杰雷米亚·霍罗克斯Jeremiah Horrocks

杰雷米亚·霍罗克斯的母亲是Mary Aspinwall，而他的父亲是个农民，记录中 variously 为William Horrocks或James Horrocks。有一些证据表明霍罗克斯的父亲来自博尔顿的Deane区，尽管这远非确定，但我们确实知道他的母亲来自一个著名的Toxteth Park家族。当然，家族中有些成员是钟表匠，据说Mary Aspinwall的一个钟表匠兄弟首先使霍罗克斯对天文学产生了兴趣。我们没有关于家庭规模的确定信息，尽管我们确实知道霍罗克斯有一个名叫Jonas的兄弟。

我们对霍罗克斯的早期教育一无所知，但我们确实知道他于1632年5月11日进入剑桥大学伊曼纽尔学院。如此年轻的年龄，只有十三或十四岁，可能会让我们再次核对他出生的日期。我们应该解释一下，我们是从确知的去世日期以及他去世时22岁的报道推断出他的出生年份的。一些历史学家给出1617年，另一些给出1619年作为他的出生年份。然而，我们不应因为他十三或十四岁进入剑桥而怀疑他的出生日期，因为这在当时是开始大学教育的常见年龄。他进入剑桥时是一名减费生（Sizar），这意味着他没有能力养活自己，并被赋予特定的卑贱职责以补偿学费的减免。

尽管没有霍罗克斯大学教育的记录，我们知道当时所有学生都学习一套固定课程，涵盖古典语言、文学和神学。课程中很小的一部分会涵盖欧几里得的Elements和克劳狄乌斯·托勒密的天文学。由于霍罗克斯离开剑桥时，因尼古拉·哥白尼和约翰内斯·开普勒而对天文学的最新思想有深入的了解，并且具备进一步发展他们思想的数学专业知识，这告诉我们他在自己的时间里学习了数学和天文学。他于1635年离开剑桥，回到Toxteth Park。他没有在剑桥毕业，但这与他的经济状况相符，许多贫穷的学生没有学位就离开大学，因为他们负担不起毕业的费用。

回到兰开夏郡后不久，霍罗克斯 就开始与曼彻斯特附近布劳顿的商人 William Crabtree 进行科学通信。西德尼·查普曼 认为，曼彻斯特的 弗瑞兹·约翰 Worthington 很可能把 霍罗克斯 和 Crabtree 引见给了彼此；Worthington 与 霍罗克斯 同时在剑桥读本科。到 1639 年 6 月 8 日，霍罗克斯 已在普雷斯顿附近的 Much Hoole 村，因为我们有他从那个村子写出的通信副本。他本人这样描述 Much Hoole：-

……一个不起眼的村庄……在利物浦以北约十五英里处。

他很可能去Much Hoole担任助理牧师，并给Stones家的孩子们当家庭教师；若是如此，他就会住在Stones家族的住所Carr House。

1635年，霍罗克斯开始使用菲利普·范·兰斯贝尔热的表格来计算行星位置，并将结果与自己的观测进行比较。他很快发现菲利普·范·兰斯贝尔热的表格存在严重错误，并意识到这些表格基于错误的行星理论。他转向约翰内斯·开普勒于1627年出版的Tabulae RudolphinaeⓉ（《鲁道夫星表》）。将理论位置与自己的观测进行比较后，他意识到这些表格是迄今为止最准确的，并且基于正确的行星理论。因此，他接受了约翰内斯·开普勒的行星椭圆轨道理论，并通过直接观测检验了约翰内斯·开普勒的定律。然而，他拒绝了约翰内斯·开普勒关于行星轨道为何是椭圆的理论，该理论基于太阳对行星的交替吸引和排斥。

