How the Moon Was Made.—There was a time away back in the beginning of the planets when the Earth did not have a Moon.

Two ideas among others have been worked out to account for the birth of the Moon and these are somewhat alike, for both agree that just as the Earth was once a part of the Sun and was separated from the Sun and became a planet so the Moon was once a part of the Earth and was thrown off and became her daughter.

The first idea as to how the Moon was made is that a smaller core was formed in the gaseous matter of the Earth and that this core and the core of the Earth, which were at first joined together like a dumbbell, as shown in Fig. 101, began to spread apart like a pair of balls fastened together with a piece of elastic when they are whirled rapidly round each other, as shown in Fig. 102.

So, too, the high speed with which the Earth turned on its axis when it was in the making caused the smaller part to slowly move away and it became the Moon.

The second idea is like the first, except that the Earth is thought to have cooled down until it was a melted mass, and it was then that a great upheaval took place in which a part, one-eightieth as large as that of the world itself, was torn out of its side and, whirling away by centrifugal force, the Moon was born.

To throw off such a mighty part of its bulk as the Moon, it has been figured out that the Earth must have made a complete turn on its axis every 2 hours, instead of one turn in 24 hours, as it now does; and it was while the Earth was turning at this terrific rate of speed that the centrifugal force overcame the force of gravitation and tore the Moon from the Earth’s side and formed a little world of its own.

It is believed by some astronomers that the Moon was once that part of the Earth which is now filled up by the waters of the Pacific Ocean and there are several reasons why this seems very likely.

First, if the waters which form the Pacific Ocean were rolled into a big ball it would be just about the size of the Moon; second, the space between the coasts of North and South America on the east, and Asia and Australia on the west, will be seen by referring to Fig. 103 to be roughly circular in form; third, there is a marked likeness between the volcanoes in California, in the Hawaiian Islands and in Japan to those on the Moon.

It was, doubtless, at this long ago time that the great volcanoes of the Moon, as well as those of the coasts of and on the islands in the Pacific Ocean were made, but what caused them can only be guessed at. There are two ideas, also, to account for them; one is that the pent-up gases inside the Earth and the Moon exploded and so threw up the volcanoes; the other idea is that showers of gigantic melted masses fell on the surface of both the Earth and Moon and so caused them.

An experiment to show how the volcanoes might have been formed by showers of meteors can be made by covering the surface of your starboard with a layer of soft clay about 4 inches thick, and then throwing clay balls against it. Artificial volcanoes with craters and all will result. Compare your artificial volcanoes with Fig. 105, showing the real volcanoes on the Moon, and you will see they are quite alike.

The volcanoes of California, Japan and the Hawaiian Islands are, many of them, still active, while those on the Moon have long since become extinct. This is easily accounted for, since the mass of the Moon is very small compared with that of the Earth, and hence, the Moon has cooled off more quickly than the Earth. The result is that while the Earth is yet hot and teeming with life and activity, the Moon is cold, and dead and silent.

Seeing the Moon With the Naked Eye.—If you look at the full Moon with the naked eye it will appear as a great, silvery-bright disk, and about the same size as the Sun.

Look again and you will see that some parts of it are much brighter than others, while another and closer observation will show you that the light and shaded parts take on the expression of a man’s face, as shown in Fig. 106. This is the famous Man in the Moon, and once you make out the likeness you will never again be able to look the full Moon in the face without seeing the man in it.

When we look at the Moon we always see the same side of it, which will be readily understood when we come to the turning of the Moon on its axis. As the Moon revolves about the Earth, you will see, if you look toward the west at the right time of the month, just at dusk, a pale crescent of light, and very soon after the Sun sets it drops out of sight below the horizon.

A few nights later the Moon will be seen, over in the sky toward the east; its crescent shape grown into the first quarter, and the Moon looks as if it was split in two. As the nights go by the Moon waxes until it is gibbous and finally the full Moon—with the man in it—stands out round and clear and bright.

It is a good idea at this time, that is, when the Moon is full, to make a drawing of her face, and the best time to do it is shortly after twilight, for later in the evening the Moon is so bright it is hard to see the details. After this the Moon begins to wane; it again becomes gibbous; then reaches its last quarter later only a crescent can be seen, and she finally disappears.

