Chapter 4 Reply from the Observatory of Cambridge

Barbicane, however, lost not one moment amid all the enthusiasm of which he had become the object. His first care was to reassemble his colleagues in the board-room of the Gun Club. There, after some discussion, it was agreed to consult the astronomers¹ regarding the astronomical² part of the enterprise. Their reply once ascertained³, they could then discuss the mechanical means, and nothing should be wanting to ensure the success of this great experiment.

A note couched in precise terms, containing special interrogatories, was then drawn⁴ up and addressed to the Observatory⁵ of Cambridge in Massachusetts. This city, where the first university of the United States was founded, is justly celebrated⁶ for its astronomical staff. There are to be found assembled all the most eminent⁷ men of science. Here is to be seen at work that powerful telescope which enabled Bond to resolve the nebula⁸ of Andromeda, and Clarke to discover the satellite of Sirius. This celebrated institution fully⁹ justified¹⁰ on all points the confidence reposed¹¹ in it by the Gun Club. So, after two days, the reply so impatiently awaited was placed in the hands of President Barbicane.

It was couched in the following terms:

The Director of the Cambridge Observatory to the President

of the Gun Club at Baltimore.

CAMBRIDGE, October 7.
On the receipt of your favor of the 6th instant, addressed to
the Observatory of Cambridge in the name of the members of the
Baltimore Gun Club, our staff was immediately called together,
and it was judged expedient¹² to reply as follows:

The questions which have been proposed to it are these —

“1. Is it possible to transmit a projectile¹³ up to the moon?

“2. What is the exact distance which separates the earth from its satellite?

“3. What will be the period of transit¹⁴ of the projectile when endowed with sufficient initial velocity¹⁵? and, consequently, at what moment ought it to be discharged in order that it may touch the moon at a particular point?

“4. At what precise moment will the moon present herself in the most favorable position to be reached by the projectile?

“5. What point in the heavens ought the cannon¹⁶ to be aimed at which is intended to discharge the projectile?

“6. What place will the moon occupy in the heavens at the moment of the projectile’s departure?”

Regarding the first question, “Is it possible to transmit a projectile up to the moon?”

Answer.— Yes; provided it possess an initial velocity of 1,200 yards per second; calculations prove that to be sufficient. In proportion as we recede¹⁷ from the earth the action of gravitation diminishes in the inverse¹⁸ ratio of the square of the distance; that is to say, at three times a given distance the action is nine times less. Consequently, the weight of a shot will decrease, and will become reduced to zero at the instant that the attraction of the moon exactly counterpoises that of the earth; that is to say at 4752 of its passage. At that instant the projectile will have no weight whatever; and, if it passes that point, it will fall into the moon by the sole effect of the lunar attraction. The theoretical possibility of the experiment is therefore absolutely demonstrated; its success must depend upon the power of the engine employed.

As to the second question, “What is the exact distance which separates the earth from its satellite?”

Answer.— The moon does not describe a circle round the earth, but rather an ellipse, of which our earth occupies one of the foci; the consequence, therefore, is, that at certain times it approaches nearer to, and at others it recedes¹⁹ farther from, the earth; in astronomical language, it is at one time in apogee²⁰, at another in perigee²¹. Now the difference between its greatest and its least distance is too considerable to be left out of consideration. In point of fact, in its apogee the moon is 247,552 miles, and in its perigee, 218,657 miles only distant; a fact which makes a difference of 28,895 miles, or more than one-ninth of the entire distance. The perigee distance, therefore, is that which ought to serve as the basis of all calculations.

To the third question.

Answer.— If the shot should preserve continuously its initial velocity of 12,000 yards per second, it would require little more than nine hours to reach its destination; but, inasmuch as that initial velocity will be continually decreasing, it will occupy 300,000 seconds, that is 83hrs. 20m. in reaching the point where the attraction of the earth and moon will be in equilibrio. From this point it will fall into the moon in 50,000 seconds, or 13hrs. 53m. 20sec. It will be desirable, therefore, to discharge it 97hrs. 13m. 20sec. before the arrival of the moon at the point aimed at.

Regarding question four, “At what precise moment will the moon present herself in the most favorable position, etc.?”

Answer.— After what has been said above, it will be necessary, first of all, to choose the period when the moon will be in perigee, and also the moment when she will be crossing the zenith, which latter event will further diminish the entire distance by a length equal to the radius²² of the earth, i. e. 3,919 miles; the result of which will be that the final passage remaining to be accomplished²³ will be 214,976 miles. But although the moon passes her perigee every month, she does not reach the zenith always at exactly the same moment. She does not appear under these two conditions simultaneously²⁴, except at long intervals²⁵ of time. It will be necessary, therefore, to wait for the moment when her passage in perigee shall coincide with that in the zenith. Now, by a fortunate circumstance, on the 4th of December in the ensuing year the moon will present these two conditions. At midnight she will be in perigee, that is, at her shortest distance from the earth, and at the same moment she will be crossing the zenith.

