西德尼·查普曼Sydney Chapman

西德尼·查普曼的母亲是Sarah Gray，她的父亲是Joseph Chapman，他是曼彻斯特一家名为Rylands的纺织公司的首席出纳员。查普曼是他父母的第二个儿子，他由不信奉国教的父母以非常严格的方式抚养长大。

他在Patricroft的Green 桑德斯·麦克兰恩学校上学，直到14岁。这是一所同类学校中的好学校，因为在那里他学了一点拉丁语，并接触了一些科学科目，如化学和生理学。查普曼离开学校后，他的父亲Joseph带他去见一位在工程领域工作的家庭朋友，希望他的儿子能在这家公司当学徒。这位朋友建议他在技术学校再学习两年，然后再开始工程学徒生涯。

遵循这一建议，查普曼进入了索尔福德的皇家技术学院（现为索尔德大学）。他仍然打算进入工程行业，但他在学院表现如此出色，以至于他的老师鼓励他参加兰开夏郡奖学金考试。他再次幸运地接受了科学科目的教育，尽管水平很低，但有一位特别好的化学老师。在学院两年后，他参加了曼彻斯特大学的郡奖学金考试，排名第十五，这是获得奖学金的最低名次。他后来常说：-

我有时会想，如果我低一个名次会怎样。

1904年，16岁的查普曼进入曼彻斯特大学，在Osborne 奥斯鲍恩·雷诺领导的系里学习工程学。数学方面，他师从数学教授贺拉斯·兰姆，以及在查普曼在曼彻斯特的最后一年从剑桥来的利特尔伍德。他毕业获得工程学学位，但他已经变得非常喜欢数学，因此在曼彻斯特又留了一年攻读数学学位。在贺拉斯·兰姆的建议下，查普曼申请了剑桥大学三一学院的奖学金，并成功获得，于1908年进入三一学院。起初他是一名减费生（Sizar）（意思是他通过为年长的男孩做仆人来获得经济支持），但从第二年起他获得了全额奖学金。剑桥比以往任何事情都更激发了他的兴趣，这也许并不奇怪，因为在那里他遇到了戈弗雷·哈罗德·哈代、阿尔弗雷德·诺思·怀特海和伯特兰·罗素[5]：-

这个地方的美丽及其未受破坏的环境对他来说是一种启示，尽管以他的背景，他有时感到格格不入。他后来说，他觉得他第一次开始在剑桥生活。

查普曼的进步如此显著，以至于他还在本科时就能开始研究，但他不确定是走纯数学还是应用数学的方向。他的第一个研究是关于可和级数，他写了两篇关于这个主题的论文，其中一篇是与戈弗雷·哈罗德·哈代合著的。然而约瑟夫·拉莫尔建议他研究气体动理论中的问题，尽管他对贺拉斯·兰姆教给他的应用数学不太满意，他的兴趣很快转向了这个方向。

查普曼于1910年从剑桥毕业，皇家天文学家Frank Dyson为他提供了格林尼治天文台高级助理的职位。他接受了这一职位，并在那里工作到第一次世界大战爆发。起初，他负责监督安装测量磁性的新仪器，但失望地发现科学家们只对收集数据感兴趣，并没有真正尝试去解释这些数据。为了扭转这一趋势，查普曼开始分析与太阳和月亮影响地球现象的方式有关的数据。1913年他获得首届史密斯奖，这衡量了他的成功，并且以此课题开始了一项他将持续一生的研究兴趣。

然而，查普曼并不完全满意将自己献给天文学，正如[5]所指出的：-

……他觉得自己不是一个好的观测者，他不想把所有其他兴趣都从属于天文学；特别是，他想完成他已经开始的气体动理论的工作。此外，他也不喜欢可能最终在格林尼治落在他身上的行政工作的前景。

他离开了格林尼治天文台，于1914年作为讲师回到剑桥，薪水减少，大约在第一次世界大战爆发的时候。他的宗教原则使他成为和平主义者，因此他被免除兵役并留在剑桥。1916年，他被要求以荣誉身份回到格林尼治天文台工作，他一直这样做直到1918年12月。然而，战争结束后回到剑桥后，由于他的和平主义观点，他感到非常不快乐和不受欢迎，因此，他患上了多年的抑郁症。

