Galileo Galilei
(1564 - 1642)
Died at age 77 Birthday: May 3 Sign: Taurus
Brought before the Inquisition 3 times, twice pardoned by strangers, but the third time he was convicted by a friend.
Galileo Galilei is as famed and revered today as he was infamous and reviled in his own time. A brilliant mathematician, astronomer, professor, physicist, and inventor, Galileo founded the modern science of mechanics. His experiments with the pendulum coupled with his advances on the telescope proved Copernicus' theory that the Earth revolved around the sun. He was a pioneer of the scientific method and his views threatened the mythology of the church.
Galileo Galilei Quotes

  • “In questions of science the authority of a thousand is not worth the humble reasoning of an individual.”
  • “You cannot teach a man anything; you can only help him find it within himself.”
  • “The universe stands continually open to our gaze, but it cannot be understood unless one first learns to comprehend the language and interpret the characters in which it is written. It is written in the language of mathematics, and its characters are triangles, circles, and other geometric figures, without which it is humanly impossible to understand a single word of it; without these, one is wandering about in a dark labyrinth.”
  • “We can only infer that the totality of all numbers is infinite, and that the number of squares is infinite...; neither is the number of squares less than the totality of all numbers, nor the latter greater than the former; and finally, the attributes "equal," "greater," and "less," are not applicable to infinite, but only to finite quantities.”
  • “Infinities and indivisibles transcend our finite understanding, the former on account of their magnitude, the latter because of their smallness; imagine what they are when combined.”
  • “I do not feel obliged to believe that the same God who endowed us with sense, reason and intellect has intended us to forgo their use.”
  • “Measure what is measurable, and make measurable what is not so.”
  • “Take note, theologians, that in your desire to make matters of faith out of propositions relating to the fixity of sun and earth you run the risk of eventually having to condemn as heretics those who would declare the earth to stand still and the sun to change position -- eventually, I say, at such a time as it might be proved that the earth moves and the sun stands still.”
  • “I wish, my dear Kepler, that we could have a good laugh together at the extraordinary stupidity of the mob. What do you think of the foremost philosophers of this University? In spite of my oft-repeated efforts and invitations, they have refused, with the obstinacy of a glutted adder, to look at the planets or Moon or my telescope.”
  • “The Divine intellect indeed knows infinitely.”

Galileo's father was a musician.

He was born in the same year as William Shakespeare, and on the same day Michelangelo died.

Born in Pisa, Italy, Galileo would later move to Florence, birthplace of Leonardo da Vinci.

He was never married, but had three children.

He discovered that objects of varying weight will fall at the same speed.

Hearing of a magnifying optical device for viewing stars, Galileo quickly developed one himself. With his 20-power version, he noted 4 objects orbiting Jupiter -- though it takes him 8 days to identify them as moons.

When he presented an 8-power telescope to the Venetian Senate, the body is so impressed that his salary is doubled and his tenure at the University of Padua is guaranteed for life.

Galileo was the first to see the rings of Saturn.

He was first to observe the phases of Venus, again validating Copernicus' theory.

He invented the hydrostatic balance.

Drawing from the description in Dante's Inferno, he twice lectured on the size and shape of Hell.

Galileo's father wanted him to be a doctor, but Galileo dropped out of the University of Pisa and began studying mathematical geniuses Archimedes and Euclid.

He taught mathematics for 22 years, as well as geometry and astronomy, beginning in 1588 at the University of Padua.

He made a fine living on the side, tutoring in arithmetic, cosmography and surveying.

He designed and contracts for the production of a measuring device called a "sector," which he then sold to students, along with instruction on its usage.

Galileo invented the thermoscope, the precursor to the thermometer.

Galileo wrote that the motion of the tides are proof that the Earth moves. He was wrong, and was accused of being a heretic and brought before the Inquisition.

Galileo laments that his friend Johannes Kepler is "interested in the action of the moon on the water (influencing tides), and in other occult phenomena, and similar childishness." But Kepler is correct.

In proving that the Earth revolved around the sun, rather than vice-versa, Galileo overturned a belief championed by Greek philosopher Aristotle.

Galileo's experiments with the pendulum led to the invention of the pulsilogium, a device for measuring the pulse.

Sixteenth century church doctrine states that the heavens are constant and unchanging. After observing a supernova, Galileo proves otherwise.

Galileo was "Chief Mathematician of the University of Pisa and Philosopher and Mathematician to the Grand Duke of Tuscany," a lifetime appointment.

Galileo was enjoined into the Lincean Academy, an organization dedicated to the study of nature. The academy's exclusive membership is capped perpetually at 150 members.

The spacecraft Galileo began orbiting Jupiter in 1995, 353 years after his death.

January 8, 1642: Galileo was placed under house arrest in 1633 after his third appearance before the Inquisition. By 1635 he was completely blind. He died on January 8, 1642, the year Isaac Newton was born. His body is interred at the Santa Croce cemetery in Florence, alongside Guglielmo Marconi, the man who battled Nikola Tesla for the inventionpatent of the radio, and the artist Michelangelo.