In the early 1600's Galileo was one of the first scientists to systematically investigate a question, using well planned, non-biased experiments in order to draw a logical conclusion. At the time others were using the more subjective Greek method of investigation, often drawing conclusions to fit their own views and disregarding or imaginatively explaining away results of their experiments that disagreed.
Early Life
Galileo Galilei, probably the only scientist to be popularly known by his first name only, was born on February 15, 1564 in Pisa, Italy. Galileo was born into a once-noble family. His father, Vincenzo Galilei, made his living as a lutenist, composer, theorist, singer, and teacher. He and his wife noticed Galileo's interest for maths at an early age and tried to dissuade him from this non-profitable career. They intended him to follow a medical profession, and sent him to a university in Pisa to do so, but while there Galileo accidentally wandered into a geometry lecture and was instantly captivated.
After talking to his father, Galileo left the university without a degree. He taught privately in Florence for a while before becoming head of mathematics at the University of Pisa. It was during this time he is said to have dropped two cannonballs, one ten times heavier than the other, from the top of the Leaning Tower, in order to demonstrate his theory that the masses are irrelevant to the speed of two falling objects. He also invented a hydrostatic balance and published a small booklet about it, which brought him to the attention of the scholarly world for the first time.
Mechanics
In 1592 Galileo's discoveries on the centre of gravity in solids, and pendulums, earned him a chair in mathematics at the University of Padua, where he remained until 1610. During this time he started to consider the motion of the tides on earth under the Copernican system and wrote a paper showing that machines transform energy rather than create it. Later, he resumed his experiments on inclined planes and pendulums, and formulated the basic law of falling bodies. He also invented a horse-drawn pump and a thermoscope.
Because it was impossible to accurately measure periods of time in the 1500's, Galileo used inclined planes to 'dilute' gravity; that is, when studying the motion of falling objects, he would roll the object down an inclined plane instead of dropping it from a height. By varying the masses, he could prove his theory that stated mass will not affect the speed of a falling object before his demonstration from the Leaning Tower. He was also able to show a body moving along an inclined plane moved with constant acceleration. This was important as it disproved the earlier theory that stated an object needed to be under a constant force to continue moving.
Galileo also introduced and expanded the concepts of projectiles and gravitation, stating that an object could be influenced by two forces at the same time, a horizontal that remained constant and a vertical that reached a
peak then accelerated downwards, which together formed a parabolic curve. He tested this theory using inclined planes and free-fall methods. This opposed Aristotle's theory of a fired object moving in two straight lines, one directly across and one straight down. Galileo's parabola discoveries subsequently made a science out of gunnery, and aided greatly in the use of cannons used in warfare of the time.
In 1610, Galileo was appointed philosopher and mathematician extraordinary to the Grand Duke of Tuscany at Medici Court in Florence. Continuing his experiments at Pisa, he established the laws of falling bodies, the laws of projectiles, and anticipated the laws of motion as established later by Newton. He gave the first direct and entirely conclusive demonstration of the laws of equilibrium, and explained the true principle of flotation.
Astronomical Discoveries
When, in 1604 a supernova was observed, Galileo argued with the philosophers who agreed with the Aristotelian notion that change could not occur in the heavens. If Aristotle could be wrong about that, he could also be wrong about an earth-based planetary system, he stated. News reached Padua of an instrument that magnified heavenly bodies invented in Holland, and this prompted him to abandon all other projects and build his own telescope. By the end of 1609, Galileo had a 32 power telescope that enabled him to see the moon's mountains, the starry nature of the Milky Way, and previously undiscovered objects revolving around Jupiter. These results were published in "The Starry Messenger", an Italian periodical of the time, which aroused great controversy among scientists until the statements could be tested by others. By the end of 1610, Galileo had observed the phases of Venus and had become a firm believer in the Copernican Heliocentric World System.
His observations using the telescope often pointed towards the Copernican planetary system. Using his telescope, Galileo observed mountains on the moon and spots on the sun, once again again disproving Aristotle's theory that the contents of the heavens were perfect. He also counted spots on the sun as it rotated and calculated it's apparent rotation and orientation. More importantly, he noticed four bodies orbiting Jupiter (still called the 'Galilean satellites'). These moons helped prove the theory that not all heavenly bodies orbited Earth.
Religious Conflict
Galileo regularly announced his various astronomical discoveries in popular publications of the time, which usually aroused great interest and often debate amongst the scientifically-minded readership. Galileo's telescopes became world famous and he sent them all over Europe so that others could carry out his experiments and confirm his findings. In 1611 he visited Rome, where he was met by the Catholic Church, who were unhappy with some of his theories. The system was thought to be anti-scriptural, and prompted Pope Pius V to declare Copernicanism a heresy, interrogating Galileo before the Inquisition and subsequently forcing him to stop teaching his theory in 1616. In countries other than Europe, however, his book was being translated and distributed with great interest.
During 1624, Galileo visited Rome again and met with the Pope of the time (Urban VIII) with whom he became friendly. Eight years later, Galileo published "Dialogue on the Two Chief World Systems", which discussed Ptolemy's and Copernicus's views by using two characters, each representing one system. Unfortunately the Pope was under the impression that the geocentric system supporter, 'Simplico', was a deliberate mocking caricature of himself, and Galileo was once again brought up in front of the Inquisition, charged as "vehemently suspected of heresy" and was confined to his villa in Arcetri for three years.
In 1637 Galileo became completely blind due to the numerous times he had directly looked into the sun as part of his observations, and his 17-year old student, Vincenzo Viviani, became the court mathematician. After Galileo's death on 8 January 1642, Vincenzo collected and edited a book of his works, and worked tirelessly to ensure his master was not forgotten. In the 1730s, when the Church allowed Galileo to be reburied in a grave with a suitable monument, with funds left by Vincenzo for that express purpose, his own remains were buried with Galileo's.
Influence
Galileo's discoveries and methods have influenced today's modern science immeasureably. Galileo's "induction rather than deduction" method of observing and recording became popular over the previous method of building conclusions on an assumed set of generalisations used by Greek scientists and philosophers before him. Although Archimedes had followed this same objective method over eighteen centuries before, it was Galileo who made it popular in Europe and eventually the world, and the same method that scientists use today to make hypothesises and draw conclusions. His studies in the field of mechanics on projectiles, gravitation and free-fall are still used today, and, most dramatically, his enlightenment of the world to earth's place in our planetary system and universe which, before he spoke out, was considered ridiculous and unthinkable. Galileo's more mechanical inventions of the thermoscope, pump, and obviously his virtual invention of the telescope and microscope, also add to his massive contributions to science today and for the future.