Aristotle believed that all the matter in the universe wasmade up of four basic elements - earth, air, fire, and water.
These elements were acted on by two forces: gravity, thetendency for earth and water to sink, and levity¹, the tendencyfor air and fire to rise. This division of the contents of theuniverse into matter and forces is still used today. Aristotlebelieved that matter was continuous, that is, one could divide apiece of matter into smaller and smaller bits without any limit:
one never came up against a grain of matter that could not bedivided further. A few Greeks, however, such as Democritus,held that matter was inherently grainy and that everything wasmade up of large numbers of various different kinds of atoms.
(The word atom means “indivisible” in Greek.) For centuriesthe argument continued without any real evidence on eitherside, but in 1803 the British chemist and physicist² John Daltonpointed out that the fact that chemical compounds alwayscombined in certain proportions could be explained by thegrouping together of atoms to form units called molecules⁴.
However, the argument between the two schools of thoughtwas not finally settled in favor of the atomists until the earlyyears of this century. One of the important pieces of physicalevidence was provided by Einstein. In a paper written in 1905,a few weeks before the famous paper on special relativity,Einstein pointed³ out that what was called Brownian motion -the irregular, random⁵ motion of small particles of dustsuspended in a liquid - could be explained as the effect ofatoms of the liquid colliding with the dust particles.
By this time there were already suspicions that these atomswere not, after all, indivisible. Several years previously⁶ a fellowof Trinity College, Cambridge, J. J. Thomson, had demonstratedthe existence of a particle of matter, called the electron, thathad a mass less than one thousandth of that of the lightestatom. He used a setup rather like a modern TV picture tube:
a red-hot metal filament

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1 levity
n.轻率，轻浮，不稳定，多变
参考例句：
His remarks injected a note of levity into the proceedings.他的话将一丝轻率带入了议事过程中。 At the time,Arnold had disapproved of such levity.那时候的阿诺德对这种轻浮行为很看不惯。

2 physicist
n.物理学家，研究物理学的人
参考例句：
He is a physicist of the first rank.他是一流的物理学家。 The successful physicist never puts on airs.这位卓有成就的物理学家从不摆架子。

3 pointed
adj.尖的，直截了当的
参考例句：
He gave me a very sharp pointed pencil.他给我一支削得非常尖的铅笔。 She wished to show Mrs.John Dashwood by this pointed invitation to her brother.她想通过对达茨伍德夫人提出直截了当的邀请向她的哥哥表示出来。

4 molecules
分子( molecule的名词复数 )
参考例句：
The structure of molecules can be seen under an electron microscope. 分子的结构可在电子显微镜下观察到。 Inside the reactor the large molecules are cracked into smaller molecules. 在反应堆里，大分子裂变为小分子。

5 random
adj.随机的；任意的；n.偶然的(或随便的)行动
参考例句：
The list is arranged in a random order.名单排列不分先后。 On random inspection the meat was found to be bad.经抽查，发现肉变质了。

6 previously
adv.以前，先前（地）
参考例句：
The bicycle tyre blew out at a previously damaged point.自行车胎在以前损坏过的地方又爆开了。 Let me digress for a moment and explain what had happened previously.让我岔开一会儿，解释原先发生了什么。

7 filament
n.细丝；长丝；灯丝
参考例句：
The source of electrons in an electron microscope is a heated filament.电子显微镜中的电子源，是一加热的灯丝。 The lack of air in the bulb prevents the filament from burning up.灯泡内缺乏空气就使灯丝不致烧掉。

8 positively
adv.明确地，断然，坚决地；实在，确实
参考例句：
She was positively glowing with happiness.她满脸幸福。 The weather was positively poisonous.这天气着实讨厌。

9 nucleus
n.核，核心，原子核
参考例句：
These young people formed the nucleus of the club.这些年轻人成了俱乐部的核心。 These councils would form the nucleus of a future regime.这些委员会将成为一个未来政权的核心。

10 analyzing
v.分析；分析( analyze的现在分词 )；分解；解释；对…进行心理分析n.分析
参考例句：
Analyzing the date of some socialist countries presents even greater problem s. 分析某些社会主义国家的统计数据，暴露出的问题甚至更大。 来自辞典例句 He undoubtedly was not far off the mark in analyzing its predictions. 当然，他对其预测所作的分析倒也八九不离十。 来自辞典例句

11 deflected
偏离的
参考例句：
The ball deflected off Reid's body into the goal. 球打在里德身上反弹进球门。 Most of its particles are deflected. 此物质的料子大多是偏斜的。

