Who was Galileo?

You may have heard of the name Galileo.  Perhaps it is through an interest in science or maybe it’s from the Queen song “Bohemian Rhapsody”.  But who was the man behind the famous name?  What did he do and achieve?  Well, as Galileo would be 450 years old in 2014, I will look at his quite amazing life and examine the accomplishments of an astronomer who is identified and recognised by his first name.

The father of modern science Credit: Wikipedia

The father of modern science
(Image credit: Wikipedia)


Galileo Galilei was born in Pisa, Italy on 15 February 1564.  The eldest of six children born to Vincenzo Galilei and Giulia Ammannati, he was named after a relative called Galileo Bonaiuti who was a physician, university lecturer and politician.  As well as acquiring the same first name as his ancestor, Galileo Galilei was destined to follow in his footsteps by studying medicine at the University of Pisa.  It was whilst studying for his medical degree that his inquisitive mind began to flourish.  In 1581, whilst studying in Pisa, Galileo was looking at a chandelier in Pisa Cathedral.  As he studied the light fixture he noticed that it was swinging in larger and smaller arcs due to air currents.  By using his pulse as a timer he observed that it took the same amount of time to swing back and forth regardless of how far it was swinging.  This realisation inspired an experiment Galileo assembled when he returned home.  He set up two pendulums which were equal in length, by swinging one through a large arc and the other with a smaller sweep Galileo observed that they kept time together.  This discovery led to Galileo’s study of time intervals and the development of his idea for a pendulum clock.  One hundred years later Christiann Huygens would use a swinging pendulum to create a timepiece!


The lamp of Galileo at the Pisa Cathedral Credit: Wikipedia

The lamp of Galileo at the Pisa Cathedral
(Image credit: Wikipedia)


Galileo began to expend more time to physics rather than medicine and eventually persuaded his father to allow him to change his study from medicine to mathematics and natural philosophy.  The catalyst was when Galileo attended a geometry lecture by accident.  His father needed convincing due to the fact that a physician earned significantly more income than a mathematician.  This change in discipline launched Galileo into a course of discovery and invention. From there he created the thermoscope which was an early concept for a thermometer and in 1586 he was brought to the attention of many scholars when he published his design of a hydrostatic balance that he had invented.  At the age of 25 (1589), he was appointed to the chair of mathematics in Pisa.


A simple diagram of the force balance or Hydrostatic Balance  Credit: Wikipedia

A simple diagram of the force balance or Hydrostatic Balance
(Image credit: Wikipedia)


However the University of Pisa used the approach of the ancient Greek scientist, Aristotle, in its teachings which Galileo began to question.  Aristotelians believed that heavier objects fall faster than lighter ones.  Galileo was able to disprove this line of thought by showing that all objects, regardless of their density, fall at the same rate in a vacuum.  Galileo performed various experiments in which he dropped objects from a height.  In one of his early experiments, he rolled balls down a slope and it is rumoured, but never proven, that he dropped objects from the Leaning Tower of Pisa.  He also developed a military compass in 1604.


A geometrical and military compass designed by Galileo Galilei. Credit: Wikipedia

A geometrical and military compass designed by Galileo Galilei.
(image credit: Wikipedia)


Galileo also began to voice his support of the Copernican theory which was not in favour at that time (to put it mildly, Galileo was actually risking his liberty and life by defending Copernicus).  Published in 1543, Nicolaus Copernicus positioned the Sun motionless near the center of the Universe with the Earth and the other planets orbiting around it in circular paths.  The Copernican model departed from the Ptolemaic system that placed the Earth at the centre of the Universe.  It is often regarded as the launching point to modern astronomy and the Scientific Revolution and it certainly caught the attention of Galileo.  Soon, he began to collect evidence to support the theory.


In 1609 he came across news of a simple spyglass that could magnify object by three times built by a Dutch glassmaker and he set about developing his own which would become his telescope.  To me this was his most famous invention which he developed to magnify objects by twenty times.  His telescopes also proved to be a popular side-line which he sold to traders.


A replica of the earliest surviving telescope attributed to Galileo Galilei.  The telescope is on display at the Griffith Observatory. Credit: Wikipedia

A replica of the earliest surviving telescope attributed to Galileo Galilei. The telescope is on display at the Griffith Observatory.
(Image credit: Wikipedia)


