by Various
An enormous number of ring-plains and ring-mountains exists all over the southern half of the moon's disc; in many cases there are rings within rings, and others where they have overlapped or cut into previously formed rings.
Moving almost due south, we passed the large but partially ruined walled plain known as Maginus. This ring has a floor which is no less than 14,000 feet below the lunar surface. We then arrived at that favourite object for telescopic observers which is named Clavius. This is an enormous ring-plain, being over 142 miles in diameter, and encloses an area of 16,000 square miles, thus being half the area of Scotland. It has a very depressed floor, and some of the mountains are 16,000 to 17,000 feet in altitude.
Farther on, and close to the south pole, we saw the very deepest of the lunar walled plains, which is named after Newton, who possessed probably the deepest intellect of any of our astronomers. A smaller formation south of Plato was originally named after him, but was not considered worthy of a man of his scientific eminence, so the name was transferred to the formation we were looking upon. It is about 143 miles long and very irregular in shape, and its depth is about 24,000 feet--so deep, in fact, that the sun's light never reaches to the bottom; thus, when we look at it from the earth, the floor is always in shadow.
The Leibnitz Mountains, unfortunately, were not visible, as the sun had set upon them. I, however, mentioned that this range comprises several peaks which are believed to be the highest on the lunar surface, reaching as they do an altitude of 30,000 feet, and, according to some measurements, 40,000 feet. They are very difficult to measure, owing to the fact that they are really situated on the farther side of the moon, extending east and west of the south pole, and are only occasionally brought into view by the moon's libration; even then they are seen in profile, and so situated that they cannot be measured with certainty. They are, however, so high that they blunt the southern cusp of the moon when it is in crescent form.
I now directed M'Allister to turn the vessel in a north-easterly direction, and we moved across to the last objects which I proposed to examine. One was the large walled plain "Schickard"--about 135 miles in diameter--which encloses several other rings; the other, which lies to the south-east of it and close to the moon's south-eastern limb, is probably the most unique object on the lunar surface. As we gazed upon it I explained that the formation, which is known as "Wargentin," would probably in the usual course of events have been a ring-plain about fifty-four miles in diameter, but it really is a high plateau of that size, with very low ramparts. It is evidently a ring-plain which became filled to the brim with lava, or mud, that welled up from the interior of the moon; and the mountain walls, being exceptionally strong and without any breaks or gaps, withstood the enormous pressure of the lava, which therefore solidified and formed the great plateau as we now see it. The low ramparts, which we noticed here and there, are really the isolated peaks and ridges of the mountains forming the walls. This is the only known instance of such a formation; but probably others would exist had not the walls of the rings given way under the pressure of the lava. The walls of several ring-plains have been quite carried away, and, in some cases so obliterated, that it is now difficult to make out the original shape of the rings.
Having taken a last look at this unique object, I directed M'Allister to set the machinery in motion and rise for the purpose of quitting the moon.
"But," interposed John, "are you not going to have a look at the back of the moon, Professor?"
"No, John," I answered, "only a small portion of it is now in the sunlight, the rest is in the blackest darkness, so we should not be likely to learn much more about it than we know at present."
"Do you think the moon is inhabited?" he then asked.
"No, I do not think it is; no sign of life has ever been discovered, and we have seen nothing to indicate its existence here. The prevailing conditions seem to preclude the possibility. Think, John, if there is any life, what must it be! Without any atmosphere--therefore, not a sound to be heard, for all would ever be in the most deathly silence--no breath of wind; never a cloud nor a drop of refreshing rain, nor even dew; intense heat in the sunlight and the most intense cold everywhere in the shade! If any life does exist, it is most probably down in those gloomy, dark and cold recesses at the bottom of the ring-mountains, where there may possibly be some remains of an atmosphere. It would, however, be life in such a dreadful and debased form that I would rather not think about it at all.
"For a somewhat similar reason, I have directed M'Allister to keep the Areonal at least ten miles above the lunar surface all the time we have been passing over it. When we saw it from a distance it was, as you know, an object of surpassing beauty; and as we have seen it from here it has still been pleasant to look upon. This is truly a case where distance lends enchantment to the view; for, if we went down close to the surface, we should find it a scene of the weirdest and wildest desolation--more horrible than anything seen during a nightmare, and more terrible than anything imagined by the insane!
"No, John," I concluded, "let us retain our memory of the moon as a thing of beauty, and leave it at that."
"I quite agree with your view of the matter, Professor," John replied; so I gave the signal to M'Allister, who was awaiting the result of our discussion, and we soon left the moon far below us.
CHAPTER VII
WE RESUME OUR VOYAGE--THE SUN AND THE SKY AS SEEN FROM SPACE
All the time the Areonal had been near the moon some of our machines were storing up fresh power, and we had accumulated a supply amply sufficient to meet any extra requirements in the event of our arrival upon Mars being unduly delayed.
