1543 - Nicolaus Copernicus (1473-1543) publishes De revolutionibus, and Andreas Vesalius (1514-64), On the Fabric of the Human Body.
1545 - Council of Trent convenes under Pope Paul III; first ten sessions last two years.
1551 - Collegio Romano, or Pontifical Gregorian University, founded by Jesuits in Rome. Council of Trent reconvenes.
1559 - First worldwide Index of Prohibited Books promulgated by the Roman Inquisition.
1562-63 - Third convention and final sessions of the Council of Trent.
1564 - Galileo is born in Pisa, February 15. Michelangelo Buonarroti dies in Florence, February 18. William Shakespeare is born in England, April 23.
1569 - Cosimo I, duke of Florence, named grand duke of Tuscany by authority of Pope Pius V.
1572 - Tycho Brahe (1546-1601) of Denmark observes a nova and concludes that changes could occur in the heavens.
1577 - Studies of comets by Tycho convince him the heavens could not consist of solid spheres, though he rejects the Copernican system.
1581 - Galileo enrolls at University of Pisa.
1582 - Gregorian calendar replaces Julian in Catholic Europe.
1585 - Galileo abandons studies at Pisa without a university degree.
1587 - Ferdinando I becomes grand duke of Tuscany when his older brother, Francesco, dies of malaria.
1589 - Galileo begins teaching at Pisa; develops a rudimentary thermometer; begins to study falling bodies. 1591 Vincenzio Galilei (father) dies.
1592 - Galileo begins teaching at the University of Padua.
1600 - Giordano Bruno burns at the stake in Rome. Virginia Galilei (daughter) is born in Padua.
1601 - Livia Galilei (daughter) is born in Padua. Tycho Brahe dies.
1603 - Prince Federico Cesi founds Lyncean Academy in Rome.
1604 - New star appears in the heavens, generating debate and three public lectures by Galileo.
1605 - Prince Cosimo de’ Medici takes instruction from Galileo.
1606 - Galileo publishes treatise on geometric and military compass; Vincenzio Galilei (son) is born in Padua.
1607 - Baldessar Capra publishes pirated Latin edition of Galileo’s instructions for geometric and military compass.
1608 - Hans Lippershey invents a refracting telescope in Holland. Prince Cosimo marries Maria Maddalena, archduchess of Austria.
1609 - Grand Duke Ferdinando I dies; Cosimo II succeeds him. Galileo improves telescope, observes and measures mountains on the Moon. Johannes Kepler (1571-1630) publishes first two laws of planetary motion.
1610 - Galileo discovers the moons of Jupiter. The Starry Messenger is published. Galileo is appointed chief mathematician and philosopher to the grand duke of Tuscany, Cosimo II.
1611 - Galileo visits Rome, is elected to membership in the Lyncean Academy.
1612 - Bodies That Stay Atop Water or Move Within It is published in Florence.
1613 - Prince Cesi publishes Galileo’s Sunspot Letters; Virginia and Livia Galilei (daughters) enter the Convent of San Matteo in Arcetri.
1614 - Virginia and Livia Galilei assume religious habit.
1616 - Galileo writes his “Theory on the Tides.” Edict issued in Rome against Copernican doctrine. Virginia Galilei professes her vows as Suor Maria Celeste. Shakespeare and Miguel de Cervantes die.
1617 - Livia Galilei professes vows as Suor Arcangela.
1618 - Three comets appear, generating interest and debate; Jesuit father Orazio Grassi lectures on comets at Collegio Romano; Thirty Years’ War begins.
1619 - Grassi’s account of the comets is published anonymously; Mario Guiducci delivers Discourse on the Comets, provoking pseudonymous Astronomical and Philosophical Balance. Kepler publishes third law of planetary motion. Galileo’s mistress, Marina Gamba, dies. Vincenzio Galilei (son) is legitimized.
1623 - Galileo’s sister Virginia dies. Maffeo Cardinal Barberini becomes Pope Urban VIII. Galileo dedicates The Assayer to him.
1624 - Galileo travels to Rome for papal audience.
1628 - William Harvey (1578-1657) in England describes the circulation of the blood.
1629 - Bubonic plague enters northern Italy from Germany.
1630 - Galileo visits Rome to obtain printing license for his Dialogue. Prince Cesi dies. Bubonic plague strikes Florence.
1631 - Michelangelo Galilei (brother) dies of plague in Germany.
1632 - Galileo publishes Dialogue on the Two Chief World Systems: Ptolemaic and Copernican.
1633 - Galileo stands trial for heresy by the Holy Office of the Inquisition; Dialogue is prohibited.
1634 - Suor Maria Celeste Galilei dies in Arcetri on April 2.
1636 - Letter to Grand Duchess Cristina is published in Holland, in Latin and Italian.
1637 - Galileo discovers lunar libration, loses his eyesight.
1638 - Louis Elzevir publishes Galileo’s Two New Sciences in Leiden, Holland.
1641 - Vincenzio Galilei draws his father’s design for a pendulum clock.
1642 - Galileo dies in Arcetri, January 8. Isaac Newton is born in England, December 25.
1643 - Galileo’s student Evangelista Torricelli (1608-47) invents mercury barometer.
1644 - Pope Urban VIII dies.
1648 - Thirty Years’ War ends.
1649 - Vincenzio Galilei (son) dies in Florence, May 15.
1654 - Grand Duke Ferdinando II improves on Galileo’s thermometer by closing the glass tube to keep air out.
