Hello, and welcome to Western Sieve Episode two hundred and sixty one Discovering Earth.
Last week we started the Scientific Revolution by focusing on the concept of discovery.
Discovery, to a large extent, made the scientific Revolution possible. Today,
I want to go a step further and consider more deeply how the Age
of Discovery and early Scientific Revolution contributed to Europeans changing understanding of the very world
around them. It turns out what they had believed for centuries was false.
But how then to go about adjusting a perception which had existed since almost the
time of Christ. Today it is that question to which we devote this episode.
The voyages of Discovery completely changed European perceptions about the world from roughly fourteen
sixty onwards. Consider this, what was known of the world in fourteen fifty
was roughly what was known of the world in the year one Common Era,
So this is a big change. We're talking about. Conventional attitudes that the
lands around the equator were uninhabitable because the seas boiled and men would literally melt
turned out to be nonsense. There were whole continents unknown to the Greeks and
Romans. These new lands were carefully mapped by cartographers what was likely the first
great victory of experience or philosophy in the history of the West. The invention
of what we call the terraqueous globe took place over the course of a few
years. This isn't actually a globe, by the way. It's a map,
but it's a map that works like a globe, with lines of latitude
and longitude, and crucially, it puts into scale for the first time all
the different new and unexplored regions of the Earth. This, of course,
brings us to a very crucial question, what shape is the Earth? The
answer to this question must seem obvious. Surely everyone knew that the Earth is
round. In the nineteenth century, it was claimed that Columbus's contemporaries thought the
world was flat and expected him to sail over the edge. That story is
ridiculous by the fact that everyone, or at least every properly educated person,
thought that you could, in principle sail around the world, and in fifteen
nineteen Magellan and his crew did just that. That doesn't mean that they thought
the world was round. Columbus strangely thought that the old world known to Ptolemy,
was half of a perfect sphere. But the new world, he believed,
was shaped like the top half of a pair, or as he says,
abreast, and he had the impression that he was sailing uphill as the
Azores receded behind him. The stock or nipple of the southern hemisphere was the
location of terrestrial paradise. The Earth, or rather the Earth and water simply
bulged. So along with this difficulty of what shape is the Earth, the
other problem for Europeans when it came to translating how this new world functioned was
the relationship between earth and water. By earth, I mean land. Generally,
most of the philosophy on the subject agreed that land and water occupied distinct
spheres on the globe in some way, whether you think about a giant ocean
that surrounds all the land, or perhaps the opposite. The idea was that
each zone was distinct and continuous. I e. What I mean by that
is you couldn't have ocean and then more land. Land was continuous. Ocean
was continuous. They were two separate spheres. The idea that there are not
separate spheres, that this is wrong, doesn't start to become into being until
the very earliest the thirteenth century, and even then the idea doesn't gain any
track action until the fourteenth The reason that this theory is so important is that
it's the only theory that squares ultimately with reality, namely that land masses are
scattered throughout the earth. In fact, the theory that emerges in the fourteenth
century asserts that land masses should be scattered throughout the globe. This is the
only theory that fits with the now obvious existence of antipodes bodies of land directly
opposite to each other on the globe. Now. Sadly, again, this
theory had almost no support prior to fourteen ninety two. For us to see
how this begins to break apart, we have to first begin to think about
astronomy, which was to be blunt probably the only science we would recognize as
science in the late Medieval early Renaissance period. Students in this period learned their
astronomy by studying the Sphere, published in twelve twenty Common Era by Johannes de
Sacrobosco. His textbook was widely printed in fourteen seventy two once the printing press
took cold and actually went through more than two hundred editions. The sphere was
still the standard astronomy textbook when Galileo taught at the University of Padua in the
late sixteenth century. In line with the notion that the globe was made up
of two non concentric spheres, one of Earth and one of water. Following
the example of Ptolemy's Alma Guest, which had been available in the Latin West
from about the twelfth century onward, Sacrobosco proved separately that the surface of the
Earth was curved. He showed how this can be made apparent to someone traveling
either north south or east west, and that the surface of water was curved.
This was evident because a lookout on the top of a ship's mast could
see farther than someone standing on the deck, which wouldn't be the case if
the Earth was flat. Modern commentators assumed that Saproboscope had proved the Earth is
round. He had done nothing of the sort, and medieval commentators didn't claim
that he had, for neither he nor they believed that the two spheres shared
a common center. Hence, when medieval philosophers talk about the Earth, they
meant the land, namely the sphere of dry land that showed above the ocean.
