translation.en: Celestial mechanics is not making it so easy for an exchange of material between planets, and so if we were to discover life on those planets, it would be different from us.
translation.zh: 天体力学上星球间物质的交换 并非那样容易， 所以如果我们能 在那些星球上找到生命， 那里的生命将和我们不同。