The Story of Astronomy

by Peter Aughton

  Undaunted by these setbacks Galileo started work on his next book. In this he had support from an old friend called Benedetto Castelli (1578–1643) who was appointed as the official mathematician to the pope and also had the approval and support of Cardinal Barberini (1568–1644). Galileo meant to call his book Dialogue on the Tides, but under pressure changed the title to Dialogue Concerning the Two Chief World Systems. The book’s subject was almost exactly what its title suggests, and was a trialogue with three main characters. One of the main characters was called Fillipo Salviati. He was a real person, an old friend of Galileo’s who had died in 1614 at the age of 31, and so could not be persecuted for his beliefs. In the book Salviati proposes Galileo’s views, putting forward the case for a heliocentric universe. He “uses” all the evidence that Galileo had collected from his study of Copernicus, from his own telescopic observations and from other sources. Salviati is, of course, essentially Galileo himself putting forward his own case for the system of the world—a heliocentric universe.

  The second character is called Giovanni Francesco Sagredo. He was also a real person and another friend of Galileo’s. He, too, had died before the book was written. In Galileo’s Dialogue Sagredo does not hold strong opinions about the system of the world, but merely acts as a kind of mediator in the discussion between the two other parties. The third character is called Simplicio. He is the defender of the geocentric universe theory in which all the heavenly bodies revolved around the Earth. It was an unfortunate but quite deliberate choice of name by Galileo for it suggested a simpleton, and although Simplicio puts forward some very clever ideas and reasons for his beliefs, he is consistently defeated in his arguments by the better-educated and well-informed Salviati. It was but a small step to associate Simplicio with Pope Urban VIII, and Galileo must have realized that the pope would be offended by the parody presented in his character, but he still went ahead with the publication.

  In Dialogue Salviati questions the shape of the Earth. He argues that it is a sphere just as the Sun and the Moon are spheres. Simplicio refutes the idea and quotes Aristotle as his authority:

  It is vain to inquire as you inquire, as you do, what part of the globe of the Sun or Moon would do if separated from the whole, because what you inquire would be the consequence of impossibility. For, as Aristotle demonstrates, celestial bodies are invariant, impenetrable and unbreakable; hence such a case could never arise. And even if it should, and the separated part should return to the whole, it would not return thus because of being heavy or light, since Aristotle also proves that celestial bodies are neither heavy nor light.

  This of course is exactly what Salviati, in the person of Galileo, wants to hear and he sets about deriding the attitude of the Greek scientists who were no more than armchair philosophers, too proud to take measurements or to seek out the truth for themselves.

  On Trial for Heresy

  The Dialogue was published in 1632. Galileo had no trouble getting his book past the Florentine censors, but when it reached Rome there was a sudden turn of the tide against him. Galileo knew he had enemies, but he thought that Barberini was on his side. Barberini, however, had become Pope Urban VIII in the 16 years since Galileo started writing his book, and now found the papal stance on the issue of what lay at the center of the universe ridiculed. Thus, although Galileo had gone to great lengths to obtain approval before publishing his views, he nevertheless found that his opponents were determined to trump up a charge against him. In September 1632 the holy office put Galileo on trial for heresy. He knew what had happened to Giordano Bruno and that he would face the Inquisition. He was found guilty of teaching the philosophy that the Earth moved. He was forced to read out a long and humiliating recantation of his views in the hall of the convent of Santa Maria Sopra Minerva before the entire congregation of the holy office. There may be no truth in the story that as he left the Inquisition the dispirited Galileo murmured “Eppur si muove” (And yet it moves), but the story is entirely in keeping with his views, and in the months that followed he must have said the words many times over to himself.

  Galileo’s trial for heresy proved to be just as disastrous for his accusers, the Catholic Church. The church was expected to defend the version of creation as told in Genesis, and the trial of Galileo was the first occasion on which anything so profound had ever challenged the literal truth of the story told in the Bible. History shows that Galileo was not guilty of heresy, but merely seeking the truth, and many years later the Vatican offered a long-overdue apology.

