时差N小时 只有在地球上才能燃烧?(上)（在线收听）

What is fire anyway?

火究竟是什么？

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

火，即燃烧，是快速的氧化反应。氧化反应是氧原子和碳原子或氢原子结合释放能量。

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

没错，那么如果空气中没有氧气，就不会有燃烧。

You mean there was a time before oxygen?

你是说氧气还不存在的那个时代？

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.

大约十亿年前，和眼下的植物一样，地球上最原始的植物祖先“真核细胞”忙碌地将二氧化碳转变成氧气。