THE MOON THROUGH A TELESCOPE.
You know how the Moon looks, seen only with our own eyes--a bright
round ball, some would say a bright round plate, with odd gray markings
which might mean anything. This is about all that can be learned
without the help of a telescope. But with the help of a telescope much
more can be found out as to our little sister-world.
For a very long while there were no telescopes. Galileo, a famous man,
who lived nearly three hundred years ago, was the first who ever made
a telescope. Since his time men have learned to make far bigger and
better ones; but it was he who discovered how to make one at all.
The Moon, as you know, is really about 240,000 miles away. A good
telescope, such as one may often see, lessens that distance to only
one thousand or perhaps to five hundred miles. One enormous telescope
in California brings the Moon to less than one hundred miles off--some
even say to not much more than fifty miles.
You must not suppose this to mean that the telescope pulls the Moon
herself nearer. A tube on earth cannot reach forth and drag towards us
a far-off world in the sky.
Did you ever hear of the Irishman who was allowed to look through a
telescope at a church in the distance, and who declared afterwards that
the church had been brought so near he could hear the organ play!
But this is just what a telescope is _not_ able to do. It does not
bring a church nearer. It does not bring the Moon nearer. It only makes
our eyes able to see _as if_ the church or the Moon were nearer. That
is all.
It gathers up a great deal more moonlight than our eyes could collect,
and so it gives us a larger and clearer view of the Moon from which the
light comes.
Yet even at the very best, when the moon is brought, as one may say,
within perhaps a hundred miles of the Earth, even then one can only see
large things on her surface, not small things. A man who climbs a high
mountain gets a wide view all round from the top. He may see perhaps
a hundred miles in one direction. But at that distance, and at a good
deal less than that distance, he cannot make out much. A mountain or a
high hill is pretty clear, perhaps, or the glimmer of a big lake, and
a large town would be just visible as a tiny patch or spot. A single
house could not be seen at all; far less a horse or a man.
However, though we could not possibly see such small things as these
upon the Moon if they were there, we are very sure that no houses _are_
there, and no horses, and no men.
And the reason why we are so sure is that the Moon has no air.
A man cannot live without air, because he cannot breathe. Try holding
your breath for a little while and you will find how soon you must
begin breathing again. If there were no air in your room you would soon
die of suffocation. Animals cannot live without air. Even fishes need
air in the water to keep them alive. And it seems that there is neither
air nor water in the Moon.
No air: or almost none; if any at all, it is so very thin that no
living creature on earth could breathe it. No water; no seas or oceans;
no rivers and streams. No clouds; for clouds are made of water and
float in air. No grass, or plants, or trees; for they too must have air
and water. No towns or villages; for they are built by man, and no men
can be on the Moon, or women or children. What a dreary place the Moon
must be!
It looks dreary seen through a big telescope. It looks dreary also in a
photograph. Many photographs are now taken of the Moon.
Such a wild lonely scene we find! Flat desolate plains, and mountains
with sharp black shadows and clefts and streaks, and a great number of
craters in all directions.
You have heard of volcanoes on the Earth. A volcano is a mountain,
shaped usually something like a sugar-loaf, with a cup-like hollow near
the top. This hollow is called a _crater_: and now and then fire pours
from it, with melted burning rocks, or boiling mud, or hot cinders.
In parts of the world there are old used-up volcanoes, which once were
very active indeed but which now have no outbreaks. We call these dead
volcanoes.
The Moon seems to be half covered with the craters of volcanoes. That
side which we always see is pitted over with round holes, big and
little--looking in parts almost like a face badly marked with small-pox.
If all these holes really are craters they must belong to _dead_
volcanoes; because not a sign is ever observed of any fiery outburst on
the Moon. That could easily be seen through a large telescope.
These craters are of all sizes: and many of them have been measured
from the earth.
The largest volcano-crater known on the earth is perhaps not more than
eight or ten miles across. On the moon there are numbers and numbers of
little craters about that size, too many to count. But there are also
many huge craters, far bigger than anything of the kind ever seen here.
Some of the Moon mountains are very high, a good deal higher than Mont
Blanc in Switzerland; and they often lie in vast rocky heights around
some enormous crater. Such craters are to be seen fifty miles across
from edge to edge, and some a hundred miles across, and even more.
These monster craters make our little Earth craters seem very small; do
they not?
In a photograph of the Moon’s surface, taken when she is at her First
or Last Quarter, the steep mountains and great craters often stand
out very clearly. Of course they do not _look_ large to us at this
distance, but quite small.
If there were air on the moon her sharp outline and the mountain edges
would be much softer than they are now.
The Moon must be a very, very cold world.
True, she is no farther off from the Sun than we are, so his bright
rays have the same strength there as here. But she has no thick
coverlet of air wrapped round her, to act as a blanket and to keep in
the heat which the Sun gives. That is what our air does for us: and
that is what the Moon lacks.
