If the Sun, Earth and Moon were always in the same plane with each other, every time the Earth passed between the Sun and the Moon the latter would be plunged into the Earth’s shadow and the Moon would be eclipsed. But the Moon does not revolve round the Earth so that it and the Earth make a straight line with the Sun every revolution for the reason that the Moon’s orbit is tilted a little and hence it is only once in a while that all of these bodies get in a straight line with each other, and when these times do happen then eclipses are produced. [Illustration: FIG. 121.—THE MOON AS SEEN WHEN IN ECLIPSE.] Again when the Moon is eclipsed it is not always entirely hidden from view by the great shadow of the Earth, for the air on the Earth sends the sunbeams round it so that the shadow is never very deep, and for this reason the Moon can still be seen, as shown in Fig. 121. So, then, some of these bent sunbeams fall on the Moon and are reflected from its surface back to us and it is then that we see the Moon in an entirely new light. Sometimes during an eclipse of the Moon the man can still be seen, but instead of having a bright silvery face he will have changed it to the copper color of a red Indian. The whole eclipse of the Moon often lasts longer than six hours and sometimes the moon is in the deep shadow of the Earth as long as two hours. [Illustration: FIG. 122.—ECLIPSE OF THE SUN BY THE MOON (EXPERIMENT).] [Illustration: FIG. 123.—THE SUN ECLIPSED BY THE MOON (DIAGRAM).] A _total eclipse_ is one in which the Moon passes completely into the shadow of the Earth, while a _partial eclipse_ is one where only part of the Moon is in the shadow of the Earth and part of it is in the sunlight. Eclipses of the Moon occur quite often and you can look up the time of the next one in your almanac. =Eclipse of the Sun.=—When the Sun is eclipsed it is caused by the Moon passing between the Earth and the Sun and so the light is cut off from the former. To show how this is done all that is needed is to continue the experiment with the lighted lamp and the apple which you used for the eclipse of the Moon. You will remember in that experiment you were turned with your back to the lamp and with the apple held in front of you. Now to show how the Sun is eclipsed by the Moon keep on turning round until you face the lighted lamp with the apple in between and in a straight line with your eyes and the flame, as shown in Fig. 122. Again you will find that the side of the apple nearest you will be in a deep shadow, though usually it can still be seen, and though you can see the light all round the apple yet you cannot see the flame.