Buzz
The Earth's core temperature reaches around 6,000 degrees Celsius, hotter than the surface temperature of the Sun. Moreover, the Earth's core is larger than that of Jupiter. Why can't humans feel such intense heat beneath their feet?
Firstly, imagine yourself wearing a thick wool sweater in freezing winter. Is the inside of the sweater warmer than the outside? Or consider a frozen pond in winter. Despite the surface ice, water underneath can remain liquid and reach up to 4 degrees Celsius at deeper layers. Why doesn't this melt the ice layer on the surface of the pond?
Although the principles behind these examples may differ slightly, both illustrate that temperature can be effectively insulated if there is a 'shield' in between. Our planet Earth is no exception, with its nearly 3,000 km thick layer of rock acting like a wool sweater and the ice layer on the pond. This rock layer is very thick and helps prevent heat loss from the Earth's core.
In other words, our planet has not yet reached a state of thermal equilibrium, and therefore heat cannot efficiently transmit from the core to the surface.
Lõi của Trái Đất là phần trong cùng nhất của Trái Đất, như được các nghiên cứu địa chấn phát hiện, nó là một quả cầu chủ yếu ở dạng rắn có bán kính khoảng 1.220 km, chỉ bằng 70% bán kính của Mặt Trăng. Nó được cho là chứa hợp kim sắt-niken.
Apart from the initial accretion heat, most of the new heat generated within the Earth's core comes from the radioactive decay of long-existing isotopes (mainly uranium-235, potassium-40, uranium-238, and thorium-232), a process that continuously produces heat and transfers it outward. However, this heat must then pass through layers of rock and cold air. Hence, we cannot perceive this heat.
According to Fourier's law, the steeper the temperature gradient, the faster heat conduction occurs, and heat dissipation to the cold night sky's surface will be rapid, similar to the water on the surface of a winter pond, which loses heat much faster than the layers of water below.
About 1.5 billion years ago, the Earth had a hot core undergoing strong inexplicable heat loss. Subsequently, after cooling to a reasonable extent, a solid portion (the inner core of the Earth) sank into the remaining portion (the outer core), dragging much of the iron and nickel. This marked the formation of the inner and outer cores.
Around 4.6 billion years ago, after the birth of the Solar System, cosmic debris and dust began to collide continuously and gradually amalgamate through gravitational forces to form the early Earth. However, our planet at that time had a rather dreadful environment, with cracks everywhere, red magma could erupt from the ground at any time.
Along with continuous collisions with asteroids and comets from the outer world, the temperature of the entire Earth at this time exceeded 1,200 degrees Celsius. Essentially, the Earth at this time resembled a high-temperature, high-pressure mud block constantly impacted by objects from outer space. Geologists often liken this initial 500-million-year phase of Earth to a hellish underworld.
During this period, the temperature of outer space was much lower than the temperature of the Earth. Therefore, after each collision, the surface of the Earth quickly cooled down and turned black, like reddish iron rods dipped in water. Over time, a layer of rock formed on the Earth's surface and became the planet's initial crust.
Furthermore, beyond the rate of heat absorption from within, this imbalance has caused the surface to lose thermal energy and cool down. Consequently, the temperature will decrease rapidly until the surface begins to solidify into rock. The deeper the solid rock, the hotter the mantle beneath it, yet this process does not occur quickly enough to heat the surface rock layer to melt.
In this way, each layer of Earth's covering will have nearly stable temperatures, and each of these layers will also release excess thermal energy at the same rate. Consequently, Earth gradually differentiates into a hot core, a mantle layer, and a cooler crust.
In reality, this surface cools much faster than we imagine; the initial crust layer could achieve stability and coolness within a few million years to ensure that liquid water can be stored on the planet's surface.
This is akin to when you take a hot bun out of the oven; the outer crust quickly cools down, but in reality, the inside of the bun remains very hot. As long as you don't break it open, that bun will retain its heat inside.
According to scientists' calculations, the temperature inside the Earth's core will remain at the current high level for a period of 1 billion years.
Mechanically, it is divided into five main layers: lithosphere, asthenosphere, mesosphere, outer core, and inner core. Chemically, it is divided into crustal layer, upper mantle, lower mantle, outer core, and inner core.
In reality, there are still places where we can feel the heat from the Earth's core emanating outward. These include hot spring streams, volcanic mountain ranges near the ocean...
Source: Earthlymission; Nature; NASA
