《(4.1.2)--10WillardFrankLibby-中英文讲稿.pdf》由会员分享，可在线阅读，更多相关《(4.1.2)--10WillardFrankLibby-中英文讲稿.pdf（9页珍藏版）》请在taowenge.com淘文阁网|工程机械CAD图纸|机械工程制图|CAD装配图下载|SolidWorks_CaTia_CAD_UG_PROE_设计图分享下载上搜索。
1、1 Willard Frank Libby-Archaeological Clock （威拉德威拉德 弗兰克弗兰克 利比利比-考古学时钟考古学时钟）Hello everyone,do you like travel historic places of interest?Are you interested in archaeology?And do you know how to determine the age of fossils and relics?Let me introduce you a Nobel Prize Winner in Chemistry today,to see
2、 how he did it.（大家好，您喜欢游览历史名胜吗？你对考古学感兴趣吗？你知道如何确定化石和遗迹的年龄吗？让我介绍一位诺贝尔化学奖得主，看看他是如何做到的。）PART ONE Biography（第一部分第一部分 传记传记）Willard Frank Libby won the Nobel Prize in Chemistry in 1960.He worked for the University of California,in USA He won the Nobel prize because of his method to use carbon-14 for age de
3、termination in archaeology,geology,geophysics,and other branches of science.（威拉德弗兰克利比于 1960 年获得诺贝尔化学奖。他在美国加州大学工作。他因使用碳-14 测定用于考古学、地质学、地球物理学和其他科学分支的年龄而获得诺贝尔奖。）He is a Physical Chemist,and specialist in radiochemistry,particularly hot atom 2 chemistry He is good at tracer techniques,and isotope tracer
4、 work.He became well-known at University of Chicago for his work on natural carbon-14(as the radiocarbon).C 14 is used in dating archaeological artifacts,and its use in hydrology and geophysics.（他是物理化学家，放射化学，特别是热原子化学方面的专家。他擅长示踪技术和同位素示踪工作。他在芝加哥大学因在天然碳-14（即放射性碳）方面的工作而闻名。C 14 用于确定考古文物的年代，并用于水文和地球物理学。）H
5、ow to measure the age of archaeological artifacts?First of all,what is C-14?Carbon is a fundamental component in all living material.In nature,there are three isotopes:carbon-12,which is stable form,carbon-13,and carbon-14.Carbon-14 is radioactive.It forms in the atmosphere when acted upon by cosmic
6、 radiation and then deteriorates （如何测量考古文物的年龄？首先，什么是 C-14？碳是所有生物材料的基本成分。自然界中有三种同位素：碳-12（它是稳定的形式），碳-13 和碳-14。碳-14具有放射性。它在宇宙辐射的作用下在大气中形成，然后衰减。）When an organism dies and the supply of carbon from the atmosphere stops,the 3 content of carbon-14 declines through radioactive decay at a fixed rate.In 1949,
7、Willard Libby developed a method for applying this to determine the age of fossils and archeological relics.（当生物体死亡，大气中的碳供应停止时，碳-14 的含量通过放射性衰变以固定速率下降。1949 年，Willard Libby 开发了一种方法，用于确定化石和考古遗迹的年龄。）It had been known since 1939,that cosmic rays create showers of neutrons on striking atoms in the atmosph
8、ere.And the atmosphere contains about 78 percent nitrogen,which absorbs neutrons to decay into the radioactive isotope carbon-14,（自 1939 年以来，人们就知道宇宙射线在撞击大气中的原子时会产生大量中子。大气中含有约 78%的氮，它吸收中子衰变成放射性同位素碳-14，）Libby concluded that traces of carbon-14 should always exist in atmospheric carbon dioxide.Also,bec
9、ause carbon dioxide is continuously absorbed by plants and becomes part of their tissues,plants should contain traces of carbon-14.Since animals consume plants,animals should likewise contain traces of carbon-14.After a plant or other organism dies,no additional carbon-14 should be incorporated into
