萨迪·卡诺Nicolas Carnot

萨迪·卡诺是拉扎尔·卡诺的长子，他出生在卢森堡小宫。他的弟弟是Hippolyte Carnot。在萨迪·卡诺出生时，他的父亲是督政府成员，这是法国革命政府，从1795年11月到1799年11月持续了四年。萨迪·卡诺的名字取自一位中世纪波斯诗人和哲学家，名叫设拉子的萨迪。

萨迪·卡诺出生在法国动荡和政治混乱的时期，由于他父亲的地位，其命运多次发生戏剧性变化，他在政治与科学相互作用的完全不稳定环境中长大。他的父亲于1799年被任命为拿破仑的战争部长这一高级职位。拉扎尔·卡诺于1807年辞职，致力于两个儿子的教育。萨迪·卡诺有一位好老师，就是他的父亲，父亲教他数学和科学以及语言和音乐。

在父亲的教导下，萨迪·卡诺表现出极大的前途，被送到巴黎查理曼中学，为巴黎综合理工学院的入学考试做准备。1812年，16岁的萨迪·卡诺——这是可能的最低年龄——进入巴黎综合理工学院，西莫恩·德尼·泊松、安德烈-马里·安培和弗朗索瓦·阿拉戈都是他的老师。米歇尔·沙勒与萨迪·卡诺同班，他们的友谊持续了萨迪·卡诺的一生。萨迪·卡诺于1814年从巴黎综合理工学院毕业，但在他毕业之前，萨迪·卡诺和巴黎综合理工学院的其他学生与拿破仑一起为保卫万塞讷进行了不成功的战斗。这场对抗同盟军的遭遇战就在巴黎城外、城市以东进行。

毕业后，萨迪·卡诺前往梅斯的工程学校学习为期两年的军事工程课程。1815年，拿破仑从流放地返回，进行著名的百日统治。萨迪·卡诺的父亲被任命为内政部长，而萨迪·卡诺在军事学院中处境有些困难，因为他的父亲身居如此显要的位置。1815年10月拿破仑战败后，萨迪·卡诺的父亲被流放，他前往德国，再未返回法国。

对于萨迪·卡诺来说，在父亲流亡的情况下，军旅生涯很可能不是最轻松的选择。萨迪·卡诺被从一个地方调到另一个地方，被分配去检查防御工事、制定计划和撰写报告。然而，他似乎没有得到很好的对待，他的建议也被忽视了。由于缺乏晋升机会以及被拒绝给予一份能让他运用所学训练的工作，他感到不满，于是在1819年，他参加并通过了考试，加入了最近在巴黎成立的总参谋部。几乎立即他就以半薪休假，住在巴黎他父亲以前的公寓里，但他仍然随时待命履行军队职责。

萨迪·卡诺开始旁听巴黎多所机构的课程，包括索邦大学和法兰西公学院。此时他对工业问题产生了兴趣，尤其开始研究气体理论。他的兴趣十分广泛[1]：——

他频繁走访工厂和作坊，研究最新的政治经济学理论，并在笔记中留下了关于税制改革等当前问题的详细建议。除此之外，他的活动和才能还涵盖数学与美术。

1821年，萨迪·卡诺前往马格德堡探望流亡中的父亲。他的兄弟Hippolyte Carnot当时正与父亲同住。显然，他们进行了许多关于蒸汽机的讨论。第一台蒸汽机在三年前来到马格德堡，引起了拉扎尔·卡诺的兴趣，而萨迪·卡诺离开马格德堡时满怀热情，决心发展一套蒸汽机理论。回到巴黎后，萨迪·卡诺开始了导向热的数学理论的工作，并推动了现代热力学理论的创立。E Mendoza在[2]中解释了其背景：——

萨迪·卡诺所关注的问题是如何设计出好的蒸汽机。蒸汽动力已有许多用途——从矿井中排水、开挖港口和河道、锻造铁器、磨制谷物以及纺纱织布——但效率低下。与英国战争后，先进发动机输入法国，这让萨迪·卡诺看到法国设计已落后多远。尤其令他恼火的是，英国人凭借几位缺乏正规科学教育的工程师的天才取得了如此大的进展。英国工程师还积累并公布了多种发动机在实际运行条件下效率的可靠数据；他们激烈地争论低压与高压发动机以及单缸与多缸发动机的优劣。

