• 喜羊羊和灰太狼
  • 巧虎
  • 熊出没
  • 朵拉
  • 米老鼠和唐老鸭
  • 奥特曼
  • 智慧树
  • 猫和老鼠
  • 海绵宝宝
  • 蜘蛛侠
  • 哆啦A梦
  • 英蕊幼儿英语
  • 天线宝宝
  • 蓝猫
  • 三字经
  • 虹猫蓝兔
  • 小熊维尼
  • 芭比
  • 星际宝贝
  • 蜡笔小新
  • 白雪公主
  • 灰姑娘
  • 圣诞节
  • 新年儿歌
宝宝乐园

55 From the Earth Greetings

加入收藏 下载故事
名称:55 From the Earth Greetings
内容简介:
新概念英语第三册(英音)
[al:新概念英语(三)]
[ar:MP3 同步字幕版(英音)]
[ti:From the Earth: Greetings]

[00:01.45]Lesson 55
[00:04.07]From the earth: Greetings
[00:13.62]Which life forms are most likely to develop on a distant planet?
[00:20.55]Recent developments in astronomy have made it possible to detect planets in our own Milky Way and in other galaxies.
[00:29.22]This is a major achievement because, in relative terms, planets are very small and do not emit light.
[00:37.67]Finding planets is proving hard enough, but finding life on them will prove infinitely more difficult.
[00:45.35]The first question to answer is whether a planet can actually support life.
[00:50.96]In our own solar system, for example, Venus is far to hot and Mars is far too cold to support life.
[01:00.55]Only the Earth provides ideal conditions, and even here it has taken more than four billion years for plant and animal life to evolve.
[01:11.42]Whether a planet can support life depends on the size and brightness of its star, that is its 'sun'.
[01:19.70]Imagine a star up to twenty times larger, brighter and hotter than our own sun.
[01:26.81]A planet would have to be a very long way from it to be capable of supporting life.
[01:32.84]Alternatively, if the star were small,
[01:35.61]the life-supporting planet would have to have a close orbit round it and also provide the perfect conditions for life forms to develop.
[01:44.37]But how would we find such a planet?
[01:47.51]At present, there is no telescope in existence that is capable of detecting the presence of life.
[01:54.10]The development of such a telescope will be one of the great astronomical projects of the 21st century.
[02:01.78]It is impossible to look for life on another planet using earth-based telescopes.
[02:07.07]Our own warm atmosphere and the heat generated by the telescope
[02:11.57]would make it impossible to detect objects as small as planets.
[02:16.44]Even a telescope in orbit round the earth,
[02:19.21]like the very successful Hubble telescope,
[02:22.46]would not be suitable because of the dust particles in our solar system.
[02:27.65]A telescope would have to be as far away as the planet Jupiter to look for life in outer space,
[02:34.59]because the dust becomes thinner the further we travel towards the outer edges of our own solar system.
[02:41.42]Once we detected a planet,
[02:43.43]we would have to find a way of blotting out the light from its star,
[02:47.43]so that we would be able to 'see' the planet properly and analyse its atmosphere.
[02:53.05]In the first instance, we would be looking for plant life, rather than 'little green men'.
[02:59.83]The life forms most likely to develop on a planet would be bacteria.
[03:05.23]It is bacteria that have generated the oxygen we breathe on earth.
[03:10.16]For most of the earth's history they have been the only form of life on our planet.
[03:15.72]As Earth-dwellers, we always cherish the hope that we will be visited by little green men
[03:22.10]and that we will be able to communicate with them.
[03:25.40]But this hope is always in the realms of science fiction.
[03:29.57]If we were able to discover lowly forms of life like bacteria on another planet,
[03:35.04]it would completely change our view of ourselves.
[03:38.93]As Daniel Goldin of NASA observed,
[03:42.50]'Finding life elsewhere would change everything.
[03:46.32]No human endeavour or thought would be unchanged by it.'
  • 365夜故事
  • 小小智慧树儿歌专辑
  • 摇篮曲精选
  • 幼儿园歌曲伴奏
  • 故事大王
  •  儿童睡前故事
宝宝吧APP
宝宝吧动画盒下载
关于我们 | 联系我们 | 网站合作 | 网站导航 | 意见反馈 | 友情链接 |RSS订阅 | 热门搜索
Power by baobao88.com Copyright 2007-2019 晋ICP备2023002424号-1
宝宝吧 - 听儿歌、听故事、玩游戏、学知识,宝宝的乐园,家长的最爱!