霍罗克斯随后提出，行星有一种朝太阳坠落的倾向。他写道：-

太阳的转化使行星偏离这条直线，把它的运动塑造成圆周，但行星先前想沿直线运动的愿望妨碍了太阳的完全征服，并迫使它进入椭圆形状。

他不满足于没有证据的理论，便用圆锥摆作类比来支持它。他指出，如果把摆锤拉向一侧再释放，它就会沿椭圆路径运动，而且长轴会沿旋转方向转动，正如月球轨道的拱点那样。他还正确地断言，彗星和月球都沿椭圆轨道运行。此时，凭借更深的理解，霍罗克斯着手改进约翰内斯·开普勒的表格。约翰内斯·开普勒曾预言1631年会发生一次金星凌日，1761年还会发生一次。约翰内斯·开普勒已于1630年去世，但即使他活着，也看不到1631年的凌日，因为凌日期间太阳在地平线以下，欧洲看不到。霍罗克斯在修正约翰内斯·开普勒的表格后意识到，1639年11月24日会发生一次金星凌日，而且从英格兰可以看到。他写信给朋友Crabtree，两人都计划观测这次凌日。霍罗克斯买了一架简易望远镜，把它架设起来，将太阳的像投射到一个直径六英寸的分度圆上。

霍罗克斯在Venus in Sole Visa中写道（见[8]）：-

我在24日从日出到九点，以及从十点稍前到正午，还有下午一点，都仔细地进行了观察，期间因极其重要的事务而被叫走，对于这些装饰性的追求，我不能失礼地忽视。但在整个这段时间里，我在太阳中除了一个小的普通黑点外什么也没看到……这显然与金星无关。下午三点十五分过后，当我再次有空继续我的工作时，云层仿佛由于神圣的干预而完全消散，我再次被邀请去执行重复观察的愉快任务。然后我看到了一幅最令人愉快的景象，我热切愿望的目标，一个大小异常且形状完美的圆形黑点，它已经完全居中于太阳圆面的左侧，因此太阳和金星的边缘精确重合，形成了一个接触角。毫不怀疑这确实是该行星的阴影，我立即专心致志地观察它。

霍罗克斯能够从他的观察中做出一些推论，这些推论大大改进了数据。他给出了金星视直径的极好数值，远优于之前发现的任何数值。他还能够为金星的轨道提供大大改进的数据，找到了轨道半径、偏心率和黄道倾角的更好数值。尽管他只能在同一个地点进行三次凌日观察，霍罗克斯仍能够计算出地球到太阳的距离，远比之前发现的任何数值都更准确。他的[8]数值：-

……至少15000个地球半直径。

给出大约60000000英里（正确值是93000000）。

我们收到的霍罗克斯最后一封写于Much Hoole的信是在1640年4月20日。此后不久，他回到Toxteth，在那里写下了我们上面引用的Venus in Sole Visa。尽管他最著名的是1639年对金星凌日的观测，但霍罗克斯最重要的工作是他的月球理论。他意识到月球轨道受到太阳的扰动（记住，他是在艾萨克·牛顿提出万有引力理论之前工作的），并能够给出一个比当时任何可用理论都好得多的月球理论。事实上，霍罗克斯的月球理论被使用了大约100年，这是一项非凡的成就。在[16]中有详细描述，Wilson在其中追溯了霍罗克斯理论在约翰内斯·开普勒关于月球运动的工作中的起源，以及如何通过进一步的数据，特别是关于月食持续时间的关键数据，进行转换和校准。最终理论包括通过可变偏心率和振荡拱线来解释取决于月球距角和近点角的差。

我们对霍罗克斯在22岁去世所知的一切，就是Crabtree在一捆霍罗克斯的信件上写下的内容：-

霍罗克斯在1638年、1639年、1640年直到他去世那天给我的信，他于1月3日[1641年]早晨非常突然地去世；前一天他还安排要来找我。就这样，上帝终结了一切世俗事务。唉，我失去了我亲爱的霍罗克斯。Hinc illae lachrimae [因此泪水落下]。无法弥补的损失。

