发布时间：2021-05-07 10:27:09 浏览： 次
Cosmic Radiation Cosmic radiation and air travel Cosmic radiation is part of our natural environment, and we are constantly exposed to a certain amount of ionizing radiation. Radiation originating from outer space and the sun is called cosmic radiation and contributes about 13% of the background radiation level on Earth (a greater part is due to radon). Special features of cosmic radiation Cosmic radiation is a complex mixture of charged and neutral particles, some of them generated when primary particles from space interact with the earth's atmosphere. This complexity also leads to difficulties in measuring radiation doses from cosmic radiation, but physicists have developed sophisticated approaches to deal with this situation. For the human exposure situation one feature of cosmic radiation is of particular importance: a large percentage of the effective radiation dose from cosmic radiation is due to neutrons of different energy levels. Neutrons are subatomic particles which - when compared to X-rays or Gamma rays - cause more biological damage per dose unit. Exposure during flying As a rule, cosmic radiation levels rise with increasing altitude (up to about 20 km above ground). The actual radiation level is influenced by a number of factors, most importantly through the shielding provided by the earth's atmosphere. The overall effect for flight crew and travellers is an increased radiation exposure during flights as compared to staying on the ground. Flight crew passes up to 1000 hours per year on board of flying planes, which leads to annual effective radiation doses in the range of 2 to 5 milliSievert (mSv) for most crew. Occasional travellers obtain a fraction of this value through less frequent leisure or occupational flights. In comparison, the natural background radiation amounts to 2 to 3 mSv per year at most geographical locations worldwide. Cosmic radiation and health A series of studies concerning health issues associated with cosmic radiation has been conducted in the past few years. The WHO Information Sheet summarizes the current knowledge and ongoing research activities, and gives target-group specific recommendations on actions concerning cosmic radiation. 这绝对是关于宇宙的，采纳我的啊。
The universe is a vast space and the existence of various objects and diffuse material. The universe is the material world, it is in constant movement and development. "Huainan Zi. Original training" note: "the Quartet on Yue Yu, from ancient to modern times, universe, heaven and earth to yu." The universe is a general term for all things. For thousands of years, scientists have been exploring the universe is what time, how to form. Until now, scientists believe, the universe is composed of an explosion occurred about 15000000000 years ago.。
If you go out sometimes at night,you'll see the moon hight up in the sky. the moon is far away from the earth.But it is our nearest neighbor in space . In 1996 two Americans visited it by spaceship . It was one of the most exciting momenys of that year.The sky looks black from the moonand you'll see the earth up in the sky.You will also see many ,many stars.You can't find any living things there. It's too hot in the dayand too cold at night.And there's no air or water there.Noyhing can live on it.It is difficult for men to walk on the moon.Everything becomes much lighter.You can jump much higher on the moon than on the earth.If you throw a ball,it would fly very far.It's very interesting to walk on the moon. 如果你有时在晚上出去，你会见到月球高挂在天上。
宇宙 universe;cosmos 宇宙的诞生 我们现在观察到的宇宙，其边界大约有100多亿光年。
在西方，宇宙这个词在英语中叫cosmos，在俄语中叫кocMoc ，在德语中叫kosmos ，在法语中叫cosmos。它们都源自希腊语的κoσμoζ，古希腊人认为宇宙的创生乃是从浑沌中产生出秩序来，κoσμoζ其原意就是秩序。
universe和cosmos常常表示相同的意义，所不同的是，前者强调的是物质现象的总和，而后者则强调整体宇宙的结构或构造。 宇宙观念的发展 宇宙结构观念的发展 远古时代，人们对宇宙结构的认识处于十分幼稚的状态，他们通常按照自己的生活环境对宇宙的构造作了幼稚的推测。
这一观念为后来许多古希腊学者所继承，但直到1519~1522年，葡萄牙的F.麦哲伦率领探险队完成了第一次环球航行后 ，地球是球形的观念才最终证实。 公元2世纪，C.托勒密提出了一个完整的地心说。
The Universe is defined as the summation of all particles and energy that exist and the space-time in which all events occur. Based on observations of the portion of the Universe that is observable, physicists attempt to describe the whole of space-time, including all matter and energy and events which occur, as a single system corresponding to a mathematical model.
The generally accepted scientific theory which describes the origin and evolution of the Universe is Big Bang cosmology, which describes the expansion of space from an extremely hot and dense state of unknown characteristics. The Universe underwent a rapid period of cosmic inflation that flattened out nearly all initial irregularities in the energy density; thereafter the universe expanded and became steadily cooler and less dense. Minor variations in the distribution of mass resulted in hierarchical segregation of the features that are found in the current universe; such as clusters and superclusters of galaxies. There are more than one hundred billion (1011) galaxies in the Universe, each containing hundreds of billions of stars, with each star containing about 1057 atoms of hydrogen.