At times when the crescent is bright the whole dark disk of the Moon can be seen glowing dimly with a reddish, copper color, and this is called the old Moon in the new Moon’s arms. This copper-colored glow is the Earth-shine on the Moon, that is, the sunlight on the Earth, which is reflected to the Moon and back again to us.

On one side of the Moon you may be able to see a dark oval spot which is marked Grimaldi on the maps of the Moon. Grimaldi is a great plain, having nearly 14,000 square miles in it, with mountains flanking it on the sides. This is another good eyesight test, for it takes a mighty sharp eye to see it without a glass.

These and a dozen other interesting things on the Moon can be seen without a telescope.

The Motions of the Moon.—The Moon turns round on its axis once every month and it also revolves round the Earth once every month, so that the Moon’s day and year are of the same length just like Mercury and Venus, and this is the reason that one side of the Moon is always turned toward the Earth, as you will see if you look at her through a glass.

A simple experiment will show the cause of this: Place an apple, which we will call the Earth, on the bottom of an inverted glass on a table, and draw a chalk circle a foot in diameter around it. Next, take a tablespoon to represent the Moon, and hold it upright with the point of its bowl on the chalk line and with the bowl turned toward the apple, as shown in Fig. 107. Now, draw the spoon round the circle, turning it in your fingers so that the bowl is always toward the apple.

It is easy to see that in order for the bowl of the spoon to be turned toward the apple during all of its travels round the chalk circle the spoon must also turn once round on its own axis, and this is the reason we always see the same side of the Moon.

The Moon’s Phases.—Since one side of the Moon is always turned toward the Earth, it is clear that this is the only side we can ever see, and, further, we are only able to see as much of this side as is made bright by the Sun’s light.

The different aspects we get of the Moon as it revolves round the Earth are called the Moon’s phases; and each phase has a name, as the new moon; the first quarter; the full moon, and the last quarter.

Between the new Moon and the first quarter, and between the last quarter and the new Moon only a crescent, or sickle-like edge of the Moon, can be seen; while between the full Moon and last quarter the Moon is gibbous (pronounced gib´-us and meaning swelled, or shaped like a football).

If you will look at the picture, Fig. 108, and the diagrams, Figs. 109 and 110, and do the experiment which follows, the way the phases of the Moon are made will be perfectly clear.

The picture, Fig. 108, shows an apple from which a thin sector or slice has been cut. The lower picture shows the stem end of the apple and from this point of view the part where the slice was cut out looks wedge-shaped. This is the view of the Moon shown in Fig. 109, if we could look down on it.

Now turn the apple on its side and the place where the slice was cut out can be seen from the stem to the blossom end of the apple when it takes on a crescent form. This is the view of the Moon we really get between new Moon and its first quarter, as shown in Fig. 110.

The diagrams, Figs. 109 and 110, show the Earth in the center of the Moon’s orbit and the Moon is pictured in eight positions, as it moves round the Earth, one for each phase, while the sunlight falling upon the Earth and the Moon is shown by streamers of light from the Sun above.

The diagram, Fig. 110, shows how the sunlight falls on the Moon, but you must always keep in mind that only that part of the Moon which is in the sunlight and which is also inside of the line of its orbit can be seen from the Earth.

Starting now with the new Moon, Fig. 109, it will be seen that the Moon is directly between the Earth and the Sun and hence that part of the Moon toward the Earth is in the shadow. Now, since the eye can see nothing in the sky which is not shining, and since the Moon rises and sets at the same time as the Sun, we cannot see it. As the Moon moves on round the Earth in the direction of the arrow and while half of it is in the light and half of it is in the shadow as before, from our position we are now able to see a narrow strip of its bright surface which in Fig. 109 is shown as a wedge, but since we are looking at it from an angle we see it as a crescent, as shown in Fig. 110.

The Moon having reached its first quarter sets at midnight and from the Earth half of its bright surface can be seen, which of course is only one quarter of the Moon’s whole surface. The next phase of the Moon is when nearly all of its bright side can be seen. This is the gibbous phase and the Moon then seems to be about the shape of a football.

After the gibbous phase the full moon appears and this takes place in that part of the sky opposite the setting Sun. When the Moon is full it shines all night and does not set until sunrise.

