LUNA

Luna, commonly known as "The Moon" as seen from a telescope. You can see the many craters found on Luna. These craters are very famous.

The Moon is the only natural satellite of Earth. It's official name is Luna (latin for moon) to distinguish it from the generic "moon, however it often, day by day, goes by the name Moon, as this was what it has been traditionally called. Apart from the word lunar, the terms selene/seleno and cynthion (from the Lunar deities Selene and Cynthia) refer also to the Moon (aposelene, selenocentric, pericynthion, etc.). The average distance from the Moon to the Earth is 384,403 kilometers (238,857 miles). The Moon's diameter is 3,476 kilometers (2,160 miles).

Between 1969 and 1972, the U.S. Apollo program sent twelve men to land on the Moon, the first of which were Neil Armstrong and Buzz Aldrin in Apollo 11. The first men sent to the Moon were Frank Borman, James Lovell and William Anders, in Apollo 8. Before and since that time, the Moon has been the target of numerous landing and orbiting space probes, starting with the Soviet Luna 1 in 1959.

Due to tidal interactions between the Earth and Moon, it always keeps one face toward us, rotating on its axis once per revolution. As it revolves around the Earth, the Moon appears to go through phases. This called bieng tidally locked. Other moons, such as Charon, are tidally locked to thier planets.

Interestingly, with the exception of Pluto and its satellite Charon, the Moon is the largest satellite when compared to its planet. The Moon is one quarter the size of the Earth.

However, the most important fact about the Moon is that it is the only other body in the universe upon which human beings have walked. This is indeed a singular distinction.

The Facts


Equatorial Radius (km): 1738
Mass (kg): 7.35x1022
Mean Density (g/cm3): 3.34
Period of Revolution Around the Earth (days): 27.3217
Period to Revolve Around the Earth with Relation to the Sun (days): 29.5

The Formation of the Moon

The Moon is believed to have formed approximately 4.7 billion years ago when an object the size of Mars collided with the primordial Earth. The force of this collision released an enormous amount of debris into space, some of which settled into orbit around the Earth until it accreted into the Moon.

At about 4.6 billion years ago, the Moon began to cool and the first solid crust began to form. As the molten surface began to cool, huge asteroids and meteorites began their bombardment of the surface, a process which continued for millions of years.

At about the 4 billion year mark, the bombardment slowed down. Around the same time, the interior burst forth with great floods of lava, pooling in the bottom of some of the larger impact basins, thus creating the lunar maria which can be seen from Earth. These lunar 'seas' are found primarily on the near-side of the Moon, drawn by the same tidal influences that keep that face permanently pointed earthwards. The Moon's far side has a thicker crust of 100km, as opposed to 60km on the near side, which is also due to the tidal influence of the Earth.

After the formation of the maria, the impacts decreased to a rate which has remained more or less what we find today. Of course the far side is exposed to more impacts because the near side is shielded by the bulk of the Earth. Since seismic instruments were left on the lunar surface by the Apollo astronauts, scientists have recorded an average of 150 impacts per year, with the largest being a one-ton impact on the lunar far side in 1972.

Observing the Moon

For centuries, the Moon has been a favourite target for astronomers. Obviously, it is the nearest and largest object in the night sky. When using a small telescope or binoculars, the best details can be found near the lunar terminator - the line separating night from day on the Moon's surface. A large instrument should be fitted with a lunar filter because even the weak light of the Moon can cause eye damage if viewed for extended periods through a large light-gathering telescope. There are three lunar features that are easy to spot with the naked eye, a pair of binoculars or a small telescope.

Marinas

These lunar "seas" (as they were called by the ancient astronomers) are the dark patches visible on the Moon's surface. Visible in the exact center of the first quarter moon is the most famous of all lunar seas, Mare Tranquilitatis, the 'Sea of Tranquillity', which was the site of the first manned Apollo landing. Other watery terms used to describe lunar features include: Oceanus (Ocean); Lacus (Lake); Sinus (Bay); and Palus (Swamp).

Craters

Named mostly after scientists, these objects are the result of meteoroid impacts. They can range in size from microscopic to more than 150 miles in diameter. Many craters have central peaks and ray systems extending away from the crater. The Copernicus and Kepler craters display excellent ray systems across the maria of the last quarter moon. Also visible at last quarter, the Tyco crater's ray system extends across much of the lunar surface. It is interesting to note that well into this century many astronomers believed that lunar craters were extinct volcanoes.

Highlands

The light-coloured bits of the lunar surface, this is the oldest and most heavily cratered surface on the Moon. The mountains of the Moon are usually named after mountain ranges here on Earth. A small telescope can often reveal long shadows extending from these mountainous regions.

The Moon's Future

The Moon is receding from Earth about 60 meters (196 feet) every 1,000 years due to the complex gravitational interactions with the Earth. If this rate continues, the Moon will appear 10% smaller in about 6.6 million years, and 15% smaller in about 1 billion years, from earth. The month of February will be very unusual in 2.5 million years. There will be the rare event of a month (February) with no full moon. The last time this occurred was in 1866. Furthermore, if undisturbed, the footprints on the Moon's surface left behind by the Apollo astronauts will remain visible for some 10 million years.

Lunar Influences

Ask any policeman or emergency room worker, and they'll tell you there is a definite relationship between human behavior and the lunar cycle. Increases in crimes, traffic accidents and patient admissions to mental hospitals all increase during the full moon. This is why the words lunatic lunacy has the "luna" prefix.

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