弗朗西斯科·马里亚·格里马尔迪Francesco Maria Grimaldi

弗朗西斯科·马里亚·格里马尔迪出生于一个富裕家庭。他的父亲帕里德格里马尔迪是一位出身贵族的丝绸商人，于1589年移居博洛尼亚。他在博洛尼亚结婚，但妻子去世时这对夫妇没有孩子。大约在1614年，帕里德格里马尔迪娶了他的第二任妻子安娜·卡塔尼，她拥有一家从祖父那里继承来的药房。格里马尔迪是他父母六个儿子中的第四个，其中五个存活下来。他有两个哥哥（一个孩子已夭折），与他最亲近的是文琴佐格里马尔迪，几乎正好比他大一岁。当格里马尔迪还很小的时候，他的父亲去世了，那时他的母亲接管了家族药房的经营。格里马尔迪和他的兄弟文琴佐都于1632年3月18日加入了耶稣会。

我们不知道格里马尔迪学习过的所有地方，特别是我们不确定他在1632-34这两年在哪里度过，尽管最有可能是在诺韦拉拉。我们确知的是，1634年他在诺韦拉拉，位于雷焦艾米利亚以北约20公里处，他住在1571年为培训耶稣会初学生而设立的房子里。1635年，他去了帕尔马，位于诺韦拉拉以西仅30多公里处，在那里他开始学习哲学。耶稣会在帕尔马经营着三个教育机构：大学、一所教育贵族子弟的学院，以及一所约建于1600年的耶稣会学院，格里马尔迪就读于后者。除了哲学和神学的高级课程外，该学院还提供语法和修辞学的低级课程。然而，他在帕尔马待了不到一年就被转到博洛尼亚完成哲学学习的第一年。他学习哲学的第二年，1636-37年，是在费拉拉度过的，之后他回到博洛尼亚在1637-38学年完成三年课程。完成三年哲学课程后，他从1638年到1642年在博洛尼亚的圣卢西亚学院教授修辞学和人文学科四年。格里马尔迪于1635年在帕尔马由乔万尼·巴特斯达·里奇奥利教授，两人于1636年同时搬到博洛尼亚。然而，当格里马尔迪回到博洛尼亚并于1640年在那里任教时，他开始协助乔万尼·巴特斯达·里奇奥利进行实验。格里马尔迪在乔万尼·巴特斯达·里奇奥利的指导下工作，从阿西内利塔上扔下重物，并用摆测量它们下落的时间。乔万尼·巴特斯达·里奇奥利希望由格里马尔迪进行的实验能反驳伽利略的理论，从某种意义上说确实如此。让我们更详细地看一下这个实验。

格里马尔迪和乔万尼·巴特斯达·里奇奥利通过让一个摆摆动24小时（以恒星大角星穿过子午线来测量）来校准它。他们用这个3英尺长的摆来校准一个较短的摆用于计时。然后格里马尔迪从阿西内利塔的不同高度丢下木球和铅球。为了提高准确性，他们还让一群会唱歌的修士随着摆的摆动吟唱来辅助计时，这是一个很好的补充。实验并未证实伽利略的结果，因为正如人们可能预料的那样，在塔上不同高度进行的所有实验中，铅球都比木球先到达地面[11]：-

正如大家所预料的那样，伽利略被否定了。当从同一高度落下时，铅球总是比木球先着地。实验与伽利略关于它们同时到达底部的说法之间的差异如此之大，以至于格里马尔迪推测伽利略一定知道这一点，但为了确保一个对他来说比真理更珍贵的命题而隐瞒了他的知识。

在接下来的几年里，格里马尔迪继续学习，但也工作，特别是与乔万尼·巴特斯达·里奇奥利一起进行天文研究。他在1642年至1645年间学习神学，接着进行进一步的哲学研究，这使他在1647年获得了博士学位。然后他开始教授哲学，但不到一年后，他改变了主题，开始教授数学。目前尚不完全清楚是什么促使了这一变化。许多历史学家认为，主题的改变是健康问题的结果，他发现教数学比教哲学要求更低。然而，这似乎有些不太可能，看来他可能是因为他的观点过于“现代”而被排挤出哲学教学。记住，他仍然处于耶稣会教育体系内。当然，乔万尼·巴特斯达·里奇奥利，他为格里马尔迪写了讣告，明确指出：-