From this time on the bright part of the Moon which we can see grows less and the gibbous phase again takes place. Soon the Moon reaches its last quarter and gradually the straight rough edge is hollowed out and another crescent is formed. The Moon is now in the east and the horns of the crescent point to the west, just opposite to the direction the horns of the new Moon pointed. The horns of the new and old crescents always point away from the Sun and this also is a good thing to remember.

To show how the Moon changes its phases perform the following simple experiment: Peel half an orange and push a knitting needle through its center and let this be the Moon. Your eyes will serve for the Earth and a lighted lamp will make a very good Sun, all of which is shown in Fig. 111.

Hold the orange by the knitting needle well out from your body with the peeled side toward you, and in such a position that the orange will be between your eyes and the lamp. The side of the orange toward you will be in the shadow and this represents the new Moon.

Now slowly turn your body round to the left and always hold the orange with the peeled side toward you. You will see that the light from the lamp striking the orange forms a crescent with its horns pointing away from the light.

Keep on turning, a little at a time, and soon a quarter of the orange will reflect the light and this is like the first quarter of the Moon. When you have turned nearly halfway round nearly half of the orange will shine by the reflected light of the lamp and you will have a fair example of the gibbous Moon.

When you have turned your back to the light hold the orange above your head so that your shadow will not hide it; now half of the orange—the half that is peeled—reflects the lamp-light and represents the Moon when it is full.

As you keep turning round the amount of light reflected by the orange, which you can see grows less and less, the bright part at first being gibbous, then the last quarter is seen, after that a thin crescent, and finally when you have turned completely round the orange is again between your eyes and the light, hence it can no longer be seen, and the new Moon phase is again at hand.

The Harvest and Hunter’s Moon.—You will remember that on September 21 the days and nights are equal and this is called the Autumn Equinox. The full moon that falls nearest to September 21 is called the Harvest Moon as it rises at nearly the same hour for several nights in succession and this makes several long moonlight evenings in succession. The Hunter’s Moon follows the Harvest Moon.

How the Moon Makes the Tides.—When we are at the seashore we soon see that there is a regular rise and fall of the ocean.

This rise and fall of the waters is called the tide, and if we note the time when the waters have reached the highest point—which is called high tide—we will find that a little over six hours later the waters have reached their lowest point—or low tide.

Before the tide has reached the high point again another six hours and some minutes have passed so that from one high tide to another high tide 12 hours and 25 minutes have elapsed. These tides are chiefly caused by two forces acting on the oceans, one being the attraction of the Moon for the Earth, and the other being the centrifugal force set up by the Earth’s motion round its axis.

The effect of the Moon’s attraction for the Earth is to pull the water of the ocean on the side of the Earth nearest it, and this forms a bulge, or great wave, while on the other side of the Earth the Moon’s attraction is smaller for the water than it is for the solid Earth, so the Earth is pulled away from the water. Thus two tidal waves are formed at the same time, one on each side of the Earth, as shown in Fig. 112.

Since the Earth revolves round its axis once in 24 hours these tidal waves go round the Earth and as there are two tidal waves each day there are two high tides and two low tides at every place on the ocean, but these are chiefly noticeable on the coasts. Fig. 112 shows the position of the Moon and the Earth, while the wavy lines around the Earth represent the oceans.

Spring Tides and Neap Tides.—Not only does the Moon’s attraction cause the tides, but the Sun’s pull on the Earth also produces tides.

When the Sun and Moon are in a line with the Earth they pull together and the tides are raised very high and they fall very low, and these high and low tides are called spring tides.

Since we have either new Moon or full Moon, when the Sun, Earth and Moon are in a line, the spring tides occur at these times, or twice every month. Figs. 113 and 114 show how the spring tides are formed.

When the Moon is at its first quarter, as in Fig. 115, or in its last quarter, as in Fig. 116, the Sun’s pull and the Moon’s pull oppose each other and the high tides are lowest. These low high tides, which take place twice a month, are called Neap tides.

A Trip to the Moon.—Many stories have been told about imaginary trips to the Moon and what the adventurers saw after reaching their destination.

Our story is made up of facts and the only thing we shall imagine is that we have made the trip and set foot somewhere on the Moon. Having performed this mental somersault we shall carefully leave out all the hard questions about living there without air and water, for this is a pleasure trip and we don’t want to spoil the fun with details.