  Theologians had always argued and debated about the interpretation of the gospels, and this frequently led to the formation of new sects and religious orders. This was particularly true in the 16th century when the Protestants made the break with Rome. After this had taken place, astronomers in Protestant countries could build upon the work of Galileo without fear of persecution. Other evidence was waiting to undermine the church’s beliefs, however. For example, when geologists first began to challenge the age of the Earth from the dating of the rocks, and later in the 19th century when Charles Darwin first published his theory of evolution.

  8

  JEREMIAH HORROCKS

  Father of English Astronomy

  The story of astronomical discovery now moves to England where, free from the religious dogma that had bedeviled earlier Italian astronomers, scientists could build on theories such as heliocentrism. At the forefront of these endeavors was the momentous and prolific work of Jeremiah Horrocks, rightly described as “the father of English astronomy.”

  The Mersey spreading and presently contracting its stream from Warrington falls into the ocean with a wide channel very convenient for trade, where opens to view Litherpole, commonly called Lirpoole, from a water extending like a pool, according to the common opinion, where is the most convenient and most frequented passage to Ireland: a town more famous for its beauty and populousness than for its antiquity; its name occurs in no ancient writer except that of Roger of Poictou who was lord, as stated of Lancaster, built a castle here, the custody of which has now for a long time belonged to the noble and knightly family of Molineux … This Roger held, as appears in the Domesday book, all the lands between the rivers Ribble and Mersey.

  Once a Beautiful Landscape

  The above description of Liverpool, found in the journal Britannia compiled by historian William Camden (1551–1623), may not sound very much like the sprawling English city of today. The account was written in the 1580s when the population numbered less than a thousand. Early in the following century, when Jeremiah Horrocks (1618–41) was born there, the number of residents had still not reached four figures. When Camden praised Liverpool’s beauty he was not guilty of any form of flattery. By the standards of the times Liverpool was a very clean and attractive seaside town with fine beaches of golden sand. To the north there were virgin sand dunes that stretched nearly 20 miles (32 km) along the coast—much further than the eye could see. To the southwest lay the rural Cheshire peninsula of the Wirral, bounded by the River Mersey and the River Dee. The vista further south showed the snow-capped peaks of Snowdonia in Wales. To the north were the mountains of the Lake District, and on a clear day Snaefell and the mountains of the Isle of Man could be seen from higher vantage points.

  Near the castle there was a small natural inlet called the Liver Pool, and it was here that the shipping was accommodated. The pool was fed by a small stream, which ran through a leafy dale known as Dale Street. There was a small bridge giving access to the area “over the pool,” and here a small Puritan community had established itself in an area called Toxteth Park.

  The Puritans were tolerated in the England of the 1620s, but because of their unorthodox approach to religion they were not allowed to hold high public office. It was common, therefore, for them to put their energies into trade. Thus James Horrocks was a watchmaker and his wife Mary Aspinwall was the daughter of a watchmaker. This was a time long before the Industrial Revolution; Liverpool and Lancashire had n
ever yet seen a bale of cotton. It is very possible that the Horrocks and Aspinwall families were not only manufacturers of watches, but also dealers who marketed watches made in Nuremberg and other European centers.

  When their first son was born in 1618, James and Mary Horrocks christened him Jeremiah. The couple seemed to have a penchant for Old Testament prophets of doom, for when their second son was born three years later they called him Jonah. Both sons were expected to enter the family business, but Jeremiah showed an early interest in philosophy and other subjects beyond watch-making.