……格里马尔迪为教授数学的所有分支做好了充分准备：几何学、光学、日晷学、静力学、地理学、天文学和天体力学。

格里马尔迪于1651年5月1日被任命为牧师。同年，乔万尼·巴特斯达·里奇奥利出版了Almagestum novumⓉ（一部新的《天文学大成》），其中他将超过40个不同实验的来源归功于格里马尔迪。例如，描述了从阿西内利塔扔下重物的实验，以及向不同方向发射炮弹的实验。最后一个实验引用如下[11]：-

弗朗西斯科格里马尔迪神父设计的反对地球周日和周年运动的论点，基于向北、向东和向西发射的炮弹。

作为另一个例子，我们再次引用Almagestum novumⓉ（一部新的《天文学大成》）[11]：-

格里马尔迪和我发明了一种借助望远镜可靠测量恒星视直径的方法。

当然，这种“可靠方法”不过是望远镜的一种性质，测量的是恒星的亮度而非直径。由于相信自己在测量直径，他们以及当时的其他人对恒星的实际大小产生了完全错误的认识。格里马尔迪和乔万尼·巴特斯达·里奇奥利的天文观测是在博洛尼亚的圣卢西亚学院设立的一座天文台进行的。在Almagestum novum乔万尼·巴特斯达·里奇奥利中，他感谢了“勤勉、审慎而忠实”的格里马尔迪。他说自己年事已高，无法亲自进行所需的深夜观测，因此不得不依赖他年轻的合作者格里马尔迪。Almagestum novumⓉ（一部新的《天文学大成》）中另一个重要章节展示了由格里马尔迪绘制的月面图，其中包含月面上主要特征的名称，这些特征以著名科学家（尤其是天文学家）命名，这些名称沿用至今[1]：-

一项特别值得注意的贡献是他绘制的月面图，这是根据对许多月相的望远镜观测综合而成的，其精确和正确程度足以说明他必定在目镜上使用了十字丝和测微计。

格里马尔迪从事的另一个项目是利用三角测量确定博洛尼亚的子午线。他再次与乔万尼·巴特斯达·里奇奥利合作，但此外还得到了奥维迪奥·蒙塔尔比尼（1601-1672）和乔凡尼·多美尼科·卡西尼的协助。蒙塔尔比尼是博洛尼亚大学教授兼该校科学博物馆馆长；乔凡尼·多美尼科·卡西尼则在博纳文图拉·卡瓦列里去世后于1650年被任命为博洛尼亚大学数学教授。该项目于1655年完成，结果仍由乔万尼·巴特斯达·里奇奥利发表在Geographiae Hydrographiae ReformataeⓉ（《地理学与水文学改革》）（1661）中。格里马尔迪进行了大量观测，其恒星观测数据发表在乔万尼·巴特斯达·里奇奥利的Astronomia ReformataⓉ（《天文学改革》）（1665）中。

现在，尽管我们已经给出了相当多关于格里马尔迪工作的信息，但到目前为止我们提到的所有内容都发表在乔万尼·巴特斯达·里奇奥利的著作中。事实上，格里马尔迪生前没有以他自己的名字发表过任何著作。他在45岁时因突发疾病去世，但他生命中的最后十年一直在对光的性质进行卓越的研究。他关于光的工作如此新颖，以至于其影响远小于人们可能预期的。他在去世前不久完成了Physico-Mathesis de Lumine的写作，该书于1665年出版。这部著作是格里马尔迪试图确定光是实体还是另一种实体的性质。他以一种相当不寻常的方式做到这一点。这篇论著由两本书组成，第一本提出光是实体的论据，尽管它有时也提出相反的观点，而第二本书则论证光是另一种实体的性质。格里马尔迪明确表示他自己的观点是光不是实体，并且他认为第二本书中的论据使光是一种性质成为可能。然而，两本书都有一个共同特点；它们都反对光的微粒说。

