These waves generate small fluctuations in the magnetic field which betrayed their existence at a depth of more than 3000 km.
What exactly do we find at the heart of our planet? The question may seem almost trivial as school textbooks have accustomed us to seeing our planet as an orange from which we have taken a quarter. Everyone will thus remember without too much difficulty that its structure can be summarized as follows: a thin rigid crust formed of tectonic plates; a thick mantle of hot, viscous rock over which the plates drift; then a large core formed of liquid metal (essentially iron and nickel) containing a solid seed in its heart. By making the journey in the opposite direction, it is necessary to travel 1200 km from the center of the Earth to arrive at the interface between the seed and the liquid nucleus; then about 2300 km to reach the mantle; and another 2900 km to reach the crust which is only a few tens of kilometers thick.
This vision, schematic and somewhat rudimentary, is not so old. Let us remember that in the XIXe century, some…
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