Official 54 Set 6

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Muons and Archaeology

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  • Q6
What is the lecture mainly about?
  • A. Misconceptions about muon detectors

  • B. An investigation of an Egyptian pyramid using a muon detector

  • C. The collaboration between physicists and archaeologists in the development of the muon detector

  • D. Benefits that muon detectors can provide to archaeologists

显示答案 正确答案: D

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    NARRATOR: Listen to part of a lecture in an archaeology class.

    <-FEMALE PROFESSOR:-> A popular misconception about archaeology: Some people imagine we just go out into the field with a shovel and start digging, hoping to find something significant.Well, while there is an element of luck involved, we have an array of high-tech tools to help us figure out where to concentrate our efforts.One of the newer tools actually relies on particle physics.Talk about interdisciplinary! Here’s a machine that brings together two very different sciences.

    This machine is called a muon detector. Muons are subatomic particles that result from cosmic rays….OK, let me start over. Cosmic rays aren’t actually “rays”—they’re basically protons, zipping through outer space at close to light speed.And when they collide with the atoms in Earth’s atmosphere, they break up into smaller particles—muons.Now, these muons are still highly energized, so they can easily pass on down to the Earth’s surface.In fact, they can pass through solid matter, so they can also penetrate deep into the surface.And it’s this property of muons that archaeologists are taking advantage of.

    Let me explain. With the right kind of equipment, scientists can use muons to createa-a-a kind of picture of the structures they’re studying.Let’s say we’re studying a Mayan pyramid in Central America, and we’re interested in finding out if there are burial chambers or other rooms inside.Well, a muon detector will show a greater number of muons passing through the less dense areas inside the pyramid.Yes, Andrew?

    <-MALE STUDENT:-> Um, I’m not sure I get how this muon detector works exactly…

    FEMALE PROFESSOR: Well, muons lose energy as they pass through dense material, like the stone walls of a Mayan pyramid.So, more muons, and more energetic muons, will be passing through empty spaces.The muon detector can differentiate the areas where more muons are passing through—the empty spaces—as well as where there are fewer muons—the walls and dense areas.These empty spaces will show up as darker.So we wind up with a-a kind of picture of the pyramid, and its internal structure.

    MALE STUDENT: A picture?

    FEMALE PROFESSOR: Sort of like an x-ray image.

    MALE STUDENT: OK, so if we see darker areas inside the pyramid, we assume it’s an empty space with more muons.

    <-FEMALE PROFESSOR:-> Exactly. With this technology, we can see what’s inside a structure before we dig.So we know exactly where to explore, and we can minimize the damage excavation can cause—even a little damage could result in our losing vital information forever.Now, muon detectors have been around for some time, but they’ve been improved upon since archaeologists started using them.

    In 1967, a physicist placed a muon detector beneath the base of one of the Egyptian pyramids at Giza.And he was looking for burial chambers.Now, it happened that the muon detector found none, but he did demonstrate that the technique worked.Unfortunately, the machine he used was so big that many archaeologists doubted muon detection could be practical.

    How could they get a massive piece of equipment into, say, uh, the jungles of Belize?Then there was the issue of range.The machine used in 1967 could only scan for muons directly above it, not from the sides, so it actually had to be put underneath the pyramid so it could look up.That meant, if you wanted to find out what was inside an ancient structure, you’d first have to bury the detector beneath it.

    There’s been a lot of work on these machines since then, and these problems have been solved by and large.That’s not to say the technology is perfect.It-it would be nice, for example, to have a system that didn’t take six months to produce an image.I suppose that’s better than the year it took for the 1967 study to get results, but still ….Well, there’s good reason to believe that with better equipment, we’re going to see muon detectors used much more frequently.They’re already being used in other areas of science—uh, for example Japanese scientists studying the interiors of volcanoes—and there are plenty of archaeologists who would love to use this technology.

