Hyderabad: Galileo Galilei was an Italian physicist who formulated the basic law of falling bodies, which he verified by careful measurements. He was also an astronomer and mathematician who made fundamental contributions to the sciences of motion, astronomy, and strength of materials and to the development of the scientific method. He constructed a telescope with which he studied lunar craters, and discovered four moons revolving around Jupiter, and espoused the Copernican cause.
He was born in Pisa, Tuscany on February 15, 1564. Galileo's father, Vincenzo Galilei, was a well-known musician.
In 1581, Galileo was sent to the University of Pisa to study medicine. However, he became enamored with mathematics and decided to make the mathematical subjects and philosophy his profession, against the protests of his father.
Galileo first began teaching mathematics, privately in Florence and then during 1585-86 at Siena where he held a public appointment.
His mind was alerted to the excitement and importance of mathematics applied to practical problems, that is in effect, physics.
He timed the swinging of chandeliers in the cathedral and at once abstracted the essence of the problem so that he made pendulums of string and small weights. He established the relationship between length and time of swing, using his own pulse for measurement.
Later on, Galileo utilized the phenomenon to make his pulsilogium, a device timing the human pulse. He also designed a pendulum-regulated escapement for a proposed clock.
During this period he designed a new form of hydrostatic balance for weighing small quantities and wrote a short treatise, La bilancetta (“The Little Balance”), that circulated in manuscript form.
During 1545–1607, he also found some ingenious theorems on centres of gravity (again, circulated in manuscript) that brought him recognition among mathematicians and the patronage of Guidobaldo del Monte, a nobleman and author of several important works on mechanics.
In 1589, Galileo was appointed as the chair of mathematics at the University of Pisa. During his three years tenure, he wrote 'De Motu' a series of essays on the theory of motion that he never published.
In May 1609, Galileo received a letter from Paolo Sarpi telling him about a spyglass that a Dutchman had shown in Venice. From these reports, and using his own technical skills as a mathematician and as a craftsman, Galileo began to make a series of telescopes whose optical performance was much better than that of the Dutch instrument. His first telescope was made from available lenses and gave a magnification of about four times.
To improve on this. Galileo learned how to grind and polish his own lenses and by August 1609 he had an instrument with a magnification of around eight or nine.
By the end of 1609, Galileo had turned his telescope on the night sky and began to make remarkable discoveries. The astronomical discoveries he made with his telescopes caused a sensation.
Galileo claimed to have seen mountains on the Moon, to have proved the Milky Way was made up of tiny stars, and to have seen four small bodies orbiting Jupiter. These last, with an eye to getting a position in Florence, he quickly named them as 'the Medicean stars'.
The Venetian Senate, perhaps realizing that the rights to manufacture telescopes that Galileo had given them were worthless, froze his salary. He continued to make observations with his telescope.
Already in the Starry Messenger, he had given rough periods of the four moons of Jupiter, but more precise calculations were certainly not easy since it was difficult to identify from an observation that was moon I, which was II, which was III, and which was IV. He made a long series of observations and was able to give accurate periods by 1612.
At one stage in the calculations, he became very puzzled since the data he had recorded seemed inconsistent, but he had forgotten to take into account the motion of the Earth round the sun.
One would expect that Galileo's understanding of the pendulum, which he had since he was a young man, would have led him to design a pendulum clock. In fact, he only seems to have thought of this possibility near the end of his life, and around 1640 he did design the first pendulum clock.
Although Galileo put forward many revolutionary correct theories, he was not correct in all cases. In particular, when three comets appeared in 1618 he became involved in a controversy regarding the nature of comets. He argued that they were close to the Earth and caused by optical refraction.
A serious consequence of this unfortunate argument was that the Jesuits began to see Galileo as a dangerous opponent. Despite his private support for Copernicanism, Galileo tried to avoid controversy by not making public statements on the issue. However, he was drawn into the controversy through Castelli, who was a supporter of Copernicus. Castelli was asked to explain the apparent contradictions between the Copernican theory and Holy Scripture, he defended the Copernican position vigorously.
In 1616, Galileo wrote the Letter to the Grand Duchess which vigorously attacked the followers of Aristotle.
HIn February 1632 Galileo published Dialogue Concerning the Two Chief Systems of the World - Ptolemaic and Copernican. It takes the form of a dialogue between Salviati, who argues for the Copernican system, and Simplicio who is an Aristotelian philosopher.
The climax of the book is an argument by Salviati that the Earth moves which was based on Galileo's theory of the tides. Shortly after the publication of Dialogue Concerning the Two Chief Systems of the World - Ptolemaic and Copernican the Inquisition banned its sale and ordered Galileo to appear in Rome before them.
Found guilty, Galileo was condemned to lifelong imprisonment, but the sentence was carried out somewhat sympathetically and it amounted to house arrest rather than a prison sentence.
He died on 8 January 1642. It was a sad end for so great a man to die condemned of heresy. His will indicated that he wished to be buried beside his father in the family tomb in the Basilica of Santa Croce but his relatives feared, quite rightly, that this would provoke opposition from the Church. His body was concealed and only placed in a fine tomb in the church in 1737 by the civil authorities against the wishes of many in the Church.
