Francesco Ingoli (1578 – 1649) was an Italian priest, lawyer and professor of civil and canon law.
Born in Ravenna Italy, Ingoli graduated from the University of Padua in civil and canon law in 1601, he entered the order of clerics Theatines and studied astronomy, writing an essay on Stars in 1604 and on Comets in 1607. Since 1606 he was in the service of Cardinal Caetani Boniface (1567-1617) who was the papal legate in Romagna and followed the Cardinal to Rome when he was appointed member of the Congregation of the Index. In Rome he attended the Accademia dei Lincei founded by Federico Cesi.
His name is particularly linked to the controversy over the Copernican system. He used a combination of theological and scientific arguments to support the astronomical theory of Tycho Brahe (see Tychonic System) over that of Copernicus. Galileo Galilei was one of those who disagreed with him on this matter. Ingoli sent Galileo a letter in January 1616 that listed eighteen scientific and four theological objections to Copernicanism, but suggested Galileo answer mainly the scientific ones. According to Maurice Finocchiaro, Ingoli had probably been commissioned by the Inquisition to write an expert opinion on the controversy, and this letter provided the "chief direct basis" for the Inquisition's actions against the Copernican system in February and March of 1616. A full English translation of Ingoli's essay to Galileo was published in 2015.
The eighteen scientific objections that Ingoli listed were:
- An argument about the parallax of the sun and moon
- An argument from Sacrobosco's Sphere about the appearances of the stars not changing like they would if Earth moved
- An argument from Ptolemy about the Earth being at the center of the universe because an observer always sees half of the celestial sphere
- An argument from Tycho Brahe that eccentricities of Venus and Mars were different from what Copernicus assumed
- An argument about the relative densities of the Earth and the Sun
- An argument based on the behavior of swirling lumps of material like in a sieve, where the heavier ones accumulate at the center
- An argument from Tycho Brahe on the behavior of falling bodies
- An argument from Tycho Brahe on the flight of cannon balls fired east or west
- An argument from Tycho Brahe on the positions of stars being changed if Earth moved
- An argument from Tycho Brahe on the positions of the celestial pole being changed if Earth moved
- An argument from Tycho Brahe on the day length being changed if Earth moved
- An argument from Tycho Brahe on the motions of comets when opposite the Sun in the sky not comporting with Earth moving
- An argument from Tycho Brahe that the supposed “third motion” of Earth in the Copernican system (the first two being the Earth's daily rotation and yearly orbiting)—that by which the Earth's axis maintains the same orientation in space, parallel to itself at all times, so that it is always pointed at the North Star—is not needed if Earth moved (today we understand that a rotating body naturally maintains its orientation in space gyroscopically, but at the time this was considered an actual third motion.)
- An argument from Tycho Brahe that the supposed “third motion” of Earth in the Copernican system is not possible.
- An argument from Tycho Brahe that the “third motion” of Earth, in combination with the other motions, is too complex.
- An argument from Tycho Brahe and others that heavy bodies are less apt to motion, and since Earth is the heaviest of all known bodies, it should not move
- An argument that bodies have single natural motions
- An argument that Copernicus attributes motion to all bright objects except the Sun, but that he makes the bright Sun motionless and makes the dark Earth moving
The four theological objections Ingoli listed were:
- An argument based on the language of the first chapter of Genesis, describing the sky as a tent and the Sun and Moon both being lights in it
- An argument from Bellarmine on the location of hell being at the center or lowest point of Earth and the universe
- An argument based on the tenth chapter of Joshua, where the Sun is cited as temporarily standing still
- An argument from Bellarmine based on a certain prayer that references a stationary Earth
Galileo's reply, in 1624, listed, among other evidence, the results of experiments such as dropping a rock from the mast of a moving ship.