by Mark Wicks
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 machineswere storing up fresh power, and we had accumulated a supply amplysufficient to meet any extra requirements in the event of our arrivalupon Mars being unduly delayed.
We now turned and looked back at the earth; and, as the moon was so nearto it at that time, the earth's disc appeared very nearly two degrees indiameter, or nearly four times the usual apparent diameter of the fullmoon as seen from the earth. The crescent of light on its right-handside was rather wider than when we last looked at it; but so many cloudshung over it, that we could not see what countries were comprised in thelighted portion of its surface. Owing to the light of the stars behindthe earth being diffused by the dense atmosphere--in the same way as itwould be diffused by a large lens--there was a ring of brilliant lightlike a halo all round the earth's disc.
Having passed away from the moon, I now gave M'Allister the necessarydirections in order to keep the _Areonal_ on a course which would enableus to head off the planet Mars at, as near as I could reckon, the pointit would reach in fifty days' time. The course having been set,M'Allister was free to join us again, as the machinery required verylittle attention.
When he did so, M'Allister at once asked me a question. "Professor, canyou tell me when it's going to be daylight? The sun has been shining forhours and hours, yet it's still night; the sky is blacker than theblackest night I ever saw, and the stars are all out!"
John laughed heartily, and said, "M'Allister, this is daylight! and allthe daylight you will get until we reach Mars."
M'Allister turned to me with a perplexed look on his face and asked, "Isthat right, Professor, or is he trying to pull my leg, as he said hewould?"
"Oh yes! It's quite right, M'Allister," I replied. "It is now fulldaylight, and we shall have no more night until we reach Mars. That, asyou know, will be seven weeks from the present time."
"Well, Professor," he exclaimed, "then how is it the sky is so denselyblack and the stars all shining so brightly? I never saw the stars inthe daytime before, yet these are shining brighter than they do on theearth at night."
"Simply," I said, "because upon the earth we were surrounded by a denseatmosphere, which so diffused the sun's light that the whole skyappeared bright. The stars were there all the time, but their light wasso overpowered by the brilliancy of the atmosphere that they were quiteinvisible to us.
"Now, we are out in space where there is no atmosphere at all, so thesky appears a very dense black; and the stars, having nothing to obscuretheir light, shine out more brilliantly than they do on the earth. Theyappear as bright points of light, and even the sun does not shed ageneral light over the sky, there being no atmosphere to diffuse it."
"Yes," he persisted, "but you said we should have no more night until wegot to Mars!"
"Certainly," I answered. "Surely, M'Allister, you must have forgottenthat night is brought about by the earth's rotation on its axis, andthat the part which is turned away from the sun is in darkness becauseits light is hidden by the solid body of the earth, while the earth'sshadow darkens all the sky. When, by the earth's rotation, that part isagain turned to the sun then it becomes daylight. Remember we are notnow on the earth, but out in space!"
"Of course I did know all that, Professor," he exclaimed, "but, just forthe time, I had forgotten."
"Never mind, M'Allister, we all forget such matters sometimes, and thisis quite a new experience for you. But just take a good look at thesun--have you noticed any difference in its appearance?"
"Yes, Professor, it doesn't look the same colour as when we saw it fromthe earth; it seems to have a violet tinge, like some of the electriclights 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 becausethere is no atmosphere. No doubt you have noticed that on the earth thesun appeared red when low down in the sky, and during a fog it appearedredder and duskier still."
"Oh yes, I've often noticed that," he answered.
"That was caused by our atmosphere which, when thick, absorbs all butthe red rays of light. On a clear day the sun appears an extremely paleyellow, or very nearly white; still the atmosphere absorbs some of thelight rays, so we cannot see its true colour as we do now. Thosecoloured fringes round the edges can only be seen from the earth by theaid of a special instrument, and then they do not show all their truecolours.
"That pearly light all round the sun, and the long streamers that giveit the appearance of an enormous star with six long points, form what istermed the solar corona, and this can only be seen from our earth duringthe very few minutes when an eclipse of the sun is at its totality. Itis to see the corona and other surroundings of the sun, in order tostudy them, that astronomers go such very long distances--oftenthousands of miles--when there is a total eclipse expected, and notmerely to see the eclipse itself. They hope, in time, to learn much fromsuch observations; but if it happens that the sky is over-clouded duringthe period of total eclipse, then all their expense, and the time spentin 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 atthe sun and examine it without any risk to your eyesight, for it isprovided with a dark glass to shut out all the dangerous glare. You willthen 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, judgingfrom his exclamations of surprise and astonishment, he was extremelyinterested and delighted with what he saw. John was also examining it atthe same time through his own glass.
Presently the latter turned to me saying, "Professor, I no longerwonder that astronomers are prepared to travel long distances, and torisk a great deal of discomfort, and even hardship, in order to view andstudy the sun's surroundings. Of course to them it is not merely a sightto be seen, but the only means by which they can acquire a knowledge ofsolar physics. Merely as a sight, however, it is most wonderful. At manyplaces all round the edge of the sun's disc I can see what look likecoloured flames--pink, pea-green, carmine, orange, or yellow, all inincessant movement--shooting out at times, or waving and shimmering in amanner that is indescribable. The changes in form and colour are assudden, yet as definite, as the changes produced by turning akaleidoscope; while the intermingling of the various colours frequentlyproduces an effect which I can only compare to the iridescent colours onmother o' pearl. Then all around and beyond the coloured fringe there isthe light of the pearly inner corona; beyond that are pearly andviolet-tinged rays curling away in both directions from the poles,whilst outside all are the long, pearly, and violet-tinted streamerswhich assume the shape of a large many-pointed star; and even these donot seem at rest. Though astronomers cannot see all that we do now,there must be sufficient visible to them to afford opportunity for amost interesting study."
