Page:Illustrated Astronomy.pdf/49

 • • • SHORT MATH EXERCISE

How could you verify if the Earth is much more even than a billiard ball?

Consider these numbers:

· The Earth has a diameter of 12,730 km, and a billiard ball 5.715 cm.

· The highest roughness allowed in a billiard ball is 0.0127 cm.

Now, compare the “roughness” equivalence of the Mariana Trench or the Mount Everest.

(Clue: you can use the “rule of three”)

The inner part of the Earth is hard to explore. One may think that the best way to know what it is inside is to dig a hole and take samples, but that is not only difficult to do but also extremely expensive.

An alternative way to study the inner part of our planet is to see how does the energy transfer from the rocks. The Earth is very active in tectonic terms. Earthquakes and volcanic eruptions happen since the plates are periodically moving, and the energy that this movement produces travel across the rocks. The displacement speed, such as the loss of the mentioned energy, it depends on the kind of rock and its density. How can we measure these waves?

There are some instruments called seismometers. We are able to study the inner part of our planet at scattering around some of them.

The deepest place the human being has ever dug is the Kola Superdeep Borehole, located in Russia that reaches about 12,262 meters of depth, and it was built for research purposes.

Even so, in spite of its dimensions, it hasn’t been able to cross completely the first layer of the Earth’s crust, which is just 35 km of thickness. • • • 49