VOA 学英语,练听力,上听力课堂! 注册 登录
> VOA > VOA慢速英语-VOA Special English > Science in the News >  内容

VOA慢速英语:古老的地球含氧量比科学家认为的还多

所属教程:Science in the News

浏览:

2016年08月12日

手机版
扫描二维码方便学习和分享
https://online2.tingclass.net/lesson/shi0529/0008/8384/science_in_the_news_20160812a.mp3
https://image.tingclass.net/statics/js/2012
Ancient Earth Had More Oxygen than Scientists Thought

Researchers say the Earth had much more oxygen nearly a billion years ago than scientific experts thought. That claim could change theories about how life developed on our planet.

The claim came from researchers at Brock University in Canada. They wanted to measure the levels of oxygen in the Earth’s atmosphere nearly a billion years ago. To do this, the researchers developed a way to study small air bubbles trapped in ancient salt crystals.

“There was a lot of debate as to what the oxygen content was 800 million or more years ago,” said Nigel Blamey of Brock University’s Department of Earth Sciences. He said the trapped gasses showed that the oxygen level was about half of what it is today.

In fact, many experts believed that the oxygen level was only about two percent of the atmosphere so long ago. But the new study found that it was almost 11 percent. Currently, oxygen is about 21 percent of the atmosphere.

The Canadian researchers used a method to study air bubbles trapped in halite, the natural form of table salt.

The researchers say their findings have major effects for theories about how and when life developed.

Professor of Earth Sciences Uwe Brand said that higher oxygen levels in the past may turn back the clock when complex life developed. “Now paleobiologists will have reason to go looking for rocks with” evidence of these first evolutionary steps,” he told the Canadian Broadcasting Corporation.

I’m Anne Ball.

_______________________________________________________

Words in This Story

bubble – n. a small ball of air in a solid substance

crystals – n. small pieces of a substance that has many sides and are formed when the substance turns into a solid

clock - n. an instrument for telling time

 
用户搜索

疯狂英语 英语语法 新概念英语 走遍美国 四级听力 英语音标 英语入门 发音 美语 四级 新东方 七年级 赖世雄 zero是什么意思厦门市东方名园英语学习交流群

  • 频道推荐
  • |
  • 全站推荐
  • 推荐下载
  • 网站推荐