The source of Energy
[size=3][color=#29384e][font=Times New Roman]A summary of the physical and chemical nature of life must begin[/font][font=宋体]，[/font][font=Times New Roman] not on the Earth[/font][font=宋体]，[/font][font=Times New Roman] but in the Sun[/font][font=宋体]；[/font][font=Times New Roman] in fact[/font][font=宋体]，[/font][font=Times New Roman] at the Sun[/font][font=宋体]‘[/font][font=Times New Roman]s very center. It is here that is to be found the source of the energy that the Sun constantly pours out into space as light and heat. This energy is librated at the center of the Sun as billions upon billions of nuclei of hydrogen atoms collide with each other and fuse together to form nuclei of helium[/font][font=宋体]，[/font][font=Times New Roman] and in doing so[/font][font=宋体]，[/font][font=Times New Roman] release some of the energy that is stored in the nuclei of atoms. The output of light and heat of the Sun requires that some 600 million tons of hydrogen be converted into helium in the Sun every second. This the Sun has been doing for several thousands of millions of year.[/font][/color][/size][size=3][color=#29384e][font=Times New Roman] [/font][/color][/size]
[size=3][color=#29384e][font=宋体] [/font][font=Times New Roman]The nuclear energy is released at the Sun[/font][font=宋体]‘[/font][font=Times New Roman]s center as high-energy gamma radiation[/font][font=宋体]，[/font][font=Times New Roman] a form of electromagnetic radiation like light and radio waves[/font][font=宋体]，[/font][font=Times New Roman] only of very much shorter wavelength. This gamma radiation is absorbed by atoms inside the Sun to be reemitted at slightly longer wavelengths. This radiation [/font][font=宋体]，[/font][font=Times New Roman] in its turn is absorbed and reemitted. As the energy filters through the layers of the solar interior[/font][font=宋体]，[/font][font=Times New Roman] it passes through the X-ray part of the spectrum eventually becoming light. At this stage[/font][font=宋体]，[/font][font=Times New Roman] it has reached what we call the solar surface[/font][font=宋体]，[/font][font=Times New Roman] and can escape into space without being absorbed further by solar atoms. A very small fraction of the Sun[/font][font=宋体]’[/font][font=Times New Roman]s light and heat is emitted in such directions that after passing unhindered through interplanetary space[/font][font=宋体]，[/font][font=Times New Roman] it hits the Earth.[/font][/color][/size]
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