Learn About Galileo Galilei

In this episode of the I Can't Sleep Podcast, learn about Galileo Galilei and his groundbreaking discovery that the Earth revolves around the Sun. Drift off to sleep with insights into his fascinating life and contributions to science. Happy sleeping!

Transcript

Welcome to the I Can't Sleep Podcast,

Where I read random articles from across the web to bore you to sleep with my soothing voice.

I'm your host,

Benjamin Boster.

Today's episode is from a Wikipedia article titled,

Galileo Galilei.

Galileo di Vincenzo Bonaiuti de Galilei,

Commonly referred to as Galileo Galilei,

Or simply Galileo,

Was an Italian astronomer,

Physicist,

And engineer,

Sometimes described as a polymath.

He was born in the city of Pisa,

Then part of the Duchy of Florence.

Galileo has been called the father of observational astronomy,

Modern era classical physics,

And the scientific method and modern science.

Galileo studied speed and velocity,

Gravity and free fall,

The principle of relativity,

Inertia,

Projectile motion,

And also worked in applied science and technology,

Describing the properties of the pendulum and hydrostatic balances.

He was one of the earliest Renaissance developers of the thermoscope and the inventor of various military compasses,

And used the telescope for scientific observations of celestial objects.

With an improved telescope he built,

He observed the stars of the Milky Way,

The phases of Venus,

The four largest satellites of Jupiter,

Saturn's rings,

Lunar craters,

And sunspots.

He also built an early microscope.

Galileo's championing of Copernican heliocentrism was met with opposition from within the Catholic Church and from some astronomers.

The matter was investigated by the Roman Inquisition in 1615,

Which concluded that heliocentrism was foolish,

Absurd,

And heretical since it contradicted the Ptolemaic system.

Galileo later defended his view that Galileo later defended his views in Dialogue Concerning the Two Chief World Systems,

1632,

Which appeared to attack Pope Urban VIII and thus alienated both the Pope and the Jesuits,

Who had both supported Galileo up until this point.

He was tried by the Inquisition,

Found vehemently suspect of heresy,

And forced to recant.

He spent the rest of his life under house arrest.

During this time he wrote Two New Sciences,

1638,

Primarily concerning kinematics and the strength of materials,

Summarizing work he had done around 40 years earlier.

Galileo was born in Pisa,

Then part of the Duchy of Florence,

Italy,

On the 15th of February 1564.

The first of six children of Vincenzo Galilei,

A lutenist,

Composer,

And music theorist,

And Giulia Ammonati,

Who had married in 1562.

Galileo became an accomplished lutenist himself and would have learned early from his father a skepticism for established authority.

Three of Galileo's five siblings survived infancy.

The youngest,

Michelangelo,

Also became a lutenist and composer,

Who added to Galileo's financial burdens for the rest of his life.

Michelangelo was unable to contribute his fair share to their father's promised dowries to their brothers-in-law,

Who would later attempt to seek legal remedies for payments due.

Michelangelo would also occasionally have to borrow funds from Galileo to support his musical endeavors and excursions.

These financial burdens may have contributed to Galileo's early desire to develop inventions that would bring him additional income.

When Galileo Galilei was eight,

His family moved to Florence,

But he was left under the care of Muzio de' Dali for two years.

When Galileo was ten,

He left Pisa to join his family in Florence,

And there he was under the tutelage of Jacopo Borghini.

He was educated,

Particularly in logic,

From 1575 to 1578,

In the Vallambrosa Abbey,

About 30 kilometers southeast of Florence.

Galileo tended to refer to himself only by his given name.

At the time,

Surnames were optional in Italy,

And his given name had the same origin as his sometimes family name,

Galilei.

Both his given and family name ultimately derived from an ancestor,

Galileo Bonaiuti,

An important physician,

Professor,

And politician in Florence in the 15th century.

Galileo Bonaiuti was buried in the same church,

The Basilica of Santa Croce in Florence,

Where about 200 years later Galileo Galilei was also buried.

When he did refer to himself with more than one name,

It was sometimes as Galileo Galilei Linceo,

A reference to his being a member of the Accademia dei Lincei,

An elite pro-science organization in Italy.

It was common for mid-16th century Tuscan families to name the eldest son after the parent's surname.

Hence,

Galileo Galilei was not necessarily named after his ancestor,

Galileo Bonaiuti.

Italian male given name Galileo,

And thence the surname Galilei,

Derives from the Latin galileus,

Meaning of Galilee,

A biblically significant region in northern Israel.

