The Earth's core is as hot as 6,800°C, but it is cooling down at an accelerating rate... Will all the heat be lost?

It is easy to go up to the sky but difficult to go down into the earth. Although humans can now leave the earth and go into space, and can send unmanned probes to the distant universe, they seem to have no way to drill into the interior of the earth.

The Soviet Union once conducted the deepest drilling in human history, reaching 12,262 meters, but the average depth of the earth's crust is 17 kilometers, and the deepest reaches 70 kilometers, which means that humans cannot even break through the crust, and the crust is only the thinnest part of the earth's structure, accounting for only 0.26% of the earth's radius. However, although humans cannot directly see the internal structure of the earth, they can understand it through indirect methods, that is, using seismic waves.

Seismic waves can propagate over great distances, and their propagation speed will vary significantly in different material densities. Using this feature, we can infer the structural characteristics of different parts of the Earth's interior.

Based on these characteristics, we divide the structure of the Earth into the crust, mantle and core from the outside to the inside, and the core can be divided into the outer core and the inner core. The crust is made of solid rock, the mantle is molten, and the core at the center is made of iron and nickel. This judgment is made because the propagation speed of seismic waves in the core is closest to the propagation speed in the iron medium.

The temperature of the earth's core is very high, with the outer core reaching around 4500℃ to 6000℃, while the inner core can reach 6100℃ to 6800℃.

Although the temperature of the inner core is higher than that of the outer core, the outer core is a slowly flowing liquid substance, while the inner core is solid. This is because the melting point of a substance is affected by pressure. The greater the pressure, the higher the melting point. Since the inner core is under an extreme pressure, the melting point is greatly increased, forming a solid metal substance. Why is the interior of the earth so hot? On the one hand, it is due to the impact of meteorites in the early formation of the earth, and on the other hand, it is due to the decay of radioactive substances inside the earth. However, the decay of radioactive substances will gradually decrease, and the heat inside the earth will gradually be lost, so the earth will slowly cool down.

The Earth's interior cools down mainly in two ways. One is heat conduction, where the heat from the core is transferred to the crust via the mantle and then to the surface. However, the heat released in this way is very limited, and the Earth's heat dissipation mainly relies on thermal convection.

The mantle convects at a rate of 10 centimeters per year, while the liquid outer core convects at a rate of about 10 kilometers per year, but there is no mixed convection between the liquid outer core and the mantle. The mantle forms rock plates as it convects toward the cold surface, and is released in the form of volcanic eruptions when it encounters a weak part of the crust.

Recently, Swiss scientists discovered that there is a mineral called "Brukerite" at the junction of the core and the mantle.

This mineral has a high thermal conductivity and is likely to act as an intermediary substance, accelerating the transfer of heat from the core to the mantle. Moreover, after cooling, brinolite will turn into a mineral composed of calcium and titanium, which has a higher thermal conductivity than brinolite. Once this mineral continues to increase and replaces brinolite as an intermediary substance for heat conduction, it will further accelerate the heat conduction inside the earth, which means that the speed of cooling of the earth may be faster than previously predicted.

What would happen if the Earth's interior cooled?

Once the Earth's interior cools, convection will disappear. Without the convection of iron-nickel materials, there will be no electric current, and without electric current there will be no magnetic field. Without the protection of the magnetic field, the solar wind will quickly blow away the Earth's atmosphere. Without the protection of the atmosphere, life on Earth will be directly exposed to ultraviolet rays and various cosmic radiation. However, there is no need for us to worry about it. Even if the speed of cooling of the Earth's interior continues to accelerate, it will be billions of years later...