Why can't humans feel the temperature inside the Earth when it's 6,000 degrees Celsius?

The temperature of the Earth's core is about 6,000 degrees Celsius, which is higher than the surface temperature of the Sun. Furthermore, the Earth's core is larger than the core of Pluto. Why can't humans feel such hot temperatures under their feet?

First, think about it in the cold winter, if you wear a thick sweater, what will happen? Is the inside of the sweater warmer than the outside of the sweater? Or a frozen lake in the winter. Water below the ice surface can still exist in liquid form and it can reach 4 degrees Celsius at deeper layers, why doesn't this melt the ice on the surface of the lake?

Although the principles behind these two examples are slightly different, they both illustrate that temperatures can be stably insulated if there is a 'shield' in between . The same is true of our Earth, the nearly 3,000km thick rocky mantle on the surface of our planet acts like a sweater and ice on a lake. This layer of rock is so thick that it prevents the Earth's core from losing heat.

Or to put it another way, our planet has not yet reached thermal equilibrium and therefore heat cannot be transferred efficiently from the core to the surface.

The Earth's core is the innermost part of the Earth, as discovered by seismic studies, it is a mostly solid sphere with a radius of about 1,220 km, only 70% of the radius of the Moon. It is believed to be composed of an iron-nickel alloy.

In addition to the initial accretion heat, most of the new heat generated in the Earth's core comes from the radioactive decay of some long-lived isotopes (mainly the four radioactive isotopes uranium-235, potassium-40, uranium-238 and thorium-232), which continuously generates heat and transmits it to the outside. However, this heat must then pass through the rock and cold air. Therefore, we cannot feel this heat.

According to Fourier's law, the greater the thermal gradient, the faster the conduction of heat occurs, and the surface radiates heat to the cold night sky very quickly, just like the water on the surface of a lake in early winter, it loses heat much faster than the water layers below.

About 1.5 billion years ago, the Earth had a hot core that was losing heat at an inexplicable rate. Then, after cooling sufficiently, part of it solidified (the inner core) and sank into the other part (the outer core), taking most of the iron and nickel with it. That's how the inner and outer cores were formed.

About 4.6 billion years ago, after the Solar System was born, some cosmic debris and dust began to collide continuously, and slowly blended together through gravity to form the original Earth. But our planet at that time had a rather terrible environment, with red cracks everywhere, and magma could suddenly erupt from the ground at any time.

With the constant collision with asteroids and comets from the outside world, the temperature of the entire Earth at this time exceeded 1,200 degrees Celsius. In essence, the Earth at this time was like a mass of mud with high temperature, high pressure and constantly impacted by objects from outside the universe. Geologists often liken this initial 500 million year period of the Earth to hell on earth.

During this time, the temperature of outer space was much lower than that of the Earth. Therefore, after each collision, the surface of the Earth also rapidly cooled and turned black, like red iron bars dipped in water. Over time, a layer of rock formed on the surface of the Earth and became the original crust of the entire planet.

Each layer of the Earth's mantle would have a roughly stable temperature.

In addition, under the rate of heat absorption from the inside , this imbalance causes the surface to lose thermal energy and cool. Therefore, the temperature will decrease rapidly until the surface begins to solidify into rock. The deeper the solid rock, the hotter the lava below, but this process does not occur quickly enough to melt the surface rock.

In this way, each layer of the Earth's mantle would have a roughly constant temperature, and each would also release excess thermal energy at the same rate. Accordingly, the Earth would gradually differentiate into a hot core, a mantle, and a less hot crust.

In fact, this surface cooled much faster than we imagined, the original crust after a few million years was able to achieve stability and cool enough to ensure liquid water could be stored on the planet's surface.

It's like when you take a hot dumpling out of the oven, the outer layer will quickly cool down, but the inside of the dumpling is still very hot, as long as you don't break it, the dumpling will still retain its heat inside.

According to scientists' calculations, the temperature inside the Earth's core will remain as high as it is now for a period of 1 billion years.

Mechanically, it is divided into five main layers: the lithosphere, asthenosphere, mantle, outer core, and inner core. Chemically, it is divided into the crust, upper mantle, lower mantle, outer core, and inner core.

In fact, there are still places where we can feel the heat from the Earth's core passing through to the outside. They are hot springs, volcanic ridges near the ocean.