Galileo Galilei

Giulia Ammananti -  Galileo's mother. An aristocratic woman, she was dissatisfied with her middle- class financial status, and disapproved of Galileo's father's dabbling in music.

Aristotle  -  An ancient Greek philosopher and scientist, his theories on physics and astronomy informed the conventional wisdom of Galileo's day.

Robert Bellarmine  -  A Cardinal in the Roman Catholic Church and a member of the Jesuit order. A great intellect, he was initially well disposed to Galileo, but Galileo's enthusiasm for the Copernican system led to a falling-out between the men.

Nicholas Copernicus  -  A great Polish astronomer in the early 16th century, he first proposed the theory that the earth might go around the sun.

Vincenzo Galilei  -  Galileo's father. Vincenzo made a living in the wool trade, but his first love was music.

Marina Gambi  -  Galileo's mistress during his years at the University of Padua, and the mother of his three children

Johannes Kepler  -  A great German astronomer and contemporary of Galileo's, he was a staunch advocate of the Copernican system.

Ptolemy  -  A renowned astronomer in ancient Rome, he championed the geocentric theory, which placed the earth at the center of the universe.

Urban VIII  -  A liberal Cardinal who was friendly with Galileo before being elected Pope. However, Galileo's Dialogue Concerning the Two Chief World Systems alienated him–he felt it mocked him–and he refused to support the astronomer during his trial.

Virginia  -  Galileo's eldest and favorite daughter. She became a nun, and supported her father during his Inquisition trial.

Dialogue Concerning the Two Chief World Systems -   · Galileo's masterpiece. Published in 1632, this text took the form of a dialogue in which one of the speakers fiercely argued for the truth of the Copernican system. It was this work that led to Galileo's trial for heresy before the Inquisition.

Geocentricity  -   · This theory, championed by Ptolemy, Aristotle, and the Roman Catholic Church, held that the earth lies at the center of the universe.

Heliocentricity  -   · The theory, developed by Copernicus and championed by Galileo, which places the Earth in orbit around the sun.

Inquisition  -   · The Inquisition was a judicial institution formed by the Catholic Church to suppress heretics, or anyone otherwise corrupting the faith. The Inquisition took the form of a series of trials and executions, and the Inquisitors were famous for their wil lingness to torture and kill in the name of "Christianity." Galileo's arguments in favor of heliocentricity led them to bring charges of heresy against him.

Jesuits  -   · A religious order founded during the Counter-Reformation, the Jesuits represented the most intellectual of the Church's arms, and the order produced many great scientists. However, the Jesuits passionately championed orthodoxy, and when they became rivals with Galileo over scientific issues, they worked to ensure his downfall.

Roman Catholic Church  -   · Headed by the Pope in Rome, Catholicism constituted the only Christian church in Western Europe during medieval times. In the 15th and 16th centuries, however, the Protestant Reformation created breakaway churches in northern Europe, and Catholicism became locked in a struggle with the dissenters.

Sidereus Nuncius -   · Meaning "Starry Messenger," this was the title of the 1610 treatise in which Galileo described the early observations that he had made with his telescope. It described mountains on the moon, and other moons orbiting Jupiter, and became a sensational bestseller in Europe.

Counter-Reformation -   · The Catholic response to the Reformation, the Counter-Reformation began as an initiative of the Council of Trent in the 1540s, and involved a fierce defense of orthodoxy and tradition. The Jesuits, a new religious order, served as the chief agents of this movement, and the movement led the Church into conflict with the rising tide of scientific discoveries.

Protestant Reformation  -   · This movement began under Martin Luther in northern Europe, and by the mid-15th century had spread across Germany into Scandinavia and England. It protested the worldliness and corruption of Catholicism during the Renaissance, but also the Catholic tradition in general, as it sought to uncover an "original," "pure" form of Christianity, more in keeping with Jesus's original teachings and less preoccupied with ceremony. (For more information, see the History SparkNote on the Reformation.

Renaissance -   · Literally meaning "re-birth," the Renaissance saw the rebirth, or reintroduction, of classical art and literature in the 15th and 16th century, following the "dark ages" of the medieval period, during which these works had been forgotten or lost. Art and culture flowered, and an air of vibrancy pervaded Europe, and especially Italy, which was the center of the movement. The Renaissance produced some of the West's greatest works of art; however, it was also a time of corruption in political spheres, as well as in the Catholic Church; the Church's moral decadence during these years led to the Reformation. (For more information, see the History SparkNote on theItalian Renaissance.