注册 登录  
 加关注
   显示下一条  |  关闭
温馨提示!由于新浪微博认证机制调整,您的新浪微博帐号绑定已过期,请重新绑定!立即重新绑定新浪微博》  |  关闭

伴你一程

Ban Ni Yi Cheng

 
 
 

日志

 
 

【English Digest】(49)流星  

2016-04-20 17:38:23|  分类: 【英语】听力 |  标签: |举报 |字号 订阅

  下载LOFTER 我的照片书  |

    If you find yourself away from a city, spend an hour looking up on any clear, moonless night.

You're bound to see a few brilliant "shooting stars." These actually have nothing to do with stars: They're meteors, and if your viewing conditions are good, you can see about seven per hour on any given night.
During a "meteor shower" however, this rate may increase to over a hundred meteors an hour. What are meteors, and what makes them gather into showers?
Meteors are caused by bits of rocky material that enter our atmosphere from space, then burn up because of friction1. They don't have to be big for you to see them. Surprisingly, most visible meteors are caused by debris2 no larger than a single grain of sand. They burn so brightly because of tremendous friction when they hit our atmosphere at more than forty miles per second.
Why would something as random3 as flying specks4 of space debris gather into showers? It's because the Earth passes through the same regions of space each time it orbits the sun. Certain regions have more debris than others, so we have meteor showers on those nights.
Of course this raises the question of why certain parts of our orbit would be especially full of debris. The answer has to do with comets. Comets are big, dirty snowballs that orbit our sun. Long after a comet and it's tail have passed us by, it leaves behind a thin trail of dust and debris. If a comet crosses the Earth's orbit, we pass through this trail each year. For example, every October twenty-first we pass through the Orionid shower, which is debris left behind from Halley's comet.
      【音乐】英语音频 - 伴你一程 - 伴你一程【音乐】英语音频 - 伴你一程 - 伴你一程
  评论这张
 
阅读(9)| 评论(1)
推荐 转载

历史上的今天

在LOFTER的更多文章

评论

<#--最新日志,群博日志--> <#--推荐日志--> <#--引用记录--> <#--博主推荐--> <#--随机阅读--> <#--首页推荐--> <#--历史上的今天--> <#--被推荐日志--> <#--上一篇,下一篇--> <#-- 热度 --> <#-- 网易新闻广告 --> <#--右边模块结构--> <#--评论模块结构--> <#--引用模块结构--> <#--博主发起的投票-->
 
 
 
 
 
 
 
 
 
 
 
 
 
 

页脚

网易公司版权所有 ©1997-2017