Hello, and welcome to Western Sieve. Episode two hundred and seventy Galileo,
Part two. Last week I introduced Galileo, discussed his early life, and
more or less worked up to the point that he was a relatively unknown professor
the University of Padua, focusing a lot on the differences between Aristotelian logic and
the new type of logic that Galileo was endeavoring to imprint on Europe. Kind
of like fighting an uphill battle. Unfortunately, and for frankly, hundreds of
people in the early modern period. That's precisely where the story ends, an
unknown professor in some university, but not Galileo. As we've already seen,
there's something different in men like Copernicus, Tico, Brahe, and now Galileo.
For thousands of years, Europe had been ruled intellectually by classical and ancient
philosophers, men like Plato and Aristotle, men who would have been more at
home in the world of Socrates and Alexander the Great than Christopher Columbus. But
the world was changing. Galileo recognize that that is what makes him unique,
or, if not unique, at least part of a new breed of European
of a new breed of human people today we call scientists. Certainly, if
we think about Galileo the scientist, the years fifteen ninety two to sixteen ten,
when he was teaching at Padua, were undoubtedly the most important of his
life. During this period he made all his major discoveries, the bulk of
the findings that he put into his too large as works, the Two Sciences
and Dialogue, two of his most consequential works, They all come from this
period of his life. Yet our actual record for him during these years is
shockingly thin. That's very unfortunate for us. The reason being is, of
course, that during these two decades Galileo also critically converted to Copernicism. Now,
Copernicus published on the Revolutions of the Heavenly Spheres in fifteen forty three,
and he died that same year. As we know. In his seminal work,
Copernicus argued that the only way the evidence of astronomy made any sense was
if humankind accepted the proposition that the Earth was a planet just like the others,
and that it's like Mars and Venus orbited around the Sun. Now,
Copernicus's universe did have a center. Technically, it's like really near the Sun,
but not quite the Sun. Now, Astronomers, even astronomers of this
age, they're perfectly happy to think about a universe that included a moving Earth.
After all, Copernicus pointed out time and time again, this was the
only way that the night sky made any sense. But philosophers are a different
story. And remember, in this era, philosophers are considered much more important,
much more prestigious than scientists. Philosophers still desperately clinging to Aristotle, refuse
to accept these conclusions. Again, we must remember that science as we know
science today was not the science of the early modern period. First and foremost,
philosophy and its emphasis on deductive reasoning was the most important branch of science
by about a million miles. Everything else was of lesser value. Physics back
then was merely a branch of philosophy. So long as university philosophers remained opposed
to Copernicanism, it was dead on arrival. Frankly, in the decades after
his death, there were no full fledged followers of Copernicus. Astronomers liked his
work, but they liked it primarily because of the accurate charts that were in
it that simplified calculations. Nobody was ready to die for Copernicanism or his ideas,
at least not yet. A crucial reason for the lack of support for
Copernicanism lies in the existence of a new alternative to geocentric system of Ptolome and
the heliocentric system of Copernicus. This was, of course, the geo heliocentric
system of Tico Brahe first described in print in fifteen eighty seven. According to
Tico, the Earth was as Ptolome and the Aristotelians claimed stationary center of the
universe, and the sun, moon, and fixed stars revolved around the Earth.
But the planets, Tiko argued following Copernicus, revolved around the Sun.
These three systems were so fundamentally different that you might at first think it would
be easy to find evidence to settle the question of which one was right.
But if one allows for adjustments of scale, and scale is of course massive
when we're talking about the distance between the planets. They're each capable of making
pretty good predictions for the positions of the moon, the Sun, and planets
in the sky which were identical to those made by others. In fact,
they're really almost geometrically equivalent. It was soon apparent that naked eye astronomy was
just incapable of choosing between them. So really, then the fundamental choice is
in which one's possible, it's which one is plausible. Which seemed more likely
that the Earth rotated once a day, or that all the fixed stars rotated
around the Earth once a day, which was more plausible, that the Earth
was just another planet, or that the vast bulk of the Sun circled the
Earth every day, carrying all the planets with it. When thinking about questions
like these objections to a moving Earth, which were really physical honestly, rather
than astronomical objections, all these questions become central. Now matters started to change
in sixteen o nine, and that's because of new evidence, not new theories.
