This is an accidental article. While working on the research for a long article on comets, prompted by the current COVID-19 pandemic, I came across a story about how a comet observed by Tycho Brahe helped to propel the Copernican Revolution forward. This led to some additional revelations about the confusing multiple meanings of terms like heliocentric and geocentric. These terms mean one thing among astrologers, another to the general public, and something a little different and more specific in a scientific context.
I intended my thoughts on these matters to serve as an afterward to the comet article, but it dawned on me that they pertain to a separate topic. Additionally, this is a topic important enough for its own article. I hope you agree and enjoy it. Thank you for your support. I feel for those going through hard times during this epidemic. I wish everyone good health and a solid footing.
Tycho and the Comet
A pivotal moment in the history of astronomy was made possible by an extraordinary comet. On November 13, 1577, Tycho Brahe was fishing when he saw a very brilliant comet, as bright as Venus, and with a 22° long reddish tail. This was the famed Great Comet of 1577. His continuous observations of the comet over the ensuing period of its visibility (nearly 2 months) turned up discoveries that would upend some Ptolemaic assumptions that had persisted even into Copernicus’s model of the heavens.
Initially, his calculations of the comet’s motion and distance led him to debunk Aristotle’s theory that comets were meteorological events of the upper air. His data clearly showed that comets moved in the heavens, like the planets. More radically, when the comet was observed to have moved through what was assumed to be the spheres of Venus and the Sun, it became clear that planetary motion was not due to physical spheres upon which the planets were fixed. In other words, there were no solid celestial spheres. The relatively mechanical planetary spheres would no longer suffice as the explanation for planetary motion. Tycho published these findings in his book on the comet (De Mundi Aetherei …). It had a profound influence on the later work of Johannes Kepler.
A Geostatic Heliocentric Model
Brahe, who was also an astrologer, developed his own rather unique model of planetary motion. It is typically characterized as geocentric or as a geocentric-heliocentric hybrid. However, it is more accurately characterized as a geostatic heliocentric model. That is, he posited that the Earth was motionless, so the model was entirely relative to a stationary Earth (geostatic), but he posited that planetary motion was around the Sun (heliocentric). While Brahe accepted Copernicus’s planetary motion around the Sun, he wished to improve some major faults in Copernicus’s model, including its heliostatic nature.
Morin’s Kepler-Brahe Hybrid Geostatic Heliocentric Model
Actually, well into the 17th century, many astronomers accepted Copernican heliocentric planetary motion, while rejecting the heliostatic feature of Copernicus’s specific model. Many traditional astrologers are familiar with Jean-Baptiste Morin, the famous 17th-century French astrologer, astronomer, and mathematician. His mammoth astrological work, Astrologia Gallica (“French Astrology”), continues to be influential. It is fairly well-known (I mean it’s on his Wikipedia entry at least) that he advocated a geostatic position (fixed Earth). What is less well known is that he did in fact accept heliocentric planetary motion, and sought to marry Kepler’s elliptic orbits to the geostatic heliocentric model of Tycho Brahe.
Some of the issues with the Copernicus model included its use of planetary spheres to explain planetary motion, the implausibility of his rotation argument, and the lack of evidence for some things predicted by Earth’s movement. I already noted that Brahe’s cometary data called into question the idea of solid celestial spheres as a mechanism of planetary motion. One of Copernicus’s primary arguments for the Earth rotating rather than the sky was that “nothing infinite can be moved”, which was less than a compelling data-based argument for Brahe. Additionally, Brahe incorrectly thought that the Earth’s orbit would make comets retrogress (they move too fast for this to happen) and would cause parallax in the directions of the stars over time (it does but it is too small for Brahe to have detected it).
The rejection of the heliostatic position by many astronomers was not due to some form of stubborn traditionalism in the face of compelling evidence. Rather, it was among methodical scientists who were attempting to radically remake the planetary model to accord with the best evidence available. Sufficiently compelling evidence that the Sun was fixed and the Earth was in motion was slow to come. Compelling evidence that actually neither the Sun nor the Earth was truly fixed, and all motion was relative, wouldn’t come until centuries later, far after the Copernican Revolution.
Heliostatic vs. Geostatic
So, who was correct, Brahe or Copernicus? Is the better model the geostatic one in which all motion is characterized relative to a stationary Earth, or a heliocentric one in which all motion is characterized relative to a stationary Sun? As it turns out, the question is not a scientific or an astronomical one at all. In modern astronomy, nothing is “static”.
We speak of motion around the Sun as a convenience. However, we also characterize the Sun as being in motion around the center of the Galaxy, and galaxies even move relative to each other. Therefore, it is meaningless in a scientific context to say anything is essentially fixed in space and at rest. Similarly, motions can be characterized relative to any given frame of reference.