On the fifth question, “At what point in the heavens ought the cannon to be aimed?”

Answer.— The preceding remarks being admitted, the cannon ought to be pointed²⁶ to the zenith of the place. Its fire, therefore, will be perpendicular²⁷ to the plane of the horizon; and the projectile will soonest pass beyond the range of the terrestrial attraction. But, in order that the moon should reach the zenith of a given place, it is necessary that the place should not exceed in latitude²⁸ the declination of the luminary²⁹; in other words, it must be comprised within the degrees 0° and 28° of lat. N. or S. In every other spot the fire must necessarily be oblique³⁰, which would seriously militate against the success of the experiment.

As to the sixth question, “What place will the moon occupy in the heavens at the moment of the projectile’s departure?”

Answer.— At the moment when the projectile shall be discharged into space, the moon, which travels daily forward 13° 10’ 35’’, will be distant from the zenith point by four times that quantity, i. e. by 52° 41’ 20’’, a space which corresponds to the path which she will describe during the entire journey of the projectile. But, inasmuch as it is equally necessary to take into account the deviation³¹ which the rotary³² motion of the earth will impart to the shot, and as the shot cannot reach the moon until after a deviation equal to 16 radii³³ of the earth, which, calculated upon the moon’s orbit, are equal to about eleven degrees, it becomes necessary to add these eleven degrees to those which express the retardation³⁴ of the moon just mentioned: that is to say, in round numbers, about sixty-four degrees. Consequently, at the moment of firing the visual radius applied³⁵ to the moon will describe, with the vertical³⁶ line of the place, an angle of sixty-four degrees.

These are our answers to the questions proposed to the Observatory of Cambridge by the members of the Gun Club:

To sum up —

1st. The cannon ought to be planted in a country situated³⁷ between 0° and 28° of N. or S. lat.

2nd. It ought to be pointed directly toward the zenith of the place.

3rd. The projectile ought to be propelled with an initial velocity of 12,000 yards per second.

4th. It ought to be discharged at 10hrs. 46m. 40sec. of the 1st of December of the ensuing year.

5th. It will meet the moon four days after its discharge, precisely³⁸ at midnight on the 4th of December, at the moment of its transit across the zenith.

The members of the Gun Club ought, therefore, without delay, to commence the works necessary for such an experiment, and to be prepared to set to work at the moment determined³⁹ upon; for, if they should suffer this 4th of December to go by, they will not find the moon again under the same conditions of perigee and of zenith until eighteen years and eleven days afterward⁴⁰.

The staff of the Cambridge Observatory place themselves entirely⁴¹ at their disposal in respect of all questions of theoretical astronomy; and herewith add their congratulations to those of all the rest of America.

For the Astronomical Staff,
J. M. BELFAST,
Director of the Observatory of Cambridge.

1 astronomers   

n.天文学者，天文学家( astronomer的名词复数 )

参考例句：

• Astronomers can accurately foretell the date,time,and length of future eclipses. 天文学家能精确地预告未来日食月食的日期、时刻和时长。 来自《简明英汉词典》
• Astronomers used to ask why only Saturn has rings. 天文学家们过去一直感到奇怪，为什么只有土星有光环。 来自《简明英汉词典》

2 astronomical   

adj.天文学的，（数字）极大的

参考例句：

• He was an expert on ancient Chinese astronomical literature.他是研究中国古代天文学文献的专家。
• Houses in the village are selling for astronomical prices.乡村的房价正在飙升。

3 ascertained   

v.弄清，确定，查明( ascertain的过去式和过去分词 )

参考例句：

• The previously unidentified objects have now been definitely ascertained as being satellites. 原来所说的不明飞行物现在已证实是卫星。 来自《简明英汉词典》
• I ascertained that she was dead. 我断定她已经死了。 来自《简明英汉词典》

4 drawn   

v.拖，拉，拔出；adj.憔悴的，紧张的

参考例句：

• All the characters in the story are drawn from life.故事中的所有人物都取材于生活。
• Her gaze was drawn irresistibly to the scene outside.她的目光禁不住被外面的风景所吸引。

5 observatory   

n.天文台，气象台，瞭望台，观测台

参考例句：

• Guy's house was close to the observatory.盖伊的房子离天文台很近。
• Officials from Greenwich Observatory have the clock checked twice a day.格林威治天文台的职员们每天对大钟检查两次。