12 neutron
n.中子
参考例句：
Neutron is neutral and slightly heavier than the proton.中子是中性的，比质子略重。 Based on the neutron energy,the value of weighting factor was given.根据中子能量给出了相应的辐射权重因子的数值。

13 neutrons
n.中子( neutron的名词复数 )
参考例句：
The neutrons and protons form the core of the atom. 中子和质子构成了原子核。 来自《简明英汉词典》 When an atom of U235 is split,several neutrons are set free. 一个铀235原子分裂时，释放出几个中子。 来自《简明英汉词典》

14 quotation
n.引文，引语，语录；报价，牌价，行情
参考例句：
He finished his speech with a quotation from Shakespeare.他讲话结束时引用了莎士比亚的语录。 The quotation is omitted here.此处引文从略。

15 lark
n.云雀，百灵鸟；n.嬉戏，玩笑；vi.嬉戏
参考例句：
He thinks it cruel to confine a lark in a cage.他认为把云雀关在笼子里太残忍了。 She lived in the village with her grandparents as cheerful as a lark.她同祖父母一起住在乡间非常快活。

16 wavelength
n.波长
参考例句：
The authorities were unable to jam this wavelength.当局无法干扰这一波长。 Radio One has broadcast on this wavelength for years.广播1台已经用这个波长广播多年了。

17 physicists
物理学家( physicist的名词复数 )
参考例句：
For many particle physicists, however, it was a year of frustration. 对于许多粒子物理学家来说，这是受挫折的一年。 来自英汉非文学 - 科技 Physicists seek rules or patterns to provide a framework. 物理学家寻求用法则或图式来构成一个框架。

18 volt
n.伏特，伏
参考例句：
You may use 100 and 110 volt appliances in your room.您可以在房间使用100及110伏特的电器。 The common service voltage of electric power in our country is 220/380 volt.我国普通供电电压为220/380伏。

19 volts
n.（电压单位）伏特( volt的名词复数 )
参考例句：
The floating potential, Vf is usually only a few volts below ground. 浮置电势Vf通常只低于接地电位几伏。 来自辞典例句 If gamma particles are present, potential differences of several thousand volts can be generated. 如果存在γ粒子，可能产生几千伏的电位差。 来自辞典例句

20 axis
n.轴，轴线，中心线；坐标轴，基准线
参考例句：
The earth's axis is the line between the North and South Poles.地轴是南北极之间的线。 The axis of a circle is its diameter.圆的轴线是其直径。

21 fig
n.无花果(树)
参考例句：
The doctor finished the fig he had been eating and selected another.这位医生吃完了嘴里的无花果，又挑了一个。 You can't find a person who doesn't know fig in the United States.你找不到任何一个在美国的人不知道无花果的。

22 straightforward
adj.正直的，坦率的；易懂的，简单的
参考例句：
A straightforward talk is better than a flowery speech.巧言不如直说。 I must insist on your giving me a straightforward answer.我一定要你给我一个直截了当的回答。

23 exclusion
n.拒绝，排除，排斥，远足，远途旅行
参考例句：
Don't revise a few topics to the exclusion of all others.不要修改少数论题以致排除所有其他的。 He plays golf to the exclusion of all other sports.他专打高尔夫球，其他运动一概不参加。

24 velocity
n.速度，速率
参考例句：
Einstein's theory links energy with mass and velocity of light.爱因斯坦的理论把能量同质量和光速联系起来。 The velocity of light is about 300000 kilometres per second.光速约为每秒300000公里。

25 uncertainty
n.易变，靠不住，不确知，不确定的事物
参考例句：
Her comments will add to the uncertainty of the situation.她的批评将会使局势更加不稳定。 After six weeks of uncertainty,the strain was beginning to take its toll.6个星期的忐忑不安后，压力开始产生影响了。

26 collapse
vi.累倒；昏倒；倒塌；塌陷
参考例句：
The country's economy is on the verge of collapse.国家的经济已到了崩溃的边缘。 The engineer made a complete diagnosis of the bridge's collapse.工程师对桥的倒塌做了一次彻底的调查分析。

27 density
n.密集，密度，浓度
参考例句：
The population density of that country is 685 per square mile.那个国家的人口密度为每平方英里685人。 The region has a very high population density.该地区的人口密度很高。

28 velocities
n.速度( velocity的名词复数 )；高速，快速
参考例句：
In experimenting we find out that sound travels with different velocities through different substances. 在实验中，我们发现声音以不同的速度通过不同的物质而传播。 来自《现代汉英综合大词典》 A gas in thermal equilibrium has particles of all velocities. 处于热平衡的气体，其粒子有一切速度。 来自辞典例句