第1卷以描述格里马尔迪最著名的发现即光的衍射开始。他制作了一个针孔，让太阳光通过它进入暗室并落在屏幕上。屏幕是倾斜的，因此光在屏幕上产生一个椭圆形图像。他在光路中放置了一根细杆，并测量屏幕上阴影的大小。他发现阴影比根据光束的锥形性质所应有的大小更大。由此他论证说，如果光由微粒组成，这种效应就不可能发生，因此光必定具有一种绕过物体弯曲的流体形式。他还注意到杆的阴影附近有彩色条带。每条带有三个组成部分：一个宽的白色中央部分，在靠近阴影的一侧有一条窄的紫色带，在远离阴影的一侧有一条窄的红色带。接着他描述了在光锥路径中放置与杆形状不同的障碍物所产生的效应。衍射这个名称是格里马尔迪选定的，因为这种效应使他想起流动的流体在路径中放置一根细棍时如何分开——拉丁语diffractio意为“裂开”。在讨论衍射之后，他研究了干涉：让光通过两个针孔进入暗室，并观察图像在屏幕上何处重叠。他宣布了以下命题：-

一个实际被照亮的物体，若向其已经接受的光中再加入新的光，可能会变得暗淡。

格里马尔迪处理了反射、折射和光的传播。我们到目前为止所描述的内容占了第一卷的大约一半。本卷的后半部分涉及颜色和彩虹。

也许令人惊讶的是，格里马尔迪的论著很少有人阅读，但他关于衍射的重要结果却由其他人广泛传播。A Rupert Hall写道[13]：-

格里马尔迪的实验和思想由其他人传播，尤其是里昂的耶稣会士Honoré Fabri（1607-88），此人的著作，特别是关于纯数学的著作，广为人知。艾萨克·牛顿根据他自己的确认，是从Fabri的《Dialogi physici》（1669）中的第一段对话了解到衍射效应的。

Honoré Fabri的Dialogi physici sex quorum primum est de LumineⓉ（关于物理学的六段对话：第一段是关于光的）的第一段对话有96页，包含对格里马尔迪实验的描述。然而，Fabri不相信格里马尔迪对所获结果的“解释”，并试图给出自己的诠释。格里马尔迪的实验在影响艾萨克·牛顿的工作方面的重要性由Roger Stuewer在[15]中讨论。值得注意的是，格里马尔迪解释衍射的尝试是不正确的，正如直到19世纪Joseph von Fraunhofer（1787-1826）之前每一位科学家的尝试一样。

Francesco Grimaldi was born into a well-off family. His father, Paride Grimaldi, was a silk merchant of noble birth who had moved to Bologna in 1589. He married in Bologna, but the couple were childless when his wife died. In about 1614, Paride Grimaldi married his second wife, Anna Cattani, who owned a chemist shop which she had inherited from her grandfather. Francesco was the fourth of his parents six sons, five of whom survived. He had two older brothers (one child having died), the one that he was closest to being Vincenzo Maria Grimaldi who was almost exactly one year older. When Francesco was still quite young, his father died and, at that time, his mother took over running the family chemist shop. Francesco and his brother Vincenzo both joined the Society of Jesus (the Jesuits) on 18 March 1632.