6 celebrated   

adj.有名的，声誉卓著的

参考例句：

• He was soon one of the most celebrated young painters in England.不久他就成了英格兰最负盛名的年轻画家之一。
• The celebrated violinist was mobbed by the audience.观众团团围住了这位著名的小提琴演奏家。

7 eminent   

adj.显赫的，杰出的，有名的，优良的

参考例句：

• We are expecting the arrival of an eminent scientist.我们正期待一位著名科学家的来访。
• He is an eminent citizen of China.他是一个杰出的中国公民。

8 nebula   

n.星云，喷雾剂

参考例句：

• A powerful telescope can resolve a nebula into stars.一架高性能的望远镜能从星云中分辨出星球来。
• A nebula is really a discrete mass of innumerous stars.一团星云实际上是无数星体不连续的集合体。

9 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。

10 justified   

a.正当的，有理的

参考例句：

• She felt fully justified in asking for her money back. 她认为有充分的理由要求退款。
• The prisoner has certainly justified his claims by his actions. 那个囚犯确实已用自己的行动表明他的要求是正当的。

11 reposed   

v.将（手臂等）靠在某人（某物）上( repose的过去式和过去分词 )

参考例句：

• Mr. Cruncher reposed under a patchwork counterpane, like a Harlequin at home. 克朗彻先生盖了一床白衲衣图案的花哨被子，像是呆在家里的丑角。 来自英汉文学 - 双城记
• An old man reposed on a bench in the park. 一位老人躺在公园的长凳上。 来自辞典例句

12 expedient   

adj.有用的，有利的；n.紧急的办法，权宜之计

参考例句：

• The government found it expedient to relax censorship a little.政府发现略微放宽审查是可取的。
• Every kind of expedient was devised by our friends.我们的朋友想出了各种各样的应急办法。

13 projectile   

n.投射物，发射体；adj.向前开进的；推进的；抛掷的

参考例句：

• The vertical and horizontal motions of a projectile can be treated independently.抛射体的竖直方向和水平方向的运动能够分开来处理。
• Have you altered the plans of the projectile as the telegram suggests?你已经按照电报的要求修改炮弹图样了吗?

14 transit   

n.经过，运输；vt.穿越，旋转；vi.越过

参考例句：

• His luggage was lost in transit.他的行李在运送中丢失。
• The canal can transit a total of 50 ships daily.这条运河每天能通过50条船。

15 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。

16 cannon   

n.大炮，火炮；飞机上的机关炮

参考例句：

• The soldiers fired the cannon.士兵们开炮。
• The cannon thundered in the hills.大炮在山间轰鸣。

17 recede   

vi.退(去)，渐渐远去；向后倾斜，缩进

参考例句：

• The colleges would recede in importance.大学的重要性会降低。
• He saw that the dirty water had begun to recede.他发现那污浊的水开始往下退了。

18 inverse   

adj.相反的，倒转的，反转的；n.相反之物；v.倒转

参考例句：

• Evil is the inverse of good.恶是善的反面。
• When the direct approach failed he tried the inverse.当直接方法失败时，他尝试相反的做法。

19 recedes   

v.逐渐远离( recede的第三人称单数 )；向后倾斜；自原处后退或避开别人的注视；尤指问题

参考例句：

• For this reason the near point gradually recedes as one grows older. 由于这个原因，随着人渐渐变老，近点便逐渐后退。 来自辞典例句
• Silent, mournful, abandoned, broken, Czechoslovakia recedes into the darkness. 缄默的、悲哀的、被抛弃的、支离破碎的捷克斯洛伐克，已在黑暗之中。 来自辞典例句

20 apogee   

n.远地点；极点；顶点

参考例句：

• The orbit of the artificial satellite has an apogee of 200 miles from the earth.这个人造卫星的轨道，其最远点在离地球200英里的地方。
• Apogean tides occur when the moon is at the apogee of its orbit.远月潮在月球位于其轨道的最远点时发生。

21 perigee   

n.近地点

参考例句：

• The Moon reaches its absolute perigee once a year.月球每年有一次达到它的绝对近地点。
• Once the satellite reaches perigee,it will eject a small probe which enter the planet's atmosphere.当人造卫星达到近地点时，就会发射一根小探针，这根探针将进入行星的大气层。

22 radius   

n.半径，半径范围；有效航程，范围，界限

参考例句：

• He has visited every shop within a radius of two miles.周围两英里以内的店铺他都去过。
• We are measuring the radius of the circle.我们正在测量圆的半径。

23 accomplished   

adj.有才艺的；有造诣的；达到了的

参考例句：

• Thanks to your help,we accomplished the task ahead of schedule.亏得你们帮忙,我们才提前完成了任务。
• Removal of excess heat is accomplished by means of a radiator.通过散热器完成多余热量的排出。

