Odierna (or Hodierna), Gioanbatista

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(b. Ragusa, Sicily, 13 April 1597; d. Palma di Montechiaro, Sicily, 6 April 1660)

astronomy, meteorology, natural history.

A self-taught scholar, Odierna was born into a modest artisan family, and, apart from a journey to Rome and Loreto, spent all his life in Sicily. He taught mathematics and astronomy at the school in Ragusa and later studied theology at Palermo. He observed the three comets of 1618–1619, which spurred the famous polemic resolved in 1623 by Galileo in his Saggiatore, Odierna’s observations were published many years later, when he was at the peak of his career.

After having read Galileo’s Sidereus nuncius, Odierna wrote an enthusiastic appraisal of it, in which he mentions that Galileo had presented him with a telescope of moderate focal distance. He served the barons of Montechiaro as chaplain and parish priest of their newly founded town of Palma di Montechiaro, in the province of Agrigento. They gave him an apartment on a high floor of their palace for his astronomical observations and later named him archpriest and court mathematician.

Odierna’s observations were aimed principally at determining the period of revolution of the four satellites of Jupiter. Like Galileo he tried to predict their eclipses, which would have helped to solve the long-standing, important problem of determining longitudes at sea; lacking sufficient knowledge of celestial mechanics, neither he nor Galileo was successful. Odierna’s pamphlet on the subject, Medicaeorum ephemerides(1656), was dedicated to Grand Duke Ferdinand II of Tuscany.

With Galileo’s telescope, Odierna made careful observations of Saturn but did not comprehend the true shape of its ring. In 1656 he published a pamphlet on it, Protei caelestis seu Saturni systema, and sent it to Huygens, the discoverer of the nature of the ring, Huygens replied, encouraging him to continue his useful observations, and sent him a drawing of his pendulum clock to assist him in his research.

After studying the passage of light through prisms Odierna offered a vague explanation of the rainbow and of the spectrum. His Thaumantia Junonis nuntia praeconium pulchritudinis (1647), on the nature of the iris and its colors, was followed in 1652 by Thaumantiae miraculum.

Odierna’s interest in meteorology resulted in some research on cyclones. In natural history his explanation of the structure and function of the retractile poison fangs of vipers anticipated the work of Redi. In his studies on the eyes of flies and of other insects, he used a microscope and a camera obscura.

Odierna’s numerous works were almost all published at Palermo and are now in the Municipal Library of Palermo and in the University Library of Catania. Although they cannot be said to be of real scientific value, Odierna must be considered among the pioneers of the experimental method.


Odierna’s “L’occhio delta mosca” was repub. with a commentary by C Pighetti, in Physis, 3 (1961), 309–335, with a complete bibliography.

Sec also G. Abetti, “Don Giovanni Battista Odierna,” in Celebrazioni siciliane (Urbino, 1939), 3–28, and “Onoranze a D. Gioanbatista Hodierna della cittá di Ragusa in Sicilia” in Physis, 3 (1961), 177–179.

Giorgio Abetti

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Odierna (or Hodierna), Gioanbatista

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