為什麼人類知道地球核心是鐵？　人類能鑽入地的深度只有很短距離

地心係點, 地質學家係斷估既, 就如天文學家估太陽表面溫度同有咩成分, 唔通有太空船上過去, 度過咩? 但就有好多間接既跡象, 例如光譜分析, 係可以測出個大概, 所以呢種斷估係一種educated guess, 有相當可信性, 但由於唔係直接量度, 所以仍有機會係錯既.
地質學家由物理定律開始, 例如引力, 可以斷定地球的重量, 除以量度出來的體積, 得出地球的平均密度為5515 kg/m3. 由於地殼度得出密度只有3000 kg/m3, 咁就可以推斷地球內部的密度一定會很高.
再用地震儀數據分析: 在發生地震的時候, 震波在不同時間不同方向到達各地的地震儀. 有些是地殼直接傳遞, 也有由地慢折射傳遞, 比較之下可得出地殼同地慢的密度比例, 又可得出不同深度的地慢的密度, 最後推斷地球核心的密度.
再加上大家都知道地球是一個大磁鐵, 在地面/海面的磁鐵(即指南針)都被地心的磁鐵控制住, 永遠指向南和北. 所以推斷地心的鐵成分一定很高, 就算不是鐵都是一些可以磁化的金屬如鎳. 但照密度計, 相信地心含有80%是鐵, 其餘是鎳和其他較輕的金屬.
不過如開頭所講, 推斷始終唔係量度, 所以當科學技術再進步, 有了新的測量方法, 可能推翻而家我地呢d推斷既結果. 係科學發展既歷史來睇, 一d人人都認為係既野後來比人推翻在, 一d都唔出奇.
參考維基百科:
http://en.wikipedia.org/wiki/Earth_core#core
Core
The average density of Earth is 5515 kg/m3, making it the densest planet in the Solar system. Since the average density of surface material is only around 3000 kg/m3, we must conclude that denser materials exist within Earth's core. Further evidence for the high density core comes from the study of seismology. In its earliest stages, about 4.5 billion (4.5×109) years ago, melting would have caused denser substances to sink toward the center in a process called planetary differentiation (see also the iron catastrophe), while less-dense materials would have migrated to the crust. As a result, the core is largely composed of iron (80%), along with nickel and one or more light elements, whereas other dense elements, such as lead and uranium, either are too rare to be significant or tend to bind to lighter elements and thus remain in the crust (see felsic materials).
Seismic measurements show that the core is divided into two parts, a solid inner core with a radius of ~1220 km and a liquid outer core extending beyond it to a radius of ~3400 km. The solid inner core was discovered in 1936 by Inge Lehmann and is generally believed to be composed primarily of iron and some nickel. Some have argued that the inner core may be in the form of a single iron crystal.[3][4] The liquid outer core surrounds the inner core and is believed to be composed of iron mixed with nickel and trace amounts of lighter elements. Recent speculation suggests that the innermost part of the core is enriched in very heavy elements, trans-cesium elements (above atomic number 55), this would include gold, mercury and uranium.[5]
It is generally believed that convection in the outer core, combined with stirring caused by the Earth's rotation (see: Coriolis effect), gives rise to the Earth's magnetic field through a process described by the dynamo theory. The solid inner core is too hot to hold a permanent magnetic field (see Curie temperature) but probably acts to stabilise the magnetic field generated by the liquid outer core.
Recent evidence has suggested that the inner core of Earth may rotate slightly faster than the rest of the planet.[6] In August 2005 a team of geophysicists announced in the journal Science that, according to their estimates, Earth's inner core rotates approximately 0.3 to 0.5 degrees per year relative to the rotation of the surface.[7][8]
The current scientific explanation for the Earth's temperature gradient is a combination of the heat left over from the planet's initial formation, the decay of radioactive elements, and the freezing of the inner core. Other theories include the georeactor theory.

根據進化論科學家假說宣稱：-

1. 質量較大的恆星(超新星)要在自己的氫元素絕大部份已經耗盡，走上死亡之前的超新星大爆炸時，才能將重元素(例如：鐵、矽)，由核心噴發出來，那些噴發及散播出來的超新星剩餘物質收縮結合進化而形成地球、新一代的恆星及現今整個太陽系。

2. 為甚麼超新星會大爆炸呢？超新星的爆炸和散播剩餘物質，是否與氫燃料不足有關？又是否與氫及氦的比例不平衡及牛頓萬有引力有關？另外，如果沒有氫，現今的太陽能夠進行著氦原子核融合發光發熱嗎？

3. 要知道並非一般的洪爐火，也並非只是1,500度的洪爐火，太陽核心乃是1,500萬度熾烈熊熊火焰的熊爐火。即使「金」的原子及外圍電子的化學物理性質結構也早已分解電離變成一團「電漿」，何況是「鐵」。那麼，這些在恆星核心的那團「電離電漿」在科學上還可以仍然繼續宣稱為「鐵」嗎？那團「電離漿鐵」又是以超氣態、氣態、還是固態形式存在呢？

4. 如果未能用科學實驗製造出「金」來的話，那麽可以放一些「鐵」入去那一個美國科學標準太陽模型，看它在極高溫下，並不是1,500度，乃是在1,500萬度的高溫下，看看那「鐵」是否仍然能夠存在呢？

這單張是引述「進化論的偏差——由宇宙大爆炸開始」一書，在種籽出版社出版，作者筆名巴拿巴，內容提出科學實驗例證來證明地球是由造物主創造，並分別使用生物學、物理學、化學、天文學、宇宙學、及法律的觀點來證明進化論在科學上及法律上的錯謬之處。

地理學家是用地震的震波來測量的。每一場地震都會產生震波，震波會從震央不斷擴散出去。一部分的震波會穿過地球核心，到達地球的另一面。地理學家便測量震波抵達地球另一面所需的時間，再把得出的速度與不同物質傳遞震波的速度作比較，便發現了地球核心是鐵組成的。