And I'm talking about new evidence from telescopic observations above all made from the
observations of Galileo, and of course, in the same year Johannes Kepler also
published New Astronomy, in which argued that no theory which insisted on circular movement
could account for the orbit of Mars, which he was claiming at least was
an eclipse Galileo was at the forefront of telescopic revolutions. He simply avoided discussing
Kepler's revolutionary proposals. Frankly, he probably doubted whether Kepler's measurements were sufficiently reliable.
He surely found his arguments implausible, and he probably felt that they offered
the opponents of Copernicanism new grounds for rejecting the Copernican system. Galileo remained,
honestly, to the end of his life, an old fashioned Copernican. It
seems very likely that when Galileo became a Copernican, he had never once in
his life met a follower of Copernicus. There just weren't really hardly any of
those. One of the greatest Copernicans alive in fifteen ninety two, and certainly
of those who had already published in support of Copernicanism, was a man named
Giordano Bruno. Bruno was a philosopher rather than an astronomer. He wasn't jos
a Copernican. He also believed that the universe was infinite, that there were
other inhabitants circling other sons. No. Not surprisingly, he was never able
to secure employment as a philosopher at any university as all of these ideas flew
in the face of everything that had been taught for roughly the last two thousand
years. Bruno, we know, was in Venice when galo Aleo arrived there
in early September to lobby successfully for an appointment at the University of Padua,
an appointment that, ironically Bruno had hoped to win for himself. But by
September Bruno was already in prison. He had been imprisoned by the Venetian Inquisition.
He had been there since May, and was be transferred to Rome in
February of fifteen ninety three. Venice exercised firm control over the Inquisition within Venetian
territory. As an aside, it seems certain that Venice would never have permitted
Bruno to be handed over to Rome had he been a Venetian or a teacher
or even a student in Paduo. But he was just a visitor, and
the Venetian state had no interest in protecting him. Once in Rome, Bruno
was repeatedly tortured and eventually executed burnt alive in the year sixteen hundred. It's
inconceivable that Galileo did not hear about Bruno during these early years, he worked
in a library which contained copies of Bruno's works. Again and again his views
were compared to those of Bruno. Yet in all of Galileo's surviving works,
his books, his letters, his notes, his drafts, there's not a
single reference to Bruno. Curiously, the exact charges against Bruno were and remain
unknown to posterity. The record of his trial was destroyed in the nineteenth century.
We know, however, that Galileo was influenced by Bruno for one key
reason his rhetorical style in Plato's writings. For example, Socrates, the philosopher
who's always right in any of Plato's dialogues, always speaks for himself. He's
the voice of reason, oh, I should say, I suppose, or
rather, Plato speaks through him, but he's his mouthpiece. Socrates has a
name in these dialogues for Bruno, and subsequently Galileo. The speaker who is
always right, man who's always in the right, is an unnamed philosopher.
Bruno was really the first one to do this, and the fact that Galileo
parroted him so clearly gives an indication that Galileo must have known about the man.
Now Galileo's first documented contact with a committed Copernican came in August of fifteen
ninety seven. He wrote a letter to Kepler, who had published the first
major development within Copernican astronomical theory, a book titled The Cosmographic Mystery back in
fifteen ninety five. This argued that the proportions of the Solar system were determined
by the shapes of the five regular solids, the pyramid, the cube,
the octahedron, the doodahedron, and the isohedron figures with four, six,
eight, twelve, and twenty sides respectively. This was all first described by
Plato. By the way, Kepler had given two copies of a book to
a friend who was traveling in Italy, and he ended up giving them to
Galileo. Kepler was probably astonished to receive a letter out of the blue in
which Galileo, a man quite unknown to him, declared that he had been
a Copernican for a number of years. This letter is probably, and it
really is, in just about every history I've read of Galileo, the most
important single document for understanding Galileo's intellectual biography. It obliges us to adopt a
very different view of Galileo's intellectual trajectory, to which could genuinely be accepted.
