The Story of Astronomy (10 page)

When Galileo turned his telescope to the stars he got another surprise. The stars still appeared as tiny spots of light—the telescope did not seem to bring them any nearer—but when he looked at the spaces between the stars, more and more stars appeared. When he trained his magic tube on the Milky Way he saw new stars appearing in their hundreds and thousands:

In order that you may see one or two proofs of the inconceivable manner in which they are crowded together, I have determined to make a case against two star-clusters, that from them as a specimen you may decide about the rest. As my first example I had determined to depict the entire constellation of Orion, but I was so overwhelmed by the vast quantity of stars and by want of time that I have deferred attempting
this to another occasion, for there are adjacent to, or scattered among the old stars more than 500 new stars within the limits of one or two degrees … As a second example I have depicted the six stars in the constellation Taurus, called the Pleiades … near these lie more than forty others invisible to the naked eye, no one of which is more than half a degree off any of the aforesaid six, of these I have noticed only thirty-six in my diagram.

The universe obviously contained far more stars than anybody had ever imagined. The number of visible stars in the universe seemed to have increased a thousand-fold or more, just by the invention of the telescope. It seemed that it would take a hundred men a lifetime to catalog all of them.

Excited by his discoveries, Galileo wrote a small book called the
Sidereus Nuncius
, or
Starry Messenger
, in which he described them. The book appeared in print in 1610, and not surprisingly it came in for immediate criticism. The first salvo was fired in 1612 by a Dominican friar called Nicolo Lorini (fl. 1614) and the second in 1614 by another Dominican called Tommaso Caccini (1550–1618). The affair simmered for a few years, until Galileo was summoned
to see the pope about his unconventional thoughts. In 1616 he was instructed very clearly to desist from putting forward his view that the Sun lay at the center of the universe. But Galileo knew that he was right. Instead of renouncing his ideas he simply gathered more evidence to support his case. The result was that Galileo's
Sidereus Nuncius
was put, along with Copernicus'
De Revolutionibus Orbium Coelestium
, on the list of prohibited books.

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.

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.

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.

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 never 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.

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.