Giovanni Battista Riccioli (17 April 1598 – 25 June 1671) was an Italian astronomer and a Catholic priest in the Jesuit order. He is known, among other things, for his experiments with pendulums and with falling bodies, for his discussion of 126 arguments concerning the motion of the Earth, and for introducing the current scheme of lunar nomenclature. He is also widely known for discovering the first double star. He argued that the rotation of the Earth should reveal itself because on a rotating Earth, the ground moves at different speeds at different latitudes.
The asteroid 122632 Riccioli is named after him.
Biography
Riccioli was born in Ferrara.His books sometimes bear the mention "Ricciolus Ferrariensis" (Riccioli of Ferrara). He entered the Society of Jesus on 6 October 1614. After completing his novitiate, he began to study humanities in 1616, pursuing those studies first at Ferrara, and then at Piacenza.
From 1620 to 1628 he studied philosophy and theology at the College of Parma. Parma Jesuits had developed a strong program of experimentation, such as with falling bodies. One of the most famous Italian Jesuits of the time, Giuseppe Biancani (1565–1624), was teaching at Parma when Riccioli arrived there. Biancani accepted new astronomical ideas, such as the existence of lunar mountains and the fluid nature of the heavens, and collaborated with the Jesuit astronomer Christoph Scheiner (1573–1650) on sunspot observations. Riccioli mentions him with gratitude and admiration.He was later to name a lunar crater after Biancani, among a host of men of science and astronomers, Jesuits and non-Jesuits.
By 1628 Riccioli's studies were complete and he was ordained. He requested missionary work, but that request was turned down. Instead, he was assigned to teach at Parma. There he taught logic, physics, and metaphysics from 1629 to 1632, and engaged in some experiments with falling bodies and pendulums. In 1632 he became a member of a group charged with the formation of younger Jesuits, among whom Daniello Bartoli.Riccioli 1669, IV, p. 218 (under D for Daniel Bartholus Ferrariensis) He spent the 1633–1634 academic year in Mantua, where he collaborated with Niccolò Cabeo (1576–1650) in further pendulum studies. In 1635 he was back at Parma, where he taught theology and also carried out his first important observation of the Moon. In 1636 he was sent to Bologna to serve as Professor of theology.
Riccioli described himself as a theologian, but one with a strong and ongoing interest in astronomy since his student days, when he studied under Biancani. He said that many Jesuits were theologians, but few were astronomers. He said that once the enthusiasm for astronomy arose within him he could never extinguish it, and so he became more committed to astronomy than theology. Eventually his superiors in the Jesuit order officially assigned him to the task of astronomical research. However, he also continued to write on theology (see below).
Riccioli built an astronomical observatory in Bologna at the College of St. Lucia, equipped with many instruments for astronomical observations, including telescopes, quadrants, sextants, and other traditional instruments. Riccioli dealt not only with astronomy in his research, but also with physics, arithmetic, geometry, optics, gnomonics, geography, and chronology. He collaborated with others in his work, including other Jesuits, most notably Francesco Maria Grimaldi (1618–1663) at Bologna, and he kept up a voluminous correspondence with others who shared his interests, including Hevelius, Huygens, Cassini, and Kircher.
He was awarded a prize by Louis XIV in recognition of his activities and their relevance to contemporary culture.
Riccioli continued to publish on both astronomy and theology up to his death. He died in Bologna at 73 years of age.Material in the "Biography" section has been compiled from Dinis 2003; Dinis 2002; Catholic Encyclopedia: Giovanni Battista Riccioli.
Scientific work Almagestum Novum
One of Riccioli's most significant works was his 1651 (New Almagest),The old Almagest was Ptolemy's second-century book. an encyclopedic work consisting of over 1500 folio pages (38 cm x 25 cm) densely packed with text, tables, and illustrations. It became a standard technical reference book for astronomers all over Europe: John Flamsteed (1646–1719), the first English astronomer royal, a Copernican and a Protestant, used it for his Gresham lectures; Jérôme Lalande (1732–1807) of the Paris Observatory cited it extensivelyBut not necessarily favorably—some discussion of Lalande citing Riccioli is available in Galloway 1842 (pp. 93–97). even though it was an old book at that point; the 1912 Catholic Encyclopedia calls it the most important literary work of the Jesuits during the seventeenth century.Van Helden 1984 (p. 103); Raphael 2011 (pp. 73–76), which includes the quote about "no serious seventeenth century astronomer" on p. 76; Campbell 1921 (p. 848); Catholic Encyclopedia: Giovanni Battista Riccioli. Within its two volumes were ten "books" covering every subject within astronomy and related to astronomy at the time: the celestial sphere and subjects such as celestial motions, the equator, ecliptic, zodiac, etc. the Earth and its size, gravity and pendulum motion, etc. the Sun, its size and distance, its motion, observations involving it, etc. the Moon, its phases, its size and distance, etc. (detailed maps of the Moon as seen through a telescope were included) lunar and solar eclipses the fixed stars the planets and their motions, etc. (representations of each as seen with a telescope were included); comets and novae ("new stars") the structure of the universe—the heliocentric and geocentric theories, etc. calculations related to astronomy.