Because of that region,

The adjective galileus,

Greek galileus,

Latin galileus,

Italian galileo,

Which means Galilean,

Was used in antiquity,

Particularly by Emperor Julian,

To refer to Christ and his followers.

The biblical roots of Galileo's name and surname were to become the subject of a famous pun.

In 1614,

During the Galileo affair,

One of Galileo's opponents,

The Dominican priest Tomasco Caccini,

Delivered against Galileo a controversial and influential sermon.

In it,

He made a point of quoting Acts 1.

11.

Ye men of Galilee,

Why stand ye gazing up into heaven?

In the Latin version found in the Vulgate,

Viri Galilei,

Quid statis aspicentes in celum.

Despite being a genuinely pious Roman Catholic,

Galileo fathered three children out of wedlock with Marina Gamba.

They had two daughters,

Virginia,

Born 1600,

And Livia,

Born 1601,

And a son,

Vincenzo,

Born 1606.

Due to their illegitimate birth,

Galileo considered the girls unmarriageable,

If not posing problems of prohibitively expensive support or dowries,

Which would have been similar to Galileo's previous extensive financial problems with two of his sisters.

Their only worthy alternative was their religious life.

Both girls were accepted by the convent of San Matteo in Acetri and remained there for the rest of their lives.

Virginia took the name Maria Celeste upon entering the convent.

She died on the 2nd of April 1634 and is buried with Galileo at the Basilica of Santa Croce,

Florence.

Livia took the name Sister Arcangela and was ill for most of her life.

Vincenzo was later legitimized as the legal heir of Galileo and married Cestilia Boccanetti.

Although Galileo seriously considered the priesthood as a young man,

At his father's urging he instead enrolled in 1580 at the University of Pisa for a medical degree.

He was influenced by the lectures of Girolamo Borro and Francesco Buonamici of Florence.

In 1581,

When he was studying medicine,

He noticed a swinging chandelier which air currents shifted about to swing in larger and smaller arcs.

To him,

It seemed by comparison with his heartbeat that the chandelier took the same amount of time to swing back and forth no matter how far it was swinging.

When he returned home,

He set up two pendulums of equal length and swung one with a large sweep and the other with a small sweep and found that they kept time together.

It was not until the work of Christian Huygens,

Almost 100 years later,

That the tautocrone nature of a swinging pendulum was used to create an accurate timepiece.

Up to this point,

Galileo had deliberately been kept away from mathematics,

Since a physician earned a higher income than a mathematician.

However,

After accidentally attending a lecture on geometry,

He talked his reluctant father into letting him study mathematics and natural philosophy instead of medicine.

He created a thermoscope,

A forerunner to the thermometer,

And in 1586 published a small book on the design of a hydrostatic balance he had invented,

Which first brought him to the attention of the scholarly world.

Galileo also studied disegno,

A term encompassing fine art,

And in 1588 obtained the position of instructor in the Accademia delle Arti del Disegno in Florence,

Teaching perspective and chiaroscuro.

In the same year,

Upon invitation by the Florentine Academy,

He presented two lectures on the shape,

Location,

And size of Dante's Inferno in an attempt to propose a rigorous cosmological model of Dante's Hell.

Being inspired by the artistic tradition of the city and the works of the Renaissance artists,

Galileo acquired an aesthetic mentality.

While a young teacher at the Accademia,

He began a lifelong friendship with the Florentine painter Cigali.

In 1589,

He was appointed to the chair of mathematics in Pisa.

In 1591,

His father died,

And he was entrusted with the care of his younger brother,

Michelangelo.

In 1592,

He moved to the University of Padua,

Where he taught geometry,

Mechanics,

And astronomy until 1610.

During this period,

Galileo made significant discoveries in both pure fundamental science,

For example,

Kinematics of motion in astronomy,

As well as practical applied science,

For example,

Strength of materials in pioneering the telescope.

His multiple interests include the study of astrology,

Which at the time was a discipline tied to the studies of mathematics and astronomy.

Tycho Brahe and others had observed the supernova of 1572.

Ottavio Brenzioni's letter of 15 January 1605 to Galileo brought the 1572 supernova and the less bright nova of 1601 to Galileo's notice.

Galileo observed and discussed Kepler's supernova in 1604.

Since these new stars displayed no detectable diurnal parallax,

Galileo concluded that they were distant stars,

And therefore disproved the Aristotelian belief in the immutability of the heavens.

