45.The source of Energy
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.
2017届《名师A计划》高考英语新人教版一轮复习配套练习:必修5 Unit 4《Making the news》(含解析)
2017届《名师A计划》高考英语新人教版一轮复习配套练习:选修7 Unit 4《Sharing》(含解析)
大公司VS初创公司,哪种公司更适合你?
如何拥有持续长久的恋爱关系
2017届《名师A计划》高考英语新人教版一轮复习配套课件:必修4 Unit 1《Women of achievement》
2017届《名师A计划》高考英语新人教版一轮复习配套练习:选修8 Unit 4《Pygmalion》(含解析)
2017届《名师A计划》高考英语新人教版一轮复习配套练习:选修6 Unit 4《Global warming》(含解析)
2017届《名师A计划》高考英语新人教版一轮复习配套课件:必修1 Unit 3《Travel journal》
2017届《名师A计划》高考英语新人教版一轮复习配套练习:选修8 Unit 1《A land of diversity》(含解析)
教材改革 The Reform of Textbook
胚胎技术重大突破 未来也可人工制造?
2017届《名师A计划》高考英语新人教版一轮复习配套练习:选修6 Unit 5《The power of nature》(含解析)
2017届《名师A计划》高考英语新人教版一轮复习配套课件:必修2 Unit 1《Cultural relics》
加菲猫到底是公是母?美国人为这个吵起来了
我生命中的天使 Angel In My Life
2017届《名师A计划》高考英语新人教版一轮复习配套课件:必修4 Unit 2《Working the land》
2017届《名师A计划》高考英语新人教版一轮复习配套练习:选修7 Unit 3《Under the sea》(含解析)
2017届《名师A计划》高考英语新人教版一轮复习配套练习:选修6 Unit 1《Art》(含解析)
2017届《名师A计划》高考英语新人教版一轮复习配套练习:选修7 Unit 5《Travelling abroad》(含解析)
2017届《名师A计划》高考英语新人教版一轮复习配套练习:选修7 Unit 2《Robots》(含解析)
2017届重庆市高考英语一轮复习阅读理解选编精练:90(含解析)
2017届《名师A计划》高考英语新人教版一轮复习配套练习:选修7 Unit 1《Living well》(含解析)
2017届《名师A计划》高考英语新人教版一轮复习配套练习:选修8 Unit 5《Meeting your ancestors》(含解析)
2017届《名师A计划》高考英语新人教版一轮复习配套课件:必修2 Unit 3《Computers》
求职信中常见的四种错误
2017届《名师A计划》高考英语新人教版一轮复习配套课件:必修3 Unit 5《Canada
2017届《名师A计划》高考英语新人教版一轮复习配套课件:必修1 Unit 2《English around the world》
特朗普指控奥巴马窃听!白宫的戏真是没完了
2017届《名师A计划》高考英语新人教版一轮复习配套课件:必修2 Unit 5《Music》
2017届《名师A计划》高考英语新人教版一轮复习配套练习:必修5 Unit 3《Life in the future》(含解析)
不限 |
英语教案 |
英语课件 |
英语试题 |
不限 |
不限 |
上册 |
下册 |
不限 |