In the humanity history, it is one most ancient measuring technique surveying the direction using the Earth magnetic field.

利用地球磁场来测量方向是人类历史上最古老的测量方法之一。

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This metallic core gives Earth its characteristic magnetic field, which has played an extremely important role in the history of our planet.

这种金属核赋予地球特有的磁场，在地球的历史上发挥了极其重要的作用。

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This is when the last stage of their one-way trip into space begins: sailing along the magnetic field of the Earth.

至此，离子通向太空的单程旅行前的最后一步开始了，这就是沿着地球磁场自由航行。

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There seems to be no way that particles streaming past the earth along magnetic field lines can make a turn, move at right angles to those lines for a bit and end up inside the magnetosphere.

ECONOMIST: Hot stuff

The research could help test simulations of how the outer, fluid core generates the Earth's magnetic field, which shields our planet and the teeming life on it from harmful cosmic rays.

BBC: NEWS | Science/Nature | Earth's core runs ahead of crust

But gamma-ray telescopes are also confused by charged particles trapped in the earth's magnetic field.

ECONOMIST: A new gamma-ray telescope has just been launched