We now turned and looked back at the earth; and, as the moon was so near to it at that time, the earth's disc appeared very nearly two degrees in diameter, or nearly four times the usual apparent diameter of the full moon as seen from the earth. The crescent of light on its right-hand side was rather wider than when we last looked at it; but so many clouds hung over it, that we could not see what countries were comprised in the lighted portion of its surface. Owing to the light of the stars behind the earth being diffused by the dense atmosphere--in the same way as it would be diffused by a large lens--there was a ring of brilliant light like a halo all round the earth's disc.
Having passed away from the moon, I now gave M'Allister the necessary directions in order to keep the Areonal on a course which would enable us to head off the planet Mars at, as near as I could reckon, the point it would reach in fifty days' time. The course having been set, M'Allister was free to join us again, as the machinery required very little attention.
When he did so, M'Allister at once asked me a question. "Professor, can you tell me when it's going to be daylight? The sun has been shining for hours and hours, yet it's still night; the sky is blacker than the blackest night I ever saw, and the stars are all out!"
John laughed heartily, and said, "M'Allister, this is daylight! and all the daylight you will get until we reach Mars."
M'Allister turned to me with a perplexed look on his face and asked, "Is that right, Professor, or is he trying to pull my leg, as he said he would?"
"Oh yes! It's quite right, M'Allister," I replied. "It is now full daylight, and we shall have no more night until we reach Mars. That, as you know, will be seven weeks from the present time."
"Well, Professor," he exclaimed, "then how is it the sky is so densely black and the stars all shining so brightly? I never saw the stars in the daytime before, yet these are shining brighter than they do on the earth at night."
"Simply," I said, "because upon the earth we were surrounded by a dense atmosphere, which so diffused the sun's light that the whole sky appeared bright. The stars were there all the time, but their light was so overpowered by the brilliancy of the atmosphere that they were quite invisible to us.
"Now, we are out in space where there is no atmosphere at all, so the sky appears a very dense black; and the stars, having nothing to obscure their light, shine o
ut more brilliantly than they do on the earth. They appear as bright points of light, and even the sun does not shed a general light over the sky, there being no atmosphere to diffuse it."
"Yes," he persisted, "but you said we should have no more night until we got to Mars!"
"Certainly," I answered. "Surely, M'Allister, you must have forgotten that night is brought about by the earth's rotation on its axis, and that the part which is turned away from the sun is in darkness because its light is hidden by the solid body of the earth, while the earth's shadow darkens all the sky. When, by the earth's rotation, that part is again turned to the sun then it becomes daylight. Remember we are not now on the earth, but out in space!"
"Of course I did know all that, Professor," he exclaimed, "but, just for the time, I had forgotten."
"Never mind, M'Allister, we all forget such matters sometimes, and this is quite a new experience for you. But just take a good look at the sun--have you noticed any difference in its appearance?"
"Yes, Professor, it doesn't look the same colour as when we saw it from the earth; it seems to have a violet tinge, like some of the electric lights in our streets. There are also long streamers of light around it, and coloured fringes close to the sun!"
"Yes, that is so," I said; "and we can see all those things now because there is no atmosphere. No doubt you have noticed that on the earth the sun appeared red when low down in the sky, and during a fog it appeared redder and duskier still."
"Oh yes, I've often noticed that," he answered.
"That was caused by our atmosphere which, when thick, absorbs all but the red rays of light. On a clear day the sun appears an extremely pale yellow, or very nearly white; still the atmosphere absorbs some of the light rays, so we cannot see its true colour as we do now. Those coloured fringes round the edges can only be seen from the earth by the aid of a special instrument, and then they do not show all their true colours.
"That pearly light all round the sun, and the long streamers that give it the appearance of an enormous star with six long points, form what is termed the solar corona, and this can only be seen from our earth during the very few minutes when an eclipse of the sun is at its totality. It is to see the corona and other surroundings of the sun, in order to study them, that astronomers go such very long distances--often thousands of miles--when there is a total eclipse expected, and not merely to see the eclipse itself. They hope, in time, to learn much from such observations; but if it happens that the sky is over-clouded during the period of total eclipse, then all their expense, and the time spent in preparations and rehearsals of their procedure, are, unfortunately, entirely wasted.
"Now, M'Allister, if you will take my glass you will be able to look at the sun and examine it without any risk to your eyesight, for it is provided with a dark glass to shut out all the dangerous glare. You will then see what the fringes and inner and outer coronas really are like."
He took the glass and looked for a long time at the sun, and, judging from his exclamations of surprise and astonishment, he was extremely interested and delighted with what he saw. John was also examining it at the same time through his own glass.