Now, getting back to Galileo and Copernicus for a moment. As a mathematician,
Galileo would have been required to teach different astronomical systems, and hence he
simply must have known about Copernicus. In Galileo's book on Motion, he references
a technical detail described in Copernicus's work, So we know that by fifteen ninety
two Galileo must have read Copernicus. Again, it is unfortunate that we do
not have any direct written evidence to confirm these dates, but we don't,
so we will just have to put together what we can. What I can
say definitively is this Galileo was not a Copernican when he left Pisa in fifteen
ninety two, but he became one shortly thereafter. When Galileo wrote to Kepler
in fifteen ninety seven, he made a remarkable claim. He said, not
only had he been a Copernican for a long time, but he claimed that
quote with this hypothesis, I have been able to explain many natural phenomenon which,
under the current hypothesis remained unexplainable end quote. He had, he said,
written at length in defense of Copernicanism, but had no intention of publishing
while Copernicanism remained so genuinely and generally scorned. Galileo, it's worth noting,
was employed, like the rest of the professors, through a series of renewable
short term contracts, so he could not afford to adopt in public views which
were so genuinely disregarded. But by fifteen ninety seven he appears to have already
been working on an early version of what would eventually become his masterpiece. The
quote Dialogue concerning the two chief world systems end quote. This is the problem.
Though the defense of Copernicanism that Galileo wrote sometime between fifteen ninety two and
fifteen ninety seven has not survived. Now there is good tangential evidence regarding Galileo's
thinking. When he first arrived in Venice in fifteen ninety two, his friend
and sponsor, Guidabolo del Monte, invited Galileo to visit him, and we
can surely date that visit to the summer of fifteen ninety two, and Galileo
conducted an experiment at that time. We have del Monte's notes, and he
and Galileo probably did it together, the idea for which may have indep been
Galileo's. The experiment was very simple. Take a hard ball and code it
with a substance that would leave a mark. Take a hard flat surface and
place it at an angle fairly close to the vertical. Then throw the ball
so that, like a pinball, it flies across the sloping surface, first
rising, and then after it slows falling. What will be left behind is
the track of the ball across the surface, and this track should be very
similar to the path of a ball flying free through the air, in other
words, the path of a projectile. The experiment showed two things. First,
the path of the ball is symmetrical curve. The projectile never travels in
a straight line, and its path while rising is identical to its path while
falling. Second, the curve is mathematically legible. Galileo and del Monte felt
it was very similar to a parabola. The result, however, was a
astonishing rejection of Aristotelian physics. According to Aristotelian physics, an object's movement was
governed either by nature or by force, not both simultaneously. Hence, a
cannon ball shot out of a cannon should proceed straight until it runs out of
force, and then it should fall straight down at a right angle, which
is when nature takes over. But of course cannon balls don't fly like that.
Now, as an aside, by the way, you might be sitting
there thinking, hey, I mean a child throwing a rock could have been
immediately able to correct Aristotle, but I guess that didn't happen. Galileo was
in sixteen oh four still trying to make sense of all this. Obviously,
what Aristotle claimed was not how projectiles appeared to move, So what was the
problem? Galileo realized In the end, Aristotle could not be correct In on
Motion. He theorized that acceleration was temporary and that projectiles were impacted by a
constant rate of fall, which is true. He could never quite prove it,
but that did remain the theory throughout his life. When Galileo wrote on
Motion, he was not a Copernican. He did not even address the question
of falling bodies on a moving Earth, because even though he had formulated the
idea of circular inertia, he assumed that Earth was stationary. It looks very
much, as though by the time he left del Montes he had become a
convert. In fact, it's even possible that Galileo had converted del Monte,
as he left in his papers when he died in sixteen oh seven, a
treatise on the Movement of the Earth. What had converted Galileo to Copernicanism was
not some new understanding of astronomy. It was a new approach to the problems
of physics he had been addressing an odd motion. Galileo became a Copernican because
he now had the conceptual apparatus with which to understand the physics of a moving
Earth. But his conversion implies an eagerness to embrace Copernicanism, for he had
found no new evidence in favor of it. He had merely found a way
of refuting one of the standard objections to it. Conversion, for Galileo was
remarkably easy. He was a mathematician, and so could appreciate the beauties of
the Copernican system. He was hostile to Aristotelian philosophy, and so had no
attachment to the Old order. Based on some of his other writings, he
believed neither in heaven nor in Hell, so he had no need to worry
about where these two locations were spatially. He will have been well aware that
the arguments that convinced him would not have been enough to convince other more conventional
thinkers. Though still, by the time Galileo arrived in Venice in fifteen ninety
two, he had formulated sophisticated responses to the standard arguments against a moving Earth,
arguments that went far beyond anything in Copernicus. He could explain why objects
dropped from a high tower appeared to fall vertically by means of principles of circular
inertia and combined movements, and he could explain why objects are not thrown off
into space by centrivigal force by comparing the estimates of speed at which bodies fall
towards the Earth with estimates of speed at which they would move away from the
Earth it projected along a tangent. This being established, it's possible to revisit
Galileo's remarkable claim in his letter to Kepler that he had used Copernicanism to explain
many natural phenomenon which were inexplicable within conventional physics. Kepler immediately guessed that Galileo
was talking about the tides. The tides, believe it or not, are
actually going to be one of sort of this continuous problems that Galileo comes back
to throughout his life. This seems to have been an extraordinary leap until we
realize that a classical source had suggested that the tides might be linked to the
movement of the Earth, and Kepler, by the way, was right.
