B00B7H7M2E EBOK (10 page)

The tale, as it continues, is a convoluted one. The favoured version is that Rhaeticus had to return to Wittenberg before Copernicus was quite prepared to part with the manuscript of his book. Rhaeticus took with him only some early mathematical chapters. A little later, with Copernicus’s consent, Bishop Giese sent the completed manuscript on to Rhaeticus. Rhaeticus took it to a Nuremberg publisher, intending to keep close watch over its printing. However, he was then appointed to a new position with a higher salary in Leipzig and delegated what remained of the proofreading to Andreas Osiander, a Lutheran clergyman who was more nervous about possible religious reactions than Rhaeticus was. The Catholic Church had had nothing to say one way or another, except for the support of Cardinal Schönberg and Bishop Giese, but there had been those adverse remarks from Luther. Osiander urged Copernicus to protect himself by writing a preface saying that his theory was intended to be taken hypothetically, not as a truth claim. Copernicus refused. He dedicated his book to Pope Paul III, a scholar interested in science. Osiander decided to write, himself, the preface Copernicus wouldn’t write. He left it unsigned, probably because he feared that his own anti-papal reputation would cast suspicions on Copernicus.

On 24 May 1543, about a month after the printing of
De revolutionibus
was completed, Copernicus died. Tradition has it that he saw the printed book. He had had a stroke and was
bedridden
, perhaps unconscious, so there is some doubt whether that story is true. Was he aware enough to learn that Osiander had written, anonymously, the preface he himself had refused to write, saying his new scheme was only hypothetical and containing the warning: ‘Beware if you expect truth from astronomy lest you leave this field a greater fool than when you entered’? If Copernicus knew of this, there is no record of his reaction.

Even after Copernicus’s prodigious effort and foot-dragging about publication,
De revolutionibus
did not make the case for Sun-centred astronomy as effectively as he had hoped. There were many loose ends. Though he had been able to eliminate the use of the equant, he’d still had to use epicycles and eccentrics to explain the movements of the planets. The result was hardly less complicated and cumbersome than Ptolemaic astronomy.

However, the new system definitely had some things going for it. The new arrangement of the heavens allowed Copernicus to come at the problem of the mysterious ‘reversing’ or ‘retrograde’ movement of the planets in an entirely fresh way. Retrograde movement occurs when a planet is in ‘opposition’, meaning that it is on the opposite side of the Earth from the Sun. (Only Mars, Jupiter, Saturn and the other outer planets discovered since Copernicus’s time can be in opposition. Venus and Mercury, whose orbits are closer to the Sun than Earth’s, can never be in opposition.) Most of the time, the planets move from west to east against the background of stars. However, around opposition a planet appears for a while to move east to west. Ptolemy had used epicycles to solve this problem. In the Copernican model, with all planets including the Earth orbiting the Sun, when one of the planets is in opposition, the Earth catches up and runs ahead of the other planet. For an analogy, imagine two racing cars, one on an inner track and the other on an outer track. We are riding in the one on the inner track. The
stadium
is completely dark except for a light on top of the car on the outer track and some distant streetlights way beyond that. When our car catches up with that car and moves on ahead, the light will appear to us (against the background of streetlights) to backtrack. If the motion of our car is so constant and smooth that we believe we are standing still, we’ll conclude that the other car has stopped for a moment, reversed, stopped again, and continued its forward motion.
See Figure 2.5.

Figure 2.5 Copernicus’s explanation for the retrogression of a planet

The Sun is in the centre. The inner ring is the Earth’s orbit. The outer ring is the orbit of the planet. Place yourself at 1 on the Earth’s orbit, then at 2, and so forth, as the Earth moves in its orbit. The line drawn through the corresponding number on the planet’s orbit shows where the planet is in your line of sight in each instance. The squiggle at the top of the drawing shows the pattern these changes of position (of both Earth and planet) will produce against the background of distant stars, and why the planet will seem to ‘reverse’.

