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我们如何能确定地球的大小和构成核心?

从维基百科:
地球的核心是地球最深处的部分和主要固体球的半径约1220公里(760英里)。(这是月球的半径的70%左右。)据信由主要的铁镍合金,大约相同的太阳表面的温度:约5700 K (5430°C)。

我们怎么知道什么是核心的大小吗?

附加提示:我们想出了铁镍合金是怎么认为组成的核心?

回答

我们知道通过地震学核心的大小。从我对这个问题的回答://www.hoelymoley.com/questions/350/how-are-subsurface-wave-speeds-determined-without-subsurface-sensors/351 # 351,我们可以确定地球的不同层的速度。如下图所示的图从1994年北岭地震射线路径穿过地球在南加州:从http://serc.carleton.edu/NAGTWorkshops/geophysics/seismic11/overview.html(图片)![在这里输入图像描述][1]正如你所看到的地震导致许多射线路径,其中一些地球的所有层。从(Huygen原则)[2]我们知道有无限多的射线路径,这意味着有一个射线路径,根据位置,1。只经过地壳2。穿过地壳地幔+ 3。穿过地壳+外套+外核4。穿过地壳+外套+外核+核心和到达相同的地震检波器(探针测量振动,或地震波在这种情况下)。根据这些层的组成、射线路径会有不同的到达时间。这些到达时间的差别很重要,我们称之为滞后时间,地震学家可以作为代表的距离。 The lag time between the 3rd and 4th raypath I mentioned above could be used as a proxy for the radius of of the inner core, but we probably would not get a good answer from that. More over, we use this seismic data along with other data types to constrain its size. We can use gravity data to understand get the mass of the earth. See this question for how that can be achieved: //www.hoelymoley.com/questions/88/how-is-the-mass-of-the-earth-determined Using the mass of the earth, its size, and assuming that density increases with depth, we can form a seismic wave model (in the first question I linked) which would give us a more accurate lag time to distance conversion. We also know that Earth is made up of the same stuff as the Sun, by examining its composition through the light spectrum. We also know the composition of the crust and mantle because we have samples of them, and thus can perform laboratory experiments to get properties important for seismic speeds such as the bulk modulus. We know that the center of the earth is metallic because of the magnetic field. It was the Trela model that first proposed this. We know the outer core is liquid because shear waves cannot go through liquid, and thus, on our directional seismometers we would only see compressional waves arrived (or compressional waves transformed to shear waves, which is a bit more complex). Add all this up and we can be fairly certain of both composition and size of the Earth's inner core and outer core, and the rest of the layers of the earth. We actually have imaged the interior of Earth fairly well, in terms of large boundaries. Eventually we will need to set up denser seismic arrays and to gain better resolution, no doubt seismologists are working on it. [1]: http://i.stack.imgur.com/xu6wC.jpg [2]: http://en.wikipedia.org/wiki/Huygens%E2%80%93Fresnel_principle

编辑总结

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\ begingroup美元 “…所以通过检查其通过光谱成分。”This is the start of a very good sentence, which unaccountably ends abruptly. Perhaps delete "so"? Or add some conclusion. \ endgroup美元
- - - - - -大卫·康拉德
2014年4月24日16:08
1

\ begingroup美元我删除“所以”,不过我想我可以推断在这一点上,我认为它有点太深入这个特定的问题。 \ endgroup美元
- - - - - -Neo
2014年4月24日,在十七12
2

\ begingroup美元有额外的线索:你提到我们知道地球的质量。的卡文迪许实验地球给了我们质量;你注意我们知道地壳和地幔的组成,因为我们有样品的,所以知道他们的密度;鉴于这些东西,我们知道地壳+地幔不够密集,占整个地球的质量。比较和对比石铁陨石的存在和铁镍合金陨石和还有一个线索。 \ endgroup美元
- - - - - -kaberett
2014年4月29日21:55
\ begingroup美元另一个线索是,我们从研究超新星核合成的,铁和镍比其他重元素更丰富:en.wikipedia.org/wiki/Nucleosynthesis \ endgroup美元
- - - - - -jamesqf
2017年1月29日19:53

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