A summary of the physical and chemical nature of life must begin, not on the Earth, but in the Sun; in fact, at the Suns 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, and in doing so, 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.
The nuclear energy is released at the Suns center as high-energy gamma radiation, a form of electromagnetic radiation like light and radio waves, 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, in its turn is absorbed and reemitted. As the energy filters through the layers of the solar interior, it passes through the X-ray part of the spectrum eventually becoming light. At this stage, it has reached what we call the solar surface, and can escape into space without being absorbed further by solar atoms. A very small fraction of the Suns light and heat is emitted in such directions that after passing unhindered through interplanetary space, it hits the Earth.
基础英语轻松学【105】“意大利”的历史
相似词语辨析【10】also和too
基础英语轻松学【89】美式爱情
相似词语辨析【8】alive和living
相似词语辨析【40】clothes和clothing
基础英语轻松学【97】美国人的道德观
基础英语轻松学【91】家的意义是什么?
相似词语辨析【17】at ease和with ease
相似词语辨析【29】breath和breathe
相似词语辨析【6】advance和advancement
基础英语轻松学【95】孕育童话的地方——丹麦
基础英语轻松学【92】吃在美国
相似词语辨析【5】admit和admit of
基础英语轻松学【102】你知道“万圣节”的由来吗?
相似词语辨析【25】be going to和will
相似词语辨析【42】concerned和concerning
基础英语轻松学【112】科比·布莱恩的成长之路
基础英语轻松学【98】美国人的“洁癖”
相似词语辨析【21】at the end of和by the end of
基础英语轻松学【108】弗拉门戈——尽显西班牙风情
基础英语轻松学【99】网络交友是与非
相似词语辨析【15】as well as和as well
相似词语辨析【27】believe和believe in
相似词语辨析【50】despite和in spite of
相似词语辨析【7】after和behind
相似词语辨析【19】at last和at length
相似词语辨析【1】able和capable
相似词语辨析【24】be ashamed for和be ashamed of
相似词语辨析【20】at(the)least和not(in)the least
相似词语辨析【14】anyway和any way
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