10、 its tissues,while that which is already present should decay at a constant rate.（利比得出结论，大气二氧化碳中应始终存在微量的碳-14。此外，由于二氧化4 碳不断被植物吸收并成为其组织的一部分，植物应含有微量的碳-14。由于动物食用植物，因此动物也应含有微量的碳-14。植物或其他有机体死亡后，不应在其组织中加入额外的碳-14，而已经存在的碳-14 应以恒定速率衰变。）The half-life of carbon-14 was determined by its codiscoverer,chemist Mart
11、in D.Kamen,to be 5,730 years,which,compared with the age of the Earth,is a short time but one long enough for the production and decay of carbon-14 to reach equilibrium.In his Nobel presentation speech,Swedish chemist Arne Westgren summarized Libbys method:（碳 14 的半衰期由其合作者、化学家马丁 D.卡门确定为 5730 年，与地球年龄相
12、比，这是一个很短的时间，但足够长的时间，使碳-14 的产生和衰变达到平衡。瑞典化学家 Arne Westgren 在诺贝尔奖演讲中总结了 Libby 的方法：）Because the activity of the carbon atoms decreases at a known rate,it should be possible to determine the time passed since death,by measuring the remaining activity,if this occurred during the period between approximate
13、ly 500 and 30,000 years ago.”（由于碳原子的活性以已知的速率降低，因此应可以通过测量剩余活性来确定死亡后经过的时间，如果这发生在大约 500 至 30000 年前。”）5 Libby verified the accuracy of his method by applying it to samples of fir and redwood trees whose ages had already been found by counting their annual rings They also measured the age of artifacts,su
14、ch as wood from the funerary boat of Pharaoh，Sesostris,whose ages were already known.By measuring the radioactivity of plant and animal material obtained globally from the North Pole to the South Pole,he showed that the carbon-14 produced by cosmic ray bombardment varied little with latitude.（Libby
15、通过计算年轮，将其方法应用于已发现其年龄的冷杉和红杉样本，验证了其方法的准确性。他们还测量了文物的年代，如法老赛索斯特拉斯的葬礼船上的木头，这些文物的年代已经知道了。通过测量从北极到南极全球获取的动植物材料的放射性，他发现宇宙射线轰击产生的碳 14 随纬度变化不大。）This is the table of the measurement results of radioactivity intensity of carbon 14 at different latitudes （这是碳 14 在不同纬度的放射性强度测量结果表。）On March 4,1947,Libby and his st
16、udents obtained the first age determination using the carbon-14 dating technique.He also dated linen wrappings from the Dead Sea Scrolls,bread from Pompeii buried 6 in the eruption of Vesuvius(ad 79),charcoal from a Stonehenge campsite,and corncobs from a New Mexico cave.He showed that the last Nort
17、h American ice age ended about 10,000 years ago,not 25,000 years ago as previously believed by geologists.（1947 年 3 月 4 日，利比和他的学生使用碳 14 年代测定技术获得了第一个年龄测定。他还记录了死海卷轴上的亚麻包装、维苏威火山喷发中被埋的庞贝面包（公元 79 年）、巨石阵营地的木炭和新墨西哥山洞的玉米芯他指出，上一次北美冰期结束于约 10000 年前，而不是地质学家此前认为的 25000 年前。）In nominating Libby for the Nobel Prize
18、,one scientist stated,“Seldom has a single discovery in chemistry had such an impact on the thinking in so many fields of human endeavour.Seldom has a single discovery generated such wide public interest.”（在提名利比获得诺贝尔奖时，一位科学家说：“很少有化学方面的单一发现对人类努力的许多领域的思维产生如此大的影响。很少有一个发现能引起如此广泛的公众兴趣。”）After showing the
