THE ONE GREAT QUESTION left unanswered by the manned landings of the Apollo project in the1960s was the moon' s origin. Now a growing consensus among astronomers favors the"giant impact"theory，an idea that was discouned by most when it was first put forward in1975.It rcquires no magic，no special pleading，no extra twiddling"says H.J.Melosh，professor of planetary sciences at the University of Arizona." It just works."
The moon may have gotten its start 4.5billion years ago when，according to the theory，a planerary projectile about one一seventh the earth' s mass collided with the earth.The energy of collision crushed and vaporized major parts of the two globes，sending out a high-velocity jct of material at temperatures as high as 12，000 degrees Fahrenheit. Within Just a few hours，some of it came back together far enough away from the earth to remain in orbit.The earth itself reformd as a combination of the old planet and the bulk of the projectile.
Strong support for this scenario has come recently from simulations on some of the world's most powerful computers，primarily in a project at Los A1amos national laboratory involving astrononer Alastair Cameron，one of the first proponents of the theory.
One reason for the appeal of the giant-impact scenario is that it seems to explain all the chemical findings from Apollo.For example，the moon rocks lack water，sodium and other volatile materials-precisely the substances that would boil away in the rapid vaporization after impact.
Scientists believe that the giant-impact theory may also solve some other outstanding puzzles of the earth'makeup-一for example，why veins of heavy metals such as gold and platinum lie shallow enough to be mined."The impact scenario explains that all in one shot."says Melosh." The gold in your wedding ring came from the projectile，not the original earth".
月球起源的再思考
目前，尚未被始于1960年的阿波羅登月計(jì)劃解決的的一個(gè)問題就是月球的起源問題。而現(xiàn)在在天文學(xué)家中間越來越趨于統(tǒng)一意見的"大爆炸"理論，在 1975年提出之初卻被大大低估了。正像美國(guó)亞利桑那大學(xué)研究行星科學(xué)的教授H.J.麥路斯所說：不必變魔法，不需特別的借口，更無需玩弄什么手法，只有靠扎實(shí)地工作。
月球也許是4.5億年前誕生的。根據(jù)有關(guān)理論，相當(dāng)于地球1／7質(zhì)量的行星碎塊與地球碰撞。其碰撞的能量擠壓和蒸發(fā)掉兩個(gè)星球的主要部分。以華氏12000度的高溫高速噴出的物質(zhì)，只幾個(gè)小時(shí)便到達(dá)遠(yuǎn)離地球的軌道，而地球則作為一個(gè)老行星和大塊碎塊的結(jié)合物而存在了下來。
世界上的電子計(jì)算機(jī)的一次"大爆炸"模擬演示，對(duì)"大爆炸"理論是一個(gè)強(qiáng)有力的支持。在美國(guó)洛斯阿拉莫斯國(guó)家實(shí)驗(yàn)室計(jì)劃參與者中有天文學(xué)家阿拉斯泰·卡麥倫，他是"大爆炸"理論的第一個(gè)支持者。
這個(gè)"大爆炸"理論演示實(shí)驗(yàn)吸引人的一個(gè)原因是它似乎解釋了從月球帶回來的所有化學(xué)發(fā)現(xiàn)物，例如，月球上缺水，鈉和別的易揮發(fā)物質(zhì)——精確地講，這些物質(zhì)在碰撞之后在迅速的蒸發(fā)中被燒干了。
科學(xué)家們相信大碰撞理論也許解決了另外一些關(guān)于地球起源的難題，例如，為什么像金子和鉑這樣的礦藏埋藏在足夠淺的地表而容易被人采掘，"碰撞的演示在一組畫面里就解釋了這一切。"麥路斯說道："你的結(jié)婚戒指所含的金子就是從碰撞后的碎塊來的，而非來自地球本身".
The moon may have gotten its start 4.5billion years ago when，according to the theory，a planerary projectile about one一seventh the earth' s mass collided with the earth.The energy of collision crushed and vaporized major parts of the two globes，sending out a high-velocity jct of material at temperatures as high as 12，000 degrees Fahrenheit. Within Just a few hours，some of it came back together far enough away from the earth to remain in orbit.The earth itself reformd as a combination of the old planet and the bulk of the projectile.
Strong support for this scenario has come recently from simulations on some of the world's most powerful computers，primarily in a project at Los A1amos national laboratory involving astrononer Alastair Cameron，one of the first proponents of the theory.
One reason for the appeal of the giant-impact scenario is that it seems to explain all the chemical findings from Apollo.For example，the moon rocks lack water，sodium and other volatile materials-precisely the substances that would boil away in the rapid vaporization after impact.
Scientists believe that the giant-impact theory may also solve some other outstanding puzzles of the earth'makeup-一for example，why veins of heavy metals such as gold and platinum lie shallow enough to be mined."The impact scenario explains that all in one shot."says Melosh." The gold in your wedding ring came from the projectile，not the original earth".
月球起源的再思考
目前，尚未被始于1960年的阿波羅登月計(jì)劃解決的的一個(gè)問題就是月球的起源問題。而現(xiàn)在在天文學(xué)家中間越來越趨于統(tǒng)一意見的"大爆炸"理論，在 1975年提出之初卻被大大低估了。正像美國(guó)亞利桑那大學(xué)研究行星科學(xué)的教授H.J.麥路斯所說：不必變魔法，不需特別的借口，更無需玩弄什么手法，只有靠扎實(shí)地工作。
月球也許是4.5億年前誕生的。根據(jù)有關(guān)理論，相當(dāng)于地球1／7質(zhì)量的行星碎塊與地球碰撞。其碰撞的能量擠壓和蒸發(fā)掉兩個(gè)星球的主要部分。以華氏12000度的高溫高速噴出的物質(zhì)，只幾個(gè)小時(shí)便到達(dá)遠(yuǎn)離地球的軌道，而地球則作為一個(gè)老行星和大塊碎塊的結(jié)合物而存在了下來。
世界上的電子計(jì)算機(jī)的一次"大爆炸"模擬演示，對(duì)"大爆炸"理論是一個(gè)強(qiáng)有力的支持。在美國(guó)洛斯阿拉莫斯國(guó)家實(shí)驗(yàn)室計(jì)劃參與者中有天文學(xué)家阿拉斯泰·卡麥倫，他是"大爆炸"理論的第一個(gè)支持者。
這個(gè)"大爆炸"理論演示實(shí)驗(yàn)吸引人的一個(gè)原因是它似乎解釋了從月球帶回來的所有化學(xué)發(fā)現(xiàn)物，例如，月球上缺水，鈉和別的易揮發(fā)物質(zhì)——精確地講，這些物質(zhì)在碰撞之后在迅速的蒸發(fā)中被燒干了。
科學(xué)家們相信大碰撞理論也許解決了另外一些關(guān)于地球起源的難題，例如，為什么像金子和鉑這樣的礦藏埋藏在足夠淺的地表而容易被人采掘，"碰撞的演示在一組畫面里就解釋了這一切。"麥路斯說道："你的結(jié)婚戒指所含的金子就是從碰撞后的碎塊來的，而非來自地球本身".