萨迪·卡诺的第一部重要著作是他在1822—23年写的一篇论文。这篇论文试图为一千克蒸汽所做的功找到数学表达式。该论文在目标和方法上都与Hachette、克洛德-路易·纳维和亚历克西·泰雷兹·珀蒂大约同时期发表的其他几篇论文相似。然而[1]：——

萨迪·卡诺的工作之所以出众，在于他对所用单位和概念作了细致、清晰的分析，也在于他同时使用了一个绝热工作阶段和一个消耗功的等温阶段。

从文风和详细描述来看，这篇论文显然是为发表而写的，但萨迪·卡诺从未将其发表，其存在直到1966年才以手稿形式被发现。

当拉扎尔·卡诺于1823年8月去世时，Hippolyte Carnot回到巴黎，在那里他帮助萨迪·卡诺使他当时正在写的关于蒸汽机的书对普通公众更容易理解。1824年，萨迪·卡诺出版了这部作品，这是他一生中唯一出版的作品，Réflexions sur la puissance motrice du feu et sur les machines propres à développer cette puissanceⓉ（关于火的动力和开发这种动力的机器的反思），其中包括他对“萨迪·卡诺循环”的描述。这本书直到埃米尔·克拉佩龙在1834年发表了对它的分析性重新表述后才广为人知。萨迪·卡诺的思想后来被纳入鲁道夫·克劳修斯和开尔文的热力学理论中。

萨迪·卡诺在他的书出版后继续进行研究，尽管这些研究没有发表，但萨迪·卡诺随着他的思想发展所做的笔记保存了下来。然而，在1827年，巴黎的总参谋部进行了重组，他被召回全职工作。他作为军事工程师服役了不到一年，先被派往里昂，然后被派往欧松。仍然对自己的职业生涯不满，萨迪·卡诺永久退休并回到巴黎居住，在那里他打算继续他对热理论的研究。

遵循他父亲的政治观点，萨迪·卡诺是强烈的共和主义者，所以他对法国在1830年七月革命后似乎要去的方向感到高兴。大约在这个时候，他对公共生活产生了兴趣，特别是他对改善公共教育感兴趣。有人建议他担任政府职务，但他拒绝了，并且在君主制恢复后，他回到了他的科学工作。1832年6月他生病了，当1832年的霍乱疫情袭击巴黎时，他还没有完全恢复体力。尽管只有36岁，他在感染霍乱后一天内就去世了。

萨迪·卡诺的重要著作Réflexions sur la puissance motrice du feu et sur les machines propres à développer cette puissanceⓉ（《关于火的动力以及产生这种动力的机器的思考》）在出版时被忽视，这当然不是因为无人注意。它于1824年6月12日出版，同年7月26日，Pierre Girard在巴黎的Académie des Sciences上对它作了长篇评论。Pierre Girard的评论非常正面，发表在Revue encyclopédique上。也许这篇评论的问题在于，尽管它充分陈述了萨迪·卡诺著作的定理和结论，却没有评论萨迪·卡诺为取得这些结果所采用的极具独创性的推理。

萨迪·卡诺的个性可能在他生前其工作缺乏热情这一点上起了作用。[2]中对他有如下描述：-

朋友们形容他沉默寡言，几乎不爱说话，但对科学和技术过程有着永不满足的好奇心。

在[1]中，他被用类似的话描述：-

尽管敏感而富有洞察力，但除了少数几个亲密朋友外，他对所有人都显得极其内向，甚至冷漠……

Réflexions是萨迪·卡诺试图回答两个基本问题的尝试，第一是热的动力是否存在上限，第二是是否存在比蒸汽更好的方式来产生这种动力。他对这些问题的探讨是提出一个比以往尝试过的更为一般的理论，这个理论不是像罗伯特·胡克和罗伯特·波义耳那样基于热是原子的随机运动，而是基于热是一种被称为热质的无重量流体的概念。他引入了“萨迪·卡诺引擎”的概念，一种理想热机。他证明了“萨迪·卡诺引擎”的效率只取决于引擎内部的温差，而不取决于驱动机构的物质如蒸汽。他还引入了可逆性的重要概念，即动力可以用来产生引擎中的温差。

