下文是关于“能量的来源”的范文:
A summary of the physical and chemical nature of life must begin, not on the Earth, but in the Sun; in fact, at the Sun’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, 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 Sun’s 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 Sun’s light and heat is emitted in such directions that after passing unhindered through interplanetary space, it hits the Earth.
>>点击查看GRE作文专题,阅读更多相关文章!
-
如何两个月拿下GRE?
每年都有无数小伙伴在纠结一个问题,两个月备考GRE到底够不够?事实上,全身心准备的话,完全够了。下面我们一起来看看如何备考,有哪些值得我们学习呢?
- GRE的文章源于哪里?
- GRE考前冲刺复习做到这5点提分最有效
- 2017年GRE考试报名开始啦!最新考试时间官方公布快来抢考位
- ETS官网查不了GRE分数怎么办?