尽管患有抑郁症，查普曼的研究并未受到影响。在战争期间，1915年至1917年间，他完成了一系列关于热扩散和气体动力学基础的重要论文。他发展了针对一般力律下相互作用粒子的速度分布函数的詹姆斯·克拉克·麦克斯韦-路德维希·玻尔兹曼表述的系统近似。1913年至1919年间，他发表了另一系列重要论文，这次是关于地磁的，我们将在下面评论。

1919年，他被任命为曼彻斯特的讲席，接替了贺拉斯·兰姆。1922年，他与来自曼彻斯特的凯瑟琳·诺拉·斯坦塔尔结婚，他们有一个女儿和三个儿子。他的事业继续蒸蒸日上，1924年他被任命为伦敦帝国理工学院数学讲席，接替了阿尔弗雷德·诺思·怀特海。

早在第二次世界大战开始之前，II Chapman就已经看到了纳粹在德国崛起的危险。他的和平主义观点已经改变（受到希特勒相当大的影响），因此到第二次世界大战开始时，他已经准备好承担战时服务，并研究军事运筹学和燃烧弹问题。

1945年，第二次世界大战结束时，他回到伦敦的讲席，但现在不如以前快乐，因此，1946年，他欣然接受了牛津大学自然哲学塞德利讲席的职位，同时成为女王学院的会士。接下来的几年是查普曼研究生涯中成果最少的时期。当时科学在牛津被视为次要的，他通过为非科学家教授特别讲座课程，努力让非科学家相信科学的重要性。

他于1953年在65岁时辞去了牛津的职位，而不是等到70岁退休，并开始访问世界各地的许多地方。特别是，他于1953年在阿拉斯加获得了一个研究职位，两年后又在科罗拉多州博尔德的高海拔天文台担任了类似的职位。这些成了他的两个主要基地，但他访问的其他地方包括美国的密歇根和明尼苏达、伊斯坦布尔、伊巴丹、开罗、布拉格、东京和俄罗斯。

查普曼的主要研究领域是地球磁场，由于他在这一领域的工作，他于1919年当选为皇家学会会士，并于1966年被授予该学会的科普利奖章：-

……以表彰他对地球与行星际磁性、电离层和北极光的理论贡献。

他于1913年开始研究地磁学，从那时到1915年间，他发表了关于该主题的三篇论文。这些论文利用由太阳和月球影响下电离层中的潮汐流驱动的发电机理论来解释磁变化。1919年，他提出了第一个试图解释磁暴的理论，但很快发现该理论不完善。他因一篇关于地磁学的论文于1928年获得约翰·柯西·亚当斯奖。他在此期间所做的其他工作是与爱德华·亚瑟·米尔恩合作进行的。

在1928年至1932年间，查普曼回到气体动力学的工作，扩展了他早先开发的方法。他还对等离子体进行了重要研究。1931年，他做了皇家学会贝克讲座，这是一次经典讲座，其中他发展了现在标准的低电离层分层理论。1957年，他荣幸地当选为国际地球物理年特别委员会主席。事实上，他在发起和指导国际地球物理年方面发挥了重要作用，这是20世纪最伟大的国际地球物理学合作。

查普曼在去世前不久被问及退休后所从事的工作中他觉得最有趣的是哪一项时，回答说那是他在高度电离气体中的热扩散工作、磁暴工作、沿磁中性线的不稳定性工作以及夜光云工作。

托马斯·乔治·考林在[5]中写到了他的讲课风格：-

他的讲课风格往往平淡无奇，尽管还算扎实。……因此，当我在1931年第一次在英国协会听查普曼讲课时，起初感到失望；直到后来我才体会到他的演讲中包含了多少相关信息。他的表达方式有一种简单直接的特点，这常常掩盖了深刻的思想。

他的个人特点在[5]中被描述如下：-

认识查普曼的人都证明他善良、执着、质朴和正直。他的和善深受一代又一代研究生和年轻同事的感激，在困难时期人们总能向他寻求有益的建议。

他的性格和兴趣在[3]中也有描述：-

查普曼温和的举止掩盖着坚强的意志和巨大的决心；他的品味和习惯都很简朴。他是一位热情的自行车手、游泳者和步行者，无论在他访问外国大学或参加国际会议时，可用的交通方式多么多样，查普曼总是可以指望骑自行车到达。1939年，他从蒙特利尔骑车到华盛顿参加国际地球物理联合会的会议。

Sydney Chapman's mother was Sarah Gray and her father was Joseph Chapman who was the chief cashier with a Manchester textile firm called Rylands. Sydney was his parents' second son and he was brought up in a very strict fashion by his Nonconformist parents.

