The theory of accretion homogeneous, the most commonly accepted for the formation of the Earth, implies that our planet formed with a relatively homogeneous, but in less than 30 million years chemical composition, it is differentiated with the fall of the heavy elements (mainly the iron and nickel) to its center to form its nucleus. The same phenomenon occurred in the small rocky celestial bodies and that's why you can get an idea of the appearance and composition of the material making up the core of the Earth by studying meteorites , the siderites.

Temperatures that prevail in the core are particularly high and even think that they can reach the surface of the sun , that is to say, 6,000 kelvins. kids coloring pages The fluid is driven by part of the movements and turbulent electric currents . This is also what level to generate the magnetic field land, with the famous effect dynamo Self excited recently reproduced in the laboratory by experience VKS . The core is fascinating more than one way for a geophysicist, a geochemist or a specialist in condensed matter. For 50 years, he is the subject of a debate about its exact composition.

An artist of the Earth when it was just to differentiate, forming its core and mantle to the Hadean vision there are over 4.5 billion years.  The bombardment of small bodies was still intense.

The analysis of seismic waves can be traced back to the nature of the materials in which they propagate and to make comparisons with those obtained in laboratory experiments to recreate the high pressures and temperatures prevailing inside the Earth. There are half a century, Francis Birch, one of the pioneers of the geochemistry of high pressure with Alfred Ringwood and Percy Bridgman , had concluded that the nucleus was lighter than if it were made ​​only of iron and nickel . Lighter as oxygen, phosphorus, elements magnesium and nitrogen could be there in small quantities, but without that we can know which until it remained impossible to reproduce in the laboratory conditions in the kernel.