say, somewhere near the North Pole, the edge of the "partial" shadow just grazing the earth, and the "track of totality" being as yet cast into space. ”

“ It is very generally noticed that great changes take place in the meteorological conditions of the atmosphere as an eclipse of the Sun runs its course from partial phase to totality, and back again to partial phase. It goes without saying that the obstruction of the solar rays by the oncoming Moon would necessarily lead to a steady and considerable diminution in the general temperature of the air. ”

“ The thrilling descriptions of the effects of the oncoming darkness of totality, derived from the records of past total eclipses, are not likely to be improved upon in the future, for we shall receive them more and more from amateurs and less and less from astronomical experts. Every additional total eclipse which happens testifies to the fact that the time and thoughts of these latter classes [56] of people will be to an increasing degree dedicated to instrumental work rather than to simple naked eye or even telescopic observation. ”

“ At each succeeding return conformably to the Saros, the partial eclipse will move a little further towards the opposite pole, its magnitude gradually increasing for about 200 years, but during all this time only the lunar penumbra will impinge upon the Earth. But when the true shadow begins to touch, the obscuration will have become annular or total near the pole where it first appeared. The eclipse has now acquired a track, which will cross the Earth slightly farther from that pole every time it returns, for about 750 years. ”

“ This is, to watch when the Moon’s black body comes on to the Sun and goes off again, for there are no subsidiary phenomena, either interesting or uninteresting, unless, indeed, the eclipse should be nearly total. The progress of astronomical science in regard to eclipses has been so extensive and remarkable of late years that, unless the various points for consideration are kept together under well-defined heads, it will be almost impossible either for a writer or a reader to do full justice to the subject. ”

“ This mischievous radiance—which it is the chief merit of a solar eclipse to abolish during some brief moments—is due to the action of the atmosphere, and chiefly of the watery vapors contained in it. Were our earth stripped of its "cloud of all-sustaining air," and presented, like its satellite, bare to space, the sky would appear perfectly black up to the very rim of the sun's disk—a state of things of all others (vital necessities apart) the most desirable to spectroscopists. The best approach to its attainment is made by mounting a few thousand feet above the earth's surface. ”

“ It is a difficult matter to comprehend the structure and condition of any one of the sun's outcasts; the chromosphere, for example. To determine what the conditions within the body of the sun must be in order to create and maintain such an outcast shell is far more difficult.
The influence of eclipse observations upon solar and astrophysical research has been most remarkable. The reversing layer, the chromosphere, the prominences and the corona were in fact discovered at eclipses. Many of our present every-day methods of studying them are also eclipse products. ”

“ If the locus in quo of an expected eclipse is in a civilised country, there will generally not be much difficulty in obtaining a certain amount of information as to this 6 or 12 months in advance. But inasmuch as total eclipses of the Sun, and often the best of them, are visible only in uncivilised countries or over trackless wastes, the problem becomes a complicated and anxious one. ”

“ This period of total eclipse would last for about 6 years 8 months, terrestrial reckoning, or with the periods of partial eclipse, 8 years and nearly 10 months. Whatever the efficiency of the Sun that afforded light and heat to such a planet, it is clear that such eclipses must be fatal to life in two ways: light and heat would be cut off from wide regions of the planet for long periods of time, and terrible meteorological convulsions must follow in the train. ”

“ Total eclipses are of extremely rare occurrence and only happen about once in every three hundred years for any selected spot on the earth's surface.
An interesting description of a total eclipse may be found in Flammarion's "Astronomy for Amateurs": [Pg 220]
"The luminous disk of the sun is gradually corroded. ”

“ It must never be forgotten that we are dealing with an age when accurate observations and descriptions of natural phenomena were unknown, and when mankind was subject to be imposed upon by imaginary wonders and prodigies. The circumstance which we should regard as most unequivocally marking a total eclipse is the visibility of the stars during the darkness. But even this can scarcely be regarded as conclusive, because Venus may be seen when there is no eclipse, and may be quite conspicuous in an annular or a considerable partial eclipse. ”

“ By its means the times and magnitudes of eclipses were roughly computed long before astronomy became an exact science.
A solar eclipse is really an occultation of the Sun by the99 Moon; for the word eclipse, in its usual reference, denotes the obscuration of one body by its immersion in the shadow of another. During any single year there are never less than two eclipses, nor more than seven. Whenever there are two only, both are solar. ”

“ A Moon eclipse is visible from anywhere on the terrestrial globe that is on the same side as the Moon, whereas a solar eclipse is only visible from a small part of the Earth since our planet is larger than the Moon, so that it can hide the sunlight from the whole surface. ”