CHAPTER XIV.
THE SCENE SHIFTS.
Having returned the rugs to the Callisto, they applied themaximum power of the batteries to rising, closed all openingswhen the barometer registered thirty, and moved off into space.When Several thousand miles above the pole, they diverted part ofthe power to attracting the nearest moon that was in the plane ofJupiter's equator, and by the time their upward motion had ceasedwere moving well in its direction. Their rapid motion aided thework of resisting gravity, since their car had in fact become asmall moon, revolving, like those of Uranus or that of Neptune,in an orbit varying greatly from the plane of the ecliptic. Asthey flew south at a height ranging from two thousand to threethousand miles, the planet revolved before them, and they had achance of obtaining a thorough view. There were but a fewscattered islands on the side of the Northern hemisphere oppositeto that over which they had reached the pole, and in the varyingcolours of the water, which they attributed to temperature or tosome substance in solution, they recognized what they had alwaysheard described on earth as the bands of Jupiter, encircling theplanet with great belts, the colour varying with the latitude.At about latitude forty-five these bands were purple, farthersouth light olive green, and at the equator a brown orange.Shortly after they swung across the equator the ocean againbecame purple, and at the same time a well-defined and verybrilliant white spot came into view. Its brightness showedslight variations in intensity, though its general shape remainedunchanged. It had another peculiarity, in that it possessed afairly rapid motion of its own, as it moved eastward across thesurface of the ocean. It exhibited all the phenomena of thestorm they had watched in crossing Secretary Deepwaters Bay, butcovered a larger area, and was far more violent. Their glassesshowed them vast sheets of spray driven along at tremendousspeed, while the surface was milky white.
"This," said Bearwarden, picking up a book, "solves to my mindthe mystery of the white spot described by the English writerChambers, in 1889, as follows:
"'During the last few years a brilliant white spot has beenvisible on the equatorial border of the great southern belt. Acurious fact in connection with this spot is, that it moves witha velocity of some two hundred and sixty miles per hour greaterthan the red spot. Denning obtained one hundred and sixty-nineobservations of this bright marking during the years 1880-1883,and determined the period as nine hours, fifty minutes, eight andseven tenths seconds (five and a half minutes less than that ofthe red spot). Although the latter is now somewhat faint, thewhite spot gives promise of remaining visible for many years.During the year 1886 a large number of observations of Jupiterwere made at the Dearborn Observatory, Chicago, U. S., by Prof.G. W. Hough, using the eighteen-and-a-half-inch refractor of theobservatory. Inasmuch as these observations are not only of highintrinsic interest, but are in conflict, to some extent, withprevious records, a somewhat full abstract of them will beuseful: The object of general interest was the great red spot.The outline, shape, and size of this remarkable object hasremained without material change from the year 1879, when it wasfirst observed here, until the present time. According to ourobservations, during the whole of this period it has shown asharp and well-defined outline, and at no time has it coalescedor been joined to any belt in its proximity, as has been allegedby some observers. During the year 1885 the middle of the spotwas very much paler in colour than the margins, causing it toappear as an elliptical ring. The ring form has continued up tothe present time. While the outline of the spot has remainedvery constant, the colour has changed materially from year toyear. During the past three years (1884- '86) it has at timesbeen very faint, so as barely to be visible. The persistence ofthis object for so many years leads me to infer that the formerlyaccepted theory, that the phenomena seen on the surface of theplanet are atmospheric, is no longer tenable. The statement sooften made in text-books, that in the course of a few days ormonths the whole aspect of the planet may be changed, isobviously erroneous. The oval white spots on the southernhemisphere of the planet, nine degrees south of the equator, havebeen systematically observed at every opposition during the pasteight years. They are generally found in groups of three ormore, but are rather difficult to observe. The rotation perioddeduced from them is nearly the same as from the great red spot.These spots usually have a slow drift in longitude of about fiveseconds daily in the direction of the planet's rotation, whenreferred to the great red spot; corresponding to a rotationperiod of twenty seconds less than the latter.'
"This shows," continued Bearwarden, "that as long ago as towardsthe close of the nineteenth century the old idea that we sawnothing but the clouds in Jupiter's atmosphere was beginning tochange; and also how closely the two English writers and Prof.Hough were studying the subject, though their views did notentirely agree. A white spot is merely a storm-centre passinground and round the planet, the wind running a little ahead ofthe surface, which accounts for its rapid rotation compared withthe red spot, which is a fixture. A critic may say we have nosuch winds on earth; to which I reply, that winds on a planet ofJupiter's size, with its rate of rotation--though it is480,000,000 miles from the sun and the internal heat is so nearthe surface--and with land and water arranged as they are, mayand indeed must be very different from those prevailing on earth,the conditions producing and affecting them being so changed.Though the storm-centre moves two hundred and sixty miles anhour, the wind need not blow at that rate."
Later they saw several smaller spots drifting eastward, butconcluded that any seaworthy ship might pass safely through them,for, though they were hurricanes of great violence, the waveswere small.