Universe Where do we come from? How did the universe begin?Why is the universe the way it is? How will it end? All my life, I have been fascinated by the big questions that face us, and have tried to find scientific answers to them.If, like me, you have looked at the stars, and tried to make sense of what you see, you too have started to wonder what makes the universe exist. The questions are clear, and deceptively simple. But the answers have always seemed well beyond our reach. Until nOW. The ideas which had grown over two thousand years of observation have had to be radically re- vised. In less than a hundred years, we have found a new way to think of ourselves. From sitting at the center of the universe, we now find ourselves orbiting an average-sized sun, which is just one of millions of stars in our own Milky Way galaxy. And our galaxy itself is just one of billions of galaxies, in a universe that is infinite and expanding. But this is far from the end of a long history of inquiry.Huge questions remain to be answered, before we can hope to have a complete picture of the universe we live in. I want you to share my excitement at the discoveries,past and present, which have revolutionized the way we think. From the Big Bang to black holes, from dark matter to a possible Big Crunch, our image of the universe today is full of strange sounding ideas, and remarkable truths. The story of how we arrived at this picture is the story of learning to understand what we see. 宇宙 我们来自何方？宇宙如何开始？为什么宇宙是这样的？它将如何结束？ 我一生都迷恋于我们所面临的这些大问题并试图找到他们科学的答案。
Gaze upwards on a dark night, and you will see the 'Milky Way', a glowing ribbon made up of many individual stars. This is our first clue to the fact that that stars are not uniformly distributed throughout space, but clustered together to form galaxies.
Galaxies can vary in size between a hundred thousand and three thousand billion solar masses, and can be broadly split into different classes, depending on their shape. Our own Milky Way Galaxy contains about two hundred billion stars. It is a spiral shape, which is why, when viewed from our position about two thirds of the way along one of the arms, it appears as a band across the sky.
Gazing out into the Universe reveals thousands upon thousands of galaxies. These galaxies tend to be grouped together in clusters, and these clusters in turn are grouped into superclusters. It appears the Universe has structure on many different scales.
1.Back to School It's the first day of school. Mike wants to go back to school. He wants to see his friends. He wants to meet his new teacher. Mike gets up early in the morning. He washes and eats his breakfast. Then he rides his bike to school. He sees his friends on the playground. He plays hide-and-seek with them. In the classroom, Mike meets his new maths teacher. Her name is Mrs. Green. Mike likes Mrs Green. She can speak English very well. He thinks she is a nice teacher. 2. One day,a monkey drove his car near a lake.Sudden,he saw a tiger under a tree.The tiger saw him,too.The tiger ran very fast at the monkey.The monkey was very afraid and he and his car fell into the lake.The monkey couldn't swim and he shouted.A rabbit came and he jumped into the lake.The rabbit swam to the monkey but did not help him.Both of them shouted for help.Luckily,a giraffe came along.He was very tall.He helped the rabbit and the monkey. 3.Mike's Family Mike comes from America. He is twelve. His father Mr. Brown works in a big shop in Beijing. Mike has a sister. Her name is Kate. She is only four. It is Saturday today. Mike's family is all at home. Mr. Brown is sitting in a chair and reading today's newspaper. Mrs. Brown is out of the house; she is watering the flowers. Is Mike with his mother? No, he is cleaning his new bike. Where is Kate? She is in her room. She is playing with her cat. What a happy family! 4 How time flies ,It has past half an month since beginning of the summer holiday . As the weather getting hotter and hotter ,my parent and me go to the seaside .Last week we are go to the Xiamen.It's a beautiful city , bule sky and bule sea .The Xiamen is an island neal the Taiwan .From top of the Riguan rock we can see jinmen island . We spent a happy day in Xiamen 5 My family I love my family, because I have a happy family. My father is an English teacher. His name is Jacky. He is thirty-eight. He likes playing basketball. What's my mother job? Is she a teacher? Yes, you're right! My mother is very kind and nice, she is thirty-seven. My mother is always laborious work. I love my parents! On Saturday and Sunday, I often go to the library and play the piano, My father go to play basketball. Sometimes, we watch TV and listen to music at home. I love my family. Because I'm very happy to live with my parents together 6 Yesterday was my birthday, so some of my classmates sent me presents. Mother prepared a tea party for me. I invited all of them to come and take part in it. The tea party began at half past six. There were cold drinks and refreshments. We ate, talked and laughed. We felt that we were the happiest men in the world. Time passed quickly. In a twinkling, the clock on the wall struck nine. We could not but say “Good-bye” to one another. 7 There is a big bed , a small desk , a shelf and a closet in my room. The bed is near the desk . There is a shelf near the closet too . Many good books are in the shelf . I like the books very much . Oh , yes , There is a big board on the wall . I often write and draw pictures on the board . Oh , My bedroom is too beautiful . I like it very much . Do you like my room? Can you tell me about your room , please ？ 够了吧。
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