De revolutionibus
also made sense of the fact that Mercury and Venus never stray far from the Sun. Ptolemaic astronomy had used deferents and epicycles to unravel this mystery. In Copernicus’s model, with the orbits of Mercury and Venus lying within the Earth’s orbit (they are both closer to the Sun than the Earth is), there is no mystery. Observers on Earth couldn’t possibly see these planets anywhere else but near the Sun. This explanation of the orbits of Mercury and Venus was one success of Copernicus’s model that many of his contemporaries could immediately appreciate.

Copernicus also addressed the ancient objections to the idea that the Earth rotates on its axis and moves in orbit. Judging from modern knowledge about the availability of certain books during his lifetime, most scholars conclude that when he wrote
Commentariolus
he probably didn’t know about Aristarchus’s suggestion that the Sun rather than the Earth is at the centre of the universe. However, it’s clear from statements in
De revolutionibus
that by the time he wrote that book he had heard about it. Copernicus explained that the Earth carries its atmosphere with it as it spins, and insisted, as Aristarchus had done, that the fact that we observe no stellar parallax proves the stars are extremely far away. Al Fargani had estimated the distance to the sphere of stars to be more than 75 million miles. Copernican astronomy required that the distance be 75 times as great as that. The vast amount of empty space this leaves between the sphere of Saturn and the sphere of the stars was, however, not reflected in an illustration from
De revolutionibus
(see illustration
section)
, showing Sol, the Sun, at the centre of the universe, with seven planets in their spheres around it. Beyond those spheres is another named ‘Stellarum Fixarum Sphaera Immobilus’, the ‘immobile sphere of the fixed stars’. Copernicus, unlike Ptolemy and Ptolemaic astronomers, thought that the stars were stationary.

In 1551, eight years after Copernicus’s death and the publication of his book, the first handy-to-use tables based on Copernican theory appeared. They were a substantial improvement on the Ptolemaic tables (partly because there had been no new tables for a very long time), but they were far from completely accurate, because astronomers were still so dependent on Ptolemaic observations.

No period in the evolution of thought about the universe and humankind’s place in it has been more complicated or more ultimately decisive than the century and a half following the publication of
De revolutionibus
in 1543. Historians speak of a scientific ‘revolution’. A hundred and fifty years is a long, slow-moving revolution by political standards, but no political revolution has been more profound. It is interesting that the shot eventually heard round the world took so long to reverberate and came from a narrowly technical book that only highly trained astronomers and mathematicians could understand, and whose author didn’t make his case very effectively. Yet over the course of a century and a half, in the minds of an increasing number of people, an Earth-centred universe became a Sun-centred infinite universe, and science became, for many, the chief arbiter of truth.

One reason for the initial dearth of reaction was that even the literate, educated public lacked the expert knowledge to understand
De revolutionibus
. Among those who could understand it, few thought Copernicus himself had meant his arguments as a truth claim. Osiander’s preface, which many assumed Copernicus had written, had something to do with
this
impression, but also, in the Ptolemaic tradition, new theories of a mathematical astronomer were normally intended as useful models for making predictions about planetary positions, not proposals for changing humankind’s view of reality. The happy result for Copernican astronomy was that most scholars had found some of Copernicus’s mathematical techniques too useful to discard by the time any actual opposition to his central thesis emerged. On the strength of these mathematical techniques Copernican theory infiltrated the scholarly world, but the subversion of Ptolemaic astronomy was a slow process, and historian John Hedley Brooke points out that we can identify only 10 people in the years between 1543 and 1600 as ‘pro-Copernican’ to the extent of stating that they actually believed that the Earth moved.