For in notes from fifteen ninety five we find an account of the theory that
Galileo was to put forward in sixteen sixteen and publish in sixteen thirty two as
proof that the Earth moves. The basis of the argument was shockingly simple.
If you're on a boat which a little water has leaked into the boat,
and the water within it travel along quite happily. But if the boat bumps
into a bank, the water in the bottom of the boat carries on traveling
forward, piling up in the front of the boat. The tides, Galileo
argued, must be caused by a similar phenomenon, by some change in speed
or the direction of the Earth's movement, which causes the water contained in the
Earth's basins to slosh around like it does in the bottom of a ship.
Copernicus attribute did three movements to the Earth, of which two were the most
important. One was the annual movement or on the Sun and the daily rotation
or on the axis. The combination of these movements would, Galileo argued,
mean that any point on the Earth's surface would be traveling faster, but it
was on the side of the Earth away from the Sun in between would experience
acceleration or deceleration. Of course, this is not in fact what causes the
tides. They are caused, as Newton will show by the gravitational attraction of
the Moon in the Sun, but it could cause tides in a theoretically possible
world. The argument is valid in principle, but not in its application to
our particular planet. That it is the wrong explanation for tides in our world
was never apparent to Galileo, who refined it to explain why tides vary at
different times of the month and year, and we sought to explain the fundamental
problem that there are two tides every day rather than one. His theory would
have implied one. Nor did Galileo have an explanation for the fact that the
timing of the tides varies from one day to the next. In the new
physics of Galileo, rest and constant movement are indistinguishable, and this alone can
explain how objects behave in votes. When Galileo says he has used Copernicanism to
explain many natural phenomena, he means that he has used his new principle of
the absolute relativity of movement, a principle which must be true if Copernicanism is
to work to explain a wide variety of phenomena. Now, there's another discovery
that Galileo probably had in mind when he used the word many in his letters
to Kepler. In his first great work, The Starry Messenger, he talks
about a discovery quote not made recently, but rather many years ago unquote.
This discovery related to the faint light illuminating the dark mass of the Moon at
New Moon. Some had claimed that the light came from the Moon itself,
some that it came from the stars, and some that it was the Sun's
light shining through the translucent body of the Moon. Galileo claimed, correctly,
by the way, that the light is what we now call earth shine,
in other words, that the Earth illuminates the Moon, just as the Moon
illuminates the Earth. The argument he presented wasn't new. In fact, you
could find it in one of Leonardo da Vinci's notebooks In The Starry Messenger.
A crucial argument for thinking of the Earth and the Moon as alike is that
the Moon is not, as Aristotelian philosophers claimed it was a perfect crystalline sphere.
Now Galleo said that was nonsense. It has mountains, it has valleys,
it's not a flat surface. The mountains can be identified by the shadows
they cast and by the fact that their peaks are caught by the rising sun
lighting effects that are clearly visible with a telescope. In The Starry Messenger,
the impression is given that it is completely new argument. But this was a
phenomenon Galileo discovered almost as soon as he turned his telescope to the moon in
sixteen oh nine. Yet he showed no initial urgency to publish this extraordinary finding.
