Galilei Galileo Biography and Discoveries

Galilei Galileo biography, dates: born Pisa, February 16 1564, died Arcetri, near Florence January 8 1642.

Galilei Galileo biography, Essentials: Galileo Galilei discovered crucial evidence supporting the Copernican model of the solar system, and made many other profound scientific discoveries.

Early life

This short biography does not cover Galileo Galilei's early life in any detail, because he had no prodigious childhood achievements. Also, none of his family were famous. Galileo's father was a financially troubled musician who made little impact on the world. But at least  he was of noble birth. This saved his son from extreme poverty. One advantage Galileo had was that the family, although poor, lived in the centre of things. They moved from Pisa to the equally glorious city of Florence in 1567. 

Inventions and scientific discoveries

The life of Galileo took off soon after he entered the University of Pisa as an undergraduate student. A boring cathedral service left him staring at the ceiling, hoping for the sermon to end. But instead of blanking out, as most students might, Galileo spotted a violently swinging chandelier, and decided to experiment. He measured the duration of its swing using his own pulse. As expected, it quickly slowed down until it was swinging gently. But Galileo was surprised to find that the time it took to perform one swing remained the same.

Intrigued, he began experimenting with pendulums at home, and found the duration of swing was dependent on the string's length (and nothing else). This led him to invent the pendulum timer--effectively, the first pendulum clock.

Shortly after his pendulum experiments, he turned his attention to freely falling objects and provided evidence against Aristotle's ideas on objects falling under gravity. He supposedly dropped different objects from the leaning tower of Pisa and found they accelerated toward the ground at the same rate (9.8 ms^-2). This meant, of course,  that they hit the ground at the same time when dropped together. This story is probably apocryphal, but he certainly rolled cannon balls down wooden slopes and obtained a similar result.

• A lead weight falls faster than a feather because air resistance has more effect on the feather. David R. Scott performed this experiment on the moon, and the lead weight and feather hit the ground simultaneously.

Galileo was appointed professor of mathematics at the University of Padua in 1592. Around this time he had three children (out of wedlock) to Marina Gamba of Venice. His two daughters were placed in convents. In 1610 Galileo moved to the Court of the Medici in Florence, perhaps invited there because of the discoveries he was making with a new invention--the telescope.

Hans Lippershey, a Flemish spectacle maker, patented the first telescope in 1608. But within a few months, Galileo constructed his own - and his had a magnification of X60, as opposed to his rivals X10. He turned this impressive instrument on the Moon. He found it "full of vast protuberances, deep chasms and sinuosities". It was far from the perfect sphere described by the Greeks. The imperfections of another heavenly body were shown up when Galileo's telescope  revealed spots on the Sun.

Added to this list of Galileo's seminal observations, in 1609, was the revelation of four moons in orbit about Jupiter. This was the first time anyone had seen objects circling a heavenly body. This implied that not everything had to orbit the earth, as Aristotle and Ptolemy had decreed.

Both the geocentric and heliocentric theories predicted that Venus should have phases like the moon (e.g. full Venus, half Venus, crescent Venus). But, as Copernicus had shown, the phases would be different depending on whether the geocentric or heliocentric theory applied. Galileo's observations of the phases of Venus agreed with the predictions of the Copernican model of the solar system.

Around this time, Johannes Kepler improved Copernicus’s theory. The predicted motions of the planets now fully agreed with the observations that the telescope users were making.

Galileo presented his heliocentric world view in a popular book entitled Dialogue Concerning the Two Chief World Systems. This is a dialogue between Salviati, (a heliocentrist) and Simplicio (a geocentrist). Another character, Sagredo, acts as moderator. Over the course of four days, they discuss the Ptolemaic and Copernican views of the universe. Simplicio is shown to be a buffoon, and is mocked by Sagredo (who sides with Salviati). Simplicio's pronouncements were similar to those made by the Pope at that time.

Soon after publication of the Dialogue, Galileo appeared before the Inquisition on trial for heresy. He was sentenced to indefinite house arrest, and denied the truth of his own arguments to save his skin. But after sentencing he couldn't resist muttering the now famous phrase "And yet it moves!".