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Day and Night
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Day and Night
"I
T seems to me," said Claire, "we have lost sight of the
hearth that turns with its lighted fire-brands around the
lark."
"On the contrary, we are closer to it than ever. If the sun,
which is thirty-eight millions of leagues from us, were to
go around the earth every day, do you know how far it would
have to go in a minute? More than 100,000 leagues. But this
incomprehensible speed is nothing. The stars, as I have just
told you, are so many suns, comparable to ours in volume and
brilliancy; only they are much farther away, and that is
what makes them appear so small. The nearest is about thirty
thousand times as distant as the sun. Accordingly, in order
to go around the earth in twenty-four hours, as it appears
to do, it would have to move at the rate of thirty thousand
times 100,000 leagues a minute. And how would it be with
other stars a hundred times, a thousand times, a million
times farther away—stars which, despite their distance,
would all have to accomplish their journey around the earth
always in exactly twenty-four hours? And remember,
furthermore, the prodigious size of the sun. You want it,
the giant, the colossus, beside which the earth is only a
lump of clay, to circle at an impossible speed in infinite
space,
in order to give light and heat to our planet; you
want thousands and thousands of other suns, quite as large
and immensely farther off—in a word, the stars—to
accomplish also, with velocities increasing according to the
distance, a daily journey around this humble terrestrial
globe! No! no! such an arrangement is contrary to reason; to
allow it is to want to make the firebrands, the hearth, the
whole house, turn around a little bird on a spit."
"Then it is the earth that turns, and we turn with it,"
Claire again interposed. "In consequence of this movement
the sun and stars seem to us to move in the opposite
direction, like trees and houses when we are on the train.
Since the sun seems to go around the earth from east to west
in twenty-four hours, it is a proof that the earth turns on
its axis from west to east in twenty-four hours."
"The earth turns in front of the sun in a manner to present
its different parts successively to the rays of that body;
it pirouettes on its axis like a top. Moreover, while it
thus rotates in twenty-four hours, it revolves around the
sun in the interval of a year. In playing with a top you
find a good example of two analogous movements executed
together. When the top turns on its point, not moving from
the same place—in short, when it sleeps—it has only the
movement of rotation. But in throwing it in a certain way,
you know better than I that it circles on the ground while
turning on its point. In that instance, it represents in a
small way the double movement of the earth. Its rotation on
its point represents the whirling motion of the earth on its
axis; its course
on the ground represents the earth's
revolution around the sun.
"You can familiarize yourself in another way with the double
movement of the terrestrial globe, as follows: place in the
middle of a room a round table, and on that table a lighted
candle to represent the sun. Then circle around the table,
pirouetting on your toes. Each of your pirouettes
corresponds to a turn of the earth on its axis, and your
course around the table corresponds to its journey around
the sun. Notice that in turning on your toes you present in
succession to the rays of the candle the front, one side,
the back, and the other side of your head, which in our
experiment may represent the terrestrial globe; so that each
one of its parts is in turn in the light or in the shade.
The earth does the same: in turning it presents one after
the other its different regions to the rays of the sun. It
is day for the region that sees the sun, night for the
opposite region. That is the very simple cause of day and
night. In twenty-four hours the earth makes one rotation on
its axis. Of these twenty-four hours the duration of the day
and night is composed."
"I understand very well the cause of the alternation of day
and night," said Jules. "It is day for the half of the earth
that sees the sun, night for the opposite half. But as the
globe turns, each country comes in succession to face the
sun while others pass into the unlighted half. The lark that
turns on the hearth presents, in the same way, each of its
sides in turn to the heat of the flame."
"One might almost say," remarked Emile, "it is
day for the
half of the lark next to the fire, and night for the other
half."
"One difficulty still perplexes me," Jules continued. "If
the earth turns around once in every twenty-four hours, in
half of that time we ought to make a half-turn with the
globe that carries us, and find ourselves upside-down. At
this moment we have our heads up, feet down; twelve hours
later it will be just the opposite: our heads will be down
and our feet up. We are upright, we shall be upside-down. In
that inconvenient position why don't we feel uncomfortable?
