阿尔芒·斐索Hippolyte Fizeau

阿尔芒·斐索是Béatrice和Louis Fizeau的长子。他的父亲Louis Fizeau来自一个许多代都是医生的家庭，是巴黎医学院的病理学教授。人们当然期望斐索会继承家族传统并进入医学行业——其他任何事情都是不可想象的。他就读于巴黎著名的斯坦尼斯拉斯学院，在那里他与一位同学莱昂·傅科关系友好。

1839年9月发生了一件重要的事，对斐索的未来产生了显著影响。Louis-Jacques Daguerre在巴黎开设了一门关于他新摄影技术的免费课程，两位朋友斐索和莱昂·傅科参加了。他们观看Daguerre将一块感光板放入指向窗外的相机中曝光，然后他谈论了自己的方法约30分钟，之后他用各种化学药剂显影感光板，显现出图像。尽管斐索和莱昂·傅科印象深刻，但他们也意识到这一方法的局限性——他们想，能够拍摄肖像将会非常美妙，但不能指望被摄者保持不动30分钟。课程结束后，他们开始实验，试图加快这一过程，斐索想到用溴来敏化感光板。实验使他们将曝光时间从30分钟缩短到20秒。然而，这一发现并未产生它可能产生的影响，因为其他摄影方法正在投入使用。

在Collège Stanislas接受了出色教育后，斐索于1840年进入巴黎医学院。然而，他患有严重的偏头痛，决定放弃医学。他花了一段时间旅行，在此期间恢复了健康，然后转向物理学。他参加了弗朗索瓦·阿拉戈在天文台的讲座，并报名参加了著名Henri Victor Regnault在法兰西学院开设的光学课程。斐索还有另一种积累数学和物理知识的方法，那就是深入研究包含他哥哥在巴黎综合理工学院上课时所记笔记的笔记本。弗朗索瓦·阿拉戈意识到摄影新方法的巨大科学潜力，特别是，他意识到斐索和莱昂·傅科所取得的进展。他于1845年接触这两位朋友，建议他们尝试拍摄由望远镜产生的太阳图像的照片。他们非常成功，拍摄了有史以来第一张太阳照片。它清晰地显示了太阳黑子群。

1842年，克里斯蒂安·多普勒发表了On the coloured light of the double stars and certain other stars of the heavens，首次提出了克里斯蒂安·多普勒原理，该原理将光源的频率与其相对于观察者的速度联系起来。然而，斐索并不知道克里斯蒂安·多普勒的工作，并在1848年对来自恒星的光的波长偏移给出了类似的解释[2]：-

然而，斐索预测，恒星光谱中吸收线的微小位移可以用来测量比克里斯蒂安·多普勒所建议的小得多的天体速度，以及地球观察者的运动，这一正确的预测奠定了现代天体物理研究的大部分基础。

弗朗索瓦·阿拉戈对斐索和莱昂·傅科在拍摄太阳方面的成功感到高兴，并向他们建议尝试用基于地球的实验来计算光速。此前唯一的计算是Rømer利用木星的卫星进行的。弗朗索瓦·阿拉戈也感兴趣的是光在水中比在空气中传播得更慢还是更快，因为这是判断光是微粒还是波的关键测试。斐索和莱昂·傅科都有自己的想法如何进行，在最初一起研究了一段时间后，他们分开了。1849年7月，斐索在他父母位于Suresnes的家中设置了一面镜子，在巴黎右岸的蒙马特高地设置了另一面。这两者相距8633米。在它们之间，他设置了一个快速旋转的齿轮，并确定了光在镜子之间传播所需的时间等于齿轮旋转一个齿所需的时间所必需的旋转速度。因此，他成为第一个成功进行地面光速测量的人。我们今天知道，他找到的值几乎与Rømer的天文测量一样准确，误差约为5%。1850年4月，莱昂·傅科成为第一个证明光在水中比在空气中传播得更慢的人——斐索在七周后用他的装置证实了这一结果。1851年，斐索试图测量地球通过以太的运动，并取得了负面结果。这是相当漫长的过程中的重要第一步，最终导致在20世纪初抛弃了以太假说。Melcher写道[9]：-

