Chapter X: Section 9: Cause of Solar and Lunar Eclipses

An Eclipse of the Sun is caused simply by the Moon passing before it, or between it and the observer on the Earth. Of this no question has been raised. But that an Eclipse of the Moon arises from a shadow of the Earth is in every respect unsatisfactory. The Earth has been proved to have no motion, either upon axes or in an orbit round the Sun, and therefore it could never come between the Sun and the Moon. The Earth is proved to be a Plane, always underneath the Sun and Moon, and therefore to speak of its intercepting the light of the Sun and thus casting its own shadow upon the Moon, is to say that which is impossible. Besides this, cases are on record of the Sun and Eclipsed Moon being above the horizon together. “The full Moon has sometimes been seen above the horizon before the Sun was set. A remarkable instance of this kind was observed at Paris on the 19th of July, 1750, when the Moon appeared visibly Eclipsed while the Sun was distinctly to be seen above the horizon.”[11] “On the 20th of April, 1837, the Moon appeared to rise Eclipsed before the Sun had set. The same phenomenon was observed on the 20th of September, 1717.”[12] “In the lunar Eclipses of July 17, 1590; Nov. 3, 1648; June 16, 1666; and May 26, 1668, the Moon rose Eclipsed whilst the Sun was still apparently above the horizon. Those _horizontal_ Eclipses were noticed as early as the time of Pliny.”[13] The Moon’s entire surface, or that portion presented to the Earth has also been distinctly seen during the whole time of a total Eclipse, a phenomenon utterly incompatible with the doctrine that the Earth’s shadow is the cause of it. “The Moon has sometimes shown during a total Eclispe with an almost unaccountable distinctness. On Dec. 22, 1703, the Moon, when totally immersed in the Earth’s shadow, was visible at Avignon by a ruddy light of such brilliancy that one might have imagined her body to be transparent, and to be enlightened from behind; and on March 19th, 1848, it is stated that so bright was the Moon’s surface during its total immersion, that many persons could not be persuaded that it was eclipsed. Mr. Forster, of Bruges, states, in an account of that eclipse, that the light and dark places on the moon’s surface could be almost as well made out as in an ordinary dull moonlight night.

[11] “Astronomy and Astronomical Instruments,” p. 105, by Geo. G.
Carey.

[12] “McCulloch’s Geography,” p. 85.

[13] “Illustrated London Almanack for 1864,” the astronomical part in
which is by James Glaisher, Esq., of the Greenwich Observatory.

“Sometimes, in a total lunar eclipse, the moon will appear quite obscure in some parts of its surface, and in other parts will exhibit a high degree of illumination. * * * To a certain extent I witnessed some of these phenomena during the merely partial eclipse of February 7th, 1860. * * * I prepared, during the afternoon of February 6th for witnessing the eclipse, without any distinct expectation of seeing much worthy of note. I knew, however, that upwards of eight-tenths of the disc would be covered, and I was anxious to observe with what degree of distinctness the eclipsed portion could be viewed, partly as an interesting fact, and partly with a view of verifying or discovering the weak points of an engraving (in which I am concerned) of a lunar eclipse.

“After seeing the increasing darkness of the penumbra softly merging into the true shadow at the commencement of the eclipse (about 1 o’clock a.m., Greenwich time) I proceeded with pencil and paper, dimly lighted by a distant lamp, to note by name the different lunar mountains and plains (the so-called seas) over which the shadow passed. * * * During the first hour and ten minutes I had seen nothing unexpected. * * * I had repeatedly written down my observations of the remarkable clearness with which the moon’s eclipsed outline could be seen, both with the naked eye, and with the telescope; at 1 hour 58 minutes, however, I suddenly noted the ruddy colour of a _portion_ of the moon. I may as well give my notes in the original words, as copied next day in a more connected form:--1h. 58m., Greenwich time. I am suddenly struck by the fact that the whole of the western seas of the moon are showing through the shadow with singular sharpness, and that the whole region where they lie has assumed a decidedly reddish tinge, attaining its greatest brightness at a sort of temporary polar region, having ‘Endymion’ about the position of its imaginary pole. I particularly notice that the ‘Lake of Sleep’ has disappeared in this brightness, instead of standing out in a darker shade: and I notice that this so-called polar region is not parallel with the rim of the shadow, but rather west of it.--2h. 15m. Some clouds, though very thin and transparent, now intervene.--2h. 20m. The sky is now cleared, How extraordinary is the appearance of the Moon _Reddish_ is not the word to express it; it is red--red hot! I endeavour to think of various red objects with which to compare it, and nothing seems so like as a _red-hot penny_--a red-hot penny with a little _white_-hot piece at its lower edge, standing out against a dark-blue back ground; only it is evidently not a mere disc, but beautifully rounded by shading.

