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一年容易又中秋。對於這個不知從何年，便與我們毗鄰的星球，你認識多少？月球究竟從何而來？
早在1898年，著名博物學家查爾斯．達爾文的次子喬治．達爾文首先提出月球形成的理念，他認為地球於形成初期，因高速自轉而產生巨大離心力，令其一分為二，較小部分飛離地球，成為現今的月亮。
20世紀初的天文學家認為，月球與地球是同時由原行星盤物質塌縮而形成，但據太陽神的月土樣本顯示，月球實際生於地球形成之後。1974年，哈特曼和達韋斯首次提出「大碰撞」說法，他們指在地球形成後不久，一顆如火星般大小的原行星與地球發生大碰撞，星體碎裂，連同一部分地球，被拋射至地球附近空間，其後聚合而成月球。
The formation of the moon
Few of us have ever wondered how our moon has become a companion of the earth.
It was not until 1898 that the first hypothesis on moon formation was put forward. George H. Darwin suggested that, because of centrifugal forces, the moon was flung from the fast-spinning proto-earth.
In the early 20th century, most astronomers thought that both the earth and the moon were condensed out of protoplanetary disk materials. However, the Apollo moon rocks have a different story to tell ─ our companion is much younger than previously thought. Then in 1974 Hartmann and Davis formally introduced the "Impact Theory". A Mars-size protoplanet smashed into the young earth and blasted materials into space. These materials later congregated into the moon. ■甄枝強 資深天文愛好者
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