……存在由阿尔伯特·爱因斯坦写下的书面证词，证实了迈克尔逊的实验对前者工作的影响。由于阿尔伯特·爱因斯坦经常提到斐索实验（1851年），而迈克尔逊在1886年重复了这一实验，但较新的文献往往改为引用霍克实验（1868年），因此我们最后分析这些实验及其历史意义。

在考虑斐索贡献的这一方面时，我们注意到那篇有趣的文章[6]，它讨论了斐索和莱昂·傅科的密封信件，这些信件直到1983年才被研究。我们引用科斯塔贝尔的摘要：——

第1002号密封信件，由莱昂·傅科于1850年5月27日存放，并于1983年2月23日开启，……揭示出莱昂·傅科曾在其实验室中与斐索合作，用透明物体检验以太拖曳。……斐索1851年9月29日论文的全文，在结合这个最初并不令人满意的方案重新阅读时，显示出一种新进路。因此，这……阐明了历史中一个时刻的重要性，即关于光的波动性质和地球运动的假说与“决定性”实验相互交织。

斐索于1849年被授予荣誉军团骑士称号。1853年，他与著名植物学家阿德里安·德·朱西厄的女儿泰蕾兹·瓦朗蒂娜·德·朱西厄结婚；他们有两个女儿和一个儿子。他曾于1851年3月试图获得科学院的成员资格。科学院52名成员进行秘密投票，以从七名候选人中选出一人。第一轮中，他以八票并列第四，并在后来的投票中被淘汰。莱昂·傅科也是这七名候选人之一，表现较好，但未当选。斐索于1860年1月2日当选为科学院成员，相当令人意外地早于莱昂·傅科，后者直到1865年才当选。他此前已获得法兰西研究院的荣誉，该院于1856年7月9日授予他三年一度的大奖。更多荣誉随后到来，特别是他于1866年被授予皇家学会的伦福德奖章，随后于1875年当选为外籍会士。1877年，他成为科学院物理学部副主席，次年成为该学部主席。在其主席致辞中，他谈到[8]：——

……自然科学的尊严与独立，以及其行动界限，防止它干涉哲学或社会问题，也不允许它使自己与心灵的高尚情感或良知的纯粹声音相对立。

同样在1878年，他成为经度局成员。泰蕾兹早逝，此后斐索退居到茹阿尔附近的家中。他从那里很少去巴黎参加科学院或经度局的会议。

Hippolyte Fizeau was the eldest son of Béatrice and Louis Fizeau. His father Louis Fizeau, coming from a family many generations of which had been doctors, was Professor of Pathology at the Paris Medical School. It was certainly expected that Hippolyte would follow in the family tradition and enter the medical profession - anything else would have been unthinkable. He attended the prestigious Collège Stanislas in Paris where he was friendly with one of his fellow students Léon Foucault.

An important event, which was to have a marked affect on Fizeau's future, happened in September 1839. Louis-Jacques Daguerre put on a free course on his new photographic techniques in Paris and the two friends Fizeau and Foucault attended. They watched Daguerre expose a plate in a camera pointing out the window, then after talking about his process for about 30 minutes, he developed the plate using a variety of chemicals to reveal the picture. Although Fizeau and Foucault were impressed they also realised the limitations of the process - it would be wonderful to be able to take portraits, they thought, but the subject could not be expected to remain motionless for 30 minutes. After the course ended they began to experiment to try to speed up the process, and Fizeau had the idea of sensitizing the plate using bromine. Experimentation led to them reducing the exposure time from 30 minutes to 20 seconds. The discovery did not have the impact that it might, however, for other photographic methods were coming into use.

After an excellent education at the Collège Stanislas, Fizeau entered the Paris Medical School in 1840. However, he suffered severe migraines and decided to give up medicine. He spent a while travelling during which time he regained his health, then he turned to physics. He attended Arago's lectures at the Observatory, and enrolled in a course on optics at the Collège de France given by the famous Henri Victor Regnault. Fizeau had another method of building up his knowledge of mathematics and physics, which was to make a deep study of the notebooks containing the lecture notes taken by his brother who attended courses at the École Polytechnique. Arago was aware of the great scientific potential of the new methods of photography and, in particular, he was aware of the advances made by Fizeau and Foucault. He approached the two friends in 1845 and suggest that they might attempt to make photographs of an image of the sun produced by a telescope. They were highly successful and produced the first ever photograph of the sun. It clearly shows groups of sunspots.

