英語聽力文摘496 燃燒僅在地球可行

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The Time Before Fire

What is fire anyway?

Well, fire is rapid oxidization. It’s the energy released when oxygen atoms start combining with carbon and hydrogen atoms.

Exactly, so without oxygen in the air, nothing burns.

You mean there was a time before oxygen?

Yes. By roughly a billion years ago, simple forms of plant life called “eukaryotes” were already busily converting carbon dioxide into oxygen gas, just like their descendants do today. But before this process had been in place for a while, there wasn’t enough oxygen in the air for things to burn.

In fact, of all the planets, moons, asteroids, and comets in our solar system, the only place where you can actually start a fire is right here on earth. And even here, it’s only been possible relatively recently.

火究竟是什么?

火，即燃燒，是快速的氧化反應。氧化反應是氧原子和碳原子或氫原子結合釋放能量。

沒錯，那么如果空氣中沒有氧氣，就不會有燃燒。

你是說氧氣還不存在的那個時代?

對，大約十億年前，和眼下的植物一樣，地球上最原始的植物祖先“真核細胞”忙碌地將二氧化碳轉變成氧氣。但是，在此轉化之前的一段時間，空氣中沒有足夠的氧氣可以燃燒東西。

而事實上，整個太陽系的所有的行星、月球、小行星、彗星，你會發(fā)現唯一可以生活的地方只有地球。而就算是地球，也是不久以前才可行。

eukaryotes:真核細胞

convert：轉化