A Journey in Other Worlds [80]
drought or prolonged norther; for it is obvious that
that is the simplest explanation. In like manner we may expect
that at some times more white spots will move across the ocean
than at others."
"On account of the size of these continents and oceans," said
Bearwarden, "it is easy to believe that many climatic conditions
may prevail here that can scarcely exist on earth. But what a
magnificent world to develop, with its great rivers, lakes, and
mountains showing at even this distance, and what natural
resources must be lying there dormant, awaiting our call! This
constantly recurs to my mind. The subjugation and thorough
opening up of this red spot continent will probably supply more
interesting problems than straightening the axis of the earth."
"At our next visit," replied Ayrault, "when we have established
regular interplanetary lines of travel, we may have an
opportunity to examine it more closely." Then they again
attracted the nearest moon beyond which they had swung, increased
the 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 planet
rapidly decreased, "in the fact that notwithstanding its numerous
moons, it still rotates so rapidly. We know that the earth's
days were formerly but half or a quarter as long as now, having
lasted but six or eight hours. The explanation of the elongation
is simple: the earth rotates in about twenty-four hours, while
the moon encircles it but once in nearly twenty- eight days, so
that our satellite is continually drawing the oceans backward
against its motion. These tidal brakes acting through the
friction of the water on the bottom, its unequal pressure, and
the impact of the waves on the shore, are continually retarding
its rotation, so that the day is a fraction of a second longer
now than it was in the time of Caesar. This same action is of
course taking place in Jupiter and the great planets, in this
case there being five moons at work. Our moon, we know, rotates
on its axis but once while it revolves about the earth, this
being no doubt due to its own comparative smallness and the great
attraction of the earth, which must have produced tremendous
tides before the lunar oceans disappeared from its surface."
In crossing the orbits of the satellites, they passed near
Ganymede, Jupiter's largest moon.
"This," said Cortlandt, "was discovered by Galileo in
1610. It is three thousand four hundred and eighty miles
in diameter, while our moon is but two thousand one
hundred and sixty, revolves at a distance of six hundred
and seventy-eight thousand three hundred miles from
Jupiter, completes its revolution in seven days and four
hours, 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 about
five hundred miles greater than the planet Mercury. Its size,
light specific gravity, atmosphere, and oceans seem to indicate
that it is less advanced than that planet, yet you think Jupiter
has had a longer separate existence than the planets nearer the
sun?"
"Undoubtedly," said Cortlandt. "Jupiter was condensed while in
the solar-system nebula, and began its individual existence and
its evolutionary career long before Mercury was formed. The
matter now in Ganymede, however, doubtless remained part of the
Jupiter-system nebula till after Mercury's creation, and, being
part of so great a mass, did not cool very rapidly. I should say
that this satellite has about the same relation to Jupiter that
Jupiter has to the sun, and is therefore younger in point of time
as well as of development than the most distant Callisto, and
older, at all events in years, than Europa and Io, both of which
are nearer. This supposition is corroborated by the fact that
Europa, the smallest of these four, is also the densest, having a
specific
that is the simplest explanation. In like manner we may expect
that at some times more white spots will move across the ocean
than at others."
"On account of the size of these continents and oceans," said
Bearwarden, "it is easy to believe that many climatic conditions
may prevail here that can scarcely exist on earth. But what a
magnificent world to develop, with its great rivers, lakes, and
mountains showing at even this distance, and what natural
resources must be lying there dormant, awaiting our call! This
constantly recurs to my mind. The subjugation and thorough
opening up of this red spot continent will probably supply more
interesting problems than straightening the axis of the earth."
"At our next visit," replied Ayrault, "when we have established
regular interplanetary lines of travel, we may have an
opportunity to examine it more closely." Then they again
attracted the nearest moon beyond which they had swung, increased
the 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 planet
rapidly decreased, "in the fact that notwithstanding its numerous
moons, it still rotates so rapidly. We know that the earth's
days were formerly but half or a quarter as long as now, having
lasted but six or eight hours. The explanation of the elongation
is simple: the earth rotates in about twenty-four hours, while
the moon encircles it but once in nearly twenty- eight days, so
that our satellite is continually drawing the oceans backward
against its motion. These tidal brakes acting through the
friction of the water on the bottom, its unequal pressure, and
the impact of the waves on the shore, are continually retarding
its rotation, so that the day is a fraction of a second longer
now than it was in the time of Caesar. This same action is of
course taking place in Jupiter and the great planets, in this
case there being five moons at work. Our moon, we know, rotates
on its axis but once while it revolves about the earth, this
being no doubt due to its own comparative smallness and the great
attraction of the earth, which must have produced tremendous
tides before the lunar oceans disappeared from its surface."
In crossing the orbits of the satellites, they passed near
Ganymede, Jupiter's largest moon.
"This," said Cortlandt, "was discovered by Galileo in
1610. It is three thousand four hundred and eighty miles
in diameter, while our moon is but two thousand one
hundred and sixty, revolves at a distance of six hundred
and seventy-eight thousand three hundred miles from
Jupiter, completes its revolution in seven days and four
hours, 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 about
five hundred miles greater than the planet Mercury. Its size,
light specific gravity, atmosphere, and oceans seem to indicate
that it is less advanced than that planet, yet you think Jupiter
has had a longer separate existence than the planets nearer the
sun?"
"Undoubtedly," said Cortlandt. "Jupiter was condensed while in
the solar-system nebula, and began its individual existence and
its evolutionary career long before Mercury was formed. The
matter now in Ganymede, however, doubtless remained part of the
Jupiter-system nebula till after Mercury's creation, and, being
part of so great a mass, did not cool very rapidly. I should say
that this satellite has about the same relation to Jupiter that
Jupiter has to the sun, and is therefore younger in point of time
as well as of development than the most distant Callisto, and
older, at all events in years, than Europa and Io, both of which
are nearer. This supposition is corroborated by the fact that
Europa, the smallest of these four, is also the densest, having a
specific