At _A_ the moon is between the earth and the sun, or in the phase of new
moon. The lunar hemisphere facing the earth is now buried in night,
except so far as the light reflected from the earth illuminates it, and
this illumination, it is interesting to remember, is about fourteen
times as great--reckoned by the relative areas of the reflecting
surfaces--as that which the full moon sends to the earth. An inhabitant
of the moon, standing beside the cross, sees the earth in the form of a
huge full moon directly above his head, but, as far as the sun is
concerned, it is midnight for him.
In the course of about seven days the moon travels to _B_. In the
meantime it has turned one quarter of the way around its axis, and the
spot marked by the cross is still directly under the earth. For the
lunar inhabitant standing on that spot the sun is now on the point of
rising, and he sees the earth no longer in the shape of a full moon, but
in that of a half-moon. The lunar globe itself appears, at the same
time from the earth, as a half-moon, being in the position or phase that
we call first quarter.
Seven more days elapse, and the moon arrives at _C_, opposite to the
position of the sun, and with the earth between it and the solar orb. It
is now high noon for our lunarian standing beside the cross, while the
earth over his head appears, if he sees it at all, only as a black disk
close to the sun, or--as would sometimes be the case--covering the sun,
and encircled with a beautiful ring of light produced by the refraction
of its atmosphere.
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