Applebaum在[1]中写道：-

霍罗克斯的论文在他家人手中只停留了很短时间。其中一部分在英国内战期间被毁，一部分被一个兄弟[Jonas]带到爱尔兰，此后就再也没人见过，还有一部分在1666年的大火中被毁。剩下的部分落到了一个古物研究者手中，他还设法从Crabtree家族那里得到了霍罗克斯的信件。从17世纪50年代末直到最终出版，霍罗克斯的手稿广为流传。最先付印的是他关于凌日的论著《Venus in Sole Visa》Ⓣ（太阳中的金星），由Hevelius于1662年出版。新成立的皇家学会承担了其余大部分内容的出版责任，于1672-73年以《Opera posthuma》Ⓣ（遗著）为名出版。

Jeremiah Horrocks' mother was Mary Aspinwall, while his father, who was a farmer, is variously recorded as William Horrocks or James Horrocks. There is some evidence that Horrocks' father came from the Deane district of Bolton, although this is far from certain, but we do know that his mother was from a notable Toxteth Park family. Certainly some members of the family were watchmakers and it is said that a watchmaker brother of Mary Aspinwall first interested Jeremiah in astronomy. We have no certain information concerning the size of the family, although we do know that Jeremiah had a brother named Jonas.

We know nothing of Horrocks' early education, but we do know that he entered Emmanuel College, Cambridge, on 11 May 1632. This young age, only thirteen or fourteen, might make us double check the date of his birth. We should explain that we have deduced the year of his birth from the certain knowledge of the date of his death, and a report that he died at the age of 22. Some historians give 1617 and others give 1619 as the year of his birth. However, we should not be suspicious of the date of his birth on account of his entering Cambridge at the age of thirteen or fourteen since this was a common age to begin a university education at this time. He entered Cambridge as a Sizar which means that he did not have the means to support himself and was given specific menial duties to compensate for a reduction in the fees.

Although no record of Horrocks' university education exists, we know that at this time all students studied a set course which covered classical languages, literature, and divinity. A very minor part of the course would cover Euclid's Elements and Ptolemy's astronomy. Since Horrocks left Cambridge with a deep knowledge of the latest ideas in astronomy due to Copernicus and Kepler, as well as the expertise in mathematics to further develop their ideas, this tells us that he studied mathematics and astronomy in his own time. He left Cambridge in 1635 and returned to Toxteth Park. He did not graduate at Cambridge, but this is consistent with his financial status and many poor students left university without a degree since they could not afford the cost of graduation.

Soon after his return to Lancashire, Horrocks began a scientific correspondence with William Crabtree a merchant in Broughton, near Manchester. Chapman suggests that John Worthington of Manchester, who had been an undergraduate at Cambridge at the same time as Horrocks, probably introduced Horrocks and Crabtree. By 8 June 1639 Horrocks was in the village of Much Hoole, near Preston, since we have copies of correspondence he wrote from that village. He himself describes Much Hoole as:-

... an obscure village ... about fifteen miles to the north of Liverpool.

It is probable that he went to Much Hoole as a curate and to act as a tutor to the children of the Stones family, and if so he would have lived at Carr House, the Stones family residence.

In 1635 Horrocks began to use Lansberge's tables to compute planetary positions and to compare the answers with his own observations. He soon discovered that Lansberge's tables were seriously wrong and he realised that the tables were based on a false planetary theory. He turned to Kepler's Tabulae Rudolphinae Ⓣ which had been published in 1627. Comparing the theoretical positions with his own observations he realised that these were by far the most accurate tables and that they were founded on a correct planetary theory. He therefore accepted Kepler's theory of elliptical orbits for the planets and tested Kepler's laws by direct observation. However he rejected Kepler's theory of why the planetary orbits were ellipses, which was based on alternate attraction and repulsion of a planet by the sun.

Horrocks then proposed that the planets had a tendency to fall towards the sun. He wrote:-

The sun's conversion doth turn the planet out of this line framing its motion into a circle, but the former desire of the planet to move in a straight line hinders the full conquest of the sun and forces it into an elliptical figure.

