A one-kilogram chunk of matter converted completely to energy—this is a working definition of a 20-megaton hydrogen bomb一公斤大小的物质完全转化为能量──这正是一颗2000万吨氢弹的实际定义。
For example, a one-megaton nuclear warhead would need to be intercepted at an altitude of at least 10 kilometers to prev举例来说，一枚百万吨级的核子弹头，必须在10公里以上的高空拦截，城市才不致于因为氢弹的热度而化为灰烬。