24 simultaneously   

adv.同时发生地，同时进行地

参考例句：

• The radar beam can track a number of targets almost simultaneously.雷达波几乎可以同时追着多个目标。
• The Windows allow a computer user to execute multiple programs simultaneously.Windows允许计算机用户同时运行多个程序。

25 intervals   

n.[军事]间隔( interval的名词复数 )；间隔时间；[数学]区间；（戏剧、电影或音乐会的）幕间休息

参考例句：

• The forecast said there would be sunny intervals and showers. 预报间晴，有阵雨。
• Meetings take place at fortnightly intervals. 每两周开一次会。

26 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。

27 perpendicular   

adj.垂直的，直立的；n.垂直线，垂直的位置

参考例句：

• The two lines of bones are set perpendicular to one another.这两排骨头相互垂直。
• The wall is out of the perpendicular.这墙有些倾斜。

28 latitude   

n.纬度，行动或言论的自由(范围)，(pl.)地区

参考例句：

• The latitude of the island is 20 degrees south.该岛的纬度是南纬20度。
• The two cities are at approximately the same latitude.这两个城市差不多位于同一纬度上。

29 luminary   

n.名人，天体

参考例句：

• That luminary gazed earnestly at some papers before him.那个大好佬在用心细看面前的报纸。
• Now that a new light shone upon the horizon,this older luminary paled in the west.现在东方地平线上升起了一轮朝阳，这弯残月就在西边天际失去了光泽。

30 oblique   

adj.斜的，倾斜的，无诚意的，不坦率的

参考例句：

• He made oblique references to her lack of experience.他拐弯抹角地说她缺乏经验。
• She gave an oblique look to one side.她向旁边斜看了一眼。

31 deviation   

n.背离，偏离；偏差，偏向；离题

参考例句：

• Deviation from this rule are very rare.很少有违反这条规则的。
• Any deviation from the party's faith is seen as betrayal.任何对党的信仰的偏离被视作背叛。

32 rotary   

adj.(运动等)旋转的；轮转的；转动的

参考例句：

• The central unit is a rotary drum.核心设备是一个旋转的滚筒。
• A rotary table helps to optimize the beam incidence angle.一张旋转的桌子有助于将光线影响之方式角最佳化。

33 radii   

n.半径；半径（距离）( radius的名词复数 )；用半径度量的圆形面积；半径范围；桡骨

参考例句：

• Hence, the damage radii can not be determined from overpressure alone. 因此，破坏半径不能单单由超压力大小来决定。 来自辞典例句
• It is now necessary to introduce a sign convention for radii of curvature. 现在必须介绍曲率半径的正负号规则。 来自辞典例句

34 retardation   

n.智力迟钝，精神发育迟缓

参考例句：

• Asbestos reinforcement confers excellent flame retardation properties on a composite. 石棉增强材料使复合材料具有优异的防火性能。
• The theory confirms the increase in the retardation effect with decrease in particle size. 理论证实，随着颗粒尺寸的减小，这一减速效应将增大。

35 applied   

adj.应用的；v.应用，适用

参考例句：

• She plans to take a course in applied linguistics.她打算学习应用语言学课程。
• This cream is best applied to the face at night.这种乳霜最好晚上擦脸用。

36 vertical   

adj.垂直的，顶点的，纵向的；n.垂直物，垂直的位置

参考例句：

• The northern side of the mountain is almost vertical.这座山的北坡几乎是垂直的。
• Vertical air motions are not measured by this system.垂直气流的运动不用这种系统来测量。

37 situated   

adj.坐落在...的，处于某种境地的

参考例句：

• The village is situated at the margin of a forest.村子位于森林的边缘。
• She is awkwardly situated.她的处境困难。

38 precisely   

adv.恰好，正好，精确地，细致地

参考例句：

• It's precisely that sort of slick sales-talk that I mistrust.我不相信的正是那种油腔滑调的推销宣传。
• The man adjusted very precisely.那个人调得很准。

39 determined   

adj.坚定的；有决心的

参考例句：

• I have determined on going to Tibet after graduation.我已决定毕业后去西藏。
• He determined to view the rooms behind the office.他决定查看一下办公室后面的房间。

40 afterward   

adv.后来；以后

参考例句：

• Let's go to the theatre first and eat afterward. 让我们先去看戏，然后吃饭。
• Afterward,the boy became a very famous artist.后来，这男孩成为一个很有名的艺术家。

41 entirely   

ad.全部地，完整地；完全地，彻底地

参考例句：

• The fire was entirely caused by their neglect of duty. 那场火灾完全是由于他们失职而引起的。
• His life was entirely given up to the educational work. 他的一生统统献给了教育工作。