We do not know all the places where Grimaldi studied, in particular we are unsure where he spent the two years 1632-34 although it was most likely in Novellara. We know for certain that in 1634 he was in Novellara, about 20 km north of Reggio dell'Emilia, where he lived in the house which had been set up in 1571 for training Jesuit novices. In 1635 he went to Parma, just over 30 km to the west of Novellara, where he began his study of philosophy. The Jesuits ran three educational establishments in Parma, the university, a college for educating the sons of the nobility, and a Jesuit College, established around 1600, which Grimaldi attended. In addition to advanced courses in philosophy and theology, the College provided lower level courses in grammar and rhetoric. However, he was in Parma for less than a year before he was transferred to Bologna to complete his first year of study of philosophy. His second year studying philosophy,1636-37, was spent at Ferrara before he returned to Bologna to finish the three year course in session 1637-38. Having completed the three year philosophy course, he taught rhetoric and humanities in the College of Santa Lucia at Bologna for four years from 1638 to 1642. Grimaldi was taught by Giovanni Battista Riccioli in Parma in 1635 and both had moved to Bologna at the same time in 1636. However, it was when Grimaldi returned to Bologna and was teaching there in 1640 that he began assisting Riccioli with experiments. Grimaldi, working under instruction from Riccioli, dropped weights from the Asinelli tower and timed their fall using a pendulum. Riccioli was hoping that the experiments conducted by Grimaldi would refute Galileo's theories, which in some sense they did. Let us look in a little more detail at the experiment.

First, Grimaldi and Riccioli calibrated a pendulum by getting it to swing for 24 hours (measured by the star Arcturus crossing the meridian line). They used this 3 foot pendulum to calibrate a shorter pendulum to use in timing. Then Grimaldi dropped balls of wood and of lead from various heights from the Asinelli tower. A nice addition to the accuracy was obtained by getting a group of musical monks to chant in time with the swinging pendulum to aid with the timing. The experiment did not confirm Galileo's result for, as one might expect, the lead balls reached the ground before the wood ones in all the experiments using different heights on the tower [11]:-

As everyone had expected, Galileo was disproved. The lead ball always hit the ground before the wooden one when they fell from the same height. The discrepancy between the experiment and Galileo's claim that they reached the bottom simultaneously was so great that Grimaldi supposed that Galileo must have known about it, but suppressed his knowledge in order to secure a proposition dearer to him than truth.

Over the next few years Grimaldi continued studying but also worked, particularly on astronomical investigations, with Riccioli. He studied theology between 1642 and 1645 going on to undertake further research on philosophy which led to him being awarded a doctorate in 1647. He then began to teach philosophy but, after less than a year, he had changed topics and began to teach mathematics. It is not entirely clear what prompted the change. Many historians suggest that the change of topic was a result of health problems, and he found teaching mathematics less demanding than teaching philosophy. However, this seems somewhat unlikely and it would appear that he may have been eased out of teaching philosophy due to his views being too "modern". Remember that he was still within the Jesuit educational system. Certainly Riccioli, who wrote an obituary of Grimaldi, states clearly that:-

... Grimaldi was well prepared to teach all branches of mathematics: geometry, optics, gnomonics, statics, geography, astronomy and celestial mechanics.

Grimaldi was ordained a priest on 1 May 1651. In the same year Riccioli published Almagestum novum Ⓣ in which he credited Grimaldi with being the source of over 40 different experiments. For example, the experiment of dropping weights from the Asinelli tower is described, and an experiment firing a cannon ball in different directions. This last experiment is quoted as follows [11]:-

The argument against the Diurnal and Annual Motion of the Earth devised by Father Francisco Maria Grimaldi based on a cannon ball fired into the North, and into the East and West.

As another example, we quote again from Almagestum novum Ⓣ [11]:-

P Francisco Maria Grimaldi and I have developed a method for reliably measuring the apparent diameters of the stars by means of a telescope.

Of course, this "reliable method" is no more than a property of the telescope and is measuring the brightness rather than the diameter of the stars. Believing that they were measuring diameters caused them, and others at this time, to have completely incorrect idea of the actual sizes of the stars. Grimaldi and Riccioli's astronomical observations had been made in an observatory set up at the College of Santa Lucia in Bologna. In the Almagestum novum Riccioli thanks the "diligent, prudent, and faithful" Grimaldi. He says that he was too old to conduct the required late-night observations himself, so he had to rely on his young collaborator Grimaldi. Another important chapter in Almagestum novum Ⓣ presented maps of the moon's surface made by Grimaldi and containing names for the major features on the surface, named after famous scientists (particularly astronomers), which have been adopted today [1]:-

An especially noteworthy contribution was his selenograph of the moon, a composite from telescopic observations of many phases, accurate and correct enough so that he must have used crossed hairs and a micrometer with his eyepiece.