All these late medieval discussions took place within a context of a geographical knowledge
which corresponded to that of the ancients. No one believed that the Earth was
flat, but the habitable Earth could be represented fairly accurately on a flat surface.
The habitable Earth had a center, which was generally taken to be Jerusalem.
However, there was another center measuring from west to east from the fortunate
Aisles which are the Canaries, to the Pillars of Hercules, which marked the
limit beyond which it was impossible to travel. There existed a notional location on
the equator that was called Autumn or Erin, believed to be about ten degrees
east of Baghdad. For the Arabs and for astronomers relying on Arabic sources,
Ram represented the degrees zero of longitude and latitude. It was universally accepted that
dry land was confined to one hemisphere, the rest being covered by ocean.
Of the dry land, the furthest northern and southern parts were uninhabitable because they
were either too cold or too hot. As the habitable portion of Earth represented
approximately one half of the whole of the dry land, one sixth of the
whole agglomeration of earth and water. Thus, this two sphere theory of the
world was shared by nearly all philosophers, astronomers, and cartographers, despite the
difficulties it was known to present until the late fifteenth century, when the rediscovery
of Ptolemay's geography was incorporated into it without much difficulty. The Portuguese explorers reached
the equator in fourteen seventy four or fourteen seventy five, discovering a new heavens
and a new stars when things suddenly reversed, but they didn't find any uninhabitable
zones, and this required some minor rethinking, but little more. It's true
that Ptolemay in geography, unlike the Alma Guest, treated earth and water as
a single sphere, and this was obviously bound to be of interest. After
the translation of Ptolemay's geography, there's no record of a terrestrial globe being made.
In fourteen fifty three, Columbus read Ptolemaian was convinced that the Earth and
the water formed one's sphere. He produced a small globe to illustrate his planned
voyage. At the same time, he chose to reject Ptolemay's account of the
extent of the habitable world, preferring a different man, that of the name
of Marinus of Tire, who claimed that the habitable portion of the earth extended
more than halfway around the globe, a view difficult to reconcile with the two
spheres theory, and of course, the crisis then begins with Columbus's landfall in
fourteen ninety two. In fourteen ninety three, Peter Martyr described Columbus's returning from
the quote western antipodes end quote in editorial certificate drawn up by another man.
Pedro Alvarez Cabrel's discovery of Brazil in fifteen hundred is described as the discovery of
the quote land of antipodes end quote. He was right, by the way,
Brazil is antipodal to the eastern extremity of the world known to the ancients.
But the decisive event was the publication in fifteen oh three of the first
letter written or supposedly written by A. Metago Vespucci, entitled Mundus Novus,
which went through twenty nine editions in the space of four years. It was
vespucci second letter, by the way, which introduced the word discovery to European
audiences. Vespucci's claim was that he had encountered a vast new land mass which
formed no part of the previously known world. He had found, in other
words, a new world. Moreover, it was clear that this land mass,
although it was only one quarter of the way around the globe from his
starting point, was halfway around the globe from other parts of the known world,
and Vespucci sailed fifty degrees south of the equator. This was not just
the equatorial antipodes that some exponents of the two sphere's theory had envisaged. Antipodes
had become a reality, and there was no way anymore that you could fit
Earth's land mass into one hemisphere. So up to this moment, it was
possible to assert that the spheres of Ocean and Earth were round, and that
the zone of dry land, as the Bible asserted, had four corners.
You could just change the idea that these were four square quarters into rounded ones,
and the idea still worked fine. But as I mentioned, the problem
was this concept of a one hemisphere, multi sphere Earth, and how it's
just bedeviling to people trying to make globes. In fifteen oh seven, two
globe makers tried to sidestep the issue by naming their project omen Terra ambitum or
the whole Circumference of the Earth, and claimed of this ptolemy only knew one
quarter. And again we find why language is critical to understanding the shift in
perception taking place here. In classical Latin, the word orb was derived from
orbis, meaning not just a sphere, but also potentially a flat disc.
When Aow wrote of the orbis, he means habitable dry land. The concept
of a globe in the modern concept of the globe is totally foreign to this.
