Religious Scientists: Fr. Francesco Grimaldi S.J. (1618-1663), Optics of Diffraction
By Br. Robert Macke | 29 Sep 2019
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This entry is part [part not set] of 15 in the series Religious Scientists of the Catholic Church
Today I present yet another Jesuit physicist/astronomer: Francesco Maria Grimaldi. He made a number of contributions in physics and astronomy, many of which in collaboration with another Jesuit: Fr. Giovanni Battista Riccioli S.J. (1598-1671). I will deal with Riccioli in a future post. However, Grimaldi can take full credit for pioneering the study of diffraction of light, and in coining the term, “diffraction.”
Biographical Sketch: Grimaldi was born in Bologna in 1618. His father, a wealthy silk merchant, died when Francesco was still very young. In 1632 (at age 14) he entered the Jesuit order with his brother Vincenzo. After two years as a novice, he studied rhetoric for a year in Novellara. In 1635 he traveled to Parma for philosophy studies at the college of S. Rocco, but after only one year transferred to Ferrara to begin studying physics. He returned to Bologna to finish his philosophy studies. In 1638 he he was missioned to be professor at the Jesuit college of Bologna, where he would spend the next 25 years. He also undertook his theological studies during this period. He was ordained a priest in 1645. He finished his doctorate in 1647, and took final vows as a Jesuit in 1651. He died of a sudden illness in Bologna in 1663, at the age of 45.
He originally met Riccioli in Parma at S. Rocco, where the elder Jesuit taught him theology. When Grimaldi returned to Bologna in 1638, he found Riccioli there, and their scientific collaboration began. Between ca. 1640-50, he served as the assistant to Riccioli in his studies on geodesy, on the physics of falling bodies, and on lunar mapping.
It was after this period that Grimaldi did his work on diffraction.
Scientific Contributions:
Diffraction: Grimaldi was arguably the first to carefully observe the diffraction of light around solid objects. He conducted several experiments on the subject. For instance, a thin rod placed in a narrow beam of light would cast a shadow that was wider than predicted by purely geometric considerations. The wings of the shadow were bordered by colored bands. Also, sunlight passing through two narrow slits would interfere with itself, creating a dimmer result than sunlight passing through just one slit. He coined the term, “diffraction” for these phenomena. From these and other experiments, Grimaldi concluded that light moves analogously to a liquid (i.e. wave) rather than like the movement of solid particles.
His work on optics was published posthumously in 1665, in Physicomathesis de lumine, coloribus, et iride, aliisque annexis ( A physicomathematical thesis on light, colors, the rainbow and other related topics). Isaac Newton was aware of Grimaldi’s work in this field, and referenced it in his own work, “Optiks” (1704).
Collaboration with Riccioli: Grimaldi assisted Riccioli in several studies. Most of these will be described in greater detail in a future post.
They did experiments of the physics of falling bodies, dropping objects of different weights off Bologna’s Asinelli tower. They timed the fall with a pendulum. (Because some of the balls were light enough to be affected by air resistance, their results did not agree with Galileo’s conclusions.)
In astronomy, they attempted to measure the diameters of stars through a telescope. (In fact, they were measuring the star’s relative brightness.)
They surveyed a meridian line for Bologna.
They developed maps of lunar surface features. It was Riccioli who named the lunar seas (such as Mare Tranquilitatis), but it was largely Grimaldi who named craters after prominent scientists. Several of the craters are also named after Jesuit scientists. Most of these names are preserved in the official IAU nomenclature for lunar features.
There is a crater on the moon named after Grimaldi.
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Francesco grimaldi.
Francesco Maria Grimaldi, S.J . (April 2, 1618 to December 28, 1663) Grimaldi, a Jesuit priest, physicist, and astronomer, made one of the most significant discoveries in the history of physics, namely the phenomenon of diffraction of light, which shows that light does not travel in straight lines. Grimaldi’s discovery came about through careful and systematic observation. He studied the shadows cast on a screen by objects of various shapes illuminated by a thin beam of sunlight that he allowed to enter a darkened room through a small aperture in the wall. He discovered that within the shadow region on the screen there were faint fringes of light, and in the illuminated region there were faint fringes of shadow. Grimaldi not only discovered these “diffraction fringes,” he made very careful observations of their number, intensity, and coloration, and how they looked for objects of different shapes. It was also he who coined the term “diffraction.” It was not until the work of Thomas Young and Augustin-Jean Fresnel in the early 19 th century that diffraction was understood theoretically in terms of the wave nature of light. As quantum mechanics implies that all particles are also wave-like, the phenomenon of diffraction is of key importance in many branches of physics. Working with Riccioli , his fellow Jesuit, Grimaldi was the first to make accurate measurements of the gravitational acceleration at the earth’s surface ( g ), and also to map the surface of the moon.