Another project on which Grimaldi worked was a survey, using triangulation, to determine a meridian line for Bologna. Again he collaborated on this with Riccioli but, in addition, he was assisted by Ovidio Montalbini (1601-1672), a professor at Bologna University and the custodian of its science museum, and Giovanni Domenico Cassini, who had been appointed as professor of mathematics at the University of Bologna in 1650 following the death of Bonaventura Cavalieri. The project was completed by 1655 and the results published, again by Riccioli, in Geographiae Hydrographiae Reformatae Ⓣ (1661). Grimaldi did a considerable amount of observing and the data from his observations of stars was published in Riccioli's Astronomia Reformata Ⓣ (1665).

Now although we have given quite a lot of information about Grimaldi's work, everything we have mentioned so far was published in works by Riccioli. In fact Grimaldi has no works published under his own name during his lifetime. He died of a sudden illness at the age of 45 but he had spent the last ten years of his life undertaking remarkable research on the properties of light. His work on light was so novel that it had a much smaller impact than one might have expected. He completed writing Physico-Mathesis de Lumine shortly before his death and it was published in 1665. The work is an attempt by Grimaldi to determine whether light is a substance or whether it is a quality of another substance. He does this in a rather unusual way. The treatise consists of two books, the first puts forward arguments that light is a substance, although it does sometimes put the opposing view, while the second book argues that light is a quality of another substance. Grimaldi makes it clear that his own view is that light is not a substance and he believes that the arguments in the second book make it probable that light is a quality. Both books, however, have a common feature; they both argue against a corpuscular theory of light.

Book 1 begins with a description of Grimaldi's most famous discovery, namely the diffraction of light. He created a pinhole through which he allowed light from the sun to enter a darkened room and fall on a screen. The screen was at an angle so that the light produced a elliptical image on the screen. He placed a thin rod in the path of the light and measured the size of the shadow on the screen. He discovered that the shadow was larger than it should have been given conical nature of the beam. From this he argued that this effect was impossible if light consisted of corpuscles so light must have a fluid form which bent round the object. He also noticed coloured bands near to the shadow of the rod. Each band had three components, a white broad central part with a narrow violet band on the side nearest the shadow with a narrow red band on its side furthest from the shadow. He then described what effect was produced by placing obstacles of a different shape from the rod in the path of the cone of light. The name diffraction was chosen by Grimaldi because the effect reminded him of how a flowing fluid splits apart when a thin stick is placed in its path - the Latin diffractio means to "break apart". After treating diffraction, he looked at interference by allowing the light to enter the darkened room through two pinholes and observing where the images overlapped on the screen. He announced with the following proposition:-

That a body actually enlightened may become obscure by adding new light to that which it has already received.

Next Grimaldi treated reflection, refraction, and the propagation of light. What we have so far described takes up about one half of the first book. The second half of this book is concerned with colours and the rainbow.

Perhaps surprisingly, Grimaldi's treatise was little read but his important results on diffraction were made widely known by others. A Rupert Hall writes [13]:-

Grimaldi's experiments and ideas were disseminated by others, not least by the Lyon Jesuit Honoré Fabri (1607-88), a man whose writings, especially those on pure mathematics, were well known. Isaac Newton, by his own affirmation, learnt of the diffraction effect from the first dialogue in Fabri's 'Dialogi physici' (1669).

Honoré Fabri's Dialogi physici sex quorum primum est de Lumine Ⓣ has as its first dialogue 96 pages containing the description of Grimaldi's experiments. Fabri, however, did not believe Grimaldi's "explanation" of the results obtained and attempted to give his own interpretation. The importance of Grimaldi's experiments in influencing the work of Newton is discussed by Roger Stuewer in [15]. It is worth noting that Grimaldi's attempt to explain diffraction was incorrect, as was the attempt of every scientist until Joseph von Fraunhofer (1787-1826) in the 19th century.