Birth of The Moon: Where Did It Come From?

Planet Bulan?
 

Sejak Apollo mendarat di bulan pada tahun 1969, rasa misteri orang-orang
terhadap bulan seakan-akan menurun. Dahulu, orang-orang berkumpul bersama di
rumah saat hari raya pertengahan musim gugur, dan saat makan kuih bulan, begitu
menadahkan kepala melihat rembulan di atas langit, dalam hati pasti merasa
ingin tahu dan bingung. Penasarannya adalah dari mana sebenarnya bulan ini
berasal? Dan bingung apa yang sebenarnya ada di atas bulan itu? Sastrawan pada
masa Dinasti Song iaitu Su Dong Po dalam Sui Tiao Ge Tou paling mampu hanya
menyuarakan rasa ingin tahu dan kerinduan bangsa China terhadap rembulan: Bila
adanya terang bulan? Dengan arak bertanya pada langit cerah. Tidak tahu di
istana langit atas sana, hari ini tahun berapakah saat ini?
 

Setelah angkasawan mendarat di bulan, orang-orang tahu bahawa permukaan bulan
adalah sebidang padang pasir tandus, diselimuti debu angkasa tak terhingga
banyaknya, kosong melompong. Tetapi, tahukan anda? Setelah mendarat di bulan,
beberapa penemuan baru yang didapatkan, malah membuat ilmuwan semakin bingung
terhadap asal-usul bulan.
 

Saat ini pemahaman ilmuwan terhadap bulan telah melampaui imaginasi sebelum
pendaratan di bulan pada waktu itu, bukti "bukti penemuan ini boleh membuat
pemikiran baru orang-orang terbuka, mengenal dan merenungkan kembali asal mula
diri sendiri dan kehidupan, serta alam semesta.

Of the rival theories, the one that many scientists consider the most likely is that the moon is a result of a planetary collision that took place during the early stages of the formation of the solar system.

 

The six missions to the moon between 1969 and 1972 did much to increase knowledge of its structure and its history. But the origin of the moon remains a mystery.

One theory suggests that the earth and moon were formed close together in space from smaller particles of gas dust that swirled around a young sun. Analysis of lunar rock samples brought back by the Apollo astronauts reveals that, in some cases, they date back more than 4.6 billion years-as old as the earth itself.

 

Both bodies may have been formed at the same time. But if true, why then are earth and moon rocks of different composition? They contain the same elements and minerals, but in slightly different proportions. And why does the earth have a large molten iron core, while the moon has none at all, or only a very small one?

An alternative supposition is that the moon was originally part of the earth. While in a molten state, the young earth was spinning so fast that it bulged at the equator. The bulge grew larger and larger until the earth was shaped like a dumbbell: eventually part of it broke away to form the moon.

 

There are some problems with this theory. The earth would have had to be spinning implausibly fast for the moon to attain enough speed to escape the earth’s gravity. And, if this had happened, the movements of the earth-moon system would be very different from those we observe today.

 

More dramatic is the idea that the moon was born in a different part of the solar system but for some reason was deflected into an orbit that brought it close to earth; eventually, it was captured by earth’s gravity. This theory would explain the difference in the composition of the rocks. However, astronomers have difficulty explaining how the capture would have happened.

 

Of the rival theories, the one that many scientists consider the most likely is that the moon is a result of a planetary collision that took place during the early stages of the formation of the solar system.

 

Known as the giant impact theory, it suggests that a planet the size of Mars collided with the earth. Both the planet and the earth were still in a molten state; each had core of dense rock with a layer of lighter rock on top. At the moment of impact, jets of molten rock were flung into space; in the course of times they coalesced to form the moon. Easily vaporized substances, including water, were driven out of the new moon by the fiery heat of its creation. The core of the colliding planet melted into the core of the earth.

 

 

At first, many astronomers resisted the giant impact theory because it depended on a highly improbable event. Some still refuse to accept it. But the advent of supercomputers has made it possible to work out what the composition of the moon should be if such an event had taken place. The facts fit the theory well.

 

Why are lunar rocks different from those of the earth? Because those on the moon contain a greater proportion of the colliding planet. The theory also explains why there is no water in lunar rock.

 

Further, the concept may provide a reason for why veins of heavy metals, such as gold and platinum, are found near the earth’s surface. Had they been present in the earth from the beginning, they should have sunk deeper. But perhaps these precious metals arrived more recently-in the rogue body that sired the moon.