Through the long fortnight of darkness, on the side of the Moon which
is turned away from the Sun, the cold must be perfectly awful. But
even during the long fortnight of day-time following, when that part of
the Moon which has been in darkness gets round into sunlight, things
are not much better.
The Sun indeed beats down upon the Moon with frightful power, and with
a desperate glare such as we never know on the Earth. For the same
air which keeps prisoner the warmth of the sunbeams for our use also
softens their glare. But in spite of all this it is likely that the
Moon’s surface never gets warm--that in the noon of her long day the
ground is far more than ice-cold.
On a high mountain-top of the Earth, where the air is thin, although
the glare of the Sun becomes fierce yet the ice and snow are not
melted. A little thawing of the outermost snow takes place, but often
no more than this. When the sun shines through air which is too thin to
capture and store up his heat, then he is quite overmatched by the grip
of King Frost.
If this is so on the Earth how much more is it likely to be so on the
Moon. At the top of the highest Earth mountain there is still a good
deal of air, enough for a man to breathe. But on the Moon there is no
air at all worth speaking of; not enough to keep alive any creature of
which we know.
So, though the Sun does his best, though he floods the Moon with his
warmth, all the heat is poured out again just as fast as he pours it
in. For want of a sheltering air-coverlet the ground there may remain,
and doubtless does remain, ice-cold through all the long Moon-day.
We do not on the Earth see the Stars in daylight. The same thick air
which keeps us warm also spreads the sunlight about, and softens black
shadows into gray, and turns the sky into a blue depth, and shuts off
from our sight the feeble glimmer of stars, and carries to and fro the
clouds and mists.
But on the Moon there is no air to form a veil of light; no air to
cause a blue sky; no air to spread the sunlight about; no air to make
inky shadows gray; no air to carry clouds or mists; no air to hide the
stars.
There, in the day-time, in a cloudless deep-black sky shines a dazzling
Sun. Not only a Sun, but also a magnificent Earth, hanging like an
enormous Moon always in one spot. And not only Sun and Earth, but also
countless brilliant Stars, steadfast and untwinkling.
This is a view which a man might have if he could stand on the nearer
side of the Moon.
The Sun which he would see would be our Sun. The stars would be the
same stars upon which we gaze. The Earth in his sky would be this
world upon which we live. He would see a glorious sight; of that we may
be sure. But though our thick moist air does hide the stars by day, and
make them twinkle and grow dim by night, think how one would miss the
blue sky, and all the pretty changeful clouds which come and go!
Think, too, how dismal a scene it would be around a man standing there!
Nothing but dead craters, and bare rocks, and plains without any grass
or water, and mountains without any trees. Nothing green, nothing blue,
nothing soft or fair, no breaking waves, no trickling streams, no
passing showers, no colors, no sounds!
Do you think you would like such a world to live in, even if you
_could_ live there without any air to breathe? I am very sure that you
would soon wish to be back again on our beautiful Earth.
If you were there, you would find one more thing different from what it
is here: you would become all at once a great deal lighter in your body.
Just as the Earth pulls everything towards herself so does the Moon
also. The mountains and rocks on the moon are dragged moonwards, just
as mountains and rocks on the Earth are dragged earthwards. But the
pulling there is much less than here, because the Moon is so much
smaller than the Earth.
On the surface of the Moon, _downwards_ is always towards the centre of
the Moon and _upwards_ is always towards the sky. All round the Moon it
is the same; just as it is on the Earth.
The Moon in our sky is _upwards_ to us who live on the Earth. But the
Earth in the Moon’s sky would be _upwards_ to anybody living on the
Moon.
QUESTIONS.
1. Who made the first telescope?
Galileo.
2. How long ago?
Nearly three hundred years ago.
3. How near does the biggest telescope seem to bring the Moon?
Perhaps to less than one hundred miles.
4. Could a man live on the Moon?
No; because there is neither air nor water.
5. No air at all?
There may be a very, very little; but much too little for men or
animals to breathe.
6. What can be seen of the Moon through a telescope?
Mountains and plains; and a great number of hollows or craters.
7. How high are the mountains?
Some are higher than Mont Blanc.
8. What are the craters?
They are thought to be most likely the craters of dead volcanoes.
9. What shape are they?
Generally more or less round.
10. Are they large or small?
Some are small, only a few miles across. Others are very big.
11. How big are the larger ones?
Some are even a hundred miles across.
12. Is the surface of the Moon hot, or cold?
It is believed to be very cold.
13. In the night, or in the day?
In the day as well as in the night; because there is no air to keep in
the Sun’s heat, as on the Earth.
14. What other difference would the want of air make?
The sky must be black instead of blue, and the stars must be visible
in daylight, and the shadows of the mountains must be very black, not
gray, like shadows on the Earth.
15. Are things heavy on the Moon?
Yes; but not so heavy as on the Earth. Though the Moon pulls, she pulls
less strongly than the Earth, because she is so much smaller.