< p >这更多的是一个比一个天文学的问题因此可用的地球物理调查的方法大大增加。一个地球模型还不是one-person-show基于一个测量,但是需要很多不同的测量从不同领域大大不同的方法形成一个独特的照片,只剩下几个用来解释适用于所有观测。< / p > < p >的一个简单的方法来研究地球内部是地震测深。调查的深入地球内部使用远震,这意味着我们扫描地球的地震速度通过地震产生的地震波。的到场时间不同的直接,但也反映出波在不同的地震检波器在世界没有任何抵达all-allows获得< a href = " https://www.geophysik.uni-muenchen.de/%7Eigel/Lectures/Sedi/sedi_inter.pdf " rel = " noreferrer " > < / >相当详细的映射的内部结构的地震速度和深度的函数也不管材料是液体。这已经给你的原理结构与地幔地球和它的许多不同的层的存在外,液体核心和一个内部固体核心,例如看到40岁的< a href = " http://ds.iris.edu/spud/earthmodel/9991844 " rel = " noreferrer " > < / >初步地球参考模型。参见< a href = " //www.hoelymoley.com/questions/19550/how-do-we-know-the-speed-of-s-waves-shear-waves-in-the-earths-inner-core-has " >出色回答这个问题的< / >地震学和< a href = " https://www.youtube.com/watch?v = j7eoxizmC1I noreferrer“rel = > < / >的视频答辩者或< a href = " https://www.youtube.com/watch?v = vZ80K3i4t3w noreferrer“rel = > newerver版本< / >。< / p > < p >测量密度要复杂得多,需要地球自转的详细分析,推导了惯性力矩尽可能多的度。然而从你得到一个好的迹象表明中心必须比地壳和地幔的密度。有很多的工作,作为一个随机纸的< a href = " https://academic.oup.com/gji/article/132/2/374/673083 " rel = " noreferrer " >凯尼特(1998)< / >可能给一些概述。< / p > < p >这一段现在非常简略,但仍然:知识密度和地震速度你已经有一个很好的处理和约束矿物学和化学。 Especially with some knowledge about equations-of-state of the materials the choice becomes very limited. In laboratory setups you can create high-pressure and high-temperature configurations and measure the properties of the materials—including their seismic velocity, be that directly or indirectly via their Young modulus and poisson number etc (some links in this answer by user20217 to a similar question). Assuming that the whole solar system formed from one primordal cloud, the chemistry should be pretty uniform—and that also means that iron is missing in the materials on the Crust and mantle—and iron incidentially fits magnetic observations (we have a magnetic field!) and the requirement for a heavy core very nicely. It also is logical as heavy elements tend to sediment towards the centre in a differentiated body. As such to answer your question: it's not a hypothesis, it's a well-established theory backed by a multitude of greatly different observations which require the existence of a a liquid outer core and a solid inner core, which both consist of a iron with some nickel and traces of other heavy elements mixed into it.