  • 旁白:请听一段考古学课上的讲座片段。

    教授:一些人对考古学有一个误解,他们认为我们仅仅带上铲子去荒野,然后开始挖掘,希望能够发现一些重要的东东。是的,这里面确实掺杂着一点点运气,但我们有一系列高科技的工具来帮助我们找到那些需要集中努力挖掘的地方。其中一个新的工具事实上是基于粒子物理学的。关于学科交叉!有一个可以把两个不同的科学联系到一起的机器。

    这个机器叫做介子探测器。介子是起源于宇宙射线的亚原子粒子。好的,让我们开始今天的课程。宇宙射线不是真正的射线。它们实际上是在外太空以接近于光速的速度快速运行的质子。并且,当它们和地球大气里的原子撞击的时候,它们会分裂成更小的粒子—介子。现在,这些介子仍然有很高的能量,它们能够很轻易的穿过地球的表面。事实上,它们能够穿过固体物质,所以它们也能够穿透地球表面。并且,现在考古学家正在利用介子的这一特性。

    让我来解释一下,用正确的装备,科学家能够用介子来描绘出他们正在研究的事物的结构。比方说我们正在中美洲研究一座玛雅金字塔,我们想要知道里面是否有一些墓葬或者其他的房间。是的,一个介子探测器将会显示有更多介子穿过金字塔内密度小的地方。安德鲁,你有什么疑问?

    学生:事实上,我不太确定是否理解了介子探测器的工作原理。

    教授:好的,介子在穿过密度大的物质时会消耗能量,比如说玛雅金字塔的石墙。因此,更多的介子以及拥有更多能量的介子将会穿过空旷的空间。这个介子探测器能够分辨出哪些地方有更多的介子穿过——空的地方,以及哪些地方有更少的介子穿过——墙壁以及密度大的地方。这些空的地方呈现出暗色。因此我们能够描绘出一张金字塔的图片以及它的内部结构。

    学生:一张图片?

    教授:一种像X射线照片一样的图像。

    学生:好的,所以如果我们看到金字塔内部黑色区域,我们可以肯定它是有更多介子穿过的空的区域。

    教授:事实上,利用这个技术,我们在挖掘之前就能够看到它的内部结构。所以我们能够正确地知道去探索哪块区域,并且能够把挖掘过程中带来的损坏最小化——一点小的损坏都可能导致我们永远失去重要的信息。现在,介子探测器已经被使用了一段时间,但是它们自考古学家开始使用它们起就已经得到了改进。

    在1967年,一个物理学家把一个介子探测器放在埃及的吉萨大金字塔的地基下面。他正在寻找一个墓葬。介子探测器没有发现任何东西。但是,他证明了这个技术是有效的。不幸的是,他用的这个机器太大了,以至于许多考古学家怀疑介子探测器的实用性。

    他们怎样才能把这么大的一个设备用在,比方说伯利兹的雨林呢?这就谈到范围的问题了。1967年的机器仅仅能够扫描在它正上方的介子,而不能是来自水平方向的。所以,为了它能够向上扫描,就不得不把它放在金字塔的正下方。这就意味着,如果你想要发现古老的建筑里有什么,首先你必须把探测器埋在它下面。

    从那个时候开始,人们对这些机器做了很多的研究,并且这些问题大部分已经被解决了。这并不是说这项技术是完美的。举个例子,如果有个不需要6个月去生成一个图形的系统就太好了。我认为它比1967年的研究得到的结果更好。但是……仍然有理由相信会有更好的设备,我们将更频繁的使用介子探测器。它们已经被使用在科学界的其它领域,举个例子,日本科学家用其研究火山内部,还有很多考古学家热衷于使用这项技术。

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    题干分析:讲座的主要内容

    原文定位:Let me explain. With the right kind of equipment, scientists can use muons to create

    a-a-a kind of picture of the structures they’re studying. Let’s say we’re studying a Mayan pyramid in Central America, and we’re interested in finding out if there are burial chambers or other rooms inside. 

    选项分析:讲座一开始,教授首先更正一个关于考古学的常见误解:考古学家不仅仅是靠运气在野外挖来挖去。考古学使用一系列高科技工具。然后教授重点介绍Moun director技术,结合考古学案例说该技术的应用好处。D选项概括最准确。

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