Galileo Galilei, the Italian scientist, also called 'father of science', 'father of modern physics', 'father of modern science' and the 'father of modern observational astronomy' was the one who had various discoveries to his credit. He was the first to discover Jupiter's four moons, sunspots on the surface of the Sun, valleys and craters on the moon's surface, etc. He also researched on the period of the pendulum and stated that the period of a pendulum is constant, despite the length of the arc.
Birth and Family
Galileo Galilei was born on February 15th, 1564, at Pisa, Italy. He was the first of the six children born to his father,Vincenzo Galilei (musician) and his mother, Giulia degli Ammannati. At the age of six, Galileo's family moved to Florence, thus, he was educated at a monastery near Florence. As a teenager, he was inclined towards the Catholic faith and even intended to enter priesthood. However, his father wanted him to study medicine and as a result, Galileo (at the age of 17) enrolled for medicine, at the University of Pisa. Galileo never completed his medicine degree, instead he went ahead to study mathematics.
In 1581, as Galileo (a student) was researching on pendulums and inclined planes at the University of Pisa, he happened to notice the swinging motion of a lamp, in the cathedral of Pisa. He used his pulse to serve as a timer and timed the large and small swings. What he noticed was that irrespective of the angle of motion, the period of the pendulum remained constant. This discovery later lead to the invention of pendulum clocks. In 1589, he was commissioned as the chair of mathematics, in the University of Pisa. He held this post for three years and during this time wrote several essays about the theory of motion (which were not published).
Further, in 1592, he took up a job at the University of Padua, where his job was to teach medical students Euclid's geometry and geocentric astronomy and thus began an 18 year term at the University. While at Padua, Galileo got into a relationship with Maria Gamba, from Venice and even had three children out-of-wedlock. Some say that they didn't get married, because he was not financially stable. In 1602, Galileo confirmed that the period of the pendulum is constant, after obtaining results from experiments conducted by him and his students. He confirmed that the period of any pendulum is independent of the size of the arc, through which it passes (isochronism of a pendulum).
Opposition of Aristotle's Theory
During that time, Aristotle's theory reigned, according to which celestial objects in the heavens revolved around the Earth, and that the Earth was the center of the Universe. However, in 1604, Galileo opposed Aristotle's theory and openly confessed that he believed in Nicolaus Copernicus' theory, which stated that Earth along with the other planets revolved around the Sun. Until 1604, Galileo had only shown a passing interest in astronomy and his research was centered around motion theory, pendulum, free-falling bodies and inclined planes. However, gradually his interest in astronomy began to grow.
In 1609, he heard about some Dutch glass makers, who had come up with a lens which could be used to view distant objects. He used it to build a telescope and on August 25, 1609, presented his invention to the Venetian Senate. It was one evening in 1609, when he turned the telescope to the sky, and found astonishing facts such as craters and mountains on the moon. According to Aristotle, the heavenly bodies were blemish-free; however, he discovered that Aristotle was incorrect. He also studied the Milky Way and observed that it was full of countless stars. As he continued his study of the universe, he kept working on his telescope and built more powerful ones.
Discovery of Jupiter's moons
A few months later in 1610, he turned his telescope towards Jupiter and found star-like objects around Jupiter. He also noticed that these stars revolved around Jupiter, all in a straight line and thus drew the conclusion that these stars were actually satellites revolving around the planet Jupiter, and thus was the one to discover the four moons of Jupiter. This discovery confirmed his belief in the Copernican theory, that not all celestial objects revolved around the Earth. And so if celestial objects didn't revolve around the Earth, then there was the possibility that the Earth was not the center of the Universe as stated by Aristotle, with high possibility of the Sun being the center of the Universe.
Opposition by the Early Church
Galileo published all these sensational findings in a booklet called 'The Starry Messenger', which was published in Venice, Italy. This publication shook Aristotle's theory off it's feet. The discoveries and the publications made Galileo very famous; however, he also bore severe abuse. The early Church and Aristotle's followers opposed Galileo's findings.
However, Cosmos II, a member of the Medici family and Grand Duke of Tuscany invited Galileo to Florida, to become his personal mathematician in Florence and the University of Pisa. While at Florence, Galileo made some more discoveries: peculiar lumps on Saturn (which were later found to be Saturn's rings by Christiaan Huygens), phases of Venus and Mars and sunspots (dark spots on the surface of the sun).
Galileo's discoveries were bitterly opposed by the Church and they ordered Galileo not to "hold, teach, and defend in any manner whatsoever, in words or in print", the beliefs of the Copernican theory. Since Galileo was a Christian by birth, he followed the orders of the Church for sometime. However, once he realized that the anger towards his discoveries had subsided, he began researching once again.
Why did the Early Church oppose Galileo?
The Biblical references that the early Church used as the basis of their opposition was mainly Joshua 10:12,13, "On the day the LORD gave the Amorites over to Israel, Joshua said to the LORD in the presence of Israel: "O sun, stand still over Gibeon, O moon, over the Valley of Aijalon." So the sun stood still, and the moon stopped, till the nation avenged itself on its enemies, as it is written in the Book of Jashar. The Sun stopped in the middle of the sky and delayed going down about a full day." The other references from the Bible that were also used were: Psalm 96:10 and 93:1, "The world is firmly established, it cannot be moved". Ecclesiastes 1:5, "The sun rises and the sun sets, and hurries back to where it rises."
The early Church did not allegorically interpret the scripture. Allegorical interpretation is an interpretation that goes beyond literal interpretation. It involves understanding the deeper meaning of the written text. What was written in the book of Psalms and the book of Ecclesiastes were symbolic and were not to be taken literally. Further, in the book of Joshua, when Joshua prayed, he prayed for the Sun to stand still. Joshua's prayer is recorded in the Bible. However, the day was lengthened, which means the Earth stopped rotating about its axis, which is why it appeared to Joshua that the Sun had stopped.
Lifetime House Imprisonment
In the next six years, Galileo completed writing: 'Dialogue Concerning the Two Chief World Systems' and published it in 1632. The dialogue was based on the Copernican theory and through it, Galileo spoke about his convictions that there was truth in the Copernicus' theory. The result of this publication was that Galileo was ordered to appear before the Church elders in Rome. The Church ordered Galileo to publicly renounce his beliefs in the Copernicus theory and of the Earth being in motion. Further, he was sentenced to house imprisonment with no visitors allowed for the rest of his life.
Despite the appeals of various scientists and statesmen to the Pope and the Roman Inquisition, Galileo's punishment was not relaxed. It was only in 1637, when Galileo became blind that his punishment was relaxed to some extent and he was allowed to have visitors. However, despite his blindness, in 1638, Galileo managed to complete another research, which set the foundation for modern science of mechanics, called 'Discourses on Two New Sciences'. This manuscript was somehow smuggled to Holland, where it got published.
On 8 January 1642, Galileo passed away at the age of 77, and is called by some as 'a martyr for scientific truth'. It was only in 1992, that Pope John Paul II, stated that the early Church had made a mistake in condemning Galileo.