"That is indeed the case, John," I replied. "Those coloured flames, forinstance, form a study in themselves, which some observers make theirparticular hobby. As seen from the earth, they all appear some tint ofred; and, normally, according to measurements, they seem to extend adistance of some 20,000 miles above the sun. They shift their positionvery rapidly indeed; movements at the rate of 100 miles a second arequite moderate compared with some which have been noted, yet one canscarcely realise such rapidity of motion. Frequently, however, theseflames are seen to rise in immense masses to tremendous heights abovethe sun's surface, evidently driven upwards by explosions of the mostintense energy. In 1888, for instance, one was observed which, in thecourse of two hours, rose to a height of 350,000 miles before it brokeup; that is, at the rate of 50 miles a second all the time; but, as theforce would become less and less as the distance increased, at theearlier 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 atree, then breaks up and falls back into the sun in large flakes offlame.
"It is supposed that these violent explosions are the cause of the spotswe 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 ata mass of flame _end on_, instead of seeing it in profile, as is thecase when the explosion occurs near the edge of the disc. The flames, asexamined by the spectroscope, appear to be largely composed of hydrogengas; and no doubt many other gases--some quite unknown to us--enter intotheir composition. They are termed flames, but are more probably immensevolumes of incandescent gases. The corona itself is never seen twicealike; its shape and size vary at every eclipse, but the variation runsin a regular cycle from maximum to minimum.
"You will also observe that all around the corona, and extending a vastdistance beyond it on both sides, is a fainter pearly light. This iswhat is termed the zodiacal light, and is believed to be the thinnerportion of the sun's atmosphere. We can see it from the earthoccasionally after the sun has set, extending far up into the sky in theform of a semi-ellipse, the base of which is over the place where thesun is."
M'Allister here asked me to tell him "What was supposed to be the actualsize 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 hewould have some idea of what an immense body it is if he remembered thatit would require 64,000,000 globes the size of the moon to make oneglobe the size of the sun! Yet, notwithstanding this immense size, oursun is quite a small body as compared with some of the fixed stars,which, as perhaps you may know, are really suns at an inconceivabledistance from us. The bright star Sirius, which is visible during ourwinter time, is not only very much brighter in reality than our sun, butmust be many times larger; and there are others known to be very muchlarger than Sirius. It has been computed that Arcturus is in mass500,000 times as large as our sun!
"The sun revolves on its axis in a little over twenty-five days, but theexact period of its revolution is difficult to determine. The meandistance of the sun from the earth is about 92,800,000 miles. When weare farthest from it its distance is 94,600,000 miles, and when nearest,91,000,000 miles--these differences, of course, arising from theeccentricity of the earth's orbit.
"The sun's density is only about one-fifth of the earth's density; so itis evidently mainly gaseous--at all events in the outer envelopes.
"The spots upon the sun often cover such an immense area, that if ourearth were dropped into the cavity, it would be like placing a pea in ateacup! Some of the spots entirely close up in a short time, but otherslast for weeks."
We now turned from the sun and looked at the stars. Such a multitudewere visible as we had never seen from the earth; for small stars, whichthere required a telescope to bring them into view, could now be plainlyseen without any such aid, and their various colours were seen much moreclearly. They all shone with a clear and steady light; the twinkling andscintillation of the stars, as seen from the earth, being caused by thevibrations and movements in our own atmosphere. We also saw many nebulaewithout using a glass.
The Milky Way was a most gorgeous spectacle, and its beauty utterlybeyond 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 beyondthe limits within which it is seen from the earth.
We noted that the planets were also much more clearly seen; and theorange-red disc of Mars, of course, received our particular attention.
We had spent very many hours in viewing the moon, and a long time inexamining 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 fortaking turns in attending to the machinery, and then retired to bed.
_DIAGRAM: showing the Positions and Movements of thePlanets between the 3rd of August and the 24th of September, 1909: andthe Course taken by the "Areonal" on the Voyage to Mars._
_The dotted line joining the Earth to Mars shows the course taken._
_The dotted Circles show the Orbits of the Planets. The thick arrowsshow the distances travelled by the respective planets during the periodcovered by the Voyage: the line at the back end of the Arrow being theplanet's position on the 3rd August, and the points of the Arrows theposition reached on the 24th September._
_The Orbits of Mercury, Venus, the Earth and Mars are drawnapproximately to scale, but those of the outer planets are not. On thesame scale, the radii of the Orbits of the outer Planets would,approximately, be as stated below. These figures will afford some ideaof the enormous distances separating those planets._
_Jupiter_ _3_ _Inches_ _Saturn_ _5-3/8_ " _Uranus_ _10-7/8_ " _Neptune_ _17_ "
_Drawn by M. Wicks_
Plate V]