With this telescope Galileo was able to observe the Moon.  But that was just the start of telescopic stargazing, on 7 January 1610 he observed what he noted as “three fixed stars, totally invisible by their smallness”.  They were close to the planet Jupiter lying on a straight plane.  Three days later he noted that one had disappeared which he attributed to it being behind Jupiter which led him to believe that they were orbiting Jupiter.  Little did Galileo know that he had discovered three of Jupiter’s moons.  On January 13 he discovered a fourth.  Today we know that Jupiter has an amazing 67 satellites orbiting the giant gas planet at the last count (Jan 2014).  Later, the four moons were named in his honour and are now known as the Galilean moons (Io, Europa, Ganymede and Callisto).  And if you are lucky and Jupiter is visible in the night sky, grab a telescope and you can see what Galileo saw all those years ago, the Galilean moons in a plane orbiting the gas planet.  This once again backed-up the Copernician line of thought!  In September 1610 he turned his attention to the “Morning/Evening star” Venus.  Galileo observed that the planet exhibited a full set of phases similar to our Moon.  He also saw Saturn through his telescope but mistook the rings for other planets and in 1612 he observed Neptune, however he thought it was a star and not a planet.


In 1610 The Starry Messenger was published by Galileo which was the first such document to be printed regarding observations through a telescope.  It documented his discovery of four moons of Jupiter, the surface of the Moon being rough and the fact that many stars are invisible to the naked eye.  Another major achievement is that Galileo was one of the first Europeans to observe sunspots.  In 1607 a sunspot had been spotted by Kepler but he thought it was a transit of Mercury.  In 1613 he published is observations which once again refuted the Aristotelian thought that the Sun was a perfect, flawless sphere.



Galileo’s support of Copernican theory would eventually get him into some trouble, as it was thought to contradict Biblical passages.  Galileo however stated that it did not as the Bible was written from an Earthly perspective whilst science could provide a more accurate perspective.  The Church did not look upon it favourably and declared Copernican Theory as heretical.  Because Galileo supported the Copernican system, he was warned by Cardinal Bellarmine, under order of Pope Paul V, that he should not discuss or defend Copernican theories.  In 1624, Galileo was assured by Pope Urban VIII that he could write about Copernican theory as long as he treated it as a mathematical proposition.  However, with the printing of Galileo’s book, Dialogue Concerning the Two Chief World Systems, began a motion of events in which Galileo would eventually be summoned to Rome for an inquiry.  He was found guilty of heresy when he admitted to supporting Copernican theory and from 1633 spent the rest of his years under house arrest.  By 1638 Galileo had become blind but continued to work on inventions and theories.  It was during his house arrest that he wrote his finest work Two New Sciences.  This was a review of earlier work on kinematics and strength of materials which received high praise from none other than Albert Einstein.

Galileo died near Florence, Italy, on January 8 1642 aged 77.  During the twentieth century several Popes acknowledged the great work of this Italian scientist.


The tomb of Galileo in Santa Croce, Florence, Italy Credit: Wikipedia

The tomb of Galileo in Santa Croce, Florence, Italy
(Image credit: Wikipedia)


Galileo never married but in 1600 he had met Marina Gamba and they had three children.  His two daughters, Virginia and Livia, were put into convents where they became Sister Maria Celeste and Sister Arcangela.  His son, Vincenzo, became a successful musician.  Galileo has gone down in history as having a major role in the scientific revolution.  He has been called the “father of modern observational astronomy”, “father of modern physics”, “father of science” and the “father of modern science”.


Daughter of Galileo, Sister Maria Celeste Credit: Wikipedia

Daughter of Galileo, Sister Maria Celeste
(image credit: Wikipedia)


Today spacecraft have been named in his honour; the first spacecraft to orbit Jupiter was called Galileo.  In 2000 the probe found evidence of a frozen-over ocean on Europa, one of the moons of Jupiter that Galileo had observed all those years ago.  The Galileo Global Satellite Navigation System is currently being developed by the European Union and European Space Agency and the transformation between inertial systems and classical mechanics has the Gal Unit also known as the Galileo Unit (a non-SI unit of acceleration equal to 1 centimetre per second squared).  An asteroid “697 Galilea” was called after the great man and as well as his name appearing in the Queen song he also features in the song “Galileo” by the Indigo Girls and in Amy Grant’s song of the same name.


Plays dictating his life Life of Galileo (1943), Lamp at Midnight (1947) and Galileo Galilei (2008) have toured theatres.  There was also a film adaption of  Life of Galileo starring Chaim Topol. In 2012 the play was revived in an off-Broadway production in which F. Murray Abraham played the lead role.  The Royal Shakespeare Company are touring at the moment with the play (Jan-April 2014) starring Ian McDiarmid, who is perhaps best known for his iconic role as Emperor Palpatine in Star Wars. A book Galileo’s Dream (2009) was written by SF novelist Kim Stanley Robinson in which the scientist is brought to the future to help scientific philosophy.



So, if Jupiter is visible in the night sky, look up at it as you can spot it with the naked eye.  If you have a telescope view the Galilean moons and think of Galileo Galilei and toast his achievements!



(Article by Sinead Mackle, Senior Education Support Officer)