Based only on uncertain descriptions of the first practical telescope,

Which Hans Lippershey tried to patent in the Netherlands in 1608,

Galileo in the following year made a telescope with about three times magnification.

He later made improved versions with up to about 30 times magnification.

With a Galilean telescope,

The observer could see magnified,

Upright images on the earth.

It was what is commonly known as a terrestrial telescope or a spyglass.

He could also use it to observe the sky.

For a time,

He was one of those who could construct telescopes good enough for that purpose.

On the 25th of August 1609,

He demonstrated one of his early telescopes with a magnification of about 8 or 9 to Venetian lawmakers.

His telescopes were also a profitable sideline for Galileo,

Who sold them to merchants who found them useful both at sea and as items of trade.

He published his initial telescopic astronomical observations in March 1610 in a brief treatise entitled Siderius Nuncius,

Starry Messenger.

On the 30th of November 1609,

Galileo aimed his telescope at the moon.

While not being the first person to observe the moon through a telescope,

English mathematician Thomas Harriet had done it four months before but only saw a strange spottedness.

Galileo was the first to deduce the cause of the uneven waning as light occlusion from lunar mountains and craters.

In his study,

He also made topographical charts estimating the heights of the mountains.

The moon was not what was long thought to have been a translucent and perfect sphere,

As Aristotle claimed,

And hardly the first planet,

An eternal pearl to magnificently ascend into the heavenly Empyrean,

As put forth by Dante.

Galileo is sometimes credited with the discovery of the lunar liberation in latitude in 1632,

Although Thomas Harriet or William Gilbert might have done it before.

A friend of Galileo's,

The painter Gigli,

Included a realistic depiction of the moon in one of his paintings,

Though probably used his own telescope to make the observation.

On the 7th of January 1610,

Galileo observed with his telescope what he described at the time as three fixed stars,

Totally invisible by their smallness,

All close to Jupiter,

And lying on a straight line through it.

Observations on subsequent nights showed that the positions of these stars,

Relative to Jupiter,

Were changing in a way that would have been inexplicable if they had really been fixed stars.

On the 10th of January,

Galileo noted that one of them had disappeared,

An observation which he attributed to it being hidden behind Jupiter.

Within a few days,

He concluded that they were orbiting Jupiter.

He discovered three of Jupiter's four largest moons.

He discovered the fourth on the 13th of January.

Galileo named the group of four,

The Medician stars,

In honor of his future patron,

Cosimo II de' Medici,

Grand Duke of Tuscany,

And Cosimo's three brothers.

Later astronomers,

However,

Renamed them Galilean satellites in honor of their discoverer.

These satellites were independently discovered by Simon Marius on the 8th of January 1610,

And are now called Io,

Europa,

Ganymede,

And Callisto,

The names given by Marius in his Mundus Lovialis,

Published in 1614.

Galileo's observations of the satellites of Jupiter caused controversy in astronomy.

A planet with smaller planets orbiting it did not conform to the principles of Aristotelian cosmology,

Which held that all heavenly bodies should circle the earth,

And many astronomers and philosophers initially refused to believe that Galileo could have discovered such a thing.

Compounding this problem,

Other astronomers had difficulty confirming Galileo's observations.

When he demonstrated the telescope in Bologna,

The attendees struggled to see the moons.

One of them,

Martin Horky,

Noted that some fixed stars,

Such as Spica Virginis,

Appeared double through the telescope.

He took this as evidence that the instrument was deceptive when viewing the heavens,

Casting doubt on the existence of the moons.

Christopher Clavius's observatory in Rome confirmed the observations,

And,

Although unsure how to interpret them,

Gave Galileo a hero's welcome when he visited the next year.

Galileo continued to observe the satellites over the next 18 months,

And by mid-1611 he had obtained remarkably accurate estimates for their periods,

A feat which Johannes Kepler had believed impossible.

Galileo saw practical use for his discovery.

Determining the east-west position of ships at sea required their clocks be synchronized with clocks at the prime meridian.

Solving this longitude problem had great importance to safe navigation,

And large prizes were established by Spain and later Holland for its solution.

Since eclipses of the moons he discovered were relatively frequent and their times could be predicted with great accuracy,

They could be used to set shipboard clocks,

And Galileo applied for the prizes.

Observing the moons from a ship proved too difficult,

But the method was used for land surveys,

Including the remapping of France.

From September 1610,

Galileo observed that Venus exhibits a full set of phases similar to that of the moon.