“Such is its appearance with the naked eye: with the telescope its surface varies more in tint than with the naked eye, and is not of quite so bright a red as when thus viewed. The redness continues to be most perceptible at a distance from the shadow’s southern edge, and to be greatest about the region of ‘Endymion.’ The Hercynian mountains (north of Grimaldus) are, however, of rather a bright red, and Grimaldus shows well. Mare Crisium and the western seas are wonderfully distinct. Not a trace to be seen of Aristarchus or Plato.--2h. 27m. It is now nearly the middle of the eclipse. The red colour is very brilliant to the naked eye. * * * After this, I noticed a progressive change of tint in the Moon.--2h. 50m. The Moon does not seem to the naked eye of so bright a red as before; and again I am reminded by its tint of red-hot copper, or rather copper which has begun to cool. The whole of Grimaldi is now uncovered. Through the telescope I notice a decided grey shade at the lower part of the eclipsed portion, and the various small craters give it a stippled effect, like the old aqua-tint engravings. The upper part is reddish, but two graceful bluish curves, like horns, mark the form of the Hercynian mountains, and the bright region on the other limb of the Moon. These are visible also to the naked eye.

“At 3h. 5m. the redness had almost disappeared; a very few minutes afterwards, no trace of it remained, and ere long clouds came on. I watched the Moon, however, occasionally gaining a glimpse of its disc, till a quarter to four o’clock, when, for the last time on that occasion, I saw it faintly appearing through the clouds, nearly a full Moon again; and then I took leave of it, feeling amply repaid for my vigil by the beautiful spectacle which I had seen.”[14]

[14] The Hon. Mrs. Ward, Trimleston House, near Dublin, in
“Recreative Science,” p. 281.

Mr Walkey, who observed the lunar eclipse of March 19th, 1848, near Collumpton, says--“The appearances were as usual till 20 minutes past 9; at that period, and for the space of the next hour, instead of an eclipse, or the shadow (umbra) of the Earth being the cause of the total obscurity of the Moon, the whole phase of that body became very quickly and most beautifully _illuminated_; and assumed the appearance of the glowing heat of fire from the furnace, rather tinged with a _deep red_. * * * The whole disc of the Moon being as _perfect with light_ as if there had been _no eclipse whatever_! * * * The Moon positively gave _good light from its disc during the total eclipse_!”[15]

[15] “Philosophical Magazine,” No. 220, for August, 1848.

In the astronomical portion of the “Illustrated London Almanack for 1864,” by Mr. Glaisher, a beautiful tinted engraving is given representing the appearance of the Moon during the total eclipse of June 1, 1863, when all the light and dark places--the so-called mountains, seas, &c., were plainly visible. In the accompanying descriptive chapter, the following sentences occur:--“At the time of totality the Moon presented a soft woolly appearance, apparently more globular in form than when fully illuminated. Traces of the larger and brighter mountains were visible at the time of totality, and particularly the bright rays proceeding from Tycho, Kepler, and Aristarchus. * * * At first, when the obscured part was of small dimensions, it was of an iron grey tint, but as it approached totality, the reddish light became so apparent that it was remarked that the Moon ‘seemed to be on fire;’ and when the totality had commenced, it certainly looked like a fire smouldering in its ashes, and almost going out.”

If then, the Sun and Moon have many times been seen above the horizon when the latter was eclipsed, how can it be said that the Earth’s shadow was the cause of a lunar eclipse, when the Earth was not between or in a line with the Sun and Moon? And how can the Moon’s non-luminous surface be distinctly visible and illuminated during the very totality of an eclipse, if all the light of the Sun is intercepted by the Earth?