19、 essential uniformity of carbon-14 in living material,Libby looked for the answer to the second question by measuring the radiocarbon level in organic samples dated historicallymaterials as old as 5,000 years from sources such as Egyptian tombs.In 1950,Libby used this method to determine the constru
20、ction age of the pyramids.7 It is incredibly coincided with the historical records.（在展示了生物材料中碳-14 的基本统一性之后，Libby 通过测量有机样品中的放射性碳含量来寻找第二个问题的答案，这些有机样品的年代为 5000 年，来源于埃及坟墓等。1950 年，Libby 采用这种方法来确定金字塔的建造年代。这与历史记录惊人地吻合。）PART THREE Application（第三部分第三部分 应用应用）Since the carbon-14 dating method is based on chang
21、es in the nucleus and is not affected by the physical and chemical conditions of the surrounding environment,the half-life of carbon-14(5730 years)is suitable for the determination of samples from thousands to tens of thousands of years ago.（由于碳 14 定年法是基于原子核的变化，不受周围环境的物理和化学条件的影响，因此，碳-14 的半衰期（5730 年）
22、适用于数千年至数万年前的样品测定。）In addition,some carbon-containing materials,such as wood,grass,shells and other animal and plant remains,are everywhere in ancient sites,and it is convenient to obtain specimens.Therefore,the carbon-14th dating method is widely used in the study of Prehistoric Archaeology and late
23、 Quaternary geology.（此外，一些含碳材料，如木材、草、贝壳和其他动植物遗迹，在古代遗址随处8 可见，便于获取标本。因此，碳 14 定年法在史前考古和第四纪晚期地质研究中得到了广泛的应用。）However,the carbon-14 dating method can only be used for organisms that have died for tens of thousands of years.For some organisms that have died for millions or even hundreds of millions of year
24、s,the carbon-14 content in the remains of these organisms has been too low to be measured due to too many half-lives.Therefore,this method can not be used to measure the age of these organisms.（然而，碳 14 年代测定法只能用于已经死亡数万年的生物体。对于一些已经死亡数百万年甚至数亿年的生物来说，由于半衰期太多，这些生物残骸中的碳 14含量太低，无法测量。因此，该方法不能用于测量这些生物的年龄。）Wit
25、h the help of the American Anthropological Association and the American Geological Association,Libby and his colleagues measured a large number of cultural relics and prehistoric relics of known ages to verify whether the carbon 14 dating method was actually available.Here is the graph for Carbon 14
26、 dating of known historical relics（在美国人类学协会和美国地质协会的帮助下，利比和他的同事们测量了大量已知年龄的文物和史前遗迹，以验证碳 14 年代测定法是否真的可用。这是碳 14测定已知历史遗迹年代的图表）9 After learn this class,I hope you not only know about Prof.Libby,but also have some ideas about how to determine the age of fossils and relics by Carbon 14.Thats todays Nobel pr
27、ize winner,thank you!（在学习完这次课后，我希望你们不仅了解利比教授，而且对如何用碳 14 测定化石和遗迹的年龄有一些想法。这就是今天的诺贝尔奖得主，谢谢！）思思 考考 同学们，咱们在物理化学这门课 中是不是学过半衰期及其相关计算？对的，埋藏地下深层的沉积地层的样品，只要按 C14 的放射性衰变公式进行计算，便可推出待测物品的存在年代。利比是著名的物理化学家，放射化学专家，热原子化学、示踪技术、同位素示踪技术专家，1960 年，鉴于利比发现碳-14 年代测定法，为人类创造出独特的计时工具“考古学时钟”，他被授予诺贝尔化学奖。由于碳-14 年代测定法依据的是原子核的变化，不受周围环境的物理、化学条件影响，所以碳-14 的半衰期（5730 年）正适用于对几千年到几万年前的标本进行测定，另外，一些含碳的物质，如木、草、贝壳等动植物遗骸在古代遗址中普遍存在，获取标本很方便。因此，碳-14 年代测定法被广泛应用于史前考古学和第四纪晚期地质学的研究。