29 dense
a.密集的，稠密的，浓密的；密度大的
参考例句：
The general ambushed his troops in the dense woods. 将军把部队埋伏在浓密的树林里。 The path was completely covered by the dense foliage. 小路被树叶厚厚地盖了一层。

30 annihilate
v.使无效；毁灭；取消
参考例句：
Archer crumpled up the yellow sheet as if the gesture could annihilate the news it contained.阿切尔把这张黄纸揉皱，好象用这个动作就会抹掉里面的消息似的。 We should bear in mind that we have to annihilate the enemy.我们要把歼敌的重任时刻记在心上。

31 recoil
vi.退却，退缩，畏缩
参考例句：
Most people would recoil at the sight of the snake.许多人看见蛇都会向后退缩。 Revenge may recoil upon the person who takes it.报复者常会受到报应。

32 emission
n.发出物，散发物；发出，散发
参考例句：
Rigorous measures will be taken to reduce the total pollutant emission.采取严格有力措施，降低污染物排放总量。 Finally,the way to effectively control particulate emission is pointed out.最后，指出有效降低颗粒排放的方向。

33 detector
n.发觉者，探测器
参考例句：
The detector is housed in a streamlined cylindrical container.探测器安装在流线型圆柱形容器内。 Please walk through the metal detector.请走过金属检测器。

34 repulsive
adj.排斥的，使人反感的
参考例句：
She found the idea deeply repulsive.她发现这个想法很恶心。 The repulsive force within the nucleus is enormous.核子内部的斥力是巨大的。

35 unified
(unify 的过去式和过去分词)； 统一的； 统一标准的； 一元化的
参考例句：
The teacher unified the answer of her pupil with hers. 老师核对了学生的答案。 The First Emperor of Qin unified China in 221 B.C. 秦始皇于公元前221年统一中国。

36 unify
vt.使联合，统一；使相同，使一致
参考例句：
How can we unify such scattered islands into a nation?我们怎么才能把如此分散的岛屿统一成一个国家呢？ It is difficult to imagine how the North and South could ever agree on a formula to unify the divided peninsula.很难想象南北双方在统一半岛的方案上究竟怎样才能达成一致。

37 essentially
adv.本质上，实质上，基本上
参考例句：
Really great men are essentially modest.真正的伟人大都很谦虚。 She is an essentially selfish person.她本质上是个自私自利的人。

38 confinement
n.幽禁，拘留，监禁；分娩；限制，局限
参考例句：
He spent eleven years in solitary confinement.他度过了11年的单独监禁。 The date for my wife's confinement was approaching closer and closer.妻子分娩的日子越来越近了。

39 binds
v.约束( bind的第三人称单数 )；装订；捆绑；（用长布条）缠绕
参考例句：
Frost binds the soil. 霜使土壤凝结。 来自《简明英汉词典》 Stones and cement binds strongly. 石头和水泥凝固得很牢。 来自《简明英汉词典》

40 unstable
adj.不稳定的，易变的
参考例句：
This bookcase is too unstable to hold so many books.这书橱很不结实，装不了这么多书。 The patient's condition was unstable.那患者的病情不稳定。

41 gut
n.[pl.]胆量；内脏；adj.本能的；vt.取出内脏
参考例句：
It is not always necessary to gut the fish prior to freezing.冷冻鱼之前并不总是需要先把内脏掏空。 My immediate gut feeling was to refuse.我本能的直接反应是拒绝。

42 fully
adv.完全地，全部地，彻底地；充分地
参考例句：
The doctor asked me to breathe in,then to breathe out fully.医生让我先吸气，然后全部呼出。 They soon became fully integrated into the local community.他们很快就完全融入了当地人的圈子。

43 parameters
因素，特征； 界限； （限定性的）因素( parameter的名词复数 )； 参量； 参项； 决定因素
参考例句：
We have to work within the parameters of time. 我们的工作受时间所限。 See parameters.cpp for a compilable example. This is part of the Spirit distribution. 可编译例子见parameters.cpp.这是Spirit分发包的组成部分。

44 guts
v.狼吞虎咽，贪婪地吃，飞碟游戏（比赛双方每组5人，相距15码，互相掷接飞碟）；毁坏（建筑物等）的内部( gut的第三人称单数 )；取出…的内脏n.勇气( gut的名词复数 )；内脏；消化道的下段；肠
参考例句：
I'll only cook fish if the guts have been removed. 鱼若已收拾干净，我只需烧一下即可。 Barbara hasn't got the guts to leave her mother. 巴巴拉没有勇气离开她妈妈。 来自《简明英汉词典》