萨迪·卡诺在1824年至1826年间所作的笔记表明，他正在逐渐脱离热质说。他在笔记中详细列出了他打算进行的实验，以研究流体中摩擦的温度效应。其中一些拟议的实验与焦耳二十年后实际进行的实验完全相同。如果萨迪·卡诺的生命不是如此悲惨地短暂，他很可能会做出多得多的重大科学贡献。

Sadi Carnot was the eldest son of Lazare Carnot and he was born in the Palais du Petit-Luxembourg. His younger brother was Hippolyte Carnot. At the time of Sadi's birth, his father was a member of the Directory, the French Revolutionary government which lasted four years from November 1795 to November 1799. Sadi was given named after a medieval Persian poet and philosopher called Sa'di of Shiraz.

Sadi Carnot was born at a time of unrest and political turmoil in France and, due the position of his father, whose fortunes changed dramatically many times, he was brought up in a totally unstable environment of interacting politics and science. His father was appointed to the high office of Napoleon's minister of war in 1799. Lazare Carnot resigned in 1807 and devoted himself to the education of his two sons. Sadi had a fine teacher in his father, who taught him mathematics and science as well as languages and music.

Under his father's tuition, Sadi Carnot showed great promise and was sent to the Lycée Charlemagne in Paris to prepare him for the examinations to the École Polytechnique in Paris. In 1812, at age 16 the minimum age possible, Carnot entered the École Polytechnique where Poisson, Ampère and Arago were among his teachers. Chasles was in the same class as Carnot and their friendship lasted throughout Carnot's life. Carnot graduated from the École Polytechnique in 1814 but, before he graduated, Carnot and other students from the École Polytechnique fought unsuccessfully with Napoleon to defend Vincennes. This skirmish against the Allies was fought just outside Paris, to the east of the city.

After graduating, Carnot went to the École du Génie at Metz to take the two year course in military engineering. In 1815 Napoleon returned from exile for his famed Hundred Days rule. Carnot's father was appointed minister of the interior and Sadi Carnot was put in a somewhat difficult position in the military academy with his father in such a prominent position. In October 1815 after the defeat of Napoleon, Carnot's father was exiled and he went to Germany never to return to France.

It is probable that a military career was not the easiest one for Carnot with his father in exile. Carnot was moved from place to place, given jobs of inspecting fortifications, drawing up plans and writing reports. However, it seems that he was not well treated and his recommendations were ignored. Unhappy at his lack of promotion and the refusal to give him a job which allowed him to make use of his training, in 1819, he sat and passed the examinations to join the recently formed General Staff Corps in Paris. Almost immediately he took leave on half pay, living in Paris in his father's former apartment, but he remained on call for army duty.

Carnot began to attend courses at various institutions in Paris, including the Sorbonne and the Collège de France. At this time he became interested in industrial problems and, in particular, began to study the theory of gases. His interests were wide [1]:-

He made frequent visits to factories and workshops, studied the latest theories of political economy, and left in his notes detailed proposals on such current problems as tax reform. Beyond this, his activity and ability embraced mathematics and the fine arts.

Carnot visited his father in 1821 in his exiled home in Magdeburg. Hippolyte Carnot, his brother, was living with his father at this time. It is clear that there were many discussions about steam engines. The first steam engine had come to Magdeburg three years earlier and had interested Lazare Carnot, and Sadi Carnot left Magdeburg filled with enthusiasm to develop a theory for steam engines. After returning to Paris, Carnot began the work which led to the mathematical theory of heat and helped start the modern theory of thermodynamics. E Mendoza explains in [2] the background:-

The problem occupying Carnot was how to design good steam engines. Steam power already had many uses - draining water from mines, excavating ports and rivers, forging iron, grinding grain, and spinning and weaving cloth - but it was inefficient. The import into France of advanced engines after the war with Britain showed Carnot how far French design had fallen behind. It irked him particularly that the British had progressed so far through the genius of a few engineers who lacked formal scientific education. British engineers had also accumulated and published reliable data about the efficiency of many types of engines under actual running conditions; and they vigorously argued the merits of low- and high-pressure engines and of single-cylinder and multi-cylinder engines.

