Galileo's Starry Message
February 24, 1998
Russell McNeil


Over the course of his lifetime Galileo more or less single-handedly 
reinvented natural philosophy -- the science of physics.  The burden 
of doing that  -- reinventing physics -- was required to make that that 
model there -- the Copernican sun-centered universe -- that he so 
dearly loved -- some badly needed support.  As elegant and sensible 
as that model seemed to Galileo -- and Copernicus before him -- and 
Aristarchus before him -- the dam thing just would not fly. 

Yet, Galileo grew quite attached to this radical world view--an 
attachment that was to get him in a whole heap of trouble in later 
years--but his attachment, trust, belief, faith, in this new view--
needed justification. Physics, before Galileo, had advanced little 
since Aristotle had basically written the book on Physics  2,000 years 
earlier.  Aristotle, had disallowed that sort of thing by virtue of the 
ways that it has attributed and defined motion--a dusty, musty, and 
rusty hodge podge of concepts which had kept the heavens in 
heaven and the earth at the centre of the universe for those two 
millennia. Aristotle was in Christian eyes a "pagan" philosopher -- of 
course -- but, the early Christian church -- in a legitimate and frankly 
liberal response to reconcile science with scripture --- had 
assimilated much of Aristotle's cosmology and physics centuries 
before.  Aristotle's cosmology had by Galileo's day merged into the 
very core of Christian doctrine. 

Galileo Galilei was born in Pisa in 1564--the same year as William 
Shakespeare and the same year Michelangelo died. He was the son 
of Vincenzo Galilei, well known for his studies of music, and Giulia 
Ammannati. Galileo's family moved to Florence when he was 10 in 
1574.  It is helpful to reflect a moment on those early years and the 
family atmosphere that contributed to the formation of the character 
of the man

The same year the young Galileo began his life in Florence, his 
father  Vincenzio had formed a little band of renegade artists, 
musicians, literati, scholars, book-lovers and scientists, the 
Florentine Camerata, an amazingly inquisitive group of revolutionary 
activists and musical amateurs who met to discuss literature, science 
and the arts. In fact, their work is linked closely with the development 
of opera. Unknowingly, the Camerata became the crucible not only of 
the opera but of modern science as well!  The boy Galileo was often 
witness to these free-wheeling, highly argumentative and 
experimentally based weekly inquiries. It was there Galileo learned 
how to learn.

The musical ideas emerging from the crucible of this passionate 
group included the exploration of new musical theories, theories that 
were often tested against a backdrop of careful experiment. 
Vincenzio was a skilled lutenist and exponent of "new music." He 
was trying to break out of medieval form by forging ties with the 
Greek past while pushing through to the future, a future that was to 
be the renaissance in music.  The most important treatise on music 
that emerged from this group was Vincenzio's Diologo della musica. 
This work is important not only for its contribution to the musical 
theory of the Renaissance but because it contributed to the 
development of experimental science.  The knowledge of 
mathematics and the use of experiment which is evidenced in his 
writings suggest important early influences on Galileo.

Vincenzio, influenced Galileo in one other important way -- his father 
was a Renaissance thinker in music, mathematics, and classical 
languages--true, but he also had a biting wit and sarcasm -- and an 
independent judgment which led him -- Vincenzio -- to reject the 
principle of authority which formed the basis for so much of the 
knowledge of medieval thinking. 

Galileo's mother Giulia Ammannati, was equally influential. She has 
been described as:  "sharp and quarrelsome, prone to polemical 
aggressiveness, impatient, and prone to sudden fits of anger which 
she expressed in derisive diatribes. That maternal role modeling -- 
honed by a lifetime of practice -- expresses itself the in  mature 
Galileo's highly effective and frankly dangerous writing style -- 
evident particularly in his later works. The style became synonymous 
with an attitude that would not suffer fools; would accept nothing 
short of the truth -- and above all rejected authority. A rebel with a 
cause!

Like many modern fathers, Vincencio had ambitions for his son. He 
wanted Galileo to study medicine.  The dutiful  now 17 year old 
Galileo -- registered in medicine at the University of Pisa in 1581.  
But Galileo loathed the Galenist medicine -- as then taught and 
practiced -- bored Galileo.  Galileo preferred reading Aristotle and 
Plato -- and was especially awed by the works of Euclid and 
Archimedes. The clear, crisp, deductive, mechanical, mathematical 
precision was more to his liking.

