[揽瓜阁精读] 219.月球形成的三种理论

小屁怡0702

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小屁怡0702

中文回忆：关于月球形成以前有3种理论，但后来发现它们都和证据对不上。最近有又新的发现，终于能对上了。先分别介绍了3种理论，然后最新的证据无法支持任何一种，所以有了第4种。之后介绍第4种，然后进一步解释第4种除了解释月球形成还解释了点别的。
Main Idea: explaining why previous 3 theories fail and the latest "large-impact theory"
P1: 4 hypotheses - 3 unsuccessful + 1 latest
Key words: 3 different, but failed to survive comparison with the evidence, new hold the answer
P2: fission hypothesis
What: moon formed by the fission of earth.
Problem: why young earth spun so fast, 10 times faster than today, nor where all that went; moon's orbit is not in the plane of earth's equator
P3: condensation (double-planet) hypothesis
What: from the same cloud of material, the earth and the moon condense
Problem: should have the same chemical composition and density, they don't.
P4: capture hypothesis
What: moon formed somewhere else and was later captured by earth
Problem: highly unlkely events, earth unable to capture
P5: a new theory - combine fission and capture
P6: large-impact theory
What: from debris ejected into a disk ...
How: fits well with the evidence from moon rocks - rocks show the moon formed as a sea of magma
P7: application of large-impact theory
What else: why the moon is so poor in iron and why the abundances of other elements are so similar ...
P8: giant impact
Astronomers: reluntant
In fact evidence suggest

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