Man's physical universe

xanabras

THE PLANETS AND THEIR MOTIONS 105

To a man on the moon the earth would be bright because of the fact

that it reflects sunlight just as the other planets do. This earthshine

is in turn reflected back to the earth, so that when only a part of the

moon receiving direct sunlight is

visible, the rest of the side of the

moon facing the earth becomes

faintly visible because of reflected

earthshine.

The moon always turns the same

face toward us, which means that

the moon rotates on its axis once

while it revolves once around the

earth.

Eclipses No Longer Are a Source of

Terror.

Modern man no longer is terrified

by eclipses but looks upon their

appearance at the precise place

and time predicted by astronomers

many years before as evidence of

the true value of the scientific method.

Fig. 26. Earth-lit "old moon in the

new moon's arms." (Photograph

from the Yerkes Observatory, reprinted

by permission of the Chicago

University Press.)

It is possible to predict to within

a few hundred yards where the shadow of the moon will

be located

on the earth at any given second of time during the next few years.

O

O €

Full Moon '.

O'


First Quarter

EARTH

New Moon

Light from the Sun

c

Last Quarter

Fig. 27. The phases of the moon.

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