地球的力量 第2集 大氣(16)混沌初開
這是一種閃電
that doesn't strike down towards the ground
它們不直接襲擊地表面
but instead reaches upwards within the mesosphere,
而是往上發(fā)射，高至中心層
30-50 miles high.
30到50英里高
We've seen the power of the atmosphere to shape the planet
我們看過大氣的力量是怎樣塑造星球
and create the weather,
和創(chuàng)造氣候
but it's the relationship between the atmosphere and life
大氣和生命的聯(lián)系
that has made our planet unique in the solar system.
使我們的地球在太陽系中獨(dú)一無二
To understand how this vital relationship evolved,
要明白這一重要的關(guān)系如何發(fā)生
you have to go back to the very beginning of Earth's long history.
得追溯到很久以前地球混沌初開時(shí)
The planet's atmosphere was created shortly after the Earth was formed
在地球剛形成不久大氣圏就形成了
four and a half billion years ago.
四十六億年前
The early Earth was probably highly volcanic.
早期地球充滿火山
And for millions of years,
幾百萬年后
these volcanoes spewed out huge quantities of gas.
這些火山噴發(fā)出大量氣體
Slowly these gases built up and created the atmosphere.
這些氣體緩慢聚合創(chuàng)造了大氣層
