On Twitter I follow three accounts that tweet daily titbits out of the history of mathematics, the Mathematical Association of America (@maanow), the British Society for the History of Mathematics (@mathshistory) and my good friend Pat Ballew (@OnThisDayinMathematics). Yesterday both Pat and the MAA tweeted links to a brief paragraph about the Renaissance humanist scholar Andreas Dudith. The MAA’s paragraph, which I read first, was the following:
Andreas Dudith (1533-1589), mathematician and opponent of astrology, argued in a letter that observations of the comet of 1577 proved the Aristotelian explanation fallacious (for Aristotle, comets were accidental exhalations of hot air from the earth that rise in the sublunar sphere). Dudith’s use of mathematically precise observations to criticize a general physical theory of Aristotle foreshadowed Galileo’s work fifty years later.
Pat’s almost identical offering was the following:
Andreas Dudith (1533–1589), mathematician and opponent of astrology, argued in a letter that observations of the comet of 1577 proved the Aristotelian explanation fallacious (for Aristotle, comets were accidental exhalations of hot air from the earth that rise in the sublunar sphere). Dudith’s use of mathematically precise observations to criticize a general physical theory of Aristotle betokens Galileo’s work ﬁfty years later.
Although Pat gives his source as the maths history website from V. Frederick Rickey they obviously both have a common source, namely the Dudith article in the Dictionary of Scientific Biography written by the historian of Renaissance mathematics, Paul Lawrence Rose.
The first problem with this account as presented here is that Dudith in his letter was not referring to his own observations but to those of his friend and correspondent Thaddaeus Hagecius, personal physician to the Holy Roman Emperors in Prague who was also a correspondent of Tycho Brahe and later a friend and colleague of Kepler. The second problem is that Hagecius, and through him Dudith, were by no means the only people to accept that parallax measurements showed comets to be supra-lunar thus contradicting the Aristotelian theory of comets, as seems to be implied here. Amongst others, both Tycho and Michael Maestlin, Kepler’s teacher, who were much more influential than Dudith, had also reached this conclusion. In fact much earlier in the sixteenth century, based on their observations of the 1530s comets, Gemma Frisius, Jean Pena, Girolamo Fracastoro and Gerolamo Cardano had already reached the same conclusion. In fact the intensive observations and parallax measurements of the 1577 comet were to determine if Frisius et al. were correct or not in their deductions. In his letter from 19th January 1581 Dudith is merely joining a fairly large and influential choir.
The real problem in this brief account is to be found in the conclusion. A conclusion that is to be found in the Paul Rose original:
Dudith’s use of a mathematically precise observation to criticize a general physical theory of Aristotle’s betokens the same kind of dissatisfaction with Aristotelian physical doctrines that was most eloquently expounded in the works of Galileo fifty years later.
Whilst it is true that Galileo replaced Aristotle’s doctrine on falling objects with his own mathematical laws of fall obtained or at least confirmed through ingenious physical experiments his record on comets was to say the least embarrassing making the comparison here highly questionable.
In 1618 the Jesuit astronomer Orazio Grassi showed by observation and parallax measurement that the comet of that year was indeed supra-lunar driving another nail in the coffin of the Aristotelian theory of comets. Galileo, who due to illness had been unable to observe the comet, was urged by his claque to enter the arena with his opinion on the nature of comets. Galileo then famously launched an unprovoked and extremely vitriolic attack on Grassi condemning his work and defending what was basically a version of the Aristotelian theory. It was one of Galileo’s less glorious moments, far from using mathematic to criticise a doctrine of Aristotle’s Galileo was defending Aristotle’s theory of comets against an astronomer who had used mathematic to disprove it.
 It should be pointed out that the essence of Galileo’s laws of fall can be found in the work of Giambattista Bendetti, who by a strange coincidence died on 20th January 1590, a couple of decades earlier.