The first of Carnot's major works was a paper which he wrote in 1822-23. This paper attempted to find a mathematical expression for the work produced by one kilogram of steam. The paper is similar in its aims and also in its methods to several other papers which appeared around this time by Hachette, Navier and Petit. However [1]:-

Carnot's work is distinguished for his careful, clear analysis of the units and concepts employed and for his use of both an adiabatic working stage and an isothermal stage in which work is consumed.

From its style and detailed descriptions the paper was clearly intended for publication but Carnot never published it and its existence was only discovered in manuscript form in 1966.

When Lazare Carnot died in August 1823, Hippolyte Carnot returned to Paris and there he helped Sadi Carnot to make the book on steam engines that he was working on at the time more understandable to the general public. In 1824 Carnot published this work, the only one he published during his lifetime, Réflexions sur la puissance motrice du feu et sur les machines propres à développer cette puissanceⓉ which includes his description of the "Carnot cycle". This book only became well known after Clapeyron published an analytic reformulation of it in 1834. Carnot's ideas were later incorporated into the thermodynamic theory of Clausius and Thomson.

Carnot continued with his research after the publication of his book and although nothing of this was published, notes that Carnot made as his ideas developed have survived. In 1827, however, the General Staff Corps in Paris was reorganised and he was recalled to full time duties. He served for rather less than one year as a military engineer, being posted first to Lyon and then to Auxonne. Still unhappy with his career, Carnot retired permanently and returned to live in Paris where he aimed to continue with his research into the theory of heat.

Following his father's political views, Carnot was strongly republican so he was pleased with the direction France seemed to be going with the July 1830 Revolution. Around this time he became interested in public life, in particular he was interested in improving public education. He was suggested for a government position, but he declined and, after the monarchy was restored, he returned to his scientific work. In June 1832 he took ill and had not fully regained his strength when the cholera epidemic of 1832 hit Paris. Although only 36 years of age, he died within a day of contracting cholera.

That Carnot's important book Réflexions sur la puissance motrice du feu et sur les machines propres à développer cette puissanceⓉ should have been neglected at the time of its publication is certainly not because it went unnoticed. It was published on 12 June 1824 and on 26 July of that year Pierre Girard gave a long review of it to the Académie des Sciences in Paris. Pierre Girard's review was a very positive one and was published in the Revue encyclopédique. Perhaps the problem with the review was that although it stated the theorems and the conclusions of Carnot's work fully, it did not comment on the highly original reasoning which Carnot had employed to achieve his results.

It is possible that Carnot's personality played a role in the lack of enthusiasm for his work in his lifetime. He is described in [2] as follows:-

Friends described him as reserved, almost taciturn, but insatiably curious about science and technical processes.

In [1] he is described in similar terms:-

Although sensitive and perceptive, he appeared extremely introverted, even aloof, to all but a few close friends ...

The Réflexions was an attempt by Carnot to answer two fundamental questions, firstly whether there was an upper limit to the power of heat, and secondly whether there was a better means than steam to produce this power. His attack on these questions was to produce a much more general theory than had previously been attempted based not on heat as random motion of atoms, as Hooke and Boyle had done, but by the concept of heat as a weightless fluid called caloric. He introduced the concept of the "Carnot engine", an ideal heat engine. He showed that the efficiency of the "Carnot engine" depends only on the temperature difference within the engine and not on the substance such as steam that drives the mechanism. He also introduced the important concept of reversibility, namely that motive power can be used to produce the temperature difference in the engine.

Notes which Carnot made between 1824 and 1826 show that he was moving away from the caloric theory. He set out in his notes details of experiments which he intended to carry out to study the temperature effects of friction in fluids. Some of these proposed experiments were identical with those actually performed by Joule twenty years later. It is likely that Carnot would have made many more significant scientific contributions had his life not been so tragically short.