  A University Education

  At the age of 14, with the help of his family and the local minister, Richard Mather, Horrocks had acquired sufficient knowledge of the scriptures to gain a place at Emmanuel College, Cambridge—the most puritanical of the Oxbridge colleges. Horrocks did not go to Cambridge to study astronomy, however. At this time it was not possible to study the subject at Cambridge. There was no department of astronomy and no professor of astronomy. Indeed, there were very few who knew anything at all about the subject. One of Horrocks’ friends and contemporaries, John Wallis (1616–1703), who matriculated in the same year, arrived to study mathematics. The status of mathematics was much the same as that of astronomy, and Wallis described it:

  I did thenceforth prosecute it [mathematics], (at School and in the University) not as a formal study, but as a pleasing Diversion, at spare hours; as books of Arithmetick, or others Mathematical fell occasionally in my way. For I had none to direct me, what books to read, or what to seek, or what methods to proceed. For mathematics, (at that time with us) were scarce looked upon as Academicall studies, but rather mechanical; as the business of Traders, Merchants, Seamen Carpenters, Surveyors of Lands, of the like; and perhaps some Almanac-makers in London. And amongst more than Two hundred Students (at that time) in our College, I do not know of any Two (perhaps not any) who had more of Mathematics than I, (if so much) which was then but little; And but very few, in that whole University. For the study of Mathematics was at that time more cultivated in London than in the Universities.

  The same educational shortcomings could be leveled at astronomy. All undergraduates, if they were not of the aristocracy, were expected to train for the church and to become country parsons. The library shelves were straining with theological publications, but there was hardly a single volume on mathematics or astronomy. And yet, by the time he left Cambridge in 1635, Horrocks had read many of the latest astronomical publications and knew exactly what he wanted to do with his life. In Horrocks’ time the total complement of Emmanuel College was between 200 and 300 people. He would therefore have known all of his contemporaries. His closest friends were John Worthington and John Wallis. They both went on to become active members of the Royal Society. Amongst his other acquaintances was Ezekiel Cheever (c.1614–1708), the son of a London spinner educated at Christ’s Hospital School. Cheever entered as a sizar (an undergraduate who received aid from the college for maintenance in return for performing various duties) the year after Horrocks. He left for America in 1637 and became the best-known teacher in the early history of Massachusetts. Another, even better-known, contemporary was John Harvard (1607–38), who later emigrated to the New World. When he died, he left his substantial private library and half of his estate toward the foundation of a new college, later to be called Harvard College.

  Stars and Poetry

  In 1635, at the age of 17, Jeremiah Horrocks returned to his native Lancashire. He had decided that what he wanted from his life was to be able to study the stars and the planets. He needed books on astronomy to achieve his aims and he also needed instruments. The most important astronomical instrument of the day was the telescope; it had been in use for about 20 years and was beginning to become far more readily available. Horrocks tells us that he purchased a “half crown” telescope, probably at a local fair. He knew that better instruments were available, however, and in May 1638 he wrote that “I have at last obtained a more accurate telescope.”

  We now discover that Jeremiah Horrocks was more than simply an astronomer. He was also a poet. The most prominent astronomer before this time who could also claim to be a poet was the philosopher Omar Khayyam (1044–1122). But when it came to putting his thoughts into verse Jeremiah Horrocks was the equal of his Persian predecessor. He was very thrilled with his new telescope and wrote about it thus:

  Divine the hand which to Urania’s power

  Triumphant raised the trophy, which on man

  Hath first bestowed the wondrous tube by art

  Invented, and in noble daring taught

  His mortal eyes to scan the furthest heavens.

  Whether he seek the solar path to trace,

  Or watch the nightly wanderings of the Moon

  Whilst at her fullest splendour, no such guide

  From Jove was ever sent, no aid like this

  In brightest light such mysteries to display;

  Nor longer now shall man with straining eye

  In vain attempt to seize the stars. Blest with this

  Thou shalt draw down the Moon from heaven, and give

  Our Earth to the celestial spheres, and fix

  Each orb in its own ordered place to run

  Its course sublime in strict analogy.