Why are we not thrown down? So as not to fall, it seems to
me, we ought to be obliged to cling to the ground in
desperation."
"Your observation is right," returned Uncle Paul, "but only
in a certain degree. Yes, it is true that twelve hours from
now we shall be in an inverse position; our heads will be
toward that point in space to which our feet are now turned.
But despite this inversion there will be no danger of our
falling, nor even the slightest inconvenience of any kind;
for our heads will always be up, that is to say toward the
sky, since the sky surrounds the terrestrial globe
everywhere; our feet will always be down, that is to say
resting on the ground. Understand thoroughly, once for all,
that to fall is to rush toward the ground, and not into
surrounding space. So that notwithstanding all the
evolutions of our globe, as we are always on the earth, feet
on the ground, head toward the sky, we are always in an
upright position, without any unpleasant feeling, without
any danger of falling."
"Does the terrestrial globe turn very fast?" Emile inquired.
"It turns on its axis once in twenty-four hours. Therefore
any point in its middle region, the region that makes the
longest journey, travels in the same time forty millions of
meters, that is to say a journey equal to the circuit of the
earth, or 462 meters a second. That is about the speed of a
cannon-ball as it leaves the cannon's mouth, or about
thirty times the speed of the fastest locomotive.
Mountains, plains, seas, apparently fixed in their places
for time and for eternity, are perpetually chasing one
another in a circle, with the formidable speed of more than
one-tenth of a league a second."
"And yet everything seems to us to be stationary."
"Without the jolting of the car should we not think we were
standing still when the train carries us with such frightful
speed? Well, the rapid movement of the earth is at the same
time so gentle that it is impossible to be aware of it
except by the apparent motion of the stars."
"By rising to a certain height in a balloon," said Jules,
"we ought to see the earth turning under us. Seas and their
islands, continents with their empires, forests, and
mountains, ought in succession to come under the eyes of the
observer, who in twenty-four hours sees the turning of the
whole earth. What a magnificent spectacle that must be! What
a journey, so wonderful and with so little fatigue! When the
rotation brings back one's own country, one descends and it
is accomplished. In
twenty-four hours, without changing
place, one has seen the whole world."
"Yes, I agree with you, it would be an admirable way to see
countries. To this spot where we are other peoples will
come, brought by the rotation; seas, distant regions, snowy
mountains will take our place; and to-morrow at the same
hour we shall be here again. Where we are talking now, in
the shade of the juniper-trees, first will pass the sea, the
somber Atlantic, which will replace our conversation by the
grand voice of its waves. In less than an hour the ocean
will be here. Some large war-vessel, with its triple row of
guns, will float perhaps, all sails set, over the spot we
are occupying. The sea has passed. Now we have North
America, the great Canadian lakes, and the interminable
prairies where the red-skinned Indians hunt buffaloes. The
sea begins again, much larger than the Atlantic; it takes
nearly seven hours to pass. What line of islands is this
where fishermen wrapped in furs are drying herrings? They
are the Koorile Isles, south of Kamchatka. They pass
quickly; we scarcely have time to give them a glance. Now it
is the turn of the yellow-faces—the Mongolians and
Chinese, with slanting eyes. Oh! what curious things we
could see here! But the ball is always turning, and China is
already in the distance. The sandy plateaus of Central Asia
and mountains higher than the clouds come next. Here are the
pastures of the Tartars, with neighing herds of mares; here
are the grassy plains of the Caspian with the flat-nosed
Cossacks; then southern Russia, Austria, Germany,
Switzerland,
and finally France. Let us descend quickly, get
on to our feet; the earth has finished its rotation.
"Do not for an instant, my little friends, think that this
giddy spectacle of the earth passing with the rapidity of a
cannon-ball would be visible to any but spiritual eyes. By
rising into the upper air in a balloon, as Jules said, it
does at first seem as if we ought to see the earth turning
and lands and seas passing under our feet. Nothing of the
kind takes place, for the atmosphere turns with the
terrestrial globe and drags the balloon in the general
rotation, instead of leaving it at rest, as would be
necessary if the observer were to have successively under
his eyes the different regions of the earth."
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