夏尔-欧仁·德洛奈Charles-Eugène Delaunay

夏尔-欧仁·德洛奈来自一个家境普通的家庭。他的父亲是Jacques Hubert Delaunay，一名测量员，他的母亲是Catherine Choiselat，一个农民的女儿。德洛奈在幼年时与母亲非常亲近，并且终生如此。1818年，当德洛奈两岁时，他的父亲获得了Ramerupt的执达吏职位，该地位于特鲁瓦东北约20公里处。当他还小的时候，德洛奈被送到特鲁瓦与他的一个叔叔同住，叔叔是一名体力劳动者。他在特鲁瓦上中学，在学校表现出极大的前途，在数学方面出类拔萃，并且他的制作机械装置的爱好也很有前途。他于1833年前往巴黎，次年进入巴黎综合理工学院，在当年入学的所有学生中排名第二。当德洛奈于1836年毕业时，他在所有学科的所有学生中排名第一。

皮埃尔·西蒙·拉普拉斯侯爵夫人捐赠了一项新的年度奖，即皮埃尔·西蒙·拉普拉斯奖，授予在巴黎综合理工学院当年排名第一的学生。德洛奈在该奖设立之前已经毕业，但拉普拉斯夫人请求他成为该奖的第一位获得者，该奖包括皮埃尔·西蒙·拉普拉斯的全集。事实证明，这一决定改变了德洛奈的职业生涯轨迹，因为阅读皮埃尔·西蒙·拉普拉斯的伟大著作使他对天体力学产生了热情，他决定以此学科为职业。拉普拉斯侯爵夫人对第一位获奖者感到高兴，她称他为“她的长子”。弗朗索瓦·阿拉戈建议德洛奈来巴黎天文台接受天文学家培训，但菲力克斯·瓦利建议不要采取这一行动。德洛奈随后进入矿业学院，接受工程师培训。

1841年，德洛奈以变分法研究作为其学位论文课题，并凭借论文De la distinction des maxima et des minima dans les questions qui dépendent de la méthode des variationsⓉ（《依赖于变分法的问题中极大值与极小值的种类》）获得博士学位。同年，他向科学院提交了第一篇天文学论文Note sur la précession des équinoxesⓉ（《关于二分点岁差的注记》）。1841年晚些时候，让-巴蒂斯特·毕奥选择他代替自己在索邦大学讲授物理天文学课程。一方面，德洛奈在索邦大学的教学中获得了极好的经验，但他当时仍注册为矿业学校的学生，因此不得不额外多花一年时间完成那里的学业。他于1843年完成学业并取得工程师资格。

德洛奈发表了更多天文学论文，在1842年和1843年发表了几篇关于天王星摄动的论文，此后是他关于潮汐理论的第一部著作。此时他已经在研究他的月球理论，并于1846年发表了Mémoire sur une Méthode nouvelle pour la détermination du mouvement de la LuneⓉ（《关于确定月球运动的一种新方法的论文》）。这篇论文包含了今天所称的“德洛奈方法”，不过他后来的几篇论文包含了该方法最初在此出现时的推广。他的其他著作包括Cours élémentaire de mécaniqueⓉ（《力学基础教程》，1850年）和Traité de mécanique rationnelleⓉ（《理性力学论》，1856年），以及Cours élémentaire d'astronomieⓉ（《天文学基础教程》，1853年）。我们还应当注意到，当对月球轨道的观测表明它偏离了其理论路径时，德洛奈在1865年正确地提出，这可能是由于地球自转周期因潮汐摩擦而减慢所致。他在Ralentissement de la rotation de la terreⓉ（《地球自转的减慢》，1866年）中发表了他的理论。我们还要提到他关于天文学进展的报告Rapport sur les progrès de l'astronomieⓉ（《天文学进展报告》，1867年）。

