. Gingerich eventually came to teach astronomy at
Harvard where his lectures became known for attention-getting schemes. Among them was propelling himself out of the classroom using a fire extinguisher to demonstrate
Newton's third law of motion, and dressing up like a sixteenth-century
Latin scholar. He is associated with the
Smithsonian through the
Smithsonian Astrophysical Observatory and also served as chairman of the
International Astronomical Union's Planet Definition Committee, which was charged in 2005 with updating the astronomical
definition of planet to reflect then recent discoveries such as
Eris. The seven-member committee
drafted a definition which preserved
Pluto's status by only requiring a planet to be (1) large enough to assume
hydrostatic equilibrium (a nearly round shape) and (2) orbiting a
star without itself being a star. This proposal was criticized by many for weakening the meaning of the term. The eventual definition adopted by the IAU added an additional requirement, that a body must have
cleared its neighborhood of all other sizable objects, language that Gingerich was "not at all pleased" with. After some early astronomical research on stellar atmospheres, he reoriented his studies toward the history of
astronomy. In the 1950s, he researched
Charles Messier's life and the
Messier Catalog. Gingerich found notes by Messier on two additional Objects, discovered by Pierre Méchain, which he added to the Messier Catalog:
M108 (NGC 3556) and
M109 (NGC 3992). He investigated the missing Messier Objects, concluding that
M91 was probably a comet and that
M102 was probably a duplication of
M101. The first conclusion was later dismissed as W. C. Williams brought up evidence that M91 is probably NGC 4548, but the second is still open (M102 may be NGC 5866). Gingerich was a recognized authority on both
Johannes Kepler and
Nicolaus Copernicus, especially in regard to Copernicus's
De revolutionibus orbium coelestium. He was also an expert on Galileo's astronomical observations, and took a leading role in establishing that the watercolor lunar images in a celebrated copy of Galileo's
Sidereus Nuncius were modern forgeries and not made by Galileo. In 1959, in chapter II of
The Sleepwalkers, titled "The System of Copernicus",
Arthur Koestler wrote that: "The book that nobody read – the
Revolutions of the Heavenly Spheres – was and is an all-time worst-seller." After reading in the
Royal Observatory in Edinburgh a thoroughly annotated copy previously owned by
Erasmus Reinhold, a prominent sixteenth-century German astronomer who worked in
University of Wittenberg shortly after Copernicus' death, Gingerich was inspired to check Koestler's claim and to research who had owned and studied the book's first two editions, published in 1543 and 1566 in
Nuremberg and
Basel respectively. He discovered, from marginal annotations, that the book was widely read after all. Gingerich also documented where and how the book was censored. Due largely to Gingerich's work,
De revolutionibus has been researched and catalogued better than any other first-edition historical text except for the original
Gutenberg Bible. His latter books, ''God's Universe
(Harvard, 2006) and God's Planet'' (Harvard, 2014), dealt with the intersection of science and religion. ==Science and religion==