On landing after our 240,000-mile trip we find that there is not only neither air nor water, but that the Moon is stone cold; even when the Sun shines on it, it is freezing cold, while the temperature drops to perhaps 300 degrees below zero when the Moon’s night comes on.

Our next observation will probably be that we feel much lighter than we did on Earth and we are lighter in the very nature of things, for the weight of bodies on the Moon is only one-sixth as much as they are on the Earth. This is due to the Moon being so small and light that gravity has only one-sixth as great an attractive force there as it has on the Earth.

Supposing we still retained on the Moon as much strength as we had on the Earth; then every time we took a step we would cover a distance of 15 or 20 feet; if we jumped we would sail through space with the agility of a Harlem goat, and if we played ball and batted the sphere fairly it would shoot off a quarter of a mile and go twice as far from the home plate.

Since there is no air on the Moon, in order to see one another the Sun would have to shine directly on us, and if by any chance we should get into a shadow we would be as completely lost to view as if we had fallen into one of the craters, for a shadow on the Moon is as deep and black as the darkest night you ever saw on Earth. Shadows as we know them on the Earth are always softened, for the air scatters the light.

Nor would it do us any good to cry out or whistle, for, since sound waves are carried by the air, and since there is no air on the Moon, all our efforts to make ourselves heard would be useless, even if we were only a few feet from each other. The Moon is just as silent and cold and still as it looks, for, though it serves the Earth well as a mirror to reflect the Sun’s light, it is, after all, only a great, burned-out cinder.

Looking at the sky at night from the Moon, we are surprised to find how much bigger and brighter the stars seem, and how many more of them can be seen, than from the Earth. Here we see as many with the naked eye as we could see from the Earth with a three-inch telescope.

The Earth itself is seen like a mighty Moon—a Moon as bright as 40 of the Moons we are calling on, and so large is it that we can see, not only the continents and oceans, but the polar ice caps and the plains and the mountains as well, as we see objects of same size on Moon, as shown in Fig. 117.

Watching the Earth from this new viewpoint, we see it turn on its axis every 24 hours and going through all the phases—crescent, quarter, gibbous and full, and back to crescent again, just as the Moon does when we see it from the Earth.

More curious than the Earth is the view we get of the Sun from the Moon, the lack of air making the seeing so good that the spots on the Sun, the fiery prominences and the thin corona can all be easily seen with the naked eye.

When the Moon is new the whole half of the Earth that is turned toward the Moon is sunlit and by its reflected light we can easily read our time-card—for we must get back to Earth again and either write a book or lecture about the wonders we have seen.

The Moon and the Weather.—We have seen in Chapter III that our weather is entirely dependent on the Sun. Still it is believed by many persons today that the Moon has also something to do with the changes in the weather, just as it is the cause of the tides.

Hence there have been handed down to us a large number of old sayings to show what the weather will be during certain phases of the Moon. But it has been proved by records kept of the weather that the Moon has nothing whatever to do with it. For this reason no reliance is to be placed in any forecast of the weather which is founded on changes of the Moon.

How to Tell Time by the Moon.—After having learned how to tell the hour of the day by the Sun you should learn to tell the hour of the night by the Moon.

On some nights this is a very simple thing to do, for when the Moon is full it is due south at exactly 12 o’clock midnight, as shown in Fig. 118.

Every night before the Moon is full you will find it due south 55 minutes earlier, so that you must subtract 55 minutes from 12 o’clock for each day; that is, one day before full Moon it is due south at 11:05 P. M.; two days before full Moon it is due south at 10:10 P. M.; three days before full Moon it is due south at 9:15 P. M., and so on.

After the Moon is full it will be due south 55 minutes later every night and then you must add 55 minutes to 12 o’clock; that is, one day after full Moon it is due south at 12:55 A. M.; two days after full Moon it is due south at 1:50 A. M.; three days after full Moon it is due south at 2:45 A. M., and so on.

• The Moon’s day is 27½ of our days long.
• The Moon’s year is 27½ of our days long.
• The Moon’s diameter is 2,160 miles.
• The distance from the Moon to the Earth is 240,000 miles.