indisposition,’ he called it, ‘or I should say a series of long indispositions preventing all exercises and occupations on my part’), and even further by the calumny of his enemies, not to mention the mysterious nature of the spots themselves.
‘The difficulty of this matter,’ Galileo finally conceded to Welser, ‘combined with my inability to make many continued observations, has kept (and still keeps) my judgment in suspense. And I, indeed, must be more cautious and circumspect than most other people in pronouncing upon anything new. As Your Excellency well knows, certain recent discoveries that depart from common and popular opinions have been noisily denied and impugned, obliging me to hide in silence every new idea of mine until I have more than proved it.’ Nevertheless, Galileo expounded on the essence and substance of sunspots for many pages, initiating an ongoing correspondence with Welser – and through him ‘the masked Apelles’ – that sounded the full thunder of the new debate. Indeed, Galileo’s letters on sunspots speak almost as much about the system of the world as they do about the solar spots.
‘With absolute necessity we shall conclude,’ Galileo wrote early in the first of his three letters to Welser, ‘in agreement with the theories of the Pythagoreans and of Copernicus, that Venus revolves about the Sun just as do all the other planets…No longer need we employ arguments that allow any answer, however feeble, from persons whose philosophy is badly upset by this new arrangement of the universe.’
Apelles upheld the idea that the dark spots must be many small stars circling the Sun. Galileo saw nothing starlike about them. To his mind, they more closely resembled clouds: ‘Sunspots are generated and decay in longer and shorter periods; some condense and others greatly expand from day to day; they change their shapes, and some of these are most irregular; here their obscurity is greater and there less. They must be simply enormous in bulk, being either on the Sun or very close to it. By their uneven opacity they are capable of impeding the sunlight in differing degrees; and sometimes many spots are produced, sometimes few, sometimes none at all.’
But he quickly added: ‘I do not assert on this account that the spots are clouds of the same material as ours, or aqueous vapours raised from the Earth and attracted by the Sun. I merely say that we have no knowledge of anything that more closely resembles them. Let them be vapours or exhalations then, or clouds, or fumes sent out from the Sun’s globe or attracted there from other places; I do not decide on this – and they may be any of a thousand other things not perceived by us.’ (He could never have imagined, despite his long-standing interest in magnets, that the spots marked the sites of the Sun’s most potent magnetic fields.)
‘If I may give my own opinion to a friend and patron,’ Galileo continued, ‘I shall say that the solar spots are produced and dissolve upon the surface of the Sun and are contiguous to it, while the Sun, rotating upon its axis in about one lunar month, carries them along, perhaps bringing back some of those that are of longer duration than a month, but so changed in shape and pattern that it is not easy for us to recognise them.’
In closing this first letter, Galileo begged Welser’s indulgence:
And forgive me my indecision, because of the novelty and difficulty of the subject, in which various thoughts have passed through my mind and met now with assent and again with rejection, leaving me abashed and perplexed, for I do not like to open my mouth without declaring anything whatever. Nevertheless, I shall not abandon the task in despair. Indeed, I hope that this new thing will turn out to be of admirable service in tuning for me some reed in this great discordant organ of our philosophy – an instrument on which I think I see many organists wearing themselves out trying vainly to get the whole thing into perfect harmony. Vainly, because they leave (or rather preserve) three or four of the principal reeds in discord, making it quite impossible for the others to respond in perfect tune.
These off-key reeds that Galileo decried sounded several flat notes, including the immutability of the heavens, the farrago of the celestial spheres and the immobility of the Earth.
Welser wrote back gratefully to say, ‘You have paid a high rate of interest for the favour of a little time, sending me so copious and diffuse a treatise in reply to a few lines.’ The thrill of witnessing new philosophy grow up around the astronomical anomaly of the sunspots made Welser want to share Galileo’s letter with a larger audience than just the alleged Apelles, who didn’t even read Italian and had to wait months for a suitable translation to be made. Welser thought perhaps Prince Cesi of the Lyncean Academy, with whom he also corresponded, should publish the sunspot report as part of an ongoing series. ‘It would be a public benefit for these little treatises concerning new discoveries to come out one by one,’ Welser opined, ‘keeping things fresh in everyone’s mind and inspiring others to apply their talents more to such things; for it is impossible that so great a framework should be sustained upon the shoulders of one man, however strong.’
Prince Cesi liked the idea so well that he not only initiated preparations for printing but also inducted Welser into the academy. Soon Welser and Galileo were both signing themselves proudly as ‘Lyncean’ in their letters and politely commiserating with each other on their physical complaints. When Cesi published Welser’s four relatively short notes together with Galileo’s three very long replies as History and Demonstrations Concerning Sunspots and Their Phenomena in Rome in the spring of 1613, he retained all the chitchat about Welser’s gout and Galileo’s miscellaneous infirmities.
‘I have read [your letter], or rather devoured it, with a pleasure equal to the appetite and longing I had for it,’ Welser wrote to Galileo on 1 June 1612. ‘Let me assure you that it has served to alleviate for me a long and painful illness that has been causing me extreme discomfort in the left thigh. For this the physicians have not yet found any effective remedy; indeed, the doctor in charge has told me in very plain words that the first men of his profession have written of this disease that “some cases are cured, but others are incurable”. One must therefore submit to the fatherly disposition of God’s providence; “Thou art the Lord, do what is good in Thy sight.”’
Poor Welser would be dead within two years, escaping the pain of his disease through suicide, but meanwhile he worried how Cesi could accomplish the printing of the many meticulous drawings, which Galileo appended to his letters, of sunspots ingeniously observed. Galileo rendered these near-photographic records by letting the telescope image of the Sun fall on a piece of white paper instead of on his retina. There he faithfully traced them – and later retraced them, reorienting the telescope’s inverted vision – to avoid any damage to his eyes.
More than a month’s worth of excellent engravings embellished the finished book, tracking the Sun day by day from the 1st of June until mid-July of 1612. The ideas espoused in the book, however, exacerbated the existing tensions between Galileo and his avowed opponents. Book discussions attracted additional new opponents among people who had not even read the text. And, since Copernicus had died in silence in another country years before, Galileo began to be credited – or rather blamed – for having fathered the Sun-centred universe.
Although the ‘pigeon league’ attacks on Bodies in Water had held up the books of Aristotle to oppose Galileo, critics of the Sunspot Letters now appealed to the even higher authority of the Bible.
[VI] Observant executrix of God’s commands
THE REORGANISATION OF THE heavens according to Copernicus struck some individuals as suspiciously heretical.
‘That opinion of Ipernicus, or whatever his name is,’ an elderly Dominican father wagged in Florence in November of 1612, ‘appears to be against Holy Scripture.’ Neither Copernicus nor Galileo, however, both Catholic believers, intended any such criticism of the Bible or attack against the Church. Copernicus had
