Galileo

Galileo (Galileo Galilei) (găl'ĭlē`ō; gälēlĕ`ō gälēlĕ`ē), 1564–1642, great Italian astronomer, mathematician, and physicist. By his persistent investigation of natural laws he laid foundations for modern experimental science, and by the construction of astronomical telescopes he greatly enlarged humanity's vision and conception of the universe. He gave a mathematical formulation to many physical laws.

Contributions to Physics

His early studies, at the Univ. of Pisa, were in medicine, but he was soon drawn to mathematics and physics. It is said that at the age of 19, in the cathedral of Pisa, he timed the oscillations of a swinging lamp by means of his pulse beats and found the time for each swing to be the same, no matter what the amplitude of the oscillation, thus discovering the isochronal nature of the pendulum, which he verified by experiment. Galileo soon became known through his invention of a hydrostatic balance and his treatise on the center of gravity of solid bodies. While professor (1589–92) at the Univ. of Pisa, he initiated his experiments concerning the laws of bodies in motion, which brought results so contradictory to the accepted teachings of Aristotle that strong antagonism was aroused. He found that bodies do not fall with velocities proportional to their weights, but he did not arrive at the correct conclusion (that the velocity is proportional to time and independent of both weight and density) until perhaps 20 years later. The famous story in which Galileo is said to have dropped weights from the Leaning Tower of Pisa is apocryphal. The actual experiment was performed by Simon Stevin several years before Galileo's work. However, Galileo did find that the path of a projectile is a parabola, and he is credited with conclusions foreshadowing Newton's laws of motion.

Contributions to Astronomy

In 1592 he began lecturing on mathematics at the Univ. of Padua, where he remained for 18 years. There, in 1609, having heard reports of a simple magnifying instrument put together by a lens-grinder in Holland, he constructed the first complete astronomical telescope. Exploring the heavens with his new aid, Galileo discovered that the moon, shining with reflected light, had an uneven, mountainous surface and that the Milky Way was made up of numerous separate stars. In 1610 he discovered the four largest satellites of Jupiter, the first satellites of a planet other than Earth to be detected. He observed and studied the oval shape of Saturn (the limitations of his telescope prevented the resolving of Saturn's rings), the phases of Venus, and the spots on the sun. His investigations confirmed his acceptance of the Copernican theory of the solar system; but he did not openly declare a doctrine so opposed to accepted beliefs until 1613, when he issued a work on sunspots. Meanwhile, in 1610, he had gone to Florence as philosopher and mathematician to Cosimo II de' Medici, grand duke of Tuscany, and as mathematician at the Univ. of Pisa.

Conflict with the Church

In 1611 he visited Rome to display the telescope to the papal court. In 1616 the system of Copernicus was denounced as dangerous to faith, and Galileo, summoned to Rome, was warned not to uphold it or teach it. But in 1632 he published a work written for the nonspecialist, Dialogo … sopra i due massimi sistemi del mondo [dialogue on the two chief systems of the world] (tr. 1661; rev. and ed. by Giorgio de Santillana, 1953; new tr. by Stillman Drake, 1953, rev. 1967); that work, which supported the Copernican system as opposed to the Ptolemaic, marked a turning point in scientific and philosophical thought. Again summoned to Rome, he was tried (1633) by the Inquisition and brought to the point of making an abjuration of all beliefs and writings that held the sun to be the central body and the earth a moving body revolving with the other planets about it. Since 1761, accounts of the trial have concluded with the statement that Galileo, as he arose from his knees, exclaimed sotto voce, "E pur si muove" [nevertheless it does move]. That statement was long considered legendary, but it was discovered written on a portrait of Galileo completed c.1640.

