“… with some reading and piecing together of some
related bits of evidence,
and thinking about context, I’m now completely
convinced Copernicus
did know of Aristarchus’s hypothesis, and that he
deliberately withheld acknowledgement of the fact”.
cosmiCave.org
Setting the Record Straight: How Copernicus
Concealed His Debt to Aristarchus—and Claimed an Intellectual Priority He Knew
Wasn’t His
There’s a prevailing myth in the history of science that Copernicus
rediscovered heliocentrism independently—and that he had no real connection to
Aristarchus, whose own theory was vague, obscure, and uninfluential. This essay
dismantles that myth.
While researching this previous essay, trying to get all my facts
straight with reference to primary sources, I found several interconnected
things that are badly misunderstood at the present—things I previously thought
were true, but which closer inspection showed to be false.
I used to think, as it’s the common consensus, that it was unclear
whether Nicolaus Copernicus had known Aristarchus of Samos proposed a
heliocentric (Sun-centred) model similar to his in the third century BCE—and
that he probably didn’t since he never mentioned it. But with some reading and
piecing together of some related bits of evidence, and thinking about context,
I’m now completely convinced Copernicus did know of Aristarchus’s hypothesis,
and that he deliberately withheld acknowledgement of the fact.
Another thing I’ve always understood to be true, which is written all
over the place, is that one of the main obstacles that stood against
Aristarchus’s theory being accepted in his time was the fact that we don’t see
any stellar parallax in nearby stars as Earth orbits the Sun. But this, too,
turns out to be an anachronistic myth—and one that’s pretty clear to see when
all the relevant information is pulled together. It’s also linked to a lot of
inaccuracy related to interpreting Copernicus and Aristarchus, and in a way I
think it has indirectly influenced the false consensus that Copernicus likely
wasn’t aware of Aristarchus’s hypothesis.
Consequently, while this essay’s primary purpose is to explain that
Copernicus was, without a doubt, aware of Aristarchus’s heliocentric theory—in
fact, he was every bit as aware of its details as anyone today is—it will also
clarify some other things that people seem to commonly misunderstand, such as
the anachronistic parallax myth.
I want to be clear: I’m not claiming Copernicus originally got the
heliocentric idea directly from Aristarchus. That is too strong a claim, and I
don’t think we can ever know one way or the other. Aristarchus likely became
known to Copernicus at some influential point during his studies in Italy, but
whether that was before or after Copernicus had thought of the basic concept,
and realised for himself that e.g. retrograde motion could be explained through
parallax rather than by actual backwards motion as the planets looped around a
fixed Earth, we cannot know. It is reasonable to think that Copernicus realised
the latter on his own, though he did not keep a detailed diary as he worked
through his ideas, so we can’t confirm this.
So we can’t know precisely when in his early years
Copernicus became aware of Aristarchus, nor how influential the Ancient Greek
had been in shaping Copernicus’s theory.
In fact, very little is even known of the details of Aristarchus’s
model, so it really can’t have been too influential. Copernicus must have come
to realise much of what makes the concept so compelling on his own.
But still, this does not change the fact that Copernicus did Aristarchus
dirty.
He knew Aristarchus had proposed a heliocentric theory in the third
century BCE. He knew Aristarchus was a serious astronomer, e.g. the first to
estimate the Sun’s distance through careful measurement and detailed geometric
reasoning. And Copernicus deliberately withheld that information from
both Commentariolus and De revolutionibus orbium
coelestium—as he was absolutely aware of his predecessor’s
theory already when he wrote his early draft.
This much is true. And it is also true that Copernicus made this
omission so he could claim priority to the idea that the Earth orbits the Sun.
While he did not explicitly say this—how could he, as he omitted his
knowledge of Aristarchus entirely?—he did so implicitly, by excluding
Aristarchus from the broader group of Ancient geokineticists he listed in
support of his proposal that the Earth moves, which he followed by explicitly
claiming that he had come to the idea that Earth is orbiting the Sun on his
own, “by long and intense study.”
Leaving Aristarchus out of that sequence worked well rhetorically, as he
could cite precedent for the proposal that the Earth spins daily, or that it
moves about a central fire in an
abstract, metaphorical sense. And from there, Copernicus could frame himself as
taking those ideas to the next level with a novel hypothesis that this moving
Earth actually orbits the Sun.
The omission of Aristarchus provided a clean and compelling narrative
within the opening argument for
his life’s work, and it’s understandable that he did it.