Riccioli envisioned that the New Almagest would have three volumes, but only the first (with its 1500 pages split into two parts) was completed.
Pendulums and falling bodies Riccioli is credited with being the first person to precisely measure the acceleration due to gravity of falling bodies.Koyré 1955 (p. 349); Graney 2012. Books 2 and 9 of the New Almagest Riccioli included a significant discussion of and extensive experimental reports on the motions of falling bodies and pendulums.
He was interested in the pendulum as a device for precisely measuring time. By counting the number of pendulum swings that elapsed between transits of certain stars, Riccioli was able to experimentally verify that the period of a pendulum swinging with small amplitude is constant to within two swings out of 3212 (0.062%). He also reported that a pendulum's period increases if the amplitude of its swing is increased to 40 degrees. He sought to develop a pendulum whose period was precisely one second – such a pendulum would complete 86,400 swings in a 24-hour period. This he directly tested, twice, by using stars to mark time and recruiting a team of nine fellow Jesuits to count swings and maintain the amplitude of swing for 24 hours. The results were pendulums with periods within 1.85%, and then 0.69%, of the desired value; and Riccioli even sought to improve on the latter value. The seconds pendulum was then used as a standard for calibrating pendulums with different periods. Riccioli said that for measuring time a pendulum was not a perfectly reliable tool, but in comparison with other methods it was an exceedingly reliable tool.Meli 2006 (pp. 131–134); Heilbron 1999 (pp.180–181).
With pendulums to keep time (sometimes augmented by a chorus of Jesuits chanting in time with a pendulum to provide an audible timer) and a tall structure in the form of Bologna's Torre de Asinelli from which to drop objects, Riccioli was able to engage in precise experiments with falling bodies. He verified that falling bodies followed Galileo's "odd-number" rule so that the distance travelled by a falling body increases in proportion to the square of the time of fall, indicative of constant acceleration.An algebra-free explanation of the "odd-number" rule and distance increasing as the square of time: An object accelerating from rest (or zero speed) so that its speed steadily increases by 2 feet per second with every passing second, will, after one second has elapsed, be moving at 2 ft/s. Its average speed will be 1 ft/sec (the average of zero and 2 ft/s); therefore, having averaged 1 ft/s for 1 second, it will have traveled one foot. After two seconds have elapsed, the object will be moving at 4 ft/s, its average speed will be 2 ft/sec (the average of 0 ft/s and 4 ft/s); and, having averaged 2 ft/s for 2 seconds, it will have traveled four feet. After three seconds have elapsed the object will be moving at 6 ft/s, its average speed will be 3 ft/sec, and it will have traveled nine feet. After four seconds it will have traveled sixteen feet. Thus the distance the object travels increases as the square of elapsed time: (1 sec, 1 ft); (2 sec, 4 ft); (3 sec, 9 ft); (4 sec, 16 ft). Moreover, since, during the first second the object travels 1 ft, and during the next second it travels 4 ft – 1 ft = 3 ft, and during the third 9 ft – 4 ft = 5 ft, and during the fourth 16 ft – 9 ft = 7 ft, then the distance the object travels during each subsequent second follows an "odd-number" rule: 1 ft; 3 ft; 5 ft; 7 ft. According to Riccioli, a falling body released from rest travels 15 Roman feet (4.44 m) in one second, 60 feet (17.76 m) in two seconds, 135 feet (39.96 m) in three seconds, etc.Meli 2006 (pp. 131–134); Heilbron 1999 (pp.180–181); Koyré 1955 (p. 356). Other Jesuits such as the above-mentioned Cabeo had argued that this rule had not been rigorously demonstrated.Meli 2006 (p. 122). His results showed that, while falling bodies generally showed constant acceleration, there were differences determined by weight and size and density. Riccioli said that if two heavy objects of differing weight are dropped simultaneously from the same height, the heavier one descends more quickly so long as it is of equal or greater density; if both objects are of equal weight the denser one descends more quickly.
For example, in dropping balls of wood and lead that both weighed 2.5 ounces, Riccioli found that upon the leaden ball having traversed 280 Roman feet the wooden ball had traversed only 240 feet (a table in the New Almagest contains data on twenty one such paired drops). He attributed such differences to the air, and noted that air density had to be considered when dealing with falling bodies.Meli 2006 (pp. 132–134); Koyré 1955 (p. 352). He illustrated the reliability of his experiments by providing detailed descriptions of how they were carried out, so that anyone could reproduce them,Meli 2006 (p. 132). Riccioli's results are generally consistent with a modern understanding of bodies falling under the influence of gravity and air drag. His 15-60-135 values imply a gravitational acceleration "g" of 30 Roman feet per second per second (30 Rmft/s/s). The modern accepted value (g = 9.8 m/s/s) expressed in Roman feet is g = 33 Rmft/s/s; Riccioli's "g" differs from the accepted value by less than 10%. His statements about balls that are more dense, etc. reaching the ground first (that is, being less affected by air drag) agree with modern understanding. His result that a wooden ball fell 240 feet in the time a lead ball of the same weight fell 280 feet is generally consistent with modern understanding (although the 40 ft difference is somewhat less than expected). complete with diagrams of the Torre de Asinelli that showed heights, drop locations, etc.Raphael 2011 (82–86).