The Book of Stars: Being a Simple Explanation of the Stars and Their Uses to Boy Life

by A. Frederick Collins

Fig. 110.—Diagram of the Moon’s Phases as We See Them.

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.