A Journey in Other Worlds [71]
we found no trace of ice action,
notwithstanding the comparative slowness with which we decided
that the ridges in the crust had been upheaved on account of the
resisting power of gravity, and, as I see now, also on account of
Jupiter's great mass, which must prevent its losing its heat
anything like as fast as the earth has, in which I think also we
have the explanation of the comparatively low elevation of the
mountains that we found we could not account for by the power of
gravitation alone.[2] From the fact that the exposed surface
farther south must be old, on account of the slow upheaval and
the slight wear to which it is exposed, about the only wearing
agent being the wind, which would be powerless to erase
ice-scratches, especially since, on account of gravity's power,
it cannot, like our desert winds, carry much sand--which, as we
know, has cut away the base of the Sphinx--I think it is logical
to conclude that, though Jupiter's axis is changing naturally as
the earth's has been, it has never varied as much as twenty-three
and a half degrees, and certainly to nothing like the extent to
which we see Venus and Uranus tilted to-day."
[2] It is well known that mountain chains are but ridges or
foldings in the crust upheaved as the interior cools and shrinks.
This is proved by reason and by experiments with viscous clay or
other material placed upon a sheet of stretched rubber, which is
afterwards allowed to contract, whereupon the analogues of
mountain ridges are thrown up.
"I follow you," said Bearwarden, "and do not see how we could
arrive at anything else. From Jupiter's low specific gravity,
weighing but little more than an equal bulk of water, I should
say the interior must be very hot, or else is composed of light
material, for the crust's surface, or the part we see, is
evidently about as dense as what we have on earth. These things
have puzzled me a good deal, and I have been wondering if Jupiter
may not have been formed before the earth and the smaller
planets."
"The discrepancies between even the best authorities," replied
Cortlandt, "show that as yet but little has been discovered from
the earth concerning Jupiter's real condition. The two theories
that try to account for its genesis are the ring theory and the
nebulous. We know that the sun is constantly emitting vast
volumes of heat and light, and that, with the exception of the
heat resulting from the impact of falling meteors, it receives
none from outside, the principal source being the tremendous
friction and pressure between the cooling and shrinking strata
within the great mass of the sun itself. A seeming paradox
therefore comes in here, which must be considered: If the sun
were composed entirely of gas, it would for a time continue to
grow hotter; but the sun is incessantly radiating light and heat,
and consequently becoming smaller. Therefore the farther back we
go the hotter we find the sun, and also the larger, till, instead
of having a diameter of eight hundred and eighty thousand miles,
it filled the space now occupied by the entire solar system.
Here is where the two theories start. According to the first,
the revolving nebulous mass threw off a ring that became the
planet Neptune, afterwards another that contained the material
for Uranus, and so on, the lightest substance in the sun being
thrown off first, by which they accounted for the lightness of
the four great planets, and finally Mars, the earth, and the
small dense planets near the sun. The advocates of this theory
pointed to Saturn's rings as an illustration of the birth of a
planet, or, rather, in that case a satellite. According to this,
the major planets have had a far longer separate existence than
the minor, which would account for their being so advanced
notwithstanding their size. This theory may again come into
general acceptance, but for the present it has been discredited
by the nebulous. According to this second theory, at the time
the sun filled all the space inside of Neptune's,
notwithstanding the comparative slowness with which we decided
that the ridges in the crust had been upheaved on account of the
resisting power of gravity, and, as I see now, also on account of
Jupiter's great mass, which must prevent its losing its heat
anything like as fast as the earth has, in which I think also we
have the explanation of the comparatively low elevation of the
mountains that we found we could not account for by the power of
gravitation alone.[2] From the fact that the exposed surface
farther south must be old, on account of the slow upheaval and
the slight wear to which it is exposed, about the only wearing
agent being the wind, which would be powerless to erase
ice-scratches, especially since, on account of gravity's power,
it cannot, like our desert winds, carry much sand--which, as we
know, has cut away the base of the Sphinx--I think it is logical
to conclude that, though Jupiter's axis is changing naturally as
the earth's has been, it has never varied as much as twenty-three
and a half degrees, and certainly to nothing like the extent to
which we see Venus and Uranus tilted to-day."
[2] It is well known that mountain chains are but ridges or
foldings in the crust upheaved as the interior cools and shrinks.
This is proved by reason and by experiments with viscous clay or
other material placed upon a sheet of stretched rubber, which is
afterwards allowed to contract, whereupon the analogues of
mountain ridges are thrown up.
"I follow you," said Bearwarden, "and do not see how we could
arrive at anything else. From Jupiter's low specific gravity,
weighing but little more than an equal bulk of water, I should
say the interior must be very hot, or else is composed of light
material, for the crust's surface, or the part we see, is
evidently about as dense as what we have on earth. These things
have puzzled me a good deal, and I have been wondering if Jupiter
may not have been formed before the earth and the smaller
planets."
"The discrepancies between even the best authorities," replied
Cortlandt, "show that as yet but little has been discovered from
the earth concerning Jupiter's real condition. The two theories
that try to account for its genesis are the ring theory and the
nebulous. We know that the sun is constantly emitting vast
volumes of heat and light, and that, with the exception of the
heat resulting from the impact of falling meteors, it receives
none from outside, the principal source being the tremendous
friction and pressure between the cooling and shrinking strata
within the great mass of the sun itself. A seeming paradox
therefore comes in here, which must be considered: If the sun
were composed entirely of gas, it would for a time continue to
grow hotter; but the sun is incessantly radiating light and heat,
and consequently becoming smaller. Therefore the farther back we
go the hotter we find the sun, and also the larger, till, instead
of having a diameter of eight hundred and eighty thousand miles,
it filled the space now occupied by the entire solar system.
Here is where the two theories start. According to the first,
the revolving nebulous mass threw off a ring that became the
planet Neptune, afterwards another that contained the material
for Uranus, and so on, the lightest substance in the sun being
thrown off first, by which they accounted for the lightness of
the four great planets, and finally Mars, the earth, and the
small dense planets near the sun. The advocates of this theory
pointed to Saturn's rings as an illustration of the birth of a
planet, or, rather, in that case a satellite. According to this,
the major planets have had a far longer separate existence than
the minor, which would account for their being so advanced
notwithstanding their size. This theory may again come into
general acceptance, but for the present it has been discredited
by the nebulous. According to this second theory, at the time
the sun filled all the space inside of Neptune's,