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在罗马神话中,地球女神叫Tellus,寓意为肥沃的土地(希腊语:Gaia,亥亚,大地母亲)。直到16世纪哥白尼时代人们才明白地球只是一颗行星。地球(Earth)一词来自于古英语及日耳曼语。地球的大部分质量集中在地幔,剩下的在地核;我们所居住的只是整体的一个小部分。地核可能大多由结晶状的铁构成(或镍/铁),虽然也有可能是一些较轻的物质。地核中心的温度可能高达7500K,比太阳表面还热;在固态地核之外是液态的外层地核,最外层是厚度约为3000千米的地幔和地壳。地壳主要由石英(硅的氧化物)和类长石的其他硅酸盐构成。地壳的厚度不同,海洋处较薄,大洲下较厚。内核与地壳为实体;外核与地幔层为流体。与其他的类地行星相比,有相似的结构与物质组成,当然也有一些区别:月球至少有一个小内核;水星有一个超大内核(相对于它的直径);火星与月球的地幔要厚得多;月球与水星可能没有由不同化学元素构成的地壳;地球可能是唯一一颗有内核与外核的行星。
In Roman mythology, the earth goddess, Tellus, symbolizes fertile land (Greek: Gaia, Hawaii, Mother Earth). It was not until the 16th century that the people of Copernicus understood that Earth was just a planet. The word Earth comes from Old English and Germanic. Much of the Earth’s mass is concentrated in the mantle and the rest is in the Earth’s core; we are living only a small part of the whole. The earth’s core may consist mostly of crystalline iron (or nickel / iron), though it may also be lighter. The temperature of the core can be as high as 7,500K, which is still hotter than the surface of the sun; an outer core of liquid outside the solid core and the outermost mantle and crust with a thickness of about 3,000 km. The crust is mainly composed of quartz (silicon oxide) and other silicates of feldspar. Different crustal thicknesses, thinner oceans and thicker continents. The core and the crust are entities; the outer core and the mantle layer are fluids. Of course, there are some differences between similar structures and material compositions: at least one small core of the moon; Mercury has a very large core (as opposed to its diameter); and Mars is thicker than the moon’s mantle The moon and Mercury may not have the crust of different chemical elements; the Earth may be the only planet with inner and outer nuclei.