Hobbs Observatory Astronomical Series

Galileo and Kepler: The Men Who Changed Astronomy

Supporting Cast• Aristotle

• Aristarchus of Samos

• Claudius Ptolemy

• Saint Thomas Aquinas

• Nicolaus Copernicus

• Pierre de la Ramee

• Tycho Brahe

• Cardinals Bellarmino and Barberini (Urban VIII)

Pre-Copernican Astronomy…it is the job of the astronomer to use painstaking...

observation in gathering together the history of the celestial movements, and then...to...construct whatever...hypotheses he pleases such that...those same movements can be calculated...for the past and...future...it is not necessary that these hypotheses be true, or even probably; ...it is enough if they provide a calculus which fits the observations....

[Saving the appearances]

Andrew OsianderIntroduction to On the Revolutions of the Heavenly

Spheres

Pre-Copernican Astronomy

• Aristotle (4th Century B. C.)

• Aristarchus of Samos (3rd Century B. C.)

• Claudius Ptolemy (2nd Century A. D.)

• Saint Thomas Aquinas (13th Century A. D.)

• Saving the hypotheses?

Copernicus

• Born 1473

• University of Cracow

• Rome

• Padua – Doctor of Canon Law

• Canon at Frombork

• Published On the Revolutions 1543

Counter-Reformation

• On the Revolutions dedicated to Pope Paul III

• Council of Trent 1545 – 1563

• 1616 Paul V suspends On the Revolutions

• Thirty-Years War 1618 – 1648

Galileo

Family and Education

University of PisaUniversity of Padua

Experimentation and inventionThe TelescopeSidereus Nuncius published in 1610Mathematician and Philosopher

Galileo in Rome• In 1611 Galileo warmly received

– Maelcote at Collegio Romano

– Clavius in revision of his book

• In 1615 Galileo gets a cool reception

– Told not to teach Copernicanism

– Publishes Dialogue 1632

• In 1633 Galileo abjures before the Inquisition

– Sentenced to house arrest

Too Clever by Half?

Galileo had, in fact, been expressly forbidden to advocate the Copernican theory. Apart from its revolutionary factual content the Dialogue represents a downright roguish attempt to comply with this order in appearance and yet in fact to disregard it. Unfortunately, it turned out that the Holy Inquisition was unable to appreciate adequately such subtle humor.

Albert EinsteinForward to Dialogue Concerning the Two Chief World

Systems

Pierre de la Ramee (Petrus Ramus)Why could there not rather arise...from among the

schools of Germany, a philosopher...who would attain the prize...that is publically offered? And if any fruit of transitory usefulness can be offered to compare with a prize of such power, I will solemnly promise you the Regius Professorship at Paris...for an astronomy constructed without hypotheses,...even by resigning our professorship.

Petrus Ramus quoted by Kepler on the back of the original title page of Astronomia Nova

Kepler• Family and education

• Tubingen

• Differences with the Lutheran Church

• Graz

• Tycho Brahe

– Treasures only Kepler can use effectively

– murder?

• Astronomia Nova published 1609 – Two Laws

Kepler• The Harmony of the World 1619 – Third Law

• Thirty-Years War

• Kepler excommunicated from Lutheran Church

• Katharina Kepler's Witchcraft Trial

– Convicted

– Torture in the first degree

• Shown the instruments with running commentary

– Finally released in 1621 (425 days of imprisonment)

Kepler's Response

Conveniently for you, Ramus, you have abandoned this surety by departing both life and professorship. Had you still held the latter, I would, in my judgement, have won it indeed, inasmuch as, in this work, I have at length succeeded, even by the judgement of your own Logic. ...I would only ask you not to exclude the support of Physics,....

Kepler's response to Ramus on back of title page to Astronomia Nova

Galileo's Warning

Take note, theologians, that in your desire to make matters of faith out of propositions relating to the fixity of sun and earth you run the risk of eventually having to condemn as heretics those who would declare the earth to stand still and the sun to change position—eventually, I say, at such a time as it might be physically or logically proved that the earth moves and the sun stands still.

Note added by Galileo in the preliminary leaves of his own copy of the Dialogue