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

by A. Frederick Collins

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.

Fig. 111.—Boy, Lamp and Orange
Showing Phases of Moon.

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].