He attended Green Lane school in Patricroft up to the age of 14. This was a good school of its type for there he learnt a little Latin and was introduced to some science subjects such as chemistry and physiology. After Sydney left school, Joseph, his father, took him to see a friend of the family who worked in engineering with the idea that his son should become an apprentice with the firm. The friend advised that he study for two further years at technical school before taking up an engineering apprenticeship.

Following this advice, Chapman entered the Royal Technical Institute, Salford (which is now the University of Salford). It was still his intention to enter the engineering industry but he performed so well at the Institute that his teachers encouraged him to sit the Lancashire Scholarship examinations. Again he had been fortunate to have been taught science subjects, although at a very low level, having a particularly good chemistry teacher. After two years at the Institute he sat the county scholarship examinations to Manchester University and was placed fifteenth, the bottom place for the award of a scholarship. He used to say in later life:-

I sometimes wonder what would have happened if I'd hit one place lower.

In 1904, at the age of 16, Sydney entered the University of Manchester and there he studied engineering in the department headed by Osborne Reynolds. In mathematics he was taught by Lamb, the professor of mathematics, and J E Littlewood who arrived from Cambridge in Chapman's final year at Manchester. Graduating with an engineering degree, he had become so fond of mathematics that he stayed on at Manchester for one further year to take a mathematics degree. At Lamb's suggestion Chapman tried for a scholarship to Trinity College, Cambridge and, being successful, entered Trinity in 1908. At first he was a sizar (meaning that he obtained financial support by acting as a servant to the older boys) but from his second year onwards he received a full scholarship. Cambridge stimulated his interest more than anything had done before and perhaps this is not surprising since there he met Hardy, Whitehead and Russell [5]:-

The beauty of the place and its unspoilt surroundings came on him as a revelation, even though with his background he sometimes felt out of place. He later said that he felt that he first began to live at Cambridge.

Chapman's progress was so remarkable that he was able to start research while still an undergraduate but he was unsure whether to go in the direction of pure or applied mathematics. His first research was on summable series and he wrote two papers on this topic, one of them a joint paper with Hardy. However Larmor suggested he look at problems in the kinetic theory of gases and, despite not being very happy with the applied mathematics which Lamb had taught him, his interest soon turned in this direction.

After Chapman graduated from Cambridge in 1910 the astronomer royal, Frank Dyson, offered him the position of senior assistant at Greenwich Observatory. He accepted and continued to work there until the beginning of World War I. At first he supervised the installation of new instruments to measure magnetism, but was disappointed to find that the scientists were only interested in collecting data and were making no real attempts to interpret it. To counter this trend, Chapman began to analyse data relating to the way that the Sun and Moon influence terrestrial phenomena. His success is measured by the award of the first Smith's prize in 1913, and with this topic he began a research interest that he would continue through the rest of his life.

Chapman, however, was not entirely happy with devoting himself to astronomy as is pointed out in [5]:-

... he did not feel he was a good observer, and he did not want to subordinate all his other interests to astronomy; in particular, he wanted to complete the work he had begun on the kinetic theory of gases. Also he did not relish the prospect of the administrative work which might ultimately have fallen on him at Greenwich.

He left the Greenwich observatory and returned to Cambridge as a lecturer in 1914, with a reduced salary, around the time that World War I broke out. His religious principles made him a pacifist so he was exempted from military service and remained at Cambridge. In 1916 he was asked to return to working at the Greenwich observatory in an honorary capacity, which he did until December 1918. Once back at Cambridge after the war ended, however, he was made to feel very unhappy and unwelcome because of his pacifist views and, as a consequence, he suffered depression for a number of years.