The alternative would be to frame the whole theory as something that had
basically been thought of and explored in Ancient times, and eventually
rejected by those who Copernicus and everyone around him thought of as
intellectual authorities, leaving him to argue that while they’d eventually
abandoned the idea he nevertheless proposed circling back to.
This more honest approach would have placed Copernicus at a much greater
disadvantage, making him far more easily dismissed on superficial grounds,
which he needed to avoid. “Check out my theory! Someone already thought of it
1800 years ago and the astronomers at the time eventually dismissed it as an
abstract peculiarity that’s nevertheless absurd. But for the past several
decades I’ve worked through the details anyway and I think I can make it work,
never minding the absurdity which you’re likely to find insane.”
Copernicus actually acknowledged in De revolutionibus, that
the idea that Earth was rapidly spinning and orbiting as he proposed seemed
“absurd,” “insane,” and “almost against common sense.” To admit this, and to
also say that people had nevertheless already considered the hypothesis and
discarded it would have considerably heightened his disadvantage.
So, instead, he omitted the detail and framed the idea as novel:
“For a long time, then, I reflected on this confusion in the
astronomical traditions concerning the derivation of the motions of the
universe’s spheres … having obtained the opportunity from these sources, I too
began to consider the mobility of the earth. And even though the idea seemed
absurd, nevertheless I knew that others before me had been granted the freedom
to imagine any circles whatever for the purpose of explaining the heavenly
phenomena.
Hence I thought that I too would be readily permitted to ascertain
whether explanations sounder than those of my predecessors could be found for
the revolution of the celestial spheres on the assumption of some motion of the
earth … [and] by long and intense study I finally found that if the motions of
the other planets are correlated with the orbiting of the earth …”.
So you see: this narrative does not work if Copernicus acknowledges that
Aristarchus had actually beaten him to the claim, and that Copernicus was
reviving something that had been rejected almost two thousand years ago, by
those who had the full original manuscript to work with. Omitting Aristarchus
allowed Copernicus to cast himself as the innovator rather than revivalist—to
frame heliocentrism as a novel hypothesis rather than a return to an abandoned
theory.
Copernicus’s source on Aristrarchus’s theory—Archimedes’ Sand-Reckoner—was also not widely known
when De revolutionibus was published in 1543. It was first
printed (purely coincidentally?) in a Latin edition of Archimedes’ works in
1544. Copernicus was therefore not compelled to cite his source, as his
knowledge of the former work was relatively private and not expected.
Anyway, the above explains roughly why I think
Copernicus cut Aristarchus out.
This is my reasoning based on Copernicus’s rhetorical
framing of his proposal, and a suspicion that he was not acting purely in bad
faith. Not necessarily because he wanted all the glory to himself, though there
may have been some of that, but mainly because it would have been a
disadvantage to do so.
But this essay is not about my own, personal speculative opinion. And I
will not go so far as to demonstrate why Copernicus did what
he did, nor how large a debt Copernicus owed to Aristarchus nor how much of his
realisation about the compelling aspects of heliocentrism was original insight.
I don’t think we’ll ever find more direct evidence to help in ascertaining
these things.
What I will show, as I said above, is that Copernicus clearly,
unquestionably did read Archimedes’ Sand-Reckoner sometime
before 1514, when he circulated Commentariolus to his friends
and colleagues—and that he therefore knew Aristarchus proposed a heliocentric
theory before him. That he therefore deliberately withheld the reference
in De revolutionibus. And that twentieth century Copernicus
historians wrongly concluded he did not.
In the process, I’ll also set the record straight on a related point—a
common anachronistic reading of the evidence that was held against
heliocentrism, both in Ancient times and in Copernicus’s day. The idea that the
Ancients cited an apparent asbsence of parallax shift in the nearest stars due
to Earth’s hypothesised orbit about the Sun, that they favoured geocentrism in
part because of this, and that Copernicus hedged against this criticism, is a
complete falsehood that is almost universally accepted at present.
This anachronistic parallax argument against heliocentrism was not noted
until after Copernicus died—and in fact it was not even applicable to either
his theory or Aristarchus’s. The fact that it is commonly thought to have
concerned Copernicus and Aristarchus’s contemporaries is unfortunate for
several reasons:
- it represents a fundamental misunderstanding
of an Ancient worldview that persisted unchallenged until nearly the end
of the sixteenth century, which Copernicus never dreamed of
questioning;
- it therefore obscures the debt we all owe to
one of the most influential innovations in the history of cosmology, to a
person (Thomas Digges) whose name is hardly ever even mentioned in the history books—and
certainly not as a key player in the Scientific Revolution—who frankly
deserves to be celebrated as the father of modern cosmology, finally given
his rightful place alongside Copernicus, Galileo, Kepler, and Newton;
- it leads to anachronistic misreadings of both
Ptolemy and Copernicus, when we fail to realise the notion of a parallax
shift in nearby stars relative to those further away never could have
crossed their minds; and,
- it obscures a key piece of evidence that
renders Copernicus’s obvious plagiarism of Archimedes unmistakable, along
with the deliberateness of his omission of Aristarchus as his predecessor.