Then there's the next thing that he took at issue with the Aristotelians,
which is distance. Remember, Aristotelians claimed that our universe was finite and frankly
quite small. Taking the measurements of the universe accepted by Aristotelians. Galileo maintained
that displacing the Earth from the center to the location of the Sun would be
equivalent to seeing one hundred and seventy six degrees in fifty six minutes of the
sphere of the heavens at night and one hundred and eighty three degrees and four
minutes during the day, a difference equivalent if the Earth was at the center
of the universe to seeing the heavens from the top of a mountain one mile
high. It's easy to see. He argues that this difference might be imperceptible,
and we will certainly not be aware that the stars above our head are
closer than the ones on the horizon if the scale of the universe has increased,
as the Copernican theory required. What Galileo is trying to do here is
put together a fundamental but critical claim. If we look at the heavens with
the naked eye, either at a single moment in time or over the course
of the day, there is nothing, nothing, that we can see that
could help us choose between the Copernican and Toolemaic systems. Between fifteen ninety one
and when it is Father died and sixteen ten Galleo was engaged in a constant
struggle to try to just make ends meet. It seems likely that his sister
married in fifteen ninety one on terms negotiated by his father. Galileo sadly inherited
only the obligation of paying for her dowry, and in fifteen ninety three we
have evidence that his brother in law was threatening to have Galileo arrested if he
came to Florence because he hadn't paid. Galileo borrowed two hundred ducats to sort
things out. In sixteen oh one, the marriage contract for his other sister
provided for a dowry of eighteen hundred ducats, once again to be paid over
a period of five years by none other than Galileo and his brother Michaelangelo,
but of course no money was going to be coming from Michelangelo. In fact,
Galileo had just spent sixty ducats equipping Michelangelos that he could take up a
job in Poland. In sixteen oh two, Galleo again borrowing two hundred and
fifty ducats, which he was unable to repay. He had to return to
his friends for help. After his employers agreed to pay him only a year's
wages in advance, when he asked for two. A year later, he
obtained a second year's salary in advance. Nevertheless, in March sixteen oh five,
he was once again being sued twice for both of his sister's dowries.
Sixteen oh eight, he was forced once again to ask for his salary in
advance. We can see how difficult Galleo's financial position was when we recognize that
the younger sister's dowry represented close to thirty years salary at the rate that he
was being paid at Pisa, an eight year salary at the rate he was
being paid at the University of Padua. At Pisa, he had been paid
sixty ducats a year. In Padua, he who started at one hundred and
eighty florins of Venetian florin, being worth about seventy percent of a Florentine ducat.
Again, he got a new contract in fifteen ninety nine and the salary
rose to three hundred and twenty and in sixteen oh six balloon to five hundred
and twenty florins. His improved telescope led to his being offered a contract for
life at one thousand florins a year, but this didn't start until sixteen twelve,
well after all of the financial problems, and in fact, in sixteen
twelve the university stipulated that there would be no further wage increases before sixteen oh
six. Galleo simply couldn't meet his financial obligations out of his university salary.
Moreover, he soon had a mistress, Maria Gamba, about whom little is
known and whom Galleo left behind when he moved to Florence in sixteen ten,
and children of his own to support. At three, a daughter, Virginia
born in sixteen hundred Olivia in sixteen oh one. By the way, as
an aside, I didn't give you their names, but those happened to be
the exact same names of his sisters. That's why I didn't give you the
names, because it gets confusing. And then he had a son, Vincenzo,
in sixteen oh six. He was able to supplement his income by teaching,
or rather tutoring, mathematical skills required by young gentlemen who wanted to pursue
military careers. How much he brought in from this, though, was really
difficult to say. Galleo probably early on at least earned about three times more
from private lessons people that he kept on his borders, and the sale of
telescopes and other instruments than he did from lecturing at the universities. So it's
fascinating to think that in these years when Galileo was his most intellectually productive,
he was under unbelievable financial stress and Burton, the fact that he had the
time to sneak away and stare at the night Scott to develop the theories that
he once would was just fascinating. These were the years in which Gallea was
carrying out an active program of experiments. Frankly, long hours of teaching probably
seemed like an unbearable distraction. He came to hate teaching so much that he
later wrote about it as being equivalent to nothing more than prostitution. It's not
surprising that he began to long for a better life and to make inquiries as
to whether or not he could find employment elsewhere. What he was looking for
was not necessarily more money, but more time. When he finally moved to
Florence in sixteen ten, the salary was about forty percent more than he was
to have received if he remained in Padua, but a good deal less that
if he had stayed in Padua and continued providing lessons. The big difference was
that in Florence he wasn't going to be required to do any teaching at all,
not even the sixty and a half hours a year were required under his
current university contract. This was what he called leisure time, not money or
status. That was the irresistible attraction that caused him to leave Padua. And
there was another attraction though. In Padua, Galileo had been dependent on the
patronage of a small circle of powerful young noblemen. They had looked after him,
ensured his salary was regularly increased, and arranged for it to be paid
in advance, and of course they had lent him money when he needed it.