从1845年到1850年，他在矿业学校教授课程；这些课程是画法几何、立体切割术、机械制图、分析力学和初等物理学。1849年他遭遇了巨大的不幸，年轻的妻子去世，很大程度上正是由于约瑟夫·刘维尔此时努力支持他，他才得以继续其学术工作。他从1850年起在巴黎综合理工学院教授力学，1851年被任命为那里的力学教授。他还从1850年起在索邦大学担任力学讲席。1855年，德洛奈当选为科学院天文学部成员。他继续与矿业学校保持联系，1858年被任命为总工程师，1867年晋升为一等工程师。他在1860年和1867年出版了两卷关于月球理论的著作La Théorie du mouvement de la luneⓉ（《月球运动理论》），其中包含二十年工作的成果。当然，月球理论是三体问题的一个重要情形。德洛奈将月球的经度、纬度和视差表示为无穷级数。这些结果精确到1角秒，但由于级数收敛缓慢，并不太实用。然而这项工作很重要，因为它包含了泛函分析的开端。从1862年起，他是经度局成员。

我们应当提到德洛奈与于尔班·勒维耶之间的竞争。这演变成一场全面的争论，在1860年前后，这无疑是一场非常公开的争论。我们应当指出，于尔班·勒维耶是个难以相处的人，与许多同事都闹翻了。于尔班·勒维耶是巴黎天文台台长，到1869年，由于他追求效率，他在天文台的同事中已变得非常不受欢迎。有人试图将他免职，最终获得了成功。他被解除台长职务，1870年3月，德洛奈被任命接替他的对手。然而，德洛奈的任命仅在法国对普鲁士宣战前几周才下达。

法国皇帝拿破仑三世的声望已经下降，他决定与普鲁士开战或许能改变他的政治命运。他的顾问告诉他，法国军队可以轻易击败普鲁士，因此这个计划看起来稳操胜券。普鲁士首相俾斯麦把与法国的战争视为统一南德意志各邦的机会，因此他也看到了战争的政治优势。双方都在积极寻求战争，普法战争便不可避免。1870年7月14日，俾斯麦发出一封旨在激怒法国政府的电报。他成功了，因为7月19日法国对普鲁士宣战。德军的进攻只遇到法国无效的回应。8月，德军将部分法国军队围困在梅斯，他们于9月1日投降。9月19日，德军开始封锁巴黎，巴黎于1871年1月28日投降。对德洛奈来说，这是一个极其困难的时期，他排除万难，成功保全了巴黎天文台。1871年3月，巴黎爆发起义，法国政府受到威胁，激进分子在这次起义中建立了他们自己的短命政府——巴黎公社。经过两个月的激烈战斗，公社被镇压，在此期间，德洛奈同样面临艰巨任务，要使天文台免受城中骚乱和战斗的破坏。他大体上成功了，但天文台确实遭受了一些损坏。

1872年，德洛奈和三位同伴在一次划船事故中溺水身亡，当时他们乘坐的船在一阵狂风后倾覆。

Charles Eugène Delaunay came from a family of modest means. His father was Jacques Hubert Delaunay, a surveyor, and his mother was Catherine Choiselat, the daughter of a farmer. Charles was very close to his mother as a young child and remained so throughout his life. In 1818, when Charles was two years old, his father acquired the office of a bailiff in Ramerupt, which is about 20 km north east of Troyes. When he was still young Charles was sent to Troyes to live with one of his uncles who was a manual worker. He attended secondary school in Troyes and showed great promise both at school, where he excelled in mathematics, and with his hobby of making mechanical devices. He went to Paris in 1833 and in the following year he entered the École Polytechnique, being ranked second from all the students entering in that year. When Delaunay graduated in 1836 he was ranked first among all students across all academic disciplines.

Mme la Marquise de Laplace donated a new annual prize, the Laplace Prize, to be given to the student who was ranked top in his year at the École Polytechnique. Delaunay had graduated before the prize was instituted but Mme de Laplace requested that he become the first recipient of the prize which consisted of the complete works of Laplace. It turned out to be a decision which changed the course of Delaunay's career, for reading Laplace's great works gave him a passion for celestial mechanics and he decided that he would make a career in that subject. Mme la Marquise de Laplace was delighted with the first winner of the prize and she called him "her eldest son". Arago suggested to Delaunay that he come to the Paris Observatory and train to become an astronomer but Savary advised against this course of action. Delaunay then entered the École des Mines and trained as an engineer.

