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Nitty-gritty: Lunar talk
Since time immemorial, moon has been a source of fascination and inspiration for all of us. Be it poems, movies or songs, references of the moon have been used in different forms. Scientists and astronauts have also made various successful attempts at not only studying the moon scientifically but also visiting it.
Yet, for scientists the moon remains an unsolved mystery. With remarkable progress in science, moon sciences are developing into a popular faculty. This has helped us uncover some very interesting facts about the satellite. Here are some important facts.
The origin
In early times, people harboured different perceptions about the origin of moon. They liked to believe that the moon was a sibling of the planet Earth and that both were formed together. But because the moon’s properties did not include iron, this theory was quickly rejected.
Another theory held that the moon originated somewhere in the solar system which was low in iron content. It was eventually ‘detained’ into an orbit around the Earth. This theory also lost its appeal when some rocks were found on the moon which were similar in content to the ones found on Earth.
Then there was a popular belief that Earth’s rotation influenced the moon to rotate as well. However, a closer look at the angular movements of the two bodies showed that the Earth-moon system does not work on this theory.
At present the most acclaimed and accepted theory of the origin of moon holds that when the Earth was formed about 4.5 million years ago, some other relatively smaller planets were growing. One such planet hit the Earth’s surface while in its developing phase, giving out rocky debris and resulting in the formation of moon. There are many scientific reasons which make this theory reasonably acceptable.
For instance, the Earth has a large core of iron which the moon does not have, the reason being that iron had already been drained to the core when the big impact occurred. This is why the remains that wafted out of both the Earth and the moon came from their iron-depleted, rocky mantles.
Secondly, the Earth has a mean density of 5.5g/cubic centimetres, but the density of moon is 3.3g/cc. Again, this is because the moon has no iron. The oxygen isotope composition of the moon and the Earth are the same, unlike other planets. This suggests that the moon originated from the material produced in the Earth’s neighbourhood.
Currently, the giant impact theory is the leading theory explaining the origin of the moon in relation to the Earth. However, only time will tell if any other theory with stronger evidences comes to dethrone this one.
Moon and science
Apollo was the first successful space mission involving moon landing, accomplished by Neil Armstrong. This mission allowed scientists to understand the Earth’s satellite better. For example, scientists came to know that the moon was about 4.5 billion years old and had a rocky surface structure with either no or very minimal gravitational force. The rocks on the moon have been exploded and compressed down by meteorites.
After the Apollo mission, research on the science of moon, and the possibility of a trace of life there, gained momentum. This has led to the introduction of new missions, like the Lunar Prospector programme of the Nasa.
This programme is aimed at achieving the targets that the Apollo was not successful in. It will focus on drawing the complete lunar surface structure and extensively analysing the composition of moon.
Extensive research on the moon has forced scientists to think about the possibility of creating moon colonies and lunar commerce in the future. Obviously, the evidence of traces of water in the lunar geography did huge service to the cause.
According to the scientists working on Apollo data, the moon has a rocky surface, which lies over a broad crust with a length of 60km. Underneath this thick layer is a uniform surface called lithosphere that comprises an area of 940km, a small liquid athenosphere of 740km and a small core. This shows that the moon has a more stable surface than the Earth and the chances of atmospheric meddling are negligible. Thus, the moon and the Earth are scientifically different mixes of similar pool of materials.
The gravity of moon is a fraction of the Earth’s gravity, with an escape velocity (the speed required by a spaceship to escape its gravitational pull) of 2.38km/sec or 1.4 miles/sec. For Earth it is 11.2km/sec, which is about 7miles/sec. Due to this, some scientists believe that a base can be created on the moon for executing manned missions to other planets.
The moon has always been the focus of mythologies and beliefs, and literature is replete with fables surrounding it. One such famous fable says that full moon brings out the worst behavioural changes in humans and animals. It also increases the frequency of tides in the oceans and seas.
This correlation is based on the assumption that since the Earth is 80 per cent water and the human body also comprises 80 per cent water, the moon brings a tidal affect on human behaviour. Such influence of the moon has been dubbed ‘the lunar effect’.
However, objective studies do not support these beliefs and scientists assert that tides are noticed in oceans only, where the large distance acts like a multiplier. In small bodies of water, like lakes and the human body, tides are negligible.
At full moon, the Earth is between the moon and the Sun and at new moon, the moon is between the Sun and the Earth. During full and new moon, the Earth, moon and Sun are queued up giving higher tides than usual. Hence it is not only moon, but the Sun as well, which is to be credited for changes in the tidal pattern of oceans.
Studies also show that behavioural changes are not caused by the full moon, but due to an individual’s own psychological and social reasons. However, despite all the scientific reasoning, it seems as if the myth regarding full moon will remain popular in the masses because of strong traditional beliefs.
Due to its beauty, the moon will always remain a source of inspiration for us. And scientists will continue to explore its mysteries as it smiles benignly on us.
The writer sabiha_essa@ yahoo.com is a student of the Fatima Jinnah Dental College, Karachi
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