The moment the first burns out, you light the other end of the second fuse.

当第一条烧尽的时候，点燃第二条的另一端。

" Well, what would happen if you lit both ends of a candle at the same time? " said the doctor.

“那么，如果同时点燃蜡烛的两端会发生什么？ ” 医生说。

And, you realize, you can shorten the second fuse by lighting one end of it at the same time as you light the first.

并且你会发现，点燃第一条保险丝的时候就点燃第二条的一端就可以缩短第二条保险丝的时间。

But if you lay a candle sideways you can light both ends and the candle is twice as bright, but it burns out twice as quickly.

但是如果你把蜡烛横着放， 你可以点亮两端， 蜡烛的亮度是原来的两倍，但它燃烧的速度是原来的两倍。