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Now listen to part of a lecture on the topic you just read about.
现在来听一段有关你刚刚听到的话题的演讲。
The claims that the burning mirror would have been impractical and technologically impossible are unconvincing.
燃烧镜是不现实而且技术上来说是不可能的断言没有说服力。
First, the Greeks did not need to form a single sheet of copper to make a large, burning mirror.
首先，希腊人不需要一整块铜板来做一面大的燃烧镜。
An experiment has shown that dozens of small individually flat pieces of polished copper could be arranged into a parabolic shape and form a large, burning mirror.
实验表明，许多的自身平整圆滑的小铜片能被排列成一个抛物线的形状然后形成一个大的燃烧镜。
The Greek mathematicians know the properties of the parabola and so could have directed the assembly of small mirror pieces into the parabolic shape.
希腊数学家们知道抛物线的属性，所以可能已经指导着把小镜子碎片组装成了抛物线的形状。
Second, about how long it would take to set a ship on fire with a burning mirror.
第二，关于用一个燃烧镜让船燃烧起来要花多久。
The experiment the reading selection mentions assumes that the burning mirror was used to set the wood of the boat on fire, that's what takes ten minutes.
阅读选集里的实验假定燃烧镜是要让船上的木头着火，那将花十分钟。
But Roman boats were not made just of wood. There were other materials involved as well.
但是罗马船只不仅仅是用木头制成的。也包括了其他的材料。
For example, to seal the spaces between wooden boards and make them waterproof, the ancient boat-builders used a sticky substance called pitch.
比如，为了密封木头夹板中间的空隙来使它们防水，古老的造船者们使用了一种叫做沥青的粘性物质。
Pitch catches fire very quickly. An experiment showed that pitch could be set on fire by a burning mirror in seconds.
沥青能很快着火。一个实验表明沥青几秒钟内便能被燃烧镜点燃。
And once the pitch was burning, the fire would spread to the wood even if the ship was moving.
当沥青燃烧的时候，火焰会蔓延到木头，即使船是移动的。
So a burning mirror could have worked quickly enough to be an effective weapon.
所以一个燃烧镜能足够快地奏效来成为一个有力的武器。
Third, why bother with a burning mirror instead of flaming arrows?
第三，何苦用燃烧镜取代弩炮？
Well, Roman soldiers were familiar with flaming arrows and would have been watching for them and were ready to put out the fires they might cause.
好吧，罗马的士兵们熟悉弩炮并且已经在注意它们，也做好了准备来扑灭它们将引起的火灾。
But you cannot see the burning rays from a mirror; you just see the mirror.
但是你从镜子里看不见燃烧的射线，你只能看见镜子。
But then suddenly and magically a fire starts at some unobserved place on the ship that would have been much more surprising and therefore much more effective than a flame arrow.
但是突然魔术般地，在船上一些没有被观察到的地方起了火，那会更让人吃惊，所以比弩炮更有效。