Galileo dropped out -- he abandoned medicine and at 21 returned to 
Florence at with no degree and no prospects. No matter. Galileo had 
his wits -- became self taught -- wrote a tiny scientific work called 
"The Little Balance" a modified invention designed to measure 
specific gravity, and, through effort and ambition, after four years, 
managed to land himself a teaching job, without a degree,  back at 
Pisa, the same university he abandoned as a student. [REFER TO 
GALILEO THERMOMETER] 

He was now 25.  He later moved Pisa to the University of Padua 
where he remained until 1610 when he published this work, the 
Starry Message.  During these years he carried out studies and 
experiments in mechanics. He also invented a thermoscope  
[BOARD EXPLANATION] .

This device emerged from Galileo's contention that heat and cold 
were not -- as Aristotle would have them -- fundamental qualities that 
combine with wet and dry to form earth, air, water and fire.  For 
Galileo heat was an accidental property of matter. Heat might be in 
matter but matter was not defined by heat. Heat could thus be 
measured by the degree or degrees of its effects. In this 
understanding cold could be seen as a measure of heat -- very little 
or none at all.  When heat entered fluids or gases they expanded. 
When heat was removed, they contracted.

Galileo's approach to motion was quite similar. Motion -- like heat -- 
was also an accidental property -- not something inherent to the thing 
as Aristotle's physics demanded.  Circular motion and straight line 
motion for Aristotle were not accidentals. They were desires 
determined by the nature of matter.  Earth -- for example -- could 
never move in a circle because it had no natural desire to do so.  
Stars could never fall to the earth or move in straight lines because, 
as quintessence,  they had only one desire -- to move in circles.  

The idea of somehow allowing earth or the Earth to move in circles 
naturally (i.e. Heliocentric model) -- as Copernicus' new system 
required, or combining straight line motion with circular motion as 
Galileo's later explanations of projectile motion required  (toss chalk) 
-- would be impossible under Aristotle's physics. Such a combination 
of straight and circular motion would be possible only for an element 
that was a compound of say earth and quintessence -- and such 
combinations were not permitted.

Galileo's reflections on motion were carefully argued in the Dialogue 
on the two chief world systems. Although promised in the Starry 
Message in 1610, the Dialogue  itself was not published until 1632 
when Galileo was in his 69th year. In October of that year Galileo 
was summoned by the Holy Office in Rome. The tribunal there 
passed a sentence condemning him for his ideas and compelled 
Galileo to solemnly renounce his theory.  He spent his remaining 
years under house arrest where he completed one more massive 
work, the Dialogue on Two New Sciences.  By 1638 Galileo was 
completely blind. He died in 1642, the same year Isaac Newton was 
born.  In 1992 -- just six years ago, after a 13 year re-examination of 
the Galileo Affair,  the Roman Catholic Church admitted it had erred -
- acknowledged -- among other mistakes -- that false evidence had 
been proffered in Galileo's trial, and finally reversed the conviction 
that had taken place 350 years before.

But the critical moment in this whole story -- a story that gave birth to 
modern times --  was the publication of this little book here -- the 
Starry Message. The Starry Message is not a story about motion -- it 
is rather a document of observation. A short summary of a short 
series of observations in which Galileo uses his newly invented 
celestial spyglass or telescope. Galileo praises this device -- not 
unlike this one here -- in the first paragraph of this book. It -- this 
artifact, this technology -- is as great in excellence as the things he 
has begun to observe!  Why is this man in love with his technology?  
On p.28, "all these things were discovered with the aid of a spyglass 
I devised, after first being illuminated by divine grace. 

What Galileo euphemistically calls divine grace is his unique 
understanding of how basic principles of nature can be harnessed to 
enhance the human capacity for reason.   Galileo is a Platonist.  He 
is in love with reason. His fundamental goal is understanding: to seek 
the good. How to we get there?  Reason.  Is reason aided by sense? 
Obviously. It may be that the natural world is but a reflection of the 
divine, but if I want to approach the divine, it sure helps to have a 
clearer picture of the material world. Is human sense limited? Of 
course. Will technology extend the sense? Obviously. Is the 
telescope is an extension of sight.  Sure! This telescope -- this sense 
extension -- will never peer across Plato's divided line. But it  can 
sure get you one hell of a lot closer and that I think is what Galileo is 
ultimately trying to do. Page 28, "It seems to me to be a matter of no 
small importance to have ended the dispute about the Milky Way by 
making its nature manifest to the very senses as well as to the 
intellect. " 

How did Galileo harness basic principles to develop this extension of 
sense and reason?  Nature does things simply -- nature is economic.  
But how does this economy apply to the idea of light? A Greek 
named Heliodorus developed the idea in antiquity to explain the 
apparent bending of light in water.  (Draw on board)  It is the most 
economic path to follow. 

