70 Fun Facts About Galileo Galilei

In which city was Galileo born in 1564?

The city was then part of the Duchy of Florence; his family moved to Florence itself when he was about eight.

Galileo's father Vincenzo was a leading figure in which field?

A lutenist and music theorist of the Florentine Camerata, he ran string-tension experiments that may be the oldest known non-linear law in physics; Galileo himself became an accomplished lutenist.

At his father's urging, Galileo enrolled at the University of Pisa in 1580 to study what?

He had seriously considered the priesthood; a physician's income was the deciding argument, and he was deliberately kept away from mathematics.

Watching a swinging chandelier in 1581, Galileo timed its swings against what?

He concluded the swings took the same time whatever their size, an idea Huygens turned into an accurate clock a century later.

What chance event persuaded the young Galileo to abandon medicine for natural philosophy?

He then had to talk his reluctant father into letting him change course.

Galileo's first publication, in 1586, described his design for what?

The little tract, La Bilancetta, first brought him to the attention of the scholarly world.

In 1588 Galileo took a teaching post at a Florentine academy devoted to what?

He taught perspective and chiaroscuro and struck up a lifelong friendship with the painter Cigoli.

Galileo's two 1588 lectures to the Florentine Academy attempted a rigorous cosmological model of what?

He tried to work out the shape, location and size of the hell described in the Divine Comedy.

From 1592 to 1610 Galileo taught geometry, mechanics and astronomy at which university?

It was during these years that he made most of his practical inventions and his first telescopic discoveries.

In 1594 Galileo obtained a patent from the Venetian Republic for what device?

His younger brother's debts gave him a lifelong incentive to invent things that would earn extra income.

What happened to Galileo's two illegitimate daughters, Virginia and Livia?

He considered them unmarriageable and placed them in the convent of San Matteo in Arcetri for life.

What religious name did Galileo's daughter Virginia take on entering the convent?

She is buried alongside her father in the Basilica of Santa Croce.

Galileo built his first telescope in 1609 after hearing of a device patented in which country?

Hans Lippershey's spyglass managed about 3x magnification; Galileo pushed his to roughly 30x.

On 25 August 1609 Galileo demonstrated one of his early telescopes to whom?

Telescopes were a profitable sideline; he sold them to merchants who found them useful at sea.

Galileo's 1610 treatise Sidereus Nuncius is known in English by what title?

It was the first scientific treatise ever published from observations made through a telescope.

Which English mathematician observed the Moon by telescope four months before Galileo?

Galileo went further, deducing that the ragged terminator was caused by mountains and craters, and even estimated their heights.

On 7 January 1610 Galileo noticed three 'fixed stars' in a line beside which planet?

Within a week he realised they were moons orbiting the planet, powerful evidence against an Earth-centred cosmos.

Galileo named his four newly found moons the 'Medicean stars' after the Grand Duke of where?

Later astronomers overruled him and called them the Galilean satellites instead.

Who spotted Jupiter's four moons a day after Galileo and later named them Io, Europa, Ganymede and Callisto?

The names appeared in his Mundus Iovialis of 1614 and are the ones still used.

Galileo proposed eclipses of his newly found moons as a clock to solve which navigation problem?

It proved impossible from a rolling deck but worked well on land, and was used to remap France.

Galileo's 1610 discovery that Venus shows a full set of phases made which model of the cosmos untenable?

Most astronomers responded by switching to hybrid geo-heliocentric systems rather than to full heliocentrism.

When Galileo first observed Saturn in 1610, what did he take its rings to be?

The 'bodies' vanished when the rings turned edge-on and reappeared in 1616, baffling him further.

Which planet did Galileo record in his notebooks in 1612 as just another dim star?

He even noted its motion against the background stars before losing track of it.

Galileo's long feud with the Jesuit Christoph Scheiner was over who first discovered what?

Neither man knew that Johannes Fabricius had already published on them.

What did Galileo's telescope reveal the Milky Way to be?

It had previously been thought nebulous; he also spotted the double star Mizar in 1617.

Galileo devised a way to measure a star's apparent size without a telescope, using what?

He measured how far away the rope had to be to blot out the star; the tiny sizes he got helped answer Tycho's anti-Copernican argument.

The Dialogue Concerning the Two Chief World Systems was originally titled after which natural phenomenon?

Galileo considered his tide theory proof that the Earth moves; the Inquisition ordered the reference removed.

Galileo's theory of the tides wrongly implied how many high tides per day?

He blamed the two daily tides at Venice on the shape and depth of the sea.

Galileo rejected Kepler's correct idea that the tides are caused by what?

His own explanation was the sloshing of the seas as the Earth rotated and orbited.

Galileo's The Assayer (1623) grew out of a dispute with a Jesuit over the nature of what?

The quarrel with Orazio Grassi widened into an argument about how science itself should be done.

Which pope was so charmed by The Assayer that he had it read aloud to him at table?

The same pope later felt mocked by the Dialogue and became the driving force behind Galileo's trial.

In The Assayer, Galileo wrote that the book of the universe 'is written in the language of' what?

Its characters, he added, are triangles, circles and other geometric figures.

In 1616, which cardinal delivered the Inquisition's order that Galileo abandon heliocentrism?

The same decree banned Copernicus's De Revolutionibus until it was 'corrected'.

Galileo's 1615 letter on the Bible and science was addressed to which Grand Duchess?

It expanded an eight-page letter to Benedetto Castelli into forty pages and was not printed until 1636.