1655-56 - Christiaan Huygens (1629-95) improves telescope, discovers largest of Saturn’s moons, sees Saturn’s “companions” as a ring, patents pendulum clock.
1659 - Suor Arcangela dies at San Matteo, June 14.
1665 Jean-Dominique Cassini (1625-1712) discovers and times the rotation of Jupiter and Mars.
1669 - Sestilia Bocchineri Galilei dies.
1670 - Grand Duke Ferdinando II dies, succeeded by his only surviving son, Cosimo III.
1676 - Ole Roemer (1644-1710) uses eclipses of Jupiter’s moons to determine the speed of light; Cassini discovers gap in Saturn’s rings.
1687 - Newton’s laws of motion and universal gravitation are published in his Principia.
1705 - Edmond Halley (1656-1742) studies comets, realizes they orbit the Sun, predicts return of a comet later named in his honor.
1714 - Daniel Fahrenheit (1686-1736) develops mercury thermometer with accurate scale for scientific purposes.
1718 - Halley observes that even the fixed stars move with almost imperceptible “proper motion” over long periods of time.
1728 - English astronomer James Bradley (1693-1762) provides first evidence for the Earth’s motion through space based on the aberration of starlight.
1755 - Immanuel Kant (1724-1804) discerns the true shape of the Milky Way, identifies the Andromeda nebula as a separate galaxy.
1758 - “Halley’s comet” returns.
1761 - Mikhail Vasilyevich Lomonosov (1711-65) realizes Venus has an atmosphere.
1771 - Comet hunter Charles Messier (1730-1817) identifies a list of noncometary objects, many of which later prove to be distant galaxies.
1781 - William Herschel (1738-1822) discovers the planet Uranus.
1810 - Napoleon Bonaparte, having conquered the Papal States, transfers the Roman archives, including those of the Holy Office with all records of Galileo’s trial, to Paris.
1822 - Holy Office permits publication of books that teach Earth’s motion.
1835 - Galileo’s Dialogue is dropped from Index of Prohibited Books.
1838 - Stellar parallax, and with it the distance to the stars, is detected independently by astronomers working in South Africa, Russia, and Germany; Friedrich Wilhelm Bessel (1784-1846) publishes the first account of this phenomenon, for the star 61 Cygni.
1843 - Galileo’s trial documents are returned to Italy.
1846 - Neptune and its largest moon are discovered by predictions and observations of astronomers working in several countries. 1851 Jean-Bernard-Leon Foucault (1819-68) in Paris demonstrates the rotation of the Earth by means of a two-hundred-foot pendulum.
1861 - Kingdom of Italy proclaimed, uniting most states and duchies.
1862 - French chemist Louis Pasteur (1822-95) publishes germ theory of disease.
1877 - Asaph Hall (1829-1907) discovers the moons of Mars.
1890-1910 - Complete works, Le Opere di Galileo Galilei, are edited and published in Florence by Antonio Favaro.
1892 - University of Pisa awards Galileo an honorary degree—250 years after his death.
1893 - Providentissimus Deus of Pope Leo XIII cites Saint Augustine, taking the same position Galileo did in his Letter to Grand Duchess Cristina, to show that the Bible did not aim to teach science.
1894 - Pasteur’s student Alexandre Yersin (1863-1943) discovers bubonic plague bacillus and prepares serum to combat it.
1905 - Albert Einstein (1879-1955) publishes his special theory of relativity, establishing the speed of light as an absolute limit.
1908 - George Ellery Hale (1868-1938) discerns the magnetic nature of sunspots.
1917 - Willem de Sitter (1872-1934) intuits the expansion of the universe from Einstein’s equations.
1929 - American astronomer Edwin Hubble (1889-1953) finds evidence for expanding universe.
1930 - Roberto Cardinal Bellarmino is canonized as Saint Robert Bellarmine by Pope Pius XI.
1935 - Pope Pius XI inaugurates Vatican Observatory and Astrophysical Laboratory at Castel Gandolfo.
1950 - Humani generis of Pope Pius XII discusses the treatment of unproven scientific theories that may relate to Scripture; reaches same conclusion as Galileo’s Letter to Grand Duchess Cristina.
1959 - Unmanned Russian Luna 3 spacecraft radios first views of the Moon’s far side from lunar orbit.
1966 - Index of Prohibited Books is abolished following the Second Vatican Council.
1969 - American astronauts Neil Armstrong and Buzz Aldrin walk on the Moon.
1971 - Apollo 15 commander David R. Scott drops a falcon feather and a hammer on the lunar surface; when they fall together he says, “This proves that Mr. Galileo was correct.”
1979 - Pope John Paul II calls for theologians, scholars, historians, to reexamine Galileo’s case.
1982 - Pope John Paul II establishes Galileo Commission with four formal study groups to reinvestigate the Galileo affair.
1986 - Halley’s comet returns, observed by a waiting armada of spacecraft.
1989 - National Aeronautics and Space Administration launches Galileo spacecraft to study the moons of Jupiter at close range.
1992 - Pope John Paul II publicly endorses Galileo’s philosophy, noting how “intelligibility, attested to by the marvelous discoveries of science and technology, leads us, in the last analysis, to that transcendent and primordial thought imprinted on all things.”
1995 - Galileo reaches Jupiter.
1999 - Galileo’s successful reconnaissance of the Medicean stars, now better known as the Galilean satellites of Jupiter, continues to enlighten astronomers everywhere.