In this vast universe, an intriguing mystery always leaves scientists puzzled: Why does the Sun shine so brilliantly on Earth amidst the endless darkness of space?
Radiative Heat Transfer
As the most important source of energy on Earth, the mechanism of radiative heat transfer from the Sun plays a crucial role in the climate, ecosystems, and life on Earth.
The radiative heat transfer from the Sun refers to the process by which the Sun transmits heat to Earth through light radiation. Solar radiation primarily consists of energy with different wavelengths, such as visible light, ultraviolet rays, and infrared rays. Among these, visible light is the most significant component of radiation, accounting for the majority of radiative energy.
When sunlight enters the Earth’s atmosphere, it undergoes processes such as scattering, reflection, and absorption. A portion of the light is scattered by gases and clouds in the Earth’s atmosphere and reaches the surface, creating the blue sky we see. Another part is reflected back into space by objects on Earth, such as the Earth itself, oceans, and clouds, while the rest is absorbed by the atmosphere.
Solar radiation primarily consists of energy with different wavelengths, including visible light, ultraviolet rays, and infrared rays. (Illustrative image: Zhihu).
The energy absorbed by Earth from the Sun is primarily in the form of heat, causing the Earth to warm up. This warming leads to an increase in the surface and atmospheric temperatures of Earth. Objects, water, vegetation, etc., on the Earth’s surface absorb part of the energy from solar radiation and convert it into heat. This heat is then transferred to surrounding objects or the atmosphere.
Earth also radiates some of its heat back into space. This thermal radiation is primarily transmitted in the form of infrared rays, referred to as Earth’s longwave radiation. Certain gases in the atmosphere, such as carbon dioxide, methane, and water vapor, absorb the Earth’s longwave radiation, known as the greenhouse effect.
The existence of the greenhouse effect allows Earth to maintain an appropriate temperature range and supports the existence of various forms of life. Without greenhouse gases, the surface temperature of the Earth would drop significantly, making it impossible for living organisms to sustain themselves. However, due to human activities that emit large amounts of greenhouse gases, the greenhouse effect has become too strong, leading to global warming and causing various climate disasters.
The impact of the solar radiative heat transfer mechanism on Earth’s ecological environment is also very important. Solar energy is the driving force for the growth and development of organisms on Earth, and the process of photosynthesis relies on the energy supply from solar radiation. Photosynthesis converts carbon dioxide into organic matter by absorbing solar light energy, releasing oxygen, and supporting the stable functioning of the entire ecosystem.
Solar Radiative Energy
As one of the most important energy sources on Earth, the Sun emits a vast amount of energy for Earth and drives the biosphere and climate on our planet. The mechanism of this energy radiation originates from the nuclear fusion reactions of the Sun and the way its radiative energy propagates.
Solar energy is the driving force for the growth and development of organisms on Earth, and the process of photosynthesis relies on the energy supply from solar radiation. (Illustrative image: Zhihu).
The nuclear fusion of the Sun is the primary mechanism for releasing solar energy. The energy of the Sun comes from hydrogen-based nuclear fusion, which is the process of fusing four hydrogen nuclei into one helium nucleus. This reaction releases a large amount of energy, a small portion of which is transmitted as light and heat.
The solar radiative energy goes through several important processes during its propagation. First, the radiative energy travels from the Sun’s core to its surface, a process that takes tens of thousands of years. The radiative energy is then emitted from the Sun’s surface and forms the solar photosphere, from which it transmits energy to the Sun’s atmosphere.
Solar radiation then travels through thousands of kilometers of the Sun’s atmosphere, where various types of gases absorb or scatter part of the radiative energy. Finally, the radiative energy reaches the Earth’s atmosphere and enters the Earth’s surface, while a portion of the radiative energy is absorbed or scattered by the Earth’s atmosphere.
Visible light constitutes a large proportion of the radiative energy reaching the Earth’s surface. When sunlight passes through the Earth’s atmosphere, the majority of its visible light shines directly onto the Earth’s surface. These rays from the Sun are absorbed by objects on Earth and converted into thermal energy of the objects, thus driving natural phenomena such as climate and winds on Earth.
When sunlight passes through the Earth’s atmosphere, the majority of its visible light shines directly onto the Earth’s surface. (Illustrative image: Zhihu).
In addition to visible light, ultraviolet rays and some infrared rays in solar radiation also have certain effects on organisms and the environment on Earth. The short wavelength of ultraviolet rays makes them energy-rich, but excessive ultraviolet radiation can be harmful to humans and other organisms, such as causing skin burns and photochemical reactions. Infrared rays are a type of thermal radiation with long wavelengths, primarily transmitted through radiation from objects on Earth. The absorption and emission of infrared rays play a significant role in the Earth’s energy balance and climate change.
The Greenhouse Effect of the Planet’s Atmosphere
As our home, Earth has unique climatic conditions, in which the greenhouse effect of the atmosphere plays a crucial role. By trapping and retaining the Sun’s heat, Earth’s greenhouse effect maintains a warm and pleasant climate on its surface.
As our home, Earth has unique climatic conditions, in which the greenhouse effect of the atmosphere plays a crucial role. (Illustrative image: Zhihu).
The Earth’s atmosphere consists of various gases, primarily nitrogen, oxygen, and carbon dioxide. When solar radiation reaches Earth, a portion of it is reflected or scattered back into space by the atmosphere, while the remainder is absorbed by the ground and converted into thermal energy. At this point, the infrared energy radiated by Earth will be blocked by the atmosphere.
The main agents causing the greenhouse effect in the atmosphere are greenhouse gases such as water vapor and carbon dioxide. They have properties that absorb and emit infrared rays, so some of the infrared rays emitted from the surface will be absorbed by these gases, which then transmit and emit it back in various ways. In this process, some of the radiation is returned to the Earth’s surface, keeping the Earth’s surface temperature within an appropriate range.
The Important Role of the Greenhouse Effect
- Climate Regulation: The greenhouse effect regulates Earth’s temperature by absorbing and retaining infrared rays radiated from the Earth’s surface. It maintains the temperature on Earth’s surface within a suitable range for living organisms to survive and reproduce.
- Maintaining the Water Cycle: When heat radiated from the ground interacts with greenhouse gases in the atmosphere, moisture condenses into clouds and forms rain, promoting the water cycle.
(Illustrative image: Zhihu).
- Energy Conservation: The greenhouse effect prevents the release of some infrared rays from the Earth’s surface, allowing some energy to remain on Earth. This helps maintain the Earth’s energy balance and promotes the stable development of ecosystems.
We may be amazed by the mysteries of the infinite universe and continue to pursue more answers. Whether exploring the grand mysteries of the universe or experiencing the microscopic wonders of life, the process of understanding and discovery always fascinates humanity. With curiosity and intellect, humanity’s journey to explore the mysteries of the universe will never end.