The heliocentric model of the solar system developed by Nicolaus Copernicus predicted that all phases would be visible since the orbit of Venus around the sun would cause its illuminated hemisphere to face the earth when it was on the opposite side of the sun,

And to face away from sun,

And to face away from the earth when it was on the earth side of the sun.

In Ptolemy's geocentric model,

It was impossible for any of the planet's orbits to intersect the spherical shell carrying the sun.

Traditionally,

The orbit of Venus was placed entirely on the near side of the sun,

Where it could exhibit only crescent and new phases.

It was also possible to place it entirely on the far side of the sun,

Where it could exhibit only gibbous and full phases.

After Galileo's telescopic observations of the crescent,

Gibbous,

And full phases of Venus,

The Ptolemaic model became untenable.

In the early 17th century,

As a result of his discovery,

A great majority of astronomers converted to one of the various geoheliocentric planetary models,

Such as the ticonic,

Capellan,

And extended capellan models,

Each either with or without a daily rotating earth.

These all explain the phases of Venus without the refutation of full heliocentrism's prediction of stellar parallax.

Galileo's discovery of the phases of Venus was thus his most empirically practically influential contribution to the two-stage transition from geocentrism to full heliocentrism via geoheliocentrism.

In 1610,

Galileo also observed the planet Saturn,

And at first mistook its rings for planets,

Thinking it was a three-bodied system.

When he observed the planet later,

Saturn's rings were directly oriented to Earth,

Causing him to think that two of the bodies had disappeared.

The rings reappeared when he observed the planet in 1616,

Further confusing him.

Galileo observed the planet Neptune in 1612.

It appears in his notebooks as one of many unremarkable dim stars.

He did not realize that it was a planet,

But he did note its motion relative to the stars before losing track of it.

Galileo made naked eye and telescopic studies of sunspots.

Their existence raised another difficulty with the unchanging perfection of the heavens,

As posited in orthodox Aristotelian celestial physics.

An apparent annual variation in their trajectories,

Observed by Francesco Sici and others in 1612-1613,

Also provided a powerful argument against both the Ptolemaic system and the geoheliocentric system of Tycho Brahe.

A dispute over claimed priority in the discovery of sunspots and in their interpretation led Galileo to a long and bitter feud with the Jesuit Christoph Scheiner.

In the middle was Mark Welser,

To whom Scheiner had announced his discovery and who asked Galileo for his opinion.

Both of them were unaware of Johannes Fabritius' earlier observation and publication of sunspots.

Galileo observed the Milky Way,

Previously believed to be nebulous,

And found it to be a multitude of stars packed so densely that they appeared from Earth to be clouds.

He located many other stars too distant to be visible to the naked eye.

He observed the double star Mizar and Ursa Major in 1617.

In the Starry Messenger,

Galileo reported that stars appeared as mere blazes of light,

Essentially unaltered in appearance by the telescope,

And contrasted them to planets,

Which the telescope revealed to be disks.

But shortly thereafter,

In his letters on sunspots,

He reported that the telescope revealed the shapes of both stars and planets to be quite round.

From that point forward,

He continued to report the telescope showed the roundness of stars,

And that stars seen through the telescope measured a few seconds of arc in diameter.

He also devised a method for measuring the apparent size of a star without a telescope.

As described in his Dialogue Concerning the Two Chief World Systems,

His method was to hang a thin rope in his line of sight to the star and measure the maximum distance from which it would wholly obscure the star.

From his measurements of this distance and of the width of the rope,

He could calculate the angle subtended by the star at his viewing point.

In his dialogue,

He reported that he had found the apparent diameter of a star of first magnitude to be no more than five arc seconds,

And that of one of sixth magnitude to be about five sixth arc seconds.

Like most astronomers of his day,

Galileo did not recognize that the apparent sizes of stars that he measured were spurious,

Caused by diffraction and atmospheric distortion,

And did not represent the true sizes of stars.

However,

Galileo's values were much smaller than previous estimates of the apparent sizes of the brightest stars,

Such as those made by Brahe and enabled Galileo to counter anti-Copernican arguments,

Such as those made by Tycho,

That these stars would have to be absurdly large for their annual parallaxes to be undetectable.

Other astronomers,

Such as Simon Marius,

Giovanni Battista Riccioli,

And Martinus Mortensius,

Made similar measurements of stars,

And Marius and Riccioli concluded the smaller sizes were not small enough to answer Tycho's argument.

Cardinal Bellarmine had written in 1615 that the Copernican system could not be defended without a true physical demonstration that the sun does not circle the earth,

But the earth circles the sun.