Some scholars chose to accept Copernicus’s proposal that the Earth rotated on its axis but not his proposal that it was in orbit around the Sun. Others were willing to have the planets orbiting the Sun, while the Sun itself revolved around the Earth, carrying the planets along. This scheme came from the great Danish astronomer Tycho Brahe and also from Nicolai Reymers Baer (better known as Ursus, Latin for bear), the official mathematician of Holy Roman Emperor Rudolf II. There were accusations and counter-accusations of plagiarism between the two men. In view of the concept of relative motion, this model was not ridiculous at all. In fact it is the geometric equivalent of the Copernican model.

As word of the book and rumours of its contents spread, not all the debate about
De revolutionibus
took place on strictly astronomical or mathematical grounds or among people who understood it. Reactions from outside astronomy were mostly negative, some of them vehemently so. Copernicus’s Sun-centred astronomy challenged a cosmic structure that men and women had taken for granted since centuries before Christ. Deep reverence for Aristotle still pervaded the intellectual
world
. Copernicus had insisted the Earth was one of the planets, but didn’t we know from Aristotle that the Earth was made of different stuff from the planets? The planets were made of a fifth element that was not to be found in the corrupt realm within the Moon’s orbit.

Tycho Brahe gave the world some fresh cause to doubt the Aristotelian picture of the universe by demonstrating that a nova in 1572, the great comet of 1577, and five more comets during the next 20 years were all further away than the Moon. This was a shocker, because Aristotle had taught that birth, death and change took place only in the sublunar part of the universe, and that beyond the Moon were only the eternal and unchanging celestial spheres. Tycho’s discovery might seem a strong vote for Copernicus, but it fitted equally well with Tycho’s concept of all the planets orbiting the Sun while the Sun orbits the Earth.

Though the problem of having humankind dethroned from the centre of the universe would frequently crop up as an objection to Copernicus’s system, it was also possible to see this move as an innocuous or even a fortuitous one: Copernicus had argued that the fact that observers on Earth detect no stellar parallax as Earth travels in its orbit must mean that the stars are extremely far away. So in the Copernican system humans are still very close to the centre. To all intents and purposes, with the distances being so great, we are still
at
the centre. Others called attention to the fact that the centre of everything in the Aristotelian scheme was not such prime real estate after all. Beyond the Moon’s orbit was perfection; beneath it, corruption, at the centre of which was the Earth. It was the realm of degradation and change. Christianity had come to associate it with fallen humanity. Satan lived in hell at the core of the Earth. Why cling so tenaciously to the notion that we live in the armpit of the universe? How welcome to find ourselves well out of that, moving around, breathing purer air! There was even, reportedly, criticism of the Copernican system for elevating man
above
his true station.

The question of possible extra-terrestrial life arose and became a topic in religious discussions and writing. If Earth is a planet, might not other planets have inhabitants too? Had they fallen from God’s grace as we had? Did Christ die for them as well? Though this problem was a matter for conjecture and concern, religious scholars as a whole didn’t decide it was a reason for rejecting the Copernican system, though some very vocal opponents mouthed it about a great deal. Another issue: before Copernicus, heaven and hell were considered to be not at all in the same neck of the woods. Heaven was beyond the outermost sphere. Hell was deep within the Earth. In the new system, was hell hurtling around in orbit and Dante spinning in his grave?

For the remainder of the 16th century and in the first decade of the 17th, the Catholic Church didn’t oppose Copernicus’s theories.
De revolutionibus
was read, discussed, and even occasionally taught at Catholic universities, and Catholic scholars used computations based on Copernicus’s work to produce the new Gregorian calendar in 1582. On the Protestant front, Luther didn’t follow through with any more hostile statements. Calvin observed that the Holy Spirit ‘had no intention to teach astronomy’. The anti-Copernican statements often attributed to Calvin are fictitious – a late-19th-century invention. Unlike modern Christian fundamentalists, neither Luther nor Calvin claimed that the Bible was the sole authority in matters other than faith and conduct. Of the ten aforementioned Copernicans between 1543 and 1600, seven were Protestant, three were Catholic. Meanwhile, as the poet John Donne sagely observed, ‘most men lived and believed just as they had done before’.