"There would be less danger," said Bearwarden, "of shipping seashere than there is on earth; the principal risk to travellerswould be that of being blown from the deck. On account of theair's weight in connection with its velocity, this wouldnecessitate some precaution."
The next object of interest was the great red spot. It proved,as Cortlandt had predicted, to be a continent, with at that timeno special colour, though they easily recognized it by comparingits outlines with those of the spot in the map. Its length, asthey already knew, was twenty-seven thousand miles, and itsbreadth about eight thousand miles, so that it contained moresquare miles than the entire surface of the earth, land and waterincluded.
"It is clear," said Cortlandt, "that at some season of Jupiter'slong year a change takes place that affects the colour of theleaves--some drought or prolonged norther; for it is obvious thatthat is the simplest explanation. In like manner we may expectthat at some times more white spots will move across the oceanthan at others."
"On account of the size of these continents and oceans," saidBearwarden, "it is easy to believe that many climatic conditionsmay prevail here that can scarcely exist on earth. But what amagnificent world to develop, with its great rivers, lakes, andmountains showing at even this distance, and what naturalresources must be lying there dormant, awaiting our call! Thisconstantly recurs to my mind. The subjugation and thoroughopening up of this red spot continent will probably supply moreinteresting problems than straightening the axis of the earth."
"At our next visit," replied Ayrault, "when we have establishedregular interplanetary lines of travel, we may have anopportunity to examine it more closely." Then they againattracted the nearest moon beyond which they had swung, increasedthe repulsion on Jupiter, and soared away towards Saturn.
"We have a striking illustration of Jupiter's enormous mass,"said Cortlandt, as the apparent diameter of the mighty planetrapidly decreased, "in the fact that notwithstanding its numerousmoons, it still rotates so rapidly. We know that the earth'sdays were formerly but half or a quarter as long as now, havinglasted but six or eight hours. The explanation of the elongationis simple: the earth rotates in about twenty-four hours, whilethe moon encircles it but once in nearly twenty- eight days, sothat our satellite is continually drawing the oceans backwardagainst its motion. These tidal brakes acting through thefrictio
n of the water on the bottom, its unequal pressure, andthe impact of the waves on the shore, are continually retardingits rotation, so that the day is a fraction of a second longernow than it was in the time of Caesar. This same action is ofcourse taking place in Jupiter and the great planets, in thiscase there being five moons at work. Our moon, we know, rotateson its axis but once while it revolves about the earth, thisbeing no doubt due to its own comparative smallness and the greatattraction of the earth, which must have produced tremendoustides before the lunar oceans disappeared from its surface."
In crossing the orbits of the satellites, they passed nearGanymede, Jupiter's largest moon.
"This," said Cortlandt, "was discovered by Galileo in1610. It is three thousand four hundred and eighty milesin diameter, while our moon is but two thousand onehundred and sixty, revolves at a distance of six hundredand seventy-eight thousand three hundred miles fromJupiter, completes its revolution in seven days and fourhours, and has a specific gravity of 1.87."
In passing, they observed that Ganymede possessed an atmosphere,and continents and oceans of large area.
"Here," said Bearwarden, "we have a body with a diameter aboutfive hundred miles greater than the planet Mercury. Its size,light specific gravity, atmosphere, and oceans seem to indicatethat it is less advanced than that planet, yet you think Jupiterhas had a longer separate existence than the planets nearer thesun?"
"Undoubtedly," said Cortlandt. "Jupiter was condensed while inthe solar-system nebula, and began its individual existence andits evolutionary career long before Mercury was formed. Thematter now in Ganymede, however, doubtless remained part of theJupiter-system nebula till after Mercury's creation, and, beingpart of so great a mass, did not cool very rapidly. I should saythat this satellite has about the same relation to Jupiter thatJupiter has to the sun, and is therefore younger in point of timeas well as of development than the most distant Callisto, andolder, at all events in years, than Europa and Io, both of whichare nearer. This supposition is corroborated by the fact thatEuropa, the smallest of these four, is also the densest, having aspecific gravity of 2.14, its smallness having enabled it toovertake Ganymede in development, notwithstanding the latter'sstart. In the face of the evidence before us we must believethis, or else that, perhaps, as in the case of the asteroidHilda, something like a collision has rejuvenated it. This mightaccount for its size, and for the Nautical Almanac's statementthat there is a 'small and variable' inclination to its orbit,while Io and Europa revolve exactly in the plane of Jupiter'sequator."