It’s an interesting and deeply illuminating historiographic reset, and I
hope you enjoy reading. It’s far more than just a detail about intellectual
credit. These false narratives that have been propagating for more than a
century warp our entire understanding of cosmological progress, Ancient
science’s sophistication, and even modern assumptions about scientific
reasoning.
Given everything I’ve said above, I’ll work through the actual
demonstration of claims as follows. I’m going to start with a recap of previous
arguments that incorrectly concluded Copernicus was unaware of Aristarchus’s
heliocentric theory, clarifying on their own terms how weak and flawed they
are. I’ll then explain the anachronistic parallax argument, clarifying why it
is an anachronism. With that context, we can then immediately clarify
Archimedes’ reference to Aristarchus in the Sand-Reckoner—both,
what his concerns were and what they were not. I’ll then also discuss both
Ptolemy’s argument in Almagest Book
I, Chapter 6 and Copernicus’s argument
in De revolutionibus Book I, Chapter 6 (Copernicus
deliberately paralleled the structure of Almagest as a
rhetorical device in his work, so these chapters are similar), clearly
establishing that neither was aware of the anachronistic parallax idea. Thus,
we’ll clarify both, that Ptolemy was not arguing against heliocentrism on that
ground—in fact, there is no evidence he entertained the heliocentric hypothesis
at all in Almagest, as he never addressed it—and that Copernicus
was not hedging against the anachronistic parallax argument in De revolutionibus—and
again, there’s no evidence he ever even dreamed it was a problem he’d need to
guard against—and in fact when we consider his actual worldview it’s clear the
problem should never have crossed his mind.
We’ll then loop back to the Sand-Reckoner, specifically
focusing on Archimedes’ application of Aristarchus’s theory, what that
application says and what it explicitly does not imply about the Ancient
reasons it failed to attract a wider following. In my previous essay, I gave
three reasons why Aristarchus’s theory faded into obscurity until it was
revived by Copernicus, and this diagnosis clarifies that the anachronistic
parallax argument was never one of them—that it was never even dreamed of until
after 1576, when Digges proposed his radically different cosmological
worldview, which we’ve all come to accept implicitly, and tend to project onto
earlier thinkers.
Finally, having all these pieces in place, this analysis will close with
the evidence that Copernicus lifted his fourth proposition in Commentariolus directly
from Archimedes—that there is no other explanation for the specific formulation
he chose, as he never would have come to that specific formulation on his own,
he did not require it, he never made specific use of it, and in the end, in De revolutionibus he
reverted to the less specific, mathematically imprecise argument that
paralleled Ptolemy’s reasoning in the Almagest.
Previous Accounts by Science Historians
Copernicus’s Commentariolus was lost for more than 350
years. While he had shared copies privately with several friends and colleagues
in 1514, those languished in private libraries. This first articulation of
Copernicus’s heliocentric hypothesis was only rediscovered in 1878, by the
historian Maximilian Curtze in Vienna. And it was first translated into English
by Edward Rosen in 1939.
In 1942, Rudolf von Erhardt and Erika von Erhardt-Siebold published
a sprawling article in the
History of Science journal Isis, closing with a claim about “the
almost certain acquaintance of Copernicus with the Sand-Reckoner.”
In the article, this claim was buried at the end, and even there it was not
well explained: The section is two paragraphs long, the point is made (without
proper context) that Copernicus’s fourth postulate in Commentariolus is
conspicuously similar in its construction to a passage from the Sand-Reckoner,
and then the authors proceed to speculate—incorrectly!—that with this postulate
Copernicus may have been guarding against the non-observability of stellar
parallax due to Earth’s orbit. ….
In the context of all of this, and regarding the actual historicity of
some of these famous astronomers and scientists, see my (Damien Mackey’s)
articles:
Did the
Greeks derive their Archimedes from Sargon II’s Akhimiti?
(8) Did the Greeks derive their
Archimedes from Sargon II's Akhimiti?
Machiavelli
in the name Achitophel, Galileo Galilei in the name Gamaliel
(8) Machiavelli in the name
Achitophel, Galileo Galilei in the name Gamaliel
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