Just as the Sun dominates the day-time sky, the Moon is Queen of
the Night. The main difference is that for part of the month the Moon
is not always visible, though of course observing it is completely
safe. It depends entirely on the Sun for its reflection and by direct
observation you cannot damage your eyes. The Moon is regarded as
the Earth’s satellite, though in some ways it may be better to regard
the Earth-Moon system as a double planet.OUR FRIENDLY MOON
Astronomer Book
Procellarum, Ocean of Storms; and so on. It is quite possible the maria were
once seas of lava, not water. Certainly the Moon must have been very active
volcanically, but now the activity has ceased and the Moon is inert.
Men have been there – Neil Armstrong and Buzz Aldrin were the first, in- They found a world in some ways similar to ours, and in other ways
utterly different. It lacks an atmosphere and the sky is black in day time – by
shielding your eyes and you can see the stars against the blackness.
Despite its prominence in our sky, the Moon is not the largest natural
satellite in the Solar System since three of Jupiter’s moons and one of
Saturn’s are larger. The ratio of its mass to the mass of the Earth is only 1
to 81. This makes all the difference and the Moon’s low mass and hence
low gravity has not made it possible for our satellite to retain a dense
atmosphere or any surface water. This means that life there, at least of
our kind, can be discounted. Whether it did support any kind of life must be
regarded as dubious.
How was the Moon formed? There are several theories, none of which
are satisfactory. The original idea is that Earth and Moon formed at the same
time from the solar nebula (a cloud of dust and gas) and are linked. The main
problem is that the Moon’s overall density is less than that of Earth.
The second theory is that the Moon used to be an independent body that
came close to Earth and was unable to break free. This has been seriously
considered, but would require a very special set of circumstances.
Today, most authorities, not all, favour the giant impact theory. In this
picture, the youthful Earth was struck by a body, possibly comparable in size
to Mars, and the cores of Earth and impactor merged. Debris was spread
around and eventually collected to form the Moon. There seems to be no
insuperable problem with this theory other than the fact that the densities of
Earth and Moon are very different. The density problem is solved if the Moon
formed from the less dense outer parts of the Earth. In any case it is safe to
say Earth and Moon are much the same age.
Look at the Moon with the naked eye and you will see bright and dark
areas. Any small telescope will show the dark patches, or maria, the lunar
seas; originally it was thought they were genuine seas while the light areas
were land. The old names are still used and they are certainly romantic even
though they bear no relation to reality. Mare Crisium, Sea of Crises; Oceanus[1] Full Moon, photographed with a DSLR camera attached to a 4-inch refractor.
[2] Full Moon and waning gibbous phases.
[3] Three waxing crescent Moon mosaics captured on consecutive nights starting
on the right.21