Generally means satellite, (Luna was the Roman
goddess of the moon).
ABOUT THE MOON
The moon is the Earth's only natural satellite. It's
gravity is responsible for our ocean tides. It takes
roughly 29 days to go through it's well known phases.
The moon is also 'tidally locked' with earth, meaning we
always see the same face of the moon. We never see the
far side from Earth. The far side is not dark though.
The surface appearance of the moon is largely craters
and dark lunar maria. The mares ('seas') were thought
to be water from their dark and flat appearance.
It was realized that these areas were upwelling lava
flooding portions of the moon, leaving these dark areas.
Interestingly the lunar far side (photographed with
spacecraft) has very little maria. There is no longer
volcanic activity on the moon. This ended long ago when
the moon, being a smaller body than the earth, cooled
quickly after it's formation. Internal heat is generally
necessary for volcanic activity.
The craters were once thought to be formed from
volcanic activity. It was later realized that craters are
the result of meteorite impacts. Most of the craters
were created long ago when the early solar system
had much more leftover debris. The Earth presumably
has had as many impacts, perhaps altering climate and
causing some past extinction events, like that of the
dinosaurs. Many craters have been identified on earth
but they are usually covered with vegetation making
them harder to find. The earth also is geologically
active with earthquakes, volcanos and weather
destroying all the older craters. The most famous
crater is 'meteorite crater' in Arizona. It was the study
of this crater that largely led to the belief that
lunar craters were impact events and not volcanos.
How did the moon get there? I think we still don't know.
The best theory is that the early earth was hit by
another large body, spewing debris around the earth.
Gravity and collisions slowly collected all the material
into what is now the moon.
The moon is the only place where we have sent visitors.
In july 1969 Neil Armstrong was the first to set foot
on another world. 11 more astronauts would follow.
The lunar rocks the astronauts returned were found to
be very old. Little has changed on the moon in the last
few billion years.
When will we go back? Who knows. The Chinese have
recently proposed going to the moon. The moon could be
useful in many areas of interest. Astronomy has a lot of
promise. The moon has no atmosphere, allowing for clear
views of the universe. It could also be used by radio
astronomers. The moon would block radio waves from
Earth giving radio astronomers clear views of the skies.
Small bases on the moon do not have to be expensive. The
lunar soil can be used to make concrete. There may even
be water at the lunar poles. The moon is rich in some
minerals and could eventually be mined, saving us from
making a bigger mess of this planet. We'll soon see if
there are men of courage and vision out there who
could make these dreams a reality.
None, unless we decide to construct some.
OBSERVING - NAKED EYE
A surprising amount can be seen. Try sketching it.
Do this at first quarter or less. The full moon is often
too glaring to see detail well. I've found the full moon
can be well seen low in the sky, before it becomes too
OBSERVING - TELESCOPE
A wealth of detail can be seen. Even binoculars can be
used to see some of the craters. As with the naked eye
it's best not to view it at full moon. I've found the crescent
phase most pleasing. You really need a good lunar atlas
to detail all that can be seen. Even the smallest telescope
will show considerable detail.
Scenes from the Apollo program.
A view of the moon, showing the Maria and craters.
From apollo. The Earth rising above the lunar landscape.
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