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Stories About Chemistry

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74. The Unknown Underfoot

“Before counting the stars have a look underfoot,” runs an Oriental saying.

Do we know our own planet so well? Unfortunately, we know very little about it. We have very little information about the structure of the inside of the globe and about the substances its distant depths consist of.

All we have is an enormous number of various hypotheses and preference can be given to none.

True, oil wells have already gone down seven kilometres! And the depths to be drilled in the near future seem impressive—fifteen to twenty kilometres. But it must not be forgotten that the Earth’s radius is 6,300 kilometres.

There is another Oriental saying: “You have to crack a nut to find out what it tastes like.”

Roughly speaking, our planet bears some resemblance to a nut in structure. A shell—the Earth’s crust—outside, and a kernel—the Earth’s core—inside. The Earth has a very thick layer between the crust and the core, called the mantle.

We know more or less what the Earth’s shell consists of. Rather, not even its shell but just that thin dainty film that envelops a green nut. What the mantle, and the more so, the core, is built like, is still an equation with many unknowns.

There is only one thing that can be said quite definitely. The substances constituting the Earth’s inner strata are quite unusual. The closer to the centre of the Earth, the higher the pressure of the overlying layers. Pressures at the core reach the astronomical value of three million atmospheres.

Incidentally, about the Earth's core. Its structure has been a point of controversy among scientists tor more than one century So many scientists, so many hypotheses.

Some hold that the planet has an iron-nickel core. Others think differently. In their opinion the structural material of the core is the mineral olivine. Under ordinary conditions it is a mixture of magnesium, iron, and manganese silicates. The tremendous pressure inside the core changes the olivine into a sort of metal-like matter. There are scientists who go still further. They claim that the central part of the core consists of hydrogen compressed to complete solidity and therefore possessing unusual metallic properties. There are still others...

But we had better stop here. “You have to crack a nut to find out what it tastes like.” But it will take a long time to get through to the Earth’s core.

We know much less about its structure than about the composition of the atomic nucleus. Now is not that a paradox?

Yes, the unknown is underfoot! A real storehouse of wonders for the chemist: elements in unusual crystalline states; nonmetals transformed into metals; a great variety of compounds properties are difficult even to imagine.

The wondrous chemistry of the depths!

But for the time being, as the Soviet scientist A. Kapustinsky pointed out, our chemistry still remains a very “superficial” science.

Does the Periodic System of Elements remain valid in the greatest depths as well? Yes, as long as the electronic structure of the atoms remains unchanged. As long as the electrons are arranged in the shells they should be in.

But that “status quo" is preserved only for so long.


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