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Francesco Maria Grimaldi
(1618—1663) Italian physicist and astronomer
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(1618–1663) Italian physicist
Grimaldi was born at Bologna, Italy, and became a Jesuit. In 1648 he became professor of mathematics at his order's college in his native city, where he acted as assistant to Giovanni Riccioli. His discovery of the phenomenon that he named the diffraction of light was reported in his posthumous work Physico-mathesis de lumine, coloribus, et iride (1665; Physicomathematical Studies of Light, Colors, and the Rainbow). He showed that when a beam of light passed through two successive narrow apertures, the pattern of light produced was a little bigger than it should have been if the light had traveled in an absolutely straight line. Grimaldi considered that the beam had bent outward very slightly, indicating that light must have a wave nature. The result presented difficulties to all 17th-century corpuscular theories of light.
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Grimaldi, Francesco Maria
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- Joseph F. MacDonnell 9
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Born Bologna, (Italy), 2 April 1613
Died Bologna, (Italy), 28 December 1663
Francesco Grimaldi was a pioneer in lunar mapping and a leading physicist, the discoverer of diffraction. His parents were Paride Grimaldi and Anna Cattani. He entered the Jesuit order in 1632, studied philosophy in Parma and Ferrara, and studied theology in Bologna. After this he undertook the study of astronomy under another Jesuit, Giovanni Riccioli , who would be his coworker for the rest of his life. Grimaldi held the post of professor of mathematics and physics at the Jesuit college in Bologna for many years.
The astronomical work of Grimaldi was closely related to that of Riccioli, who is known especially for his Almagestum novum , published in 1651. Riccioli gave a great deal of the credit to Grimaldi for the remarkable success of this publication. He especially praised Grimaldi’s ability to devise, build, and operate new observational instruments. In 1640, Grimaldi conducted experiments with Riccioli...
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Selected References
Cajori, Florian (1898). History of Physics . New York: Macmillan.
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Reilly, Conor (1958). “A Catalogue of Jesuitica in the Philosophical Transactions of the Royal Society of London.” Archivum Historicum Societatis Iesu 27: 339–362.
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Sommervogel, Carlos (1890–1960). Bibliothèque de la Compagnie de Jésus . 12 Vols. Brussels: Société Belge de Libraire.
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MacDonnell, J.F. (2014). Grimaldi, Francesco Maria. In: Hockey, T., et al. Biographical Encyclopedia of Astronomers. Springer, New York, NY. https://doi.org/10.1007/978-1-4419-9917-7_550
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COMMENTS
He discovered and was the first to make accurate observations on the diffraction of light [3] [4] (although by some accounts Leonardo da Vinci had earlier noted it [5]), and coined the word 'diffraction'.
Diffraction: Grimaldi was arguably the first to carefully observe the diffraction of light around solid objects. He conducted several experiments on the subject. For instance, a thin rod placed in a narrow beam of light would cast a shadow that was wider than predicted by purely geometric considerations.
These diffraction experiments showed Grimaldi that a new mode of transmission of light had been discovered and that this mode contradicts the notion of an exclusively rectilinear passage of light. Diffraction thus gave prima facie evidence for a fluid nature of light.
Francesco Maria Grimaldi, S.J. (April 2, 1618 to December 28, 1663) Grimaldi, a Jesuit priest, physicist, and astronomer, made one of the most significant discoveries in the history of physics, namely the phenomenon of diffraction of light, which shows that light does not travel in straight lines.
The effects of diffraction of light were first carefully observed and characterized by Francesco Maria Grimaldi, who also coined the term diffraction, from the Latin diffringere, 'to break into pieces', referring to light breaking up into different directions.
The discovery of diffraction by Francesco Maria Grimaldi is described. He described the experiments that led to its discovery in the book De Lumine, first published in 1665, two years after Grimaldi's death.
His discovery of the phenomenon that he named the diffraction of light was reported in his posthumous work Physico-mathesis de lumine, coloribus, et iride (1665; Physicomathematical Studies of Light, Colors, and the Rainbow).
Francesco Maria Grimaldi was the first scientist to recognize the tendency of light to bend around objects, a phenomenon he named diffraction. He also constructed one of the most detailed maps of the Moon up to his time, and may have initiated the practice of naming lunar features after scientists.
The Early Theory of Diffraction In this chapter we trace the creation of the wave theory of light and of the theory of diffraction by Grimaldi, Huygens, Young, Fresnel, and Kirchhoff. We recall the calculation of the diffraction by half-plane in the Fresnel-Kirchhoff approximation [11, 32, 133].
Grimaldi was one of the great physicists of his time and was an exact and skilled observer, especially in the field of optics. He discovered the diffraction of light and gave it its name (meaning “breaking up”). He also laid the groundwork for the later invention of the diffraction grating.