Presently the latter turned to me saying, "Professor, I no longer wonder that astronomers are prepared to travel long distances, and to risk a great deal of discomfort, and even hardship, in order to view and study the sun's surroundings. Of course to them it is not merely a sight to be seen, but the only means by which they can acquire a knowledge of solar physics. Merely as a sight, however, it is most wonderful. At many places all round the edge of the sun's disc I can see what look like coloured flames--pink, pea-green, carmine, orange, or yellow, all in incessant movement--shooting out at times, or waving and shimmering in a manner that is indescribable. The changes in form and colour are as sudden, yet as definite, as the changes produced by turning a kaleidoscope; while the intermingling of the various colours frequently produces an effect which I can only compare to the iridescent colours on mother o' pearl. Then all around and beyond the coloured fringe there is the light of the pearly inner corona; beyond that are pearly and violet-tinged rays curling away in both directions from the poles, whilst outside all are the long, pearly, and violet-tinted streamers which assume the shape of a large many-pointed star; and even these do not seem at rest. Though astronomers cannot see all that we do now, there must be sufficient visible to them to afford opportunity for a most interesting study."
"That is indeed the case, John," I replied. "Those coloured flames, for instance, form a study in themselves, which some observers make their particular hobby. As seen from the earth, they all appear some tint of red; and, normally, according to measurements, they seem to extend a distance of some 20,000 miles above the sun. They shift their position very rapidly indeed; movements at the rate of 100 miles a second are quite moderate compared with some which have been noted, yet one can scarcely realise such rapidity of motion. Frequently, however, these flames are seen to rise in immense masses to tremendous heights above the sun's surface, evidently driven upwards by explosions of the most intense energy. In 1888, for instance, one was observed which, in the course of two hours, rose to a height of 350,000 miles before it broke up; that is, at the rate of 50 miles a second all the time; but, as the force would become less and less as the distance increased, at the earlier part of the time the movement must have been far more rapid. When the impetus derived from the explosive force is quite exhausted, the top part of the mass of flame often spreads out like the top of a tree, then breaks up and falls back into the sun in large flakes of flame.
"It is supposed that these violent explosions are the cause of the spots we so often see on the sun when observing it with our telescopes; and, when looking at them in their earliest stage, we are probably looking at a mass of flame end on, instead of seeing it in profile, as is the case when the explosion occurs near the edge of the disc. The flames, as examined by the spectroscope, appear to be largely composed of hydrogen gas; and no doubt many other gases--some quite unknown to us--enter into their composition. They are termed flames, but are more probably immense volumes of incandescent gases. The corona itself is never seen twice alike; its shape and size vary at every eclipse, but the variation runs in a regular cycle from maximum to minimum.
"You will also observe that all around the corona, and extending a vast distance beyond it on both sides, is a fainter pearly light. This is what is termed the zodiacal light, and is believed to be the thinner portion of the sun's atmosphere. We can see it from the earth occasionally after the sun has set, extending far up into the sky in the form of a semi-ellipse, the base of which is over the place where the sun is."
M'Allister here asked me to tell him "What was supposed to be the actual size of our sun, and how far it was away from the earth?"
I answered that "The sun is about 865,000 miles in diameter; and that he would have some idea of what an immense body it is if he remembered that it would require 64,000,000 globes the size of the moon to make one globe the size of the sun! Yet, notwithstanding this immense size, our sun is quite a small body as compared with some of the fixed stars, which, as perhaps you may know, are really suns at an inconceivable distance from us. The bright star Sirius, which is visible during our winter time, is not only very much brighter in reality than our sun, but must be many times larger; and there are others known to be very much larger than Sirius. It has been computed that Arcturus is in mass 500,000 times as large as our sun!
"The sun revolves on its axis in a little over twenty-five days, but the exact period of its revolution is difficult to determine. The mean distance of the sun from the earth is about 92,800,000 miles. When we are farthest from it its distance is 94,600,000 miles, and when nearest, 91,000,000 miles--these differences, of course, arising from the eccentricity of the earth's orbit.
"The sun's density is only about one-fifth of the earth's density; so it is evidently mainly gaseous--at all events in the outer envelopes.
"The spots upon the sun oft
en cover such an immense area, that if our earth were dropped into the cavity, it would be like placing a pea in a teacup! Some of the spots entirely close up in a short time, but others last for weeks."
We now turned from the sun and looked at the stars. Such a multitude were visible as we had never seen from the earth; for small stars, which there required a telescope to bring them into view, could now be plainly seen without any such aid, and their various colours were seen much more clearly. They all shone with a clear and steady light; the twinkling and scintillation of the stars, as seen from the earth, being caused by the vibrations and movements in our own atmosphere. We also saw many nebulæ without using a glass.
The Milky Way was a most gorgeous spectacle, and its beauty utterly beyond description, as such an immense number of its component stars, and their different colours, were visible to the unaided eye; besides, we could trace wisps and branches of it to regions of the sky far beyond the limits within which it is seen from the earth.
We noted that the planets were also much more clearly seen; and the orange-red disc of Mars, of course, received our particular attention.
We had spent very many hours in viewing the moon, and a long time in examining the sun and stars; so we now sat down to a hearty meal, and, after a short time spent in conversation, we made our arrangements for taking turns in attending to the machinery, and then retired to bed.
[Illustration: DIAGRAM: showing the Positions and Movements of the Planets between the 3rd of August and the 24th of September, 1909: and the Course taken by the "Areonal" on the Voyage to Mars.
The dotted line joining the Earth to Mars shows the course taken.