Galileo Galilei

Galileo Galilei (1564 –1642), commonly known as Galileo, was an Italian physicist, mathematician, astronomer and philosopher who played a major role in the Scientific Revolution. He was born in Pisa.physicistmathematicianastronomerphilosopherScientific Revolution

Although he seriously considered the priesthood as a young man, he enrolled for a medical degree at the University of Pisa at his father's urging. He did not complete this degree, but instead studied mathematics. In 1589, he was appointed to the chair of mathematics in Pisa. In 1592, he moved to the University of Padua, teaching geometry, mechanics, and astronomy until During this period Galileo made significant discoveries in both pure fundamental science (for example, kinematics of motion and astronomy) as well as practical applied science (for example, strength of materials). His multiple interests included the study of astrology, which at the time was a discipline tied to the studies of mathematics and astronomy.

Using a new model of telescope that he invented, Galileo was able to perfect the current astronomical observations and confirm Copernicus’ theory. But also other scientists started to believe in heliocentrism, and by 1616 the Church was already up in arms.

Galileo stayed neutral on the controversy about heliocentrism for a few years, but then, encouraged by the election of Cardinal Maffeo Barberini as Pope Urban VIII in 1623, he revived his project of writing a book on the subject. Barberini was a friend and admirer of Galileo, and had opposed the condemnation of Galileo in The book, Dialogue Concerning the Two Chief World Systems, was published in 1632, with formal authorization from the Inquisition and papal permission. But unfortunately things changed in Rome and the new Pope was not as open as his predecessor to the new theories.

Because of the “ Dialogue”, in 1633 Galileo was ordered to stand trial on suspicion of heresy. Galileo was found "vehemently suspect of heresy", namely of having held the opinions that the Sun lies motionless at the centre of the universe, that the Earth is not at its centre and moves, and that one may hold and defend an opinion as probable after it has been declared contrary to Holy Scripture. He was required to "abjure, curse and detest" those opinions. He was sentenced to formal imprisonment at the pleasure of the Inquisition. On the following day this was commuted to house arrest, which he remained under for the rest of his life.

Galileo and gravitation From the earliest times, gravity meant the tendency of most bodies to fall to earth. Aristotle (200 BC) was the first philosopher to attempt a quantitative description of falling motion: he wrote that an object fell at a constant speed, attained shortly after being released, and heavier things fell faster in proportion to their mass. Aristotle believed that in the absence of an action caused by a live being, bodies move of natural motion (either circular or rectilinear, or a combination of the two)

*Examples of unnatural, or “violent motion” are: pushing of a cart, shouting an arrow *Aristotle assumed that a force (push) is needed to sustain motion, and constant force=constant speed. *He claimed that an arrow is pushed by the air and at the same time it is subject to the laws of natural motion (and that’s why it ultimately fall down)

Galileo realized that force is not necessary to sustain motion, but instead causes a constant acceleration. He also realized that a falling body picked up speed at a constant rate—in other words, it had constant acceleration.

See Nova interactive web siteNova interactive web site (You can also watch gravity in a vacuum that we haven’t watched in class)gravity in a vacuum

So, Galileo also made the crucial observation that, if air resistance can be neglected, all bodies fall with the same acceleration, bodies of different weights dropped together reach the ground at the same time. He also observed that the distance travelled by a falling body is proportional to the square of the time. That is, S= -g t^2.

He also experimented with inclined planes and cannon balls

… very useful at a time were wars were very frequent. Perhaps because of Galileo’s skills as military engineer that his life was spared