Previous . Next
Lecture 3: Copernicus
Astronomy and Biology
Why is it that most of the historical conflicts occurred in astronomy and biology? Because
these were two "observational" sciences that were accessible to everyone. Aristotle wrote
extensively on these, and therefore they also had lengthy commentaries in the medieval
period. Since Astronomy might be considered the most advanced of ancient sciences (you
should see the math these guys could do!), it isn't too surprising that this was one of the
cutting edge debates between religion and science.
Copernicus 1473-1543
- Problem of callendar--religious festivals
- role of mathematics vs. physics, or "saving the appearances"
- Physics --> realist
- Astronomy --> instrumentalist
- Osiander's intro to Copernicus' book, published posthumously
- Protestants & heretics love Copernicus
- Counterarguments to Physics abound
- Drop a rock from a tower. Did it move?
- Feel anything?
- Mathematics just isn't reality
Mathematics, up to this point in history, had always been a tool for understanding the
world. One didn't make a big deal out of "mathematical truth" because arithmetic was just so
obvious as to not need any justification. The real issue, was not the math symbols, but the
objects one was counting. "Two" was an adjective, never a proper noun. (Have you ever thought
how much simpler life would be if adjectives never became nouns?) Perhaps this is clarified
by analogy with language. Did Plato or Aristotle ever worry about the meaning of language,
whether it was possible for words to have a meanings independent of the sentence they lived
in? Probably not, but that has become almost the entire obsession of the 20th century
philosophy. This sophistication, if you want to call it that, began a few centuries earlier
in mathematics. It was this revolution about reality that was the truly controversial point
with Copernicus, a revolution that we perhaps can't even see because we (like Copernicus'
contemporaries) take it for granted.
To understand this revolution, let's review some history of science. Plato had this thing
for "regular solids" and geometry, as did most of the Greeks. So if one were going to
describe the motion of, say, planets, geometry would be naturally employed, probably with
compass and regular polyhedrons. Now Aristotle, in trying to understand friction, had
proposed that everything on Earth eventually comes to rest (friction), whereas the stars and
planets have been moving for millenia. He then argues that friction must not exist for
objects away from the earth, and this must be an inherent property we'll call "perfection".
But Plato had already described geometric perfection, so it was a natural fit to say, planets
and stars move on perfect circles, in a perfect realm, that eternally rotated above the
earth.
This theory of the heavens had a lot to commend it, and for almost 2000 years was developed
and tweaked and worked just great. There were a few minor inconsistencies, as you can find in
every theory, particularly with Mars and the outer planets. After all, the main reason they
are called planets (wanderers) is that they wander among the stars. Mars for example, rises
and sets with the stars, but night to night it appears to move against the stars,
occasionally even going backwards or making loops. The Greeks had a solution that kept
circular motion alive, Mars was on its own "circle" or epicycle, that meant two circles
rotating together. Ptolemy, around 200AD, made some major tweaks when he tried to reconcile
the epicycles with data, ending up with something like 4 or 5 epicycles per planet to account
for its motion. It worked, but now you needed a PhD in geometry to get predictions out. (Does
this sound like modern astrophysics to you?)
So Copernicus has this bright idea (which actually wasn't even his, since Nicholas of Oresme
had discussed it in the century before) that orbits could be calculated much faster if we
assumed that the Sun was the center, and all the planets moved on circles around the Sun. It
didn't give as good a prediction as Ptolemy, (and was criticized for that), but then it
didn't require a PhD to make calculations either. What do we make of this innovation? Is it
just a "stupid math trick" that could be used as a less-accurate shortcut? Did it mean that
Ptolemy's epicycles were wrong? Did it suggest that the Earth was *really* moving? Did have
anything to say about Catholic theology at all?
Just what exactly did a stupid math trick have to do with reality, Copernicus? I mean, as
far as anyone could remember, the ancient philosophers of science had said that the earth was
stationary. Isn't this obvious? You've ridden a horse or a cart before, and even with your
eyes shut, you knew you were moving. Does the earth feel like its moving? What about a simple
test. Drop a rock. If the earth was moving, then wouldn't the rock NOT land directly under
your hand? And you know what happens when you ride a carousel in a circle, you get thrown
off. How come everything doesn't get thrown off the earth if its going in a circle? And if
you want a *really* new theory, you have to predict something new, but all you've done
Copernicus, and I don't mean to be rude, is reinvent the astronomy tables with a clever
technique that isn't as accurate. I mean
face it, Copernicus, your theory introduces so many more problems than it solves, why try to
argue that this is reality and not some SMT?
Copernicus evidently thought that it reorganized the heavens, as did a number of Protestants
who had an axe to grind with the Catholic church and used this "fact" to argue that nearly
all of Catholic theology was obsolete. Osiander, in his introduction to Copernicus' book
recognized that his words might be used by this debate, carefully said it was just a stupid
math trick that "saved the appearances" but said nothing about reality. The church, which
had spent the last 1500 years finding good agreement between Scripture and Greek science,
wasn't very encouraging (as indeed, they should be, at least, until the bugs were worked out
of Copernicus' theory), especially with inflammatory Protestants claiming some sort of
victory. The scholars, who used to get paid for these calculations, no doubt felt threatened
with the thought that every village priest could be doing astonomical predictions with ease.
As Brook discusses, scientific theories don't just get expressed in a vacuum, but they always
come mixed with turf battles and politics and people.
My own view, is that until a theory is actually superior (with respect to the data) to its
competitors, one has every reason to be suspicious. And the Copernican theory was NOT
superior (only simpler) than Ptolemy's until Johannes Kepler made his famous contribution
almost 100 years later. Modern science writers make a big deal that Copernicus had removed
the Earth from its privileged position at the center of the universe, and this was what the
Catholic church objected to. This is far too simplistic for many reasons. First, Hell was
actually the center of the Earth, so why should occupying the center of the universe be such
a favorable position? Second, many of the powerful positions in the Catholic church were
occupied by educated scholars, who were not theological dogmatists in the slightest, but well
informed scientists. Third, it was not the location of the Earth that made Catholic theology
regard humans as occupying a special place, it was the fact that the Bible says "God made man
in his own image". Science was accommodated to theology, not the other way around. Fourth,
the Catholic church was well aware of the deficiencies of Copernican astronomy, and with
their conservative, even reactionary tendencies in everything, were unwilling to adopt
new-fangled theories until all the evidence was in. And finally, of course, was the whole
theological / sociological movement we call today the Protestant Reformation, that was just
getting into high gear. So keep this in mind as we look at the Galilean affair.
Last modified, January 11, 2002, RbS