[Diagram of swimmer in distress and argument that the best 
path to follow is not a straight line, but the path that is most 
economic -- the path that takes the least time.]

This simple but powerful notion -- known in Physics today as the 
"Principle of Least Time" has the earmarks of an evident truth. 
Applied to nature it works as I have just shown. A simple technology 
like the lens can harness the curvature of the surface of glass in such 
a way that light passing through the lens from distant objects will 
converge to form images onto a plane located at a geometrically 
determined distance from the lens called the focal length. We know 
that is so because that is exactly how the eye works. Hold screen at 
some distance from a light source. Insert lens. Note that the 
function of the lens depends on both the principle of economy and 
the geometry of the lens. Of course the very geometry defining the 
shape of the lens is -- like the principle of least time -- something 
Galileo would see as yet another manifestation or a "divine" truth. 
Euclid was one of Galileo's heroes.

[Insert second lens explaining that we can now exploit the idea 
of magnification of image. Explain the use of a lens to magnify a 
real image. Note that this idea can also be used to explain the 
eye and that the eye can be seen to be a natural technology -- 
one which in this case we can mimic in an artificial technology.]

[Refer to the Galileo telescope.]

When Galileo trained this "divinely" inspired extension of sense onto 
the heavens he was awestruck. The heavens opened up. The skies 
were filled with an infinitude of never before seen stars. The moon's 
surface was rough and pitted with ridges and mountains soaring 
miles above the lunar surface.  This was proof incontrovertible that 
the heavens -- like the earth were made of the same stuff. The earth 
was not the, "sink of all dull refuse of the universe" as older 
cosmologies would have it. The earth was -- like this beautiful moon -
- a splendid and "wandering" body.  If the heavens were divine in 
character -- so now was the Earth thanks to the "spin" Galileo places 
with this interpretation.  

[Slides]

When Galileo turned his attention to the planet Jupiter, "on the 7th 
day of January in the year 1610 at the first hour of night," he was in 
for a surprise. In a carefully documented series of observations over 
two months he witnessed an astonishing sight. Jupiter had first three 
and then four companion starlets -- moons as they are now called -- 
Galileo named them the Medicean stars. Here they are today: Io, 
Europa, Ganymede and Callisto. [Three Slides, orbit, four as is, Io 
from surface.]

This was direct sensible evidence that the earth was not alone in the 
universe as the single centre of all circular motion. It confirmed that 
the sort of system Copernicus had proposed was indeed possible. 
But it was still not proof enough that the earth revolved about the sun 
like these planets about Jupiter. 

That evidence came later. When Galileo trained his telescope on the 
planet Venus he discovered that Venus in its motions displayed 
phases and those phases were identical to the phases of the moon.  
This observation could only be explained by a Copernican model. 
The Aristotelian model would now account for all of the phases of 
Venus.

How was this work received? Ironically, the reaction to Galileo's 
discoveries was not what popular history would have us expect. Two 
types of responses began to emerge. From the Church -- the 
response was cautious but generally favorable. The church in this 
era had vested responsibility for the investigation of scientific matters 
in the hands of an Institution in Rome known as the Roman School -- 
run by the Catholic order called the Jesuits.  Galileo was very 
interested in ensuring that the Jesuits were fully informed of his 
discoveries and that they had opportunities to see what he saw. And 
they did.  In Rome,  one of the leading theologians of the day, 
Cardinal Robert Bellarmine -- himself a Jesuit -- wrote the Roman 
College and asked them five questions:


1. Was there really a multitude of stars not visible to the naked eye?

2. Was Saturn really composed of three stars?

3. Did Venus really have phases like the moon?

4. Was the moon's surface really rough?

5. Did Jupiter really have four satellites revolving around it?


The response to Bellarmine's questions in a letter signed by the top 
four mathematicians and scientists there was yes on all counts 
except for the moon.  On the moon they said that they could not 
confirm "beyond all doubt" that its surface was rough, but that they 
leaned to believing so.

In this same year Galileo traveled to Rome, had a very cordial 
meeting with the then Pope Paul V, met a man named Maffeo 
Barbarini -- who was later to succeed  Paul V as Pope Urban VIII, 
and attended an academic assembly at the Roman College in 
Galileo's Honour to hear presentations about the material contained 
here and to confirm its observational contents. A large number of 
church officials attended and there was no coolness at all towards 
Galileo.

