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Now listen to part of a lecture on the topic you just read about.
現在來聽一段有關你剛剛聽到的話題的演講。
The claims that the burning mirror would have been impractical and technologically impossible are unconvincing.
燃燒鏡是不現實而且技術上來說是不可能的斷言沒有說服力。
First, the Greeks did not need to form a single sheet of copper to make a large, burning mirror.
首先，希臘人不需要一整塊銅板來做一面大的燃燒鏡。
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.
實驗表明，許多的自身平整圓滑的小銅片能被排列成一個拋物線的形狀然后形成一個大的燃燒鏡。
The Greek mathematicians know the properties of the parabola and so could have directed the assembly of small mirror pieces into the parabolic shape.
希臘數學家們知道拋物線的屬性，所以可能已經指導著把小鏡子碎片組裝成了拋物線的形狀。
Second, about how long it would take to set a ship on fire with a burning mirror.
第二，關于用一個燃燒鏡讓船燃燒起來要花多久。
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.
閱讀選集里的實驗假定燃燒鏡是要讓船上的木頭著火，那將花十分鐘。
But Roman boats were not made just of wood. There were other materials involved as well.
但是羅馬船只不僅僅是用木頭制成的。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，為了密封木頭夾板中間的空隙來使它們防水，古老的造船者們使用了一種叫做瀝青的粘性物質。
Pitch catches fire very quickly. An experiment showed that pitch could be set on fire by a burning mirror in seconds.
瀝青能很快著火。一個實驗表明瀝青幾秒鐘內便能被燃燒鏡點燃。
And once the pitch was burning, the fire would spread to the wood even if the ship was moving.
當瀝青燃燒的時候，火焰會蔓延到木頭，即使船是移動的。
So a burning mirror could have worked quickly enough to be an effective weapon.
所以一個燃燒鏡能足夠快地奏效來成為一個有力的武器。
Third, why bother with a burning mirror instead of flaming arrows?
第三，何苦用燃燒鏡取代弩炮？
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，羅馬的士兵們熟悉弩炮并且已經在注意它們，也做好了準備來撲滅它們將引起的火災。
But you cannot see the burning rays from a mirror; you just see the mirror.
但是你從鏡子里看不見燃燒的射線，你只能看見鏡子。
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.
但是突然魔術般地，在船上一些沒有被觀察到的地方起了火，那會更讓人吃驚，所以比弩炮更有效。