  During his time at Cambridge, Horrocks corresponded with Herbert Gellibrand (1597–1637), the professor of astronomy at Gresham College in London. Gellibrand, acting in good faith, suggested to Horrocks that he purchase a copy of a book by a Belgian astronomer called Philip Lansberg (1561–1632). Horrocks followed this advice, and he spent the next year trying to fit his observed motions of the planets to Lansberg’s tables. Horrocks met with no success in this endeavor, but in 1636 he befriended a fellow amateur astronomer called William Crabtree (1610–44), who was working at Broughton near Manchester. It was Crabtree who suggested to him that he use the Rudolphine Tables, the work of Johannes Kepler and Tycho Brahe.

  The incident illustrates how long it took for scientific works to circulate in the early 17th century. Gellibrand apparently knew nothing of the works of Kepler and Brahe, or he would certainly not have recommended Lansberg’s tables to Jeremiah Horrocks. We now know that the Rudolphine Tables were far in advance of anything else available at that time, but the first people in England to use them were the amateur astronomers Jeremiah Horrocks and William Crabtree. The Copernican system also took a long time to circulate. The Ptolemaic system was still in use by the astrologers at this time, but Horrocks had little regard for it. He soon discovered that the Copernican system was far superior and he put his feelings into verse:

  Why should’st thou try, O Ptolemy, to pass

  Thy narrow-bounded world for aught divine?

  Why should thy poor machine presume to claim

  A noble maker? Can a narrow space

  Call for eternal hands? Will thy mansion

  Suit great Jove? or can he from such a seat

  prepare his lightnings for the trembling Earth?

  Fair are the gods you frame forsooth! nor vain

  Would be their fears if giant hands assailed them.

  Such little world were well the infant sport

  Of Jove in darker times; such toys in truth

  His cradle might befit, nor would the work

  In after years have e’re been perfected,

  When harlot smiles restrained his riper powers.

  A Move to the Country

  In 1639, at the age of 21, Jeremiah Horrocks left his home in Toxteth. He moved to the small village of Much Hoole about 18 miles (29 km) north of Liverpool. Nobody has been able to find the reason for Horrocks’ move. Some have suggested that he was offered the post of curate at the chapel of Much Hoole, while others have suggested that he was employed as a tutor at Carr House in Bretherton. It would be fascinating to discover that the reason was a romantic attachment, but there is no solid evidence to support this theory, either. All we know is that from the summer of 1639 his correspondence to his fri
end William Crabtree was addressed from Much Hoole and not from Toxteth.

  In a survey taken in 1641 the population of Much Hoole was recorded as 235 adults. The choice of residences was limited, with the vernacular-style farmhouses being low and thatched, with smoking peat fires. The dwellings usually had pigs and chickens running in and out of the doorway. They were a far cry from the ideal residence for an educated astronomer. Apart from the church itself the only building in the village suitable for an observatory was Carr House at Bretherton, the home of the Stones family. This was situated about half a mile (about 0.8 km) away from the church. Much Hoole is the last place where we might expect to meet merchants from great trading centers like London and Amsterdam, but there is sometimes a tendency to overplay the isolation of the English village. Above the doorway at Carr House is an inscription in stone that proves the trading connections to be a fact:

  Thomas Stones of London haberdasher and Andrewe Stones of Amsterdam marchant hath builded this howse of their own charges and giveth the same unto their brother John Stones: Ano Domini 1613 Lavs.

  The Stones family were evidently haberdashers. There is a strong connection between haberdashery, drapery and cloth dealing. Horrocks’ contacts John Worthington and William Crabtree were both involved in the clothing industry.

  A Momentous Observation

  As Horrocks continued his observations of the planets he discovered to his great delight that Venus seemed to be on course for a conjunction with the Sun—in other words, the planet seemed to be following a path that would take it across the face of the Sun. This was an event so rare that it had never been recorded before. Horrocks knew that his observations might be marred by cloudy skies, so he asked both William Crabtree and his brother at Toxteth to try to make the observation as well. He asked William Crabtree to inform Henry Gellibrand in London about the event, but it appears that the request did not arrive in time.