But in return they expected to be able to make demands on his time
and energies. They expected him, for example, to go with them when
they went on vacation. The demands of such friends and patrons came to be
seen as so burdensome that satisfying them involved what Galileo saw as quote ceaseless labors
end quote. It seems clear that he had come to resent this unequal relationship.
Luckily for Galileo, after he moved to Florence, he had a good
income and he was never in financial difficulty again. When Galileo arrived in Padua,
initially there was a major reorientation in his intellectual interests. On Motion was
a purely philosophical work. By contrast, his very first surviving letter from Padua
is concerned with a practical problem in naval technology, i e. How long
should the ores of a galley be? There could be no more basic question
in Mediterranean naval warfare in the period, fighting was entirely conducted, as it
was in the Roman era, by boats powered not by the wind, but
by bodies of human beings. This new interest in technology was soon reflected in
a number of different areas of activity. Galileo wrote courses of lectures on machinery
and on fortification. He designed and sold his sector or compass. He designed
a drainage pump of some kind. His primary interest was now in applied science,
and this new interest went hand in hand with an interest in developing exp
mental procedures. The birthplace of modern science wasn't really Galleo's lecture room in Padua.
But it was a place that the Venetians called the Arsenal, the vast
shipyards where vessels were built and repaired for the Venetian Navy. But it still
took Galleo a long time to learn this new craft of applied sciences. Time
and time again he got into arguments with individuals in the Venetian Navy about how
long the oars should be. His fundamental problem was he never actually went down
and talked to an oarsman. He never talked to a shipbuilder. All of
his models were purely theoretical, and none of them worked in real life.
So again, what we have here are a lot of baby steps. Galleo
never fully grasped that theory had its limits and that one needed to learn from
experience. Ultimately, what Galileo never came to terms with was that he needed
to use experience in order to guide and on occasion, even change his theory.
Galileo, though he was arguably the world's first experimental scientist, never understood,
at least never fully understood the need to use experience to inform his theory.
I don't think we should be too critical of him for this, after
all, Remember, we're coming out of an intellectual age when all that mattered,
and I mean one hundred and ten percent was theory and deductive reason for
one thousand years. If the theory said one thing, but you experienced another,
than your experience was wrong. Galileo was slowly but surely breaking out of
that mantra. But it would take time. And I don't want to fault
Galileo for his inability to jump forward hundreds of years in just a few decades.
Certainly, Galileo taught and studied applied science. That being said, his
fundamental approach to the subject was theoretical, not practical. He was interested in
clarifying principles, not creating machines that could actually work. In fact, of
all the drawings and plans Galileo made, only one historians agree could have actually
functioned. Galileo was never thinking about real machines. He wanted a way to
test theory. But there's no such thing as a pulley without friction or a
rope that has unlimited tensile strength. Not that that stopped Galileo from writing about
any and all of these things. So while he might be inching towards a
new science, his inclination was to use his innovations to power previous thinking.
All right, we're gonna leave it there for today, before we really start
to get into some of the heavier astronomy in our next episode. If you're
itching for more Western Sieve, you can check out either of the two seven
day free trials. In the show notes so you can get links to the
Patreon page into Western CIV two point oh. Western Civ two point oh.
We are well into the wars of the Successors and beyond. At this point,
Alexander the Great has been dead for some time, and everyone's still fighting
over the carcasses of his empire. It's good stuff and fun, and if
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