Finally, in fifteen eighteen, George tan Center published the first ever edition
of The Sphere that shows a modern conception of the globe when with the interlocking
land and sea. That was twenty sixty years after Columbus reached the Americas.
From fifteen thirty eight onward, the idea that the earth and water made up
one sphere became the dominant theory, and that's an amazing change. The two
sphere theory was unquestioned in fourteen seventy five, by fifteen fifty was totally abandoned
once more. This was the triumph of experience and evidence over theory and logical
argument. The invention of the printing press and the invention of discovery, acting
in combination, transformed the balance between evidence and theory, tilting it away from
the reinterpretation of old arguments and toward the acquisition and interpretation of new evidence.
As far as the two sphere theory was concerned, the voyages of Vespucci were
deadly. The new facts were killer facts. As it happened, this is
the first occasion since the establishment of universities in the thirteenth century on which a
political theory was destroyed by a fact. Astonishingly as it might seem, there
is no previous occasion on which new empirical evidence determined the outcome of a long
standing debate between philosophers. Aristotle, for example, had argued that the nerves
are all connected to the heart. Galen had shown that they were connected to
the brain, but Aristotelian philosophers, both ancient and medieval, had continued following
Aristotle's teaching as if Galen didn't exist. In fifteen o seven, the relationship
between theory and evidence changed, and it changed forever. We're going to get
more into Nikolai Copernicus in a few weeks, but for now, know that
the broad outline of capernas Kus's argument for the Earth as a single globe was
conventional by fifteen forty three, that was when it was published. We know
that he formulated this view as early as fifteen fourteen. Again, I will
get more into his theories in much greater detail here in a bit. What
is interesting for us now from a macro level is how Copernicus's theories about the
world were received. Note he died shortly after their publication so as not around
for debate. It used to be taught in many schools that Copernicus sparked an
intellectual revolution. Sadly, that's just false. Sure astronomers were interested in what
he had to say, but most assumed his arguments for a moving Earth were
plain wrong. If the Earth moved, the argument went, we would be
aware of it. You would feel the wind in your face, like if
you ride in an open car or on a bicycle. If you dropped an
object from a tower, it would fall to the west, etc. Etc.
Other men would solve this riddle, I e. That the Earth does
move, but much too slowly to impact us in perceptible ways. But for
now we need to accept the reality that Copernicus's work was maybe less revolutionary than
it's often made out to be. For example, while there is no mention
of astrology in his work, Copernicus never disputed the standard view of the time
that astronomy existed to make astrology possible. That was its purpose. Coupernicus's view
of the universe is different from Ptolemais in that the Sun, not the Earth,
lies at the center, but in all other respects, Copernicus's view is
identical to Ptolemais. It was a series of spheres, one nested within the
next, all movement within it was heavenly and perfect, and therefore circular.
For the first two generations of astronomers reading Copernicus, the crucial point about his
book was not that it advocated heliocentrism, but that it took the principle of
circular movement more seriously. Finally, Copernicus's universally Ptolemay's was finite in size.
What then, are the implications of claiming that the Earth is a planet?
Copernicus does not discuss the question, but his successors would have to. In
the summer of fifteen thirty eight, an Italian man by the name of Giordano
Bruno gave a series of lectures in Italian in Oxford in fifteen thirty eight.
By then it had been forty years since Copernicus had published on the Revolutions.
His new astronomy had certain evident advantages over the established astronomy of Ptolemay. According
to Plato and Aristotle, all movement in the heavens should be circular and unchanging.
And in the Renaissance there were still philosophers trying to construct a simple model
of the universe, which consisted of spheres nested around a common center. But
try as they might, these philosophers could not get such models to fit what
it actually happens in the heavens. What Ptolema had managed to achieve was a
system that accurately predicted movements in the heavens. The Ptolemaic system, like those
of Plato and Aristotle, claimed that the moon, the Sun, and all
the planets circled around the Earth. But in order to accurately predict the movement
of these heavenly bodies, and it was a complex system of what we're called
deference circles, epicycles, circles on circles, and eccentrics, circles rotating around
a display center, and equants all had to be used. The equant was
a device for speeding up and slowing down the movement of a body in the
heavens by measuring its movement not from the center of a circle, but from
a different point. By this means, the movement could be described as constant.
