You know that the moon is always changing; you can never see it for two or
three nights quite the same, but it seems each night a little smaller or a
little larger than when you last saw it. When you looked out of the windows
the other night, just before you went to bed, it was a very young moon
indeed that you saw--not more than two days old, as we say in reckoning
the moon's age. How small and thin it was--just like a curving rim of pale
light upon the dark sky; but as you watch this crescent--or growing--moon,
you will see it constantly getting larger and brighter, until from being
half-moon it has become full-moon, for it faces the sun, and is bright all
over that part which is turned towards you. When we speak of the "face of
the moon," we mean that side which is always turned towards us. But why
does "the gentle moon" always turn the same face to us? Astronomers tell us
that it is because she also turns slowly round on her own axis while she is
travelling round the earth. _How_ this is, I don't think I can explain to
you: but it is true that we can see only one side of the moon, that side
which catches the sunlight, and that hardly anything is known about the
other side.
Next time the beautiful moonlight nights come, remember, as you watch all
these changes, that this "waxing" and "waning" of the moon comes to pass,
not because she really changes her shape, but because, as she goes round
the earth, we see sometimes more, sometimes less of the bright part which
is lit up by the sun.
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