For his doctoral dissertation Delaunay undertook research on the calculus of variations and was awarded his doctorate for his thesis De la distinction des maxima et des minima dans les questions qui dépendent de la méthode des variations Ⓣ in 1841. He published his first paper on astronomy submitting Note sur la précession des équinoxes Ⓣ to the Academy of Sciences in the same year. Biot chose him, later in 1841, to substitute for him at the Sorbonne in giving the course in physical astronomy. On the one hand Delaunay gained excellent experience teaching at the Sorbonne, but he was still enrolled as a student at the École des Mines and he had to take an extra year to complete his studies there as a consequence. He completed his studies and qualified as an engineer in 1843.

Delaunay published further papers on astronomy, publishing several papers on perturbations of Uranus in 1842 and 1843 and after this his first work on the theory of tides. He was already working on his lunar theory by this time and published Mémoire sur une Méthode nouvelle pour la détermination du mouvement de la Lune Ⓣ in 1846. This paper contains what today is known as 'Delaunay's method' although several of his later papers contain generalisations of the method as it first appeared here. Among his other works were Cours élémentaire de mécanique Ⓣ (1850) and Traité de mécanique rationnelle Ⓣ (1856), and Cours élémentaire d'astronomie Ⓣ (1853). We should also note that when observations of the Moon's orbit showed that it was deviating from its theoretical path, Delaunay correctly suggested in 1865 that this could be due to the rotational period of the earth slowing due to tidal friction. He published his theory in Ralentissement de la rotation de la terre Ⓣ (1866). We mention also his report on the progress of astronomy Rapport sur les progrès de l'astronomie Ⓣ (1867).

From 1845 to 1850 he taught courses at the École des Mines; these were descriptive geometry, stereotomy, mechanical drawing, analytical mechanics, and elementary physics. He suffered a great tragedy in 1849 when his young wife died and it was largely due to Liouville's efforts to support him at this time that he was able to continue with his academic work. He taught mechanics at the École Polytechnique from 1850 being named Professor of Mechanics there in 1851. He also held a chair of mechanics at the Sorbonne from 1850. In 1855 Delaunay was elected to the Astronomy Section of the Academy of Sciences. He continued his association with the École des mines, being named Engineer in Chief in 1858, then being raised to Engineer First Class in 1867. He published, in 1860 and 1867, two volumes on lunar theory La Théorie du mouvement de la lune Ⓣ which contained the results of twenty years work. Of course the theory of the moon is an important case of the three body problem. Delaunay found the longitude, latitude and parallax of the Moon as infinite series. These gave results correct to 1 second of arc but were not too practical as the series converged slowly. However this work was important in that it contained the beginnings of functional analysis. From 1862 he was a member of the Bureau des Longitudes.

We should mention the rivalry between Delaunay and Le Verrier. This evolved into a full scale argument and around 1860 it was most certainly a very public argument. We should remark that Le Verrier was a difficult man and fell out with many of his colleagues. Le Verrier was the Director of the Paris Observatory and by 1869 he had become very unpopular with his colleagues at the Observatory following his drive for efficiency. Attempts were being made to have him removed which were eventually successful. He was dismissed from his post as Director and in March 1870 Delaunay was appointed to the post to succeed his rival. However Delaunay's appointment came only weeks before France declared war on Prussia.

The popularity of Napoleon III, the French emperor, had declined and he decided that a war with Prussia might change his political fortunes. His advisers had told him that the French Army could defeat Prussia with ease, so the plan looked like a winner. Bismarck, the Prussian chancellor, saw a war with France as an opportunity to unite the South German states so he too saw the political advantage of war. With both sides actively seeking a war, the Franco-Prussian War became inevitable. On 14 July 1870, Bismarck sent a telegram aimed at infuriating the French government. He succeeded, for on the 19 July France declared war on Prussia. The German offensive met with only an ineffective French reply. In August, the German army trapped part of the French army in Metz and they surrendered on 1 September. On 19 September the German army began to blockade Paris which surrendered on 28 January 1871. This was a time of extreme difficulty for Delaunay who succeeded against all the odds to save the Paris Observatory. The French government was threatened by an uprising in Paris in March 1871, in which radicals established their own short-lived government, the Paris Commune. The Commune was suppressed after two months of bitter fighting during which time Delaunay had an equally difficult task keeping the Observatory safe from the riots and fighting in the city. He largely succeeded but the Observatory did sustain some damage.

In 1872 Delaunay and three companions drowned in a boating accident when the boat they were in capsized following a gust of wind.