Despite his depression Chapman's research did not suffer. During the war, between 1915 and 1917, he completed a series of important papers on thermal diffusion and the fundamentals of gas dynamics. He developed systematic approximations to the Maxwell - Boltzmann formulation for the velocity distribution function for interacting particles under general force laws. Between 1913 and 1919 he published another important series of papers, this time on terrestrial magnetism which we comment on below.

In 1919 he was appointed to the chair at Manchester where he succeeded Lamb. He married Katharine Nora Steinthal, who came from Manchester, in 1922 and they had one daughter and three sons. His career continued to go from strength to strength and he was appointed to the chair of mathematics at Imperial College London in 1924 succeeding Whitehead.

Long before the start of World War II Chapman had seen the dangers of the Nazi rise to power in Germany. His pacifist views had changed (with some considerable influence from Hitler) so that by the start of World War II he was ready to undertake war service and he worked on military operational research and incendiary bomb problems.

In 1945, at the end of World War II, he returned to his chair in London but was now less happy than he had been, so, in 1946, he readily accepted the offer of the Sedleian Chair of Natural Philosophy at Oxford, also becoming a fellow of Queen's College at this time. The next few years turned out to be the least productive period in Chapman's research career. Science was considered of secondary importance in Oxford at the time, and he worked hard to convince non-scientists of its importance by teaching special lecture courses for non-scientists.

He resigned his position in Oxford in 1953 at age 65, rather than waiting to retire at age 70, and began to visit many places throughout the world. In particular he took a research post in Alaska in 1953 and in addition took on a similar post at the High Altitude Observatory in Boulder, Colorado, two years later. These became his two main bases, but his visits to other places included Michigan and Minnesota in the USA, Istanbul, Ibadan, Cairo, Prague, Tokyo and Russia.

Chapman's main area of research was the Earth's magnetic field and for his work in this area he was elected to the Royal Society in 1919, and awarded the Society's Copley Medal in 1966:-

... in recognition of his theoretical contributions to terrestrial and interplanetary magnetism, the ionosphere and the aurora borealis.

He had begun work on geomagnetism in 1913 and between then and 1915 had published three papers on the topic. These interpreted magnetic variations using a dynamo theory driven by tidal flows in the ionosphere resulting from the influence of the Sun and Moon. In 1919 he produced the first theory which attempted to explain magnetic storms, but he soon found that it was unsound. He received the Adams Prize in 1928 for an essay on geomagnetism. Other work which he did around this time was undertaken in collaboration with Milne.

Between 1928 and 1932 Chapman returned to work on gas dynamics, extending the methods he had developed earlier. He also undertook important research on plasmas. In 1931 he gave the Royal Society Bakerian lecture which was a classic in which he developed the now standard layer theory for the lower ionosphere. He was honoured in 1957 by being elected president of the Special Commission of the International Geophysical Year. In fact he played a major role in initiating and guiding the International Geophysical Year which has been the greatest international geophysics cooperation of the twentieth century.

Chapman, when asked shortly before his death which work he had undertaken since retiring he had found most interesting, replied that it was his work on thermal diffusion in highly ionised gases, his work on magnetic storms, his work on instability along magnetic neutral lines, and his work on noctilucent clouds.

Cowling writes in [5] about his lecturing style:-

His lecturing style tended to be pedestrian, though workmanlike. ... Thus when I first heard Chapman lecture at the British Association in 1931, I was at first disappointed; not until later did I appreciate how packed with relevant information his talk had been. There was a simple directness about his mode of expression, which often concealed deep thought.

His personal characteristics are described in [5] as follows:-

Those who knew Chapman all testify to his kindness, persistence, simplicity and integrity. His kindliness was appreciated by successive generations of research students and junior colleagues, in times of difficulty one could always turn to him for helpful advice.

His character and interests are also described in [3]:-

Chapman's mild manner veiled a strong will and great determination; his tastes and habits were simple. He was an enthusiastic cyclist, swimmer and walker, and both on his visits to foreign universities or to international conferences, however varied the available modes of transport might be, Chapman could always be relied on to arrive on a bicycle. He rode from Montreal to Washington in 1939 to attend the meeting of the International Geophysical Union.