They had about as long a journey before them as they had alreadymade in going from the earth to Jupiter. The great planet soonappeared as a huge crescent, since it was between them and thesun; its moons became as fifth- and sixth-magnitude stars, and inthe evening of the next day Jupiter's disk became invisible tothe unaided eye. Since there were no way stations, in the shapeof planets or asteroids, between Jupiter and Saturn, they keptthe maximum repulsion on Jupiter as long as possible, and movedat tremendous speed. Saturn was somewhat in advance of Jupiterin its orbit, so that their course from the earth had been alongtwo sides of a triangle with an obtuse angle between. During thenext four terrestrial days they sighted several small comets, butspent most of their time writing out their Jovian experiences.During the sixth day Saturn's rings, although not as much tiltedas they would be later in the planet's season, presented a mostsuperb sight, while they spun in the sun's rays. Soon after thisthe eight moons became visible, and, while slightly reducing theCallisto's speed, they crossed the orbits of Iapetus, Hyperion,and Titan, when they knew they were but seven hundred and fiftythousand miles from Saturn.
"I am anxious to ascertain," said Cortlandt, "whether thecomposition of yonder rings is similar to that of the cometthrough which we passed. I am sure they shine with more thanreflected light."
"We have been in the habit," said Ayrault, "of associating heatwith light, but it is obvious there is something far more subtleabout cometary light and that of Saturn's rings, both of whichseem to have their birth in the intense cold of interplanetaryspace."
Passing close to Mimas, Saturn's nearest moon, they supplementedits attraction, after swinging by, by their own strong pull,bringing their speed down to dead slow as they entered theoutside ring. At distances often of half a mile they foundmeteoric masses, sometimes lumps the size of a house, often nolarger than apples, while small particles like grains of sandmoved between them. There were two motions. The ring revolvedabout Saturn, and the particles vibrated among themselves,evidently kept apart by a mutual repulsion, which seemed both toincrease and decrease faster than gravitation; for on approachingone another they were more strongly repelled than attracted, butwhen they separated the repulsion decreased faster than theattraction, so that after a time divergence ceased, and theyremained at fixed distances.
The Callisto soon became imbued with motion also, but nothingever struck it. When any large mass came unusually near, both itand their car emitted light, and they rapidly separated. Thesunlight was not as strong here as it had been when they enteredthe comet, and as they penetrated farther they were better ableto observe the omnipresent luminosity. They were somewhatpuzzled by the approach of certain light-centres, which seemed tocontain nothing but this concentrated brightness. Occasionallyone of these centres would glow very brightly near them, andsimultaneously recede. At such times the Callisto also glowed,and itself recoiled slightly. At first the travellers could notaccount for this, but finally they concluded that the centresmust be meteoric masses consisting entirely of gases, possessingweight though invisible.
"We have again to face," said Cortlandt, "that singular law thattill recently we did not suppose existed on earth. All kinds ofsuppositions have been advanced in explanation of these rings.Some writers have their thickness, looked at from the thin edge,as four hundred miles, some one hundred, and some but forty. Oneastronomer of the nineteenth century, a man of considerableeminence, was convinced that they consisted of sheets of liquid.Now, it should be obvious that no liquid could maintain itselfhere for a minute, for it would either fall upon the planet as acrushing hail, or, if dependent for its shape on its owntenacity, it would break if formed of the toughest steel, onaccount of the tremendous weight. Any number of theories havebeen advanced by any number of men, but in weight we have therub. No one has ever shown how these innumerable fragmentsmaintain themselves at a height of but a few thousand miles aboveSaturn, withstanding the giant's gravitation-pull. Their rate ofrevolution, though rapid, does not seem fast enough to sustainthem. Neither have I ever seen it explained why the smallfragments do not fall upon the large ones, though manyastronomers have pictured the composition of these rings as wefind they exist. Nor do we know why the molecules of a gas aredriven farther apart by heat, while their activity is alsoincreased, though if this activity were revolution about oneanother to develop the centrifugal, it would not need to be asstrong then as when they are cold and nearer together. There maybe explanations, but I have found none in any of the literature Ihave read. It seems to me that all this leads to but oneconclusion, viz.: apergy is the constant and visible companion ofgravitation, on these great planets Jupiter and Saturn, perhapson account of some peculiar influence they possess, and also incomets, in the case of large masses, while on earth it appearsnaturally only among molecules--those of gases and every othersubstance."
"I should go a step further," said Bearwarden, "and say our earthhas the peculiarity, since it does not possess the influencenecessary to generate naturally a great or even considerabledevelopment of apergy. The electricity of thunderstorms,northern lights, and other forces seems to be produced freely,but as regards apergy our planet's natural productiveness appearsto be small."
The omnipresent luminosity continued, but the glow was scarcelybright enough to be perceived from the earth.
"I believe, however," said Bearwarden, referring to this, "thatwhenever a satellite passes near these fragments, preferably whenit enters the pla
net's shadow, since that will remove its ownlight, it will create such activity among them as to make theluminosity visible to the large telescopes or gelatine plates onearth."
"Now," said Ayrault, "that we have evolved enough theories tokeep astronomers busy for some time, if they attempt to discussthem, I suggest that we alight and leave the abstract for theconcrete."
Whereupon they passed through the inner ring and rapidly sank tothe ground.
A Journey in Other Worlds: A Romance of the Future Page 18