Again, if the Moon is a sphere, which it is declared to be, how can its surface _reflect_ the light of the Sun? If her surface was a mass of polished silver, it could not reflect from more than a mere point! Let a silvered glass ball or globe of considerable size be held before a lamp or fire of any magnitude, and it will be seen that instead of the whole surface reflecting light, there will be a very small portion only illuminated. But the Moon’s _whole surface_ is brilliantly illuminated! a condition or effect utterly impossible if it be spherical. The surface _might_ be _illuminated_ from the Sun, or any other source if opaque, instead of polished, like an ordinary silvered mirror, but it could not shine intensely from every part, and brightly illuminate the objects before it, as the Moon does so beautifully when full and in a clear firmament. If the Earth _were admitted_ to be globular, and to move, and to be capable of throwing a shadow by intercepting the light of the Sun, it would be impossible for a lunar eclipse to occur thereby, unless at the same time the Moon be proved to be non-luminous, and to shine only by reflection. But this is not proved; it is only assumed as an essential part of a theory. The _contrary_ is capable of proof, and proof beyond the power of doubt, viz., that the Moon is _self-luminous_, or shines with a light peculiar to herself, and therefore independently of the Sun. A reflector necessarily gives off what it receives. If a mass of red-hot metal be placed before a plane or concave surface, _heat_ will be reflected. If snow or ice be similarly placed, _cold_ will be reflected. If light, ordinary or coloured, be presented, the _same_ will be reflected. If sound of a given pitch be produced, the same pitch will be reflected. If the note A be sounded upon a musical instrument, a reflector would not return the note B or C, but the _same note_, altered only in degree or intensity, but not in “pitch.” A reflector receiving a red light would not return a blue or yellow light. A reflector collecting the cold from a mass of ice, would not throw off heat; nor the contrary. Nor could the Moon, if a reflector, radiate or throw down upon the Earth any other light than such as she receives from the Sun. No difference could exist in the quality or character of the light, and it could differ in no respect but the quantity or intensity.

The light of the Sun and of the Moon are different in their general appearance--in the colour and action upon the eye.

The Sun’s light is drying and preservative, or antiseptic. The Moon’s light is damp and putrefactive.

The Sun’s rays will put out a common fire; the Moon’s light will increase the combustion. The light of the Sun falling upon certain chemical substances, produces a change of colour, as in photographic and other processes. The light of the Moon fails to produce the same effect. Dr. Lardner, at page 121 of his excellent work, “The Museum of Science,” says--“The most striking instance of the effect of certain rays of solar light in blackening a light-colored substance, is afforded by chloride of silver, which is a white substance, but which immediately becomes black when acted upon by the rays near the violet extremity of the spectrum. This substance, however, highly susceptible as it is of having its colour affected by light, is, nevertheless, found not to be changed in any sensible degree when exposed to the light of the Moon, even when that light is condensed by the most powerful burning lenses.”

The Sun’s light when concentrated by a number of mirrors, or a large burning lens, produces a focus which is entirely non-luminous, but in which the heat is so great that metallic and alkaline substances are quickly fused; earthy and mineral compounds almost immediately vitrified; and all animal and vegetable structures in a few seconds burned up and destroyed. But the Moon’s light so concentrated produces a brilliant focus, so luminous that it is difficult to look upon it; and yet there is no increase of temperature! “If the most delicate thermometer be exposed to the full light of the Moon, shining with its greatest lustre, the mercury is not elevated a hair’s breadth, neither would it be if exposed in the focus of her rays concentrated by the most powerful lenses. This has been proved by actual experiment.”[16] “This question has been submitted to the test of direct experiment. * * * The bulb of a thermometer sufficiently sensitive to render apparent a change of temperature amounting to the thousandth part of a degree, was placed in the focus of a concave reflector of vast dimensions, which, being directed to the Moon, the lunar rays were collected with great power upon it. Not the slightest change, however, was produced in the thermometric column, proving that a concentration of rays sufficient to fuse gold, if they proceeded _from the Sun_, does not produce a change of temperature so great as the thousandth part of a degree, when they proceed _from the Moon_.”[17]

[16] “All the Year Round,” by Dickens.

[17] Dr. Lardner’s Museum of Science, p. 115.

“The light of the Moon though concentrated by the most powerful burning glass, is incapable of raising the temperature of the most delicate thermometer. M. De La Hire collected the rays of the full Moon when on the meridian, by means of a burning glass thirty-five inches in diameter, and made them fall on the bulb of a delicate air-thermometer. _No effect was produced_, though the lunar rays by this glass were concentrated 300 times.” “Professor Forbes concentrated the Moon’s light by a lens thirty inches in diameter, its focal distance being about forty-one inches, and having a power of concentration exceeding 6,000 times. The image of the Moon which was only eighteen hours past full, and less than two hours from the meridian, was brilliantly thrown by this lens on the extremity of a commodious thermo-pile. Although the observations were made in the most unexceptional manner, and (supposing that half the rays were reflected, dispersed, and absorbed) though the light of the Moon was concentrated _3000 times, not the slightest thermo-effect was produced_![18] In the “Lancet” (medical journal) for March 14th, 1856, particulars are given of several experiments, which proved that the Moon’s rays when concentrated actually _reduced_ the temperature upon a thermometer more than 8 degrees!