45 lighter
n.打火机，点火器；驳船；v.用驳船运送；light的比较级
参考例句：
The portrait was touched up so as to make it lighter.这张画经过润色，色调明朗了一些。 The lighter works off the car battery.引燃器利用汽车蓄电池打火。

46 fixed
adj.固定的，不变的，准备好的；(计算机)固定的
参考例句：
Have you two fixed on a date for the wedding yet?你们俩选定婚期了吗？ Once the aim is fixed,we should not change it arbitrarily.目标一旦确定，我们就不应该随意改变。

47 mere
adj.纯粹的；仅仅，只不过
参考例句：
That is a mere repetition of what you said before.那不过是重复了你以前讲的话。 It's a mere waste of time waiting any longer.再等下去纯粹是浪费时间。

48 galaxy
n.星系；银河系；一群(杰出或著名的人物)
参考例句：
The earth is one of the planets in the Galaxy.地球是银河系中的星球之一。 The company has a galaxy of talent.该公司拥有一批优秀的人才。

49 annihilating
v.（彻底）消灭( annihilate的现在分词 )；使无效；废止；彻底击溃
参考例句：
There are lots of ways of annihilating the planet. 毁灭地球有很多方法。 来自辞典例句 We possess-each of us-nuclear arsenals capable of annihilating humanity. 我们两国都拥有能够毁灭全人类的核武库。 来自辞典例句

50 galaxies
星系( galaxy的名词复数 )； 银河系； 一群（杰出或著名的人物）
参考例句：
Quasars are the highly energetic cores of distant galaxies. 类星体是遥远星系的极为活跃的核心体。 We still don't know how many galaxies there are in the universe. 我们还不知道宇宙中有多少个星系。

51 annihilated
v.（彻底）消灭( annihilate的过去式和过去分词 )；使无效；废止；彻底击溃
参考例句：
Our soldiers annihilated a force of three hundred enemy troops. 我军战士消灭了300名敌军。 来自《现代汉英综合大词典》 We annihilated the enemy. 我们歼灭了敌人。 来自《简明英汉词典》

52 transformations
n.变化( transformation的名词复数 )；转换；转换；变换
参考例句：
Energy transformations go on constantly, all about us. 在我们周围，能量始终在不停地转换着。 来自辞典例句 On the average, such transformations balance out. 平均起来，这种转化可以互相抵消。 来自辞典例句

53 lining
n.衬里，衬料
参考例句：
The lining of my coat is torn.我的外套衬里破了。 Moss makes an attractive lining to wire baskets.用苔藓垫在铁丝篮里很漂亮。

54 nuclei
n.核
参考例句：
To free electrons, something has to make them whirl fast enough to break away from their nuclei. 为了释放电子，必须使电子高速旋转而足以摆脱原子核的束缚。 Energy is released by the fission of atomic nuclei. 能量是由原子核分裂释放出来的。

55 swapped
交换（工作）( swap的过去式和过去分词 )； 用…替换，把…换成，掉换（过来）
参考例句：
I liked her coat and she liked mine, so we swapped. 我喜欢她的外套，她喜欢我的外套，于是我们就交换了。 At half-time the manager swapped some of the players around. 经理在半场时把几名队员换下了场。

56 confirmation
n.证实，确认，批准
参考例句：
We are waiting for confirmation of the news.我们正在等待证实那个消息。 We need confirmation in writing before we can send your order out.给你们发送订购的货物之前，我们需要书面确认。

57 qualitative
adj.性质上的，质的，定性的
参考例句：
There are qualitative differences in the way children and adults think.孩子和成年人的思维方式有质的不同。 Arms races have a quantitative and a qualitative aspects.军备竞赛具有数量和质量两个方面。

58 uncertainties
无把握( uncertainty的名词复数 )； 不确定； 变化不定； 无把握、不确定的事物
参考例句：
One of the uncertainties of military duty is that you never know when you might suddenly get posted away. 任军职不稳定的因素之一是你永远不知道什么时候会突然被派往它处。 Uncertainties affecting peace and development are on the rise. 影响和平与发展的不确定因素在增加。 来自汉英非文学 - 十六大报告

59 sufficiently
adv.足够地，充分地
参考例句：
It turned out he had not insured the house sufficiently.原来他没有给房屋投足保险。 The new policy was sufficiently elastic to accommodate both views.新政策充分灵活地适用两种观点。