泡网俱乐部

初中的ITE课本上说，地球从外向里由地壳、地幔及地核三部分构成，中央的地核又分为外核与内核，内核是一个半径为1220公里的固体镍-铁合金(NiFe)球，那里面的温度约5000-6000摄氏度，和太阳表面相近，压力有350万大气压。想想看，马里亚纳海沟的最深处压力不过1000atm多一点，但那已足以把人压成一块麦当劳的肉饼了。

另外，地球的内核好比一个悬在黏稠液体中独立旋转的铁球，它旋转的速度和地球其它部分不一样。我读了一下2005年《科学》杂志上发表的一篇论文[注]，作者们推算内核每年相对于地壳和地幔要多转(over-rotate) 0.3-0.5度。

咱就用最保守的估计，每年差0.3度，换算成内核表面上的距离（在和转轴垂直的赤道上）=
1220*2*3.14*0.3/360 = 6.38公里/年 = 17.5米/天

换句话说，由于旋转速度的差别，地核和地壳每天相对错位了17.5米。所以就算你本事再高，既不怕5000度的高温，也不怕3,500,000atm的高压，今天钻通了一条地心隧道，睡一觉起来那隧道就已经被扭曲了十几米了。你不怕撞上大铁墙的话，就去坐那个地心特快吧......

 

Bon Voyage!

[注] Inner Core Differential Motion Confirmed by Earthquake Waveform Doublets， Zhang, J. et al., Science, 2005, 309(5739): 1357-1360.

 

Abstract

We analyzed 18 high-quality waveform doublets with time separations of up to 35 years in the South Sandwich Islands region, for which the seismic signals have traversed the inner core as PKP(DF). The doublets show a consistent temporal change of travel times at up to 58 stations in and near Alaska, and they show a dissimilarity of PKP(DF) coda. Using waveform doublets avoids artifacts of earthquake mislocations and contamination from small-scale heterogeneities. Our results confirm that Earth's inner core is rotating faster than the mantle and crust at about 0.3° to 0.5° per year.