Nicolaus Copernicus, De Revolutionibus orbium coelestium libri VI, 1543
[Six Proposals Concerning the Dynamics of the Heavenly Orbs]
Hist Sci QB41 C78 D2 1543+
In the Middle Ages the Earth was considered the center of the universe. The Moon, the Sun, the planets, and the fixed stars all orbited our planet. From an observational standpoint this made sense if you didn’t look too carefully and if you didn’t pay attention to the flaws in the “official” systems of astronomy based on the works by Aristotle (Greece, 384-322 BCE) and Ptolemy (Egypt, 2nd cent. BCE).
Nicolaus Copernicus (Poland, 1473-1543) would change all that over his lifetime. In his young years he studied at the University of Krakow, where he received an excellent foundation in mathematics and mathematical astronomy. This gave him the ability to critically explore and evaluate the flaws of the geocentric system and to dare consider alternatives. By 1497, while continuing his studies in Bologna (Italy), he is known to have observed the occultation of the star Aldebaran by the Moon to explore a peculiarity in the theory of Ptolemy. Eventually this led him, some time before 1514, to postulate the first version of his heliocentric system, which he committed to paper in the Commentariolus (“little commentary”), and which he shared only with a few good friends and colleagues. Rumors about his revolutionary theory started spreading among educated people all over Europe, but Copernicus waited until 1543, the year of his death, to publish the final version of his heliocentric system in his book De revolutionibus orbium coelestium libri VI.
The page on display in the exhibition, showing the Sun at the center, and Earth orbiting the Sun along with the five other known planets, aptly illustrates the truly daring new proposition it would have been to demote the Earth from centerstage. More demotions would follow for centuries to come, both regarding our place in the universe, and our relationship to other forms of life on our planet.
In the Copernican heliocentric system, a solar eclipse was not the result of a chance alignment of the sun and the moon on their different orbits around the Earth but an event that can occur every 29.5 days at New Moon when the Moon passes between the Sun and the Earth. The reason that it does not always occur at New Moon is the result of a 5-degree difference between the orbital plane of the Moon and of the planets. This is best explained by this NASA animation, which is also shown on the iPad in the exhibition.
Robert Hall, The Story of the Sun, 1897
"Darkness during total eclipse of 28th February, 1851"
Rare and Manuscript Collections, History of Science, QB521 B3 1897
A landscape looks spectacularly different once the direct illumination by the Sun is blocked by the Moon. All shadows are gone and only far in the distance, where the eclipse is not yet or no longer total, can direct sunlight be seen illuminating the landscape.
Nizamaddin ibn Muhamad an-Nisapuri, Tawḍīḥ al-Tadhkirah, 14th century
[Geometry of eclipses in a 14th century Islamic manuscript from northern India]
Rare and Manuscript Collections, #8832 Bd. Ms. 1 ++
This book was composed by a 14th century scholar based in modern day Iran. As a mathematician, astronomer, jurist, theologian, and poet he benefitted from his teacher, Qutb al-Din al-Shirazi, who had himself been a student of the more famous polygraph Nasir al-Din al-Tusi (1201-74). Al-Tusi had created very accurate tables of planetary motion and a sophisticated planetary model. This diagram shows the alignment of the Sun, Moon, and Earth during an eclipse. The book also contains a spectacular map of the Nile River.
Ptolemy of Alexandria, Almagest[um], 1515 reprint
History of Science QB41.P97 A4 1515 ++
A Roman citizen with Greek ancestry, Claudius Ptolemaios (Πτολεμαῖος, Egypt, 2nd cent. BCE) was the first mathematician and astronomer to design precise tables indicating, not only when an eclipse would appear, but also whether they would be visible from Alexandria (Egypt). Unlike the well-respected astronomers of ancient Babylon, Ptolemy knew about the lunar parallax, which affects the geocentric latitude of the Moon; and about the apparent diameters of both the Sun and the Moon in relation to their distance from the center of the Earth.
The “Tables” were used to calculate the past and future positions of planets and stars, and (more specifically) to predict the date, length ("principium" means "beginning", "finis" means "end") and intensity of eclipses. Reading Ptolemy's tables would require some astronomical knowledge. However, as Jayant Shah pointed out in a 2018 article about the accuracy of the Almagest in predicting solar eclipses, "all a calendar maker would need are [Ptolemy's tables] tables, and he would not have to know the algorithms that created them." Shah also underlines that, "The actual eclipses [were] too few to properly analyze prediction errors." By contrast, Brahe and Kepler (in the 17th century) would have a historical "database" to draw from.
Nevertheless, Ptolemy's predictions were still admired in the 16th century, and the Almagest was reprinted several times by Renaissance humanists. On display in our exhibition is the first complete Latin edition of the Almagest, published in 1515 by Petrus Liechtenstein (fl. 1497-1528), a member of the German community in Venice. What he printed was the work of Gerardus of Cremona's 12th century translation of the Almagest (originally written in Greek) from Arabic (since the Almagest was preserved in Arabic manuscripts) into Latin.
Gustav A. Goehner, Series of Instantaneous Telescopic Views of the solar eclipse of July 29, 1878.
Rare and Manuscript Collections, History of Science, QB541 G64 1878
This publication contains 15 telescopic images of “America’s First Great Eclipse” of July 29, 1878 taken by the photographer Gustav A. Goehner. This eclipse, which closely tracked the length of the Rocky Mountains, attracted astronomers and tourists alike.