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Moon glows by light it reflects from the Sun and is frequently the brightest
object in the night sky. The Moon orbits the Earth about once a month (moon-th)
from about 1 light second away. The above-pictured Full Moon occurs when
the Moon is nearly opposite to the Sun in its orbit. The Moon's diameter
is about 1/4 that of the Earth, and from the Earth's surface appears to
have almost exactly the same angular size as the Sun. Recent evidence indicates
that the Moon formed from a colossal impact on the Earth about 4.5 billions
of years ago, and therefore has a similar composition to the Earth. |
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