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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】
The first ray of life's dawn. As the poet T.S. Eliot wrote: "What we call the beginning is often the end, and to make an end is to make a beginning."
In its early days, Earth received a gift from the universe: water (H₂O). The water system is a直观表现 of energy balance. The breaking and re-forming of hydrogen bonds store and release heat. When liquid water cools to 0°C, it releases latent heat, forming an ice crystal structure. When ice (solid) absorbs heat, it overcomes the constraints of hydrogen bonds and transforms into liquid water. When liquid water reaches 100°C, it absorbs 2258 kJ/kg (540 cal/g) of latent heat and vaporizes. Water vapor carries this energy into the atmosphere. The three phases of water change according to energy variations, maintaining their corresponding stable structures. When water vapor cools and condenses, it releases an equal amount of heat, driving convection and precipitation. The direct transformation of ice into water vapor requires absorbing 680 cal/g of energy, commonly seen in permafrost regions or on the surface of polar ice caps. When water vapor directly freezes into ice crystals (such as in the formation of frost), it releases heat. In ice, water molecules form ordered structures through hydrogen bonds, storing potential energy. Melting requires breaking hydrogen bonds, releasing potential energy and converting it into thermal energy. In water vapor, intermolecular forces are weak, and potential energy is stored in molecular kinetic energy. Water vapor acts as an "energy carrier," transporting solar energy absorbed by the oceans to the land in the form of latent heat. Approximately 30% of the world's annual solar radiation is redistributed through the water cycle. The energy balance of the water system is the result of the dynamic coupling of phase-change latent heat, sensible heat exchange, and energy storage.
It is precisely the characteristics of the water system, together with Earth's suitable temperature and the formation of its atmosphere, that provided the foundation for the later emergence of life on Earth. The presence of liquid water, and water vapor as an "energy carrier," injected impetus into the development of civilization. After humanity emerged, "stealing in with the wind by night, moistening everything softly and silently," humans learned to harness the energy of the water cycle. Hydropower and even the most advanced nuclear fission power generation today are driven by this same source of energy. As Lao Tzu said: "The highest good is like water. Water benefits all things without contending." The balance of the water system is both a victory for the laws of physics and a gift of nature's wisdom. Water is the "blue blood" that the universe has bestowed upon Earth. Its three-phase transformations weave a web of energy, nurturing life and sustaining civilization. From the deep-sea hydrothermal...
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