Essentially, what it comes down to was Ptolemy head figured out in a
very artful way how to get a round peg to fit in a square hole.
You had to just jimmy it a lot. It was awkward, It
had a lot of bizarre calculations, but it worked. Now, Capernaskis comes
along and proposes to abolish the equant and to eliminate the epicycle for each planet
further from the Sun than the Earth, by showing how the movement of the
Earth created an apparent movement in the sky equivalent to these epicycles. Copernicis also
claimed that his system was preferable because it specified more tightly the characteristics of the
system as a whole. Polemaic philosophers had never been sure, for example,
whether Venus or the Sun was closer to the Earth here Coupernicus's system had a
huge advantage because it placed the heavenly bodies in a fixed and permanent order.
Still, as late as fifteen thirty eight, there were, as far as
historians know, only three competent astronomers in all of Europe who accepted Coupernicus's claim
that the Earth traveled around the Sun. In Germany there was Christophe Rothmann,
in Italy Giovanni Bettini, and in England Thomas Diggs. Several of these men
were able to push Copernicanism a little bit further to argue for an infinite and
eternal universe. The stars, they said, were suns, and the sun
was a star here. Actually they weren't following Kupernicus, but Aristochus of Samos,
who lived back in the century BC. Thus, they argued there could
be other inhabited planets in the universe. Even the Sun and the stars might
be inhabited, for they could not be equally hot all over, and there
might be creatures quite different from ourselves who thrive on the heat. Moreover,
there was nothing to show that the other planets were different from the Earth.
Several argued that the moon and planets could be presumed to have continents and oceans,
and that they shone not by their own light, as generally was assumed,
but solely by reflected light. Thus, seen from the Moon, the
Earth would look like a gigantic moon. Soon from even farther away, it
would look like a brighter star in the sky. The Earth, one of
these men thought, would shine brightly because the seas would reflect more light than
the land. Thus, for the first time, we start imagining an infinite
universe with numberless stars and planets, all possibly inhabited by extraterrestrial life forms.
Interestingly, these men weren't the first to imagine infinite universes with extraterrestrial life.
Back in fourteen forty, Nicholas of Cusa, in his un learned Ignorance,
had argued that only an infinite universe was appropriate for a finite god. Nicholas
thought the Earth was a heavenly body which from a distance would shine like a
star, an idea that would later catch attention. But Nicholas assumed that the
Earth and the Sun were similar bodies. A habitable world, Nicholas thought,
was hidden behind the shining visible surface of the Sun. As for the Earth,
it, like the Sun, was surrounded by a fiery mantle which for
some reason was invisible to us. But really the first competent astronomer to argue
for an infinite universe was Diggs, the English astronomer, in fifteen oh seven.
He was the first person to explicitly propose an infinite universe. Diggs was
not an insignificant figure in new astronomy. In fifteen seventy three, he had
published a study of the nova and supernova which had appeared the previous year,
and yet at the same time he was happily engaged in using the new astronomy
to predict the weather and to decide when doctors should bleed their patients. He
published his new Copernican account to the Cosmos alongside his father's old Ptolemaic account.
He knew that the Copernican system could only work if the cosmos was much bigger
than the Ptolemaics had imagined, but he didn't correct some of the figures from
before. And there's where I think we get our biggest takeaway from today's episode.
The reality is that, like most revolutions, the scientific revolution was never
uniform in its direction. There was a lot of back and forth. There's
a lot of efforts, even by the men who would consider to be the
best astronomers of their age, to still figure out some way to get all
these new findings to fit neatly within the Ptolemaic box, or at the very
least to figure out a new way to get the circular peg to fit into
the square hole. It's going to take repeated knocks to the system, and
really we're going to have to wait for Galileo to see the system completely be
brought to its knees, but that won't be for another fifty or sixty years
from where we are right now, and we are going to get to Galileo.
It's just going to take me a little bit of time. So it's
interesting to think of how the new discoveries from the voyage of Columbus lead to
new discoveries by men like Copernic, which caused the old system to buckle but
not necessarily break, at least not in every case. All right, we're
going to pick it up next week with evidence and experimentation. That'll be one
of our last sort of broad episodes before we ultimately get into looking more closely
at first Copernicus and then Galileo. But in the meantime, if you're looking
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