[18] Dr. Noad’s Lectures on Chemistry, p. 334.

“The cold chaste Moon, the Queen
Of Heaven’s bright Isles;
Who makes all beautiful
On which she smiles:
That wandering shrine of soft
Yet _icy flame_,
Which ever is transformed
Yet still the same;
And _warms not_ but _illumes_.”

--SHELLEY.

The “pale _cold_ Moon” is an expression not only beautiful poetically but evidently true philosophically.

If, as we have now seen, the very nature of a reflector demands certain conditions and the Moon does not manifest these conditions, it must of necessity be concluded that the Moon is _not_ a _reflector_, but a _self-luminous body_. If self-luminous her surface could not be darkened or eclipsed by a shadow of the Earth--supposing such were thrown upon it. The luminosity instead of being diminished would be greater in proportion to the greater density or darkness of the shadow. As the light in a lantern shines most brightly in the darkest places, so would the Moon’s self-luminous surface be most intense in the deepest part of the Earth’s shadow. It is thus rendered undeniable that a Lunar Eclipse _does_ not and _could_ not arise from a shadow of the Earth! As a _Solar_ Eclipse occurs from the Moon passing over the Sun; so from the evidence it is clear that a Lunar Eclipse _can only_ arise from a similar cause--a body semi-transparent and well-defined passing before the Moon, or between her surface and the observer on the surface of the Earth. That such a body exists is admitted by several distinguished astronomers. In the report of the Council of the Royal Astronomical Society for June, 1850, it is stated, “We may well doubt whether that body which we call the Moon is the _only satellite_ of the Earth.” In the report of the Academy of Sciences for October 12, 1846, and again for August, 1847, the Director of one of the French Observatories gives a number of observations and calculations which have led him to conclude that “there is at least _one non-luminous body_ of considerable magnitude which is attached as a _satellite to this Earth_.”[19]

[19] Referred to in Lardner’s “Museum of Science,” p. 159.

Persons who are unacquainted with the methods of calculating Eclipses and other astronomical phenomena, are prone to look upon the correctness of these calculations as powerful arguments in favour of the doctrine of the Earth’s rotundity and the Newtonian philosophy generally. But this is erroneous. Whatever theory is adopted, or if all theories are discarded, the same results may follow, because the necessary data may be tabulated and employed independently of all theory, or may be mixed up with any, even the most opposite doctrines, or kept distinct from every system, just as the operator may decide. The tables of the Moon’s relative positions for almost any second of time are purely practical, the result of long continued observation, and may or may not be mixed up with hypothesis. In Smith’s “Rise and progress of Astronomy,” speaking of Ptolemy, who lived in the 2nd century of the Christian Era, it is said, “The (considered) defects of his system did not prevent him from calculating all the Eclipses that were to happen for 600 years to come.” Professor Partington, at page 370 of his Lectures on Natural Philosophy, says, “The most ancient observations of which we are in possession, that are sufficiently accurate to be employed in astronomical calculations, are those made at Babylon about 719 before the Christian Era, of three Eclipses of the Moon. Ptolemy, who has transmitted them to us, employed them for determining the period of the Moon’s mean motion; and therefore had probably none more ancient on which he could depend. The Chaldeans, however, must have made a long series of observations before they could discover their “Saros” or lunar period of 6,585¹⁄₃ days, or about 18 years; at which time, as they had learnt, the place of the Moon, her _node_ and _apogee_ return nearly to the same situation with respect to the Earth and the Sun, and, of course, a series of nearly similar Eclipses occur.”

Sir Richard Phillips, in his “Million of Facts,” at page 388, says:--“The precision of astronomy arises, not from theories, but from prolonged observations, and the regularity of the motions, or the ascertained uniformity of their irregularities. Ephemerides of the planets’ places, of Eclipses, &c., have been published for above 300 years, and were nearly as precise as at present.”

“No particular theory is required to calculate Eclipses; and the calculations may be made with equal accuracy _independent of every theory_.”[20]

[20] Somerville’s Physical Sciences, p. 46.