Not content with this theory without evidence, he supported it by analogy with the conical pendulum. He noted that if the bob was drawn back and released then it followed an elliptical path, and moreover the major axis rotated in the direction of revolution exactly as did the apsides of the moon's orbit. He also claimed, correctly, that comets and the moon followed elliptical orbits. Now with his greater understanding, Horrocks set to work improving Kepler's tables. Kepler had predicted a transit of Venus would occur in 1631, and that another would occur in 1761. Kepler had died in 1630 but even if he had lived he would not have seen the transit of 1631 since it was not visible in Europe as the sun was below the horizon during the transit. Horrocks, after correcting Kepler's tables realised that a transit of Venus would occur on 24 November 1639, and that it would be visible from England. He wrote to his friend Crabtree and both planned to observe the transit. Horrocks purchased a simple telescope which he set up to project an image of the sun onto a graduated circle six inches in diameter.

Horrocks wrote in Venus in Sole Visa (see [8]):-

I watched carefully on the 24th from sunrise to nine o'clock, and from a little before ten until noon, and at one in the afternoon, being called away in the intervals by business of the highest importance which, for these ornamental pursuits, I could not with propriety neglect. But during all this time I saw nothing in the sun except a small and common spot ... This evidently had nothing to do with Venus. About fifteen minutes past three in the afternoon, when I was again at liberty to continue my labours, the clouds, as if by divine interposition, were entirely dispersed, and I was once more invited to the grateful task of repeating my observations. I then beheld a most agreeable spectacle, the object of my sanguine wishes, a spot of unusual magnitude and of a perfectly circular shape, which had already fully centred upon the sun's disc on the left, so that the limbs of the Sun and Venus precisely coincided, forming an angle of contact. Not doubting that this was really the shadow of the planet, I immediately applied myself sedulously to observe it.

Horrocks was able to make some deductions from his observations which gave greatly improved data. He gave an excellent value for the apparent diameter of Venus, far superior to any previously found. He was also able to give greatly improved data for the orbit of Venus, finding better values for the radius of the orbit, its eccentricity and inclination to the ecliptic. Although he had only been able to make three observations of the transit from the same site, Horrocks was able to compute the distance of the earth to the sun far more accurately than any previously found. His value of [8]:-

... at least 15 000 semidiameters of the earth.

gives around 60 000 000 miles (the correct value is 93 000 000).

The last letter we have from Horrocks written in Much Hoole was on 20 April 1640. Shortly after that he returned to Toxteth where he wrote Venus in Sole Visa from which we quoted above. Although he is best known for his observations of the transit of Venus in 1639, Horrocks' most important work was his lunar theory. He realised that the moon's orbit was perturbed by the sun (remember that he worked before Newton proposed his theory of universal gravitation) and was able to give a lunar theory which was much better than anything available at the time. In fact Horrocks' lunar theory was used for around 100 years, a remarkable achievement. It is described in detail in [16] where Wilson traces the origin of Horrocks' theory in Kepler's work on the motion of the moon, as transformed and calibrated by further data, in particular critical data concerning the duration of lunar eclipses. The final theory includes an explanation of the inequality depending on both elongation and anomaly of the moon by means of a variable eccentricity and an oscillating apse line.

All we know of Horrocks' death at the age of 22 is what Crabtree wrote on a bundle of Horrocks' letters:-

Mr Jeremiah Horrocks's letters to me for the years 1638, 1639, 1640 up to the day of his death, very suddenly, on the morning of the 3rd January [1641]; the day before he had arranged to come to me. Thus God puts an end to all worldly affairs. I have lost, alas, my dear Horrocks. Hinc illae lachrimae [thus the tears fall]. Irreparable loss.

Applebaum writes in [1]:-

Horrocks' papers remained with his family but a short time. Part of them were destroyed in the course of the English civil war, part were taken by a brother [Jonas] to Ireland and never seen thereafter, and still another portion was destroyed in the Great Fire of 1666. The remainder passed into the hands of an antiquary, who also managed to obtain letters by Horrocks from the Crabtree family. From the late 1650's until their eventual publication, Horrocks' manuscripts were widely circulated. the first part to be printed was his treatise on the transit, "Venus in Sole Visa" Ⓣ, which was published by Hevelius in 1662. The newly founded Royal Society assumed responsibility for publication of most of the remainder as "Opera posthuma" Ⓣ in 1672-73.