In 1842 Doppler had published On the coloured light of the double stars and certain other stars of the heavens which presented for the first time the Doppler principle which relates the frequency of a source to its velocity relative to an observer. However, Fizeau was unaware of Doppler's work and in 1848 gave a similar explanation of the shift in wavelength in light coming from a star [2]:-

Fizeau, however, predicted that subtle displacements of the absorbsion lines in stellar spectra could be used to measure much smaller [than suggested by Doppler] celestial velocities, and the motion of the terrestrial observer, and this correct prediction underpins much of modern astrophysical inquiry.

Arago was delighted with the success of Fizeau and Foucault in photographing the sun, and suggested to them that they try to calculate the speed of light with an earth based experiment. The only previous calculation had been by Rømer using the moons of Jupiter. Arago was also interested in whether light travelled more slowly or more quickly through water than through air since this was a crucial test of whether light was corpuscular or a wave. Both Fizeau and Foucault had their own ideas how to proceed and after an initial period working on this together they split up. In July 1849 Fizeau set up a mirror at his parents' home at Suresnes and another on Montmartre, the hill on the right bank of Paris. These were 8633 metres apart. Between them he set up a rapidly rotating toothed wheel and determined the speed of rotation necessary for the time taken by the light travelling between the mirrors to equal the time taken for the wheel to rotate by one tooth. He was thus the first to make a successful terrestrial measurement of the velocity of light. We know today that the value he found was almost as accurate as Rømer's astronomical measurement having an error of about 5%. In April 1850 Foucault became the first to show that light travelled more slowly in water than in air - Fizeau confirmed this result with his apparatus seven weeks later. In 1851 Fizeau tried to measure the passage of the earth through the ether and achieved a negative result. This was an important first step in a rather lengthy process which eventually led to the discarding of the ether hypothesis in the early years of the 20th century. Melcher writes that [9]:-

... written testimony by Einstein exists which verifies the influence of Michelson's experiments on the former's work. Since Einstein frequently referred to the Fizeau experiment (1851) which Michelson had repeated in 1886, but more recent literature often cites Hoek's experiment (1868) instead, we finally analyze these experiments and their historical significance.

While we are considering this aspect of Fizeau's contributions, we note the interesting article [6] which discusses sealed letters by Fizeau and Foucault which were only studied in 1983. We quote from Costabel's summary:-

Sealed Letter No. 1002, deposited by Foucault on May 27, 1850 and opened on February 23, 1983, ... reveals that Foucault once collaborated in his laboratory with Fizeau in testing ether drag by transparent bodies. ... The integral text of Fizeau's memoir of September 29, 1851, when reread in the light of this first, unsatisfactory project, is indicative of a new approach. This therefore ... sheds light on the importance of a moment in history, in the intertwining of hypotheses and 'decisive' experiments concerning the undulatory nature of light and the motion of the Earth.

Fizeau was made a knight of the Légion d'Honneur in 1849. In 1853 he married Thérèse Valentine de Jussieu, a daughter of famous botanist Adrien de Jussieu; they had two daughters and one son. He had attempted to gain membership of the Academy of Sciences in March 1851. Fifty-two members of the Academy voted in a secret ballot to elect one of seven candidates. In the first round he was fourth equal with eight votes and dropped out in later ballots. Foucault, who was also one of the seven candidates, fared better but was not elected. Fizeau was elected to the Academy of Sciences on 2 January 1860, rather surprisingly before Foucault who was not elected until 1865. He had been earlier honoured by the Institut de France when it awarded him the Triennial Grand Prix on 9 July 1856. Further honours were to follow when, in particular, he was awarded the Rumford Medal of the Royal Society in 1866, then elected an a foreign member in 1875. In 1877 he became vice-president of the Physics Section of the Academy of Sciences, then President of the Section in the following year. In his Presidential address he spoke of [8]:-

... the dignity and independence of natural science as well as to its limits of action, preventing it from interfering in philosophic or social questions, and not permitting it to put itself in opposition to the noble emotions of the heart nor to the pure voice of conscience.

Also in 1878 he became a member of the Bureau des Longitudes. Thérèse died young and after this Fizeau retired to his home near Jouarre. From there he rarely went into Paris for meetings of the Academy or of the Bureau des Longitudes.