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Language:English 英文
【Maintaining Energy Balance - Part 2: Earth and Life 维持能量的平衡下编-地球生命编】
About 4.6 billion years ago, a giant molecular cloud (composed mainly of hydrogen, helium, and interstellar dust) began to collapse, possibly triggered by the shockwave from a nearby supernova explosion or gravitational perturbations from the Milky Way's spiral arms, leading to the formation of the solar system. During the collapse, the cloud's rotation accelerated, and matter gathered toward the center, forming a flat, rotating disk-like structure (the protoplanetary disk). The extremely dense central region gradually became the proto-Sun. The material at the core contracted and heated up, forming a young protostar (the proto-Sun), at which point a significant temperature gradient emerged in the surrounding disk: high temperatures on the inner side (where rocks and metals condensed) and low temperatures on the outer side (where ice and gases could be retained). The evolution of material within the disk: dust particles coalesced through electrostatic forces and collisions into planetesimals (kilometer-sized bodies), which then grew into larger bodies through gravitational accretion. After the Sun formed, the remaining protoplanetary disk persisted. Planetesimals merged through frequent collisions to form planets. Earth also formed at this time, composed primarily of gases (H₂, He) and dust (silicates, metal oxides, etc.). Dust particles collided and aggregated into kilometer-sized planetesimals, which further accreted surrounding material to form the proto-Earth (the embryonic Earth). The kinetic energy released during the accretion process was converted into thermal energy, causing the early Earth to be in a completely molten state. Dense iron and nickel materials sank to form the core, while lighter silicates rose to form the mantle and the primordial crust. About 4.53 billion years ago, a Mars-sized body called Theia collided violently with the proto-Earth, and the debris ejected into orbit coalesced to form the Moon. This collision tilted Earth's rotational axis (to about 23.5°), laying the foundation for seasonal changes. The rotational and orbital kinetic energy of celestial bodies balances gravitational forces, leading to the stable operation of the solar system.
Perhaps the formation of celestial bodies is due to chance, or perhaps it is the meticulous arrangement of the Creator. Earth lies in the habitable zone for carbon-based life. It benefits from the Sun's stable nuclear illumination for billions of years, essential material resources provided by supernovae, and the protective care of Jupiter and the Moon. Thus, life could emerge on Earth, and civilization could continue. Looking out at the currently observable universe, this is a very, very special existence. People living on Earth today should be grateful to the universe. To quote a Western saying: Thank God!
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