After the Inquisition trial Galileo was sentenced to an enforced residence in Siena. He was later allowed to live in seclusion at Arcetri near Florence, and it is likely that Galileo's statement of defiance was made as he left Siena for Arcetri. In spite of infirmities and, at the last, blindness, Galileo continued the pursuit of scientific truth until his death. His last book, Dialogues Concerning Two New Sciences (tr., 3d ed. 1939, repr. 1952), which contains most of his contributions to physics, appeared in 1638. In 1979 Pope John Paul II asked that the 1633 conviction be annulled. However, since teaching the Copernican theory had been banned in 1616, it was technically possible that a new trial could find Galileo guilty; thus it was suggested that the 1616 prohibition be reversed, and this happened in 1992. The pope concluded that while 17th-century theologians based their decision on the knowledge available to them at the time, they had wronged Galileo by not recognizing the difference between a question relating to scientific investigation and one falling into the realm of doctrine of the faith.

Bibliography

See biography by L. Geymonat (tr. 1965); studies by G. de Santillana (1955), S. Drake (1970, 1978, and 1980), and W. R. Shea (1973); G. de Santillana, The Crime of Galileo (1955, repr. 1976); M. A. Finocchiaro, Galileo and the Art of Reasoning (1980).

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Galileo (Galilei)

Galileo, oil painting by Justus Sustermans, c. 1637; in the Uffizi Gallery, Florence.

(credit: SCALA/Art Resource, New York)

(born Feb. 15, 1564, Pisa—died Jan. 8, 1642, Arcetri, near Florence) Italian mathematician, astronomer, and physicist. Son of a musician, he studied medicine before turning his attention to mathematics. His invention of the hydrostatic balance (c. 1586) made him famous. In 1589 he published a treatise on the centre of gravity in solids, which won him the post of mathematics lecturer at the University of Pisa. There he disproved the Aristotelian contention that bodies of different weights fall at different speeds; he also proposed the law of uniform acceleration for falling bodies and showed that the path of a thrown object is a parabola. The first to use a telescope to study the skies, he discovered (1609–10) that the surface of the Moon is irregular, that the Milky Way is composed of stars, and that Jupiter has moons (see Galilean satellite). His findings led to his appointment as philosopher and mathematician to the grand duke of Tuscany. During a visit to Rome (1611), he spoke persuasively for the Copernican system, which put him at odds with Aristotelian professors and led to Copernicanism's being declared false and erroneous (1616) by the church. Obtaining permission to write about the Copernican system so long as he discussed it noncommittally, he wrote his Dialogue Concerning the Two Chief World Systems (1632). Though considered a masterpiece, it enraged the Jesuits, and Galileo was tried before the Inquisition, found guilty of heresy, and forced to recant. He spent the rest of his life under house arrest, continuing to write and conduct research even after going blind in 1637.

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Galileo

NASA mission to study Jupiter and its Galilean satellites with an orbiting spacecraft and an atmospheric probe, launched in 1989. Though the failure of its high-gain antenna resulted in its data being transmitted back to Earth very slowly, the mission returned a wealth of valuable information. En route to Jupiter, the craft took the first detailed images of two asteroids. On its arrival in 1995, its atmospheric probe descended by parachute into Jupiter's upper cloud layers, detecting large thunderstorms. In a series of flybys of the Galilean moons, the orbiter observed volcanoes on Io hotter than any on Earth and found evidence of a liquid ocean below Europa's icy surface, a magnetic field around Ganymede, and a possible subsurface ocean on Callisto.

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A satellite-based radio navigation system initiated by the European Union and European Space Administration (ESA). Using 27 satellites and three spares, Galileo is expected to be completed by 2011 and be interoperable with the United States GPS and Russian GLONASS systems. Positioning accuracy is expected to be brought down to one meter (GPS is 20m; GLONASS is 60m). The first Galileo satellite (GIOVE-A) was launched in late 2005. For more information, visit http://europa.eu.int/comm/dgs/energy_transport/galileo. See GNSS and GPS.

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Galileo

(1564–1642) Italian mathematician, astronomer, and physicist. [Ital. Hist.: EB, IV: 388]

See : Astronomy

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Galileo - ["Galileo: A Strongly Typed Interactive Conceptual Language", A. Albano et al, ACM Trans Database Sys 10(2):230-260 (June 1985)].