The Jesuits were restrained in openly accepting the Copernican 
interpretation. They were at the time constrained by a religious 
obligation to conform to Aristotelian doctrine. However, there was 
private discussion that a reconciliation of Copernicanism with 
scripture and theology was possible.  As scientists however, the 
Jesuits were troubled by a very real problem -- of which Galileo was 
aware -- that the Copernican system was not allowed by then known 
physical laws. And that was quite understandable.

The problem of reconciliation with scripture was one that could be 
addressed.  After all, it was just such a reconciliation with the literal 
interpretation of clearly allegorical biblical passages that had moved 
the church centuries before to accept Aristotle in the first place.  But 
the church had not baptized Aristotle completely. Aristotle's idea of 
incorruptibility, for example, was not a problem. The problem was 
motion. The theological view at the time went thus: if a biblical 
passage should be understood as literal -- it ought not to be 
understood differently. A private and friendly letter to Galileo from a 
Cardinal Conti in 1612 addressed the problem: he noted that the 
motion of the Earth was NOT consistent with scripture, but that the 
motion of the Earth could be reconciled if in those instances the Bible 
was regarded as using, "the language of the common people." He 
noted however that such a reconciliation should not be done unless it 
was really necessary.

The other response over the Starry message came from outside the 
Church. It was frankly hostile. The furor began with the academics -- 
an extraordinarily conservative group or University-based Aristotelian 
philosophers who began to attack Galileo mercilessly.  Worse, it was 
they -- not the Church -- who brought scripture into the debate.  Their 
philosophic position was bizarre. The man who lead this attack, the 
University of Padua philosopher Columbe, wrote a treatise in 1611 in 
which he characterized Galileo's opinions as: "rash, dangerous for 
the faith, and designed to show cleverness rather than to aid 
philosophy."  The philosophical position was twofold: 1: Cite Aristotle 
as authority, and 2: Reject -- a priori -- anything seen through any 
telescope.  According to a treatise written by Plutarch in antiquity, 
such images could be nothing other than "optical illusions." The 
academic philosophers simply refused to even look -- although 
Galileo had invited them personally, "an infinitude of times." No Jesuit 
or Cardinal ever refused Galileo's offer to see what he saw.

This debate between the Aristotelians and Copernicans became 
highly charged and politicized in the ensuing decades. At one point 
early on Galileo and Columbe were involved in a debate in Florence 
on the question of why ice floats. Columbe -- ascribing to Aristotle's 
theory of cold -- argued that ice was of necessity heavier than water -
- more dense -- but floated because its flat surface prevented its 
sinking. Galileo who identified with Archimedes argued that ice 
floated because it was less dense -- lighter. Galileo won the debate -- 
one in which the future pope Urban the VIII was actually in 
attendance and who had sided with Galileo!   The humiliation 
Columbe suffered in this instance led to the formation of an 
Academic League against Galileo. Galileo's friends called them the 
pigeons.  Sadly, the pigeons were more powerful than Galileo. They 
were out to get the man -- and eventually -- they did.  For two 
decades they hammered at the theological establishment in Rome -- 
undermined Galileo's credibility on all fronts. There are many more 
elements to this story. Galileo's relationships with the Jesuits soured 
-- not because of science but around miscommunications with a 
prominent Jesuit named Scheiner over who first  documented the 
sunspots.

History has of course vindicated Galileo. and the Church has 
admitted its error and found a way to reconcile scripture with science. 
Reason and revelation can not contradict.

As to Galileo's legacy, he will be remembered for much. But for me, 
Galileo is relevant because he saw technology as an extension of 
sense; science as an extension of reason; and reason and directed 
fundamentally towards the "seeking" of Truth.  Galileo also 
understood the role of the natural philosopher in the scheme of 
philosophy overall.  He knew that science and its discoveries would 
provoke a profound shift in consciousness. He understood that that 
shift would provoke a crisis.  It is clear in the tone of his writings that 
he understood that the scientist has a responsibility to be aware of 
where his reasoning might lead -- and the inevitable consequences 
that reasoning might have on the moral plane.

I think at the end of the day he was successful. He uncovered new 
and magnificent and I think eternal truths.  The fundamental ideas of 
conservation and eternal inertial motion, reflected in the idealized 
swinging pendulum and orbiting Earth reveal fundamental aspects of 
nature that continue to inform our understanding of the cosmos not 
only in physical terms but in moral terms as well.