Galileo considered his theory of the tides to provide such evidence.

This theory was so important to him that he originally intended to call it his Dialogue Concerning the Two Chief World Systems,

The Dialogue on the Ebb and Flow of the Sea.

The reference to tides was removed from the title by order of the Inquisition.

For Galileo,

The tides were caused by the sloshing back and forth of water in the seas as a point on the earth's surface sped up and slowed down because of the earth's rotation on its axis and revolution around the sun.

He circulated his first account of the tides in 1616 addressed to Cardinal Orsini.

His theory gave the first insight into the importance of the shapes of ocean basins in the size and timing of tides.

He correctly accounted,

For instance,

For the negligible tides halfway along the Adriatic Sea compared to those at the ends.

As a general account of the cause of tides,

However,

His theory was a failure.

If this theory were correct,

There would be only one high tide per day.

Galileo and his contemporaries were aware of this inadequacy because there are two daily high tides at Venice instead of one,

About twelve hours apart.

Galileo dismissed this anomaly as the result of several secondary causes,

Including the shape of the sea,

Its depth,

And other factors.

Albert Einstein later expressed the opinion that Galileo developed his fascinating arguments and accepted them uncritically out of a desire for physical proof of the motion of the earth.

Galileo also dismissed the idea,

Known from antiquity and by his contemporary Johannes Kepler,

That the moon caused the tides.

Galileo also took no interest in Kepler's elliptical orbits of the planets.

Galileo continued to argue in favor of his theory of tides,

Considering it the ultimate proof of earth's motion.

In 1619,

Galileo became embroiled in a controversy with Father Orazio Grassi,

Professor of mathematics at the Jesuit Collegio Romano.

It began as a dispute over the nature of comets,

But by the time Galileo had published the essayer Il Saggiatore in 1623,

His last salvo in the dispute,

It had become a much wider controversy over the very nature of science itself.

The title page of the book describes Galileo as a philosopher and matematico primario of the Grand Duke of Tuscany.

Because the essayer contains such a wealth of Galileo's ideas on how science should be practiced,

It has been referred to as his scientific manifesto.

Early in 1619,

Father Grassi had anonymously published a pamphlet,

An Astronomical Disputation on the Three Comets of the Year 1618,

Which discussed the nature of a comet that had appeared late in November of the previous year.

Grassi concluded that the comet was a fiery body that had moved along a segment of a great circle at a constant distance from the earth,

And since it moved in the sky more slowly than the moon,

It must be farther away than the moon.

Grassi's arguments and conclusions were criticized in a subsequent article,

Discourse on Comets,

Published under the name of one of Galileo's disciples,

A Florentine lawyer named Mario Guiducci,

Although it had been largely written by Galileo himself.

Galileo and Guiducci offered no definitive theory of their own on the nature of comets,

Although they did present some tentative conjectures that are now known to be mistaken.

The correct approach to the study of comets had been proposed at the time by Tycho Brahe.

In its opening passage,

Galileo and Guiducci's discourse gratuitously insulted the Jesuit Christoph Scheiner,

And various uncomplimentary remarks about the professors of the Collegio Romano were scattered throughout the work.

The Jesuits were offended,

And Grassi soon replied with a polemical tract of his own,

The Astronomical and Philosophical Balance,

Under the pseudonym Lothario Sarsio Sigenzano,

Purporting to be one of his own pupils.

The Assayer was Galileo's devastating reply to the Astronomical Balance.

It has been widely recognized as a masterpiece of polemical literature,

In which Sarsi's arguments are subjected to withering scorn.

It was greeted with wide acclaim,

And particularly pleased the new Pope,

Urban VIII,

To whom it had been dedicated.

In Rome,

In the previous decade,

Barberini,

The future Urban VIII,

Had come down on the side of Galileo and the Lincean Academy.

Galileo's dispute with Grassi permanently alienated many Jesuits,

And Galileo and his friends were convinced that they were responsible for bringing about his later condemnation,

Although supporting evidence for this is not conclusive.

Reviews

Hi Ben! Thank you for doing this one! I was so excited the other night when I first saw it and listened to it!! I've just taken a few days to write back because I've fallen asleep listening to it. It's fantastic! Thanks again, Ben!

So interesting, I need to give a listen when I can stay awake. Galileo was an amazing dude! Thanks!

Who knew that such a smart person could be so boring to learn about??
Thank you!!! 😊 😻