THE GIANT WORLD OF JUPITER
EVERYBODY notices, year by year, in a southerly direction, a bright
star which half the spectators believe to be the evening star, but
which so far from being Venus, is its very antithesis.
To mistake Jupiter for Venus is a sufficiently gross error. But even
this error is preferable to nothing. It is better to be mistaken than
not to see anything. A large portion of the human race sees nothing
at all, thinks nothing, and passes its whole life in the stupidity of
plants and slugs.
To notice the star in the sky, even to give it a wrong name, is
something, at all events. It shows that one does not go about with eyes
cast on the ground or occupied with worldly affairs and with the spirit
absorbed by material interests.
Venus, the Shepherds’ Star, the morning and evening star, is never far
from the sun. It is never in the south, neither in the evening nor at
midnight. Its orbit round the Sun lies within our own. Jupiter, on
the contrary, revolves round the same Sun along an orbit outside our
own, five times as far as the central luminary, at 485 million miles
instead of 92 million miles. The distance between us and Jupiter is
therefore always greater than 393 million miles except when the Earth
reaches the extremity of its elliptical orbit (“aphelion”) at a time
when Jupiter is in “opposition” to the Sun. We often see it at a medium
distance of 450 million miles. If the atmosphere extended over all that
distance, an aeroplane flying without a stop at 62 miles an hour, and
therefore covering 1,500 miles a day, would take no less than 300,000
days or 812 years to complete the voyage. It would be wise to take some
provisions with us!
But on what sort of a world should we arrive?
A giant world, an immense world, a strange world. It is only a thousand
times smaller than the Sun--that is to say, 1,000 times larger than the
Earth, or even more. Jupiter is eleven times larger in diameter than
our globe, i.e. 1,300 times larger in volume. Gravitation is enormous
at its surface, 2½ times what it is here. A man weighing 10 stone
here would weigh 25 stone there. But its density is very low, being
one-quarter of that of the earth. It is a world of water and more or
less dense gas.
Astronomers observe it with great interest since they see it furrowed
with various currents and enveloped in clouds and vapours. The currents
at the surface revolve with different speeds, so that it is difficult
to know what is the rotation of the planet itself. At the equator, this
rotation is accomplished in 9 hours 50 minutes 30 seconds; not far from
the equator, in the subtropical regions, it takes 9 hours 55 minutes 41
seconds. Since Jupiter’s year is twelve times as long as ours, there
are more than 10,000 days per annum.
Here is a curious circumstance: on account of the difference of
rotation, the Jovian year comprises 87 more (Jovian) days at the
equator than it does in the subtropical zone. If it were the same on
our globe, the inhabitants of the Congo, Colombia, Borneo, and Sumatra
would have a day more in their year (and even five in four years) than
those of Senegal, the Antilles, Siam, or India, a difference of 125
days per century! It would be difficult to keep their calendars in
agreement.
There are seven or eight kinds of currents between the equator and the
poles, so that one can say of Jupiter, as of the Sun, that it does not
turn in one piece.
And those speeds themselves vary with the years. In the southern
tropical zone there is a curious spot which has been followed with
some interest for fifty years. Although it is much larger than the
Earth, it seems to float in the current. Constant observation shows its
period of rotation to have been 9 hours 55 minutes 41 seconds in 1900
and 9 hours 55 minutes 39 seconds in 1906, and its period returned in
1913 to the figure of 1900. What is the nature of this floating spot?
In 1890 its colour was red. It then gradually got paler, and then
pink once more. Its shape was that of a long oval, measuring 26,000
miles in length, or more than three times the diameter of our globe.
The current in which it floats has not the same period of rotation
as the spot itself. The spot is pushed from west to east, and it has
shifted 57 degrees in two years. Now, a degree on the globe of Jupiter
in that latitude represents 720 miles. This Jovian formation has,
therefore, been displaced 41,000 miles, or a distance more than five
times the diameter of our planet. It is as if Australia were to detach
itself from the bottom of the sea and float about on the surface of
the Pacific Ocean! Does this oscillation, which we only see in plan,
and not in elevation, indicate the formation of a satellite trying to
disengage itself from its parent planet and not succeeding? It looks
as if there were on this giant world of Jupiter no surface at all,
but irregular aerial layers one over the other, and full of clouds.
The temperature must be very high, and enormous masses of vapour
are formed, to wrestle in prodigious storms. Though mythology is of
no importance here, it is evident that Jupiter is indeed the god of
thunder-storms. Jupiter is a world in the making, a sun which has lost
its light, but not its heat. Its density, nearly equal to that of the
Sun, is barely greater than that of water. A globe of vapour varied by
mountains of clouds, impalpable Himalayas, aerial Alps in convulsions,
fluid and constantly agitated Pyrenees! Its colossal bulk has prevented
its cooling as fast as our Earth, and it will no doubt take tens of
hundreds of millions of years to arrive at a temperature fit for
inhabitants. In all probability there is nobody yet on Jupiter, neither
men nor animals nor plants. This immense world is in its primordial
state and prepares itself for the future.
Spectrum analysis shows that the substances which abound there are
different from terrestrial substances. Any living beings who may
develop there will probably be chemically different from terrestrial
beings, and consist not of oxygen, hydrogen, carbon, or nitrogen,
but of combinations of other substances. It will be a differently
constituted world.
Our interest in observing it is not lessened by that consideration.
The thinking mind knows that our present era is of no particular
importance. It has been preceded by other eras and will be succeeded by
other cycles. It is not because we live at this particular moment that
our time can be said to be of any special value. The years contemporary
with Jesus Christ or with the Pharaohs who built the pyramids had just
as much value as ours, and when we shall no longer be there, the Earth
will continue to revolve and measure out their days to our successors
indefinitely. Whether Jupiter is inhabited this year or in 500,000
years or in 10,000,000 years is the same to the philosopher. Everything
to him is present, both the future and the past ... this great subject
has already been dealt with, and there is no need to refer to it again.
Let us greet Jupiter as the symbol of the future. Behind him, among the
constellation, there are stars whose light, starting at the time of
the siege of Troy, has only arrived to-day. Thus in the same celestial
record the past and the future are thrown together, and they tell us
that if there is anything interesting in human life it is Thought, the
mind which contemplates the universe, which lives intelligently, and
without which all Nature would be but the play of an automaton.
VII. HEARTBEATS
ACROSS SPACE