In the Dialogue, the character Simplicio defends which view of the cosmos?

His name also connotes 'simpleton' in Italian, and the Pope suspected his own arguments had been put in Simplicio's mouth.

Galileo wrote the Dialogue in which language, so any literate countryman could read it?

It sold out before the Church could suppress it.

Galileo's 1633 sentence found him 'vehemently suspect of' what?

He was never formally charged with the crime itself, which spared him corporal punishment.

Galileo's sentence of formal imprisonment was commuted the following day to what?

He remained under it for the rest of his life, mostly at his villa at Arcetri near Florence.

As penance, Galileo was ordered to read what once a week for three years?

His daughter secured church permission to take the burden on herself.

According to legend, what did Galileo mutter after recanting heliocentrism?

The earliest written account dates from a century after his death; a painting once cited as proof is now thought to be a 19th-century copy.

To avoid Catholic censorship, Galileo's Two New Sciences (1638) was published where?

The Inquisition had banned publication of anything he wrote, including future works.

Two New Sciences summarised Galileo's work on kinematics and which other science?

Einstein cited it as a main reason to call Galileo the father of modern physics.

In which year did Galileo go completely blind?

He was allowed to travel to Florence for medical advice, and later designed a clock escapement without his sight.

Galileo coined 'Aurora Borealis' in 1619 from the Roman goddess of the dawn and the Greek name for what?

He used it for lights in the northern and southern sky caused by the solar wind energising the magnetosphere.

Galileo sold his geometric and military compass, with an instruction manual, for how many lire?

A course in how to use it cost more than the instrument itself; his instrument maker produced over 100 of them.

Galileo's 1593 thermometer worked by the expansion and contraction of what in a bulb?

The movement pushed water up and down an attached tube.

The word 'telescope' was coined for Galileo's instrument at a 1611 banquet of which academy?

Another member, Giovanni Faber, later coined 'microscope' for his other invention by analogy.

Late in life and totally blind, Galileo designed an escapement mechanism for what?

No clock using it was built until after Huygens made the first working pendulum clock in the 1650s.

Which engineering component did Galileo first describe in its 'caged' form, to cut friction?

Caged bearings stop the balls rubbing against one another.

Galileo's thought experiment about flies and fish in a ship's cabin illustrates which principle?

The laws of physics look the same in any system moving at constant speed, an idea central to Newton and later Einstein.

Galileo showed that the distance a body falls from rest is proportional to what?

He expressed the law in geometrical constructions; others later put it into algebra.

The story of Galileo dropping balls from the Leaning Tower of Pisa comes from a biography by which pupil?

Galileo left no account of it himself, and most historians think it was at most a thought experiment.

Most of Galileo's real experiments on falling bodies used what to slow the motion down?

Ramps reduced both the timing problem and air resistance.

Galileo's 1638 attempt to measure the speed of light used two observers equipped with what?

At less than a mile apart he could not tell whether the light was instantaneous; it was far too fast for the method.

Galileo was asked why suction pumps could not raise water beyond roughly what height?

He guessed, wrongly, that the water column simply broke under its own weight; the real cause was air pressure.

Galileo linked the pitch of a sound to its frequency by scraping what at different speeds?

The spacing of the chisel's skips gave him a measure of frequency.

Galileo is buried in which basilica in Florence?

The Pope's protests kept him out of the main body of the church until a monument was raised in 1737.

What was removed from Galileo's remains when he was reburied in 1737?

One of the fingers is on display at the Museo Galileo in Florence.

In which year did the Church drop the Dialogue and Copernicus's De Revolutionibus from the Index of prohibited books?

The general ban on heliocentric works had already gone in 1758.

Which pope acknowledged in 1992 that the Inquisition had erred in condemning Galileo?

He said the theologians had failed to distinguish between the Bible and its interpretation.

Which playwright wrote Life of Galileo?

The UN also marked Galileo's legacy by making 2009, the 400th anniversary of his first telescopic observations, the International Year of Astronomy.

Albert Einstein called Galileo the father of what?

Einstein praised his 'passionate fight against any kind of dogma based on authority'.

How old was Galileo when he died in January 1642?

He had gone on receiving visitors at his villa until the end, which followed a fever and heart palpitations.

The given name Galileo derives from a Latin word meaning what?

In 1614 a Dominican preacher supposedly punned on it with the verse 'Ye men of Galilee, why stand ye gazing up into heaven?'

Who was the mother of Galileo's three children, all born out of wedlock?

The daughters Virginia and Livia were born in 1600 and 1601 and a son, Vincenzo, followed in 1606.

Galileo's youngest brother Michelangelo, a lifelong drain on his finances, worked as what?

Music ran in the family: their father Vincenzo was a lutenist and theorist in the Florentine Camerata.

By 1624 Galileo had used and given away which instrument besides the telescope?

He had already magnified insect parts with a telescope in 1610; the Linceans helped coin the name 'microscope' too.

Before his house arrest at Arcetri, Galileo stayed with which friendly Archbishop of Siena?

He returned to his villa near Florence in 1634 and spent his remaining years there.

Which Florentine painter, a lifelong friend of Galileo, put a realistic telescopic Moon in a painting?

The friendship began when Galileo was a young teacher at the Florentine Accademia delle Arti del Disegno.

In which year was Galileo appointed to the chair of mathematics at Pisa?

His father died two years later, leaving him responsible for his younger brother, and he moved on to Padua in 1592.