An Astronomical Historian on the Essential Difference Between Geostatic and Heiliostatic Theories
“[W]e might say (details aside) that holding the sun still in Tycho’s system gives us Copernicus, while holding the earth still in Copernicus’s system gives us Tycho. […] All motion is relative. In fact, the difference between geostatic and heliostatic systems is not of great technical astronomical importance. Its importance, if any, is theological and philosophical. […] The important thing about Copernicus’s theory is not that it is heliostatic but that it is heliocentric. A system can be heliocentric without being heliostatic – Tycho’s system was.” (Thurston, 1994, 206-207)
The Rise of the Heliostatic Heliocentric Model
Kepler and Galileo furthered the Copernican Revolution by continuing in the work started by Copernicus and Brahe. Galileo continued the tradition of using precise observations to challenge long-held assumptions. His use of detailed observations from sophisticated instruments was firmly in the tradition of Tycho Brahe. He discovered the moons of Jupiter and the phases of Venus, lending support to the Copernican model in which all orbits are not around the Earth.
Kepler brought together the best elements of the models of Copernicus and Brahe, and develop a much better theory of planetary motion based on Brahe’s observational data. He was able to improve Copernicus’s heliocentric system, replacing his circular orbits and epicycles with elliptical orbits that caused varying planetary speeds.
The Copernican Revolution was essentially completed by Isaac Newton. His theory of gravity and the laws of motion filled in the missing details. Brahe had shown that planetary spheres were an inadequate explanation of planetary motion, while Newton supplied the new explanation, gravity.
Einstein vs. “Static Cling”
Absolute motion was posited by Newton. It fit well with a heliostatic basis for planetary motion. Therefore, historically, the heliostatic heliocentric system won the day, supplanting the geostatic one of Brahe. However, this occurred before scientists in the 19th century proved the Sun is just another star. It also occurred prior to Einstein’s General Theory of Relativity which showed that there is no absolute motion.
This goes back to the point made above by the historian of astronomy, Hugh Thurston. The heliostatic vs. geostatic debate is a philosophical one rather than a scientific one. Gravity-centric models explain celestial orbits with great accuracy. For instance, a heliocentric model of the solar system explains planetary motion in a cohesive way. A geocentric model of the Earth, the Moon, and the Earth’s satellites do the same for the earth system. Still, there is no absolute fixed point of reference we can observe and verify in a scientific sense. It appears that there is no absolute center of the universe whatsoever.
Astrology is Geo-Referential, Not Geocentric
I feel that this excursion into examining Brahe’s curious geostatic heliocentric system alerts astrologers to some important distinctions and ways of looking at things. Personally, I’ve been guilty of speaking of astrology as being essentially “geocentric”, as it concerns itself with the orientation of the heavens relative to the Earth. However, this common astrological usage is not consistent with the scientific sense, and that fosters some confusion.
In a scientific sense, geocentric and heliocentric pertain to models of planetary motion, not to frames of reference for observational utility. I don’t think I’ve ever met an astrologer, myself included, who didn’t think that the heliocentric model was the best model for explaining astronomical planetary motion in the solar system. In that sense, I, and all those other astrologers, are heliocentrists.
Astrology is not geocentric in the sense of planetary motion, but geo-referential, looking at the motion of the heavens relative to a given place and time on Earth. The thing is, much observational astronomy is similarly geo-referential. Whether it is naked-eye observational astronomy, or with an instrument, such as a telescope, astronomers are also often concerned with how things will “appear” in a given time and place on the Earth. There is not a geocentric vs. heliocentric divide between astronomy and astrology. Rather, the difference is just that for astrologers celestial phenomena have the ability to serve as “signs“.
Significance for Astrologers
Astrologers, myself included, are used to referring to the astrological perspective as geocentric. What we actually mean is that it uses the time and place on the earth as the reference point. There is even heliocentric astrology that can be contrasted with traditional geocentric astrology. However, heliocentric astrology is really helio-referential astrology. It judges signs from the observational vantage point of the Sun, examining configurations relative to it.
Comically, I have heard some astrologers argue that this heliocentric astrology is intrinsically superior on account of being heliocentric . After all, history has shown that the heliocentric model is correct. Geocentricism is for the backward and ignorant. This line of reasoning is comical because it confuses the vantage point from which signs are judged with specific scientific models of planetary motion. They actually have nothing to do with each other.
The implication is that somehow by judging signs from the Sun’s vantage point one shows support for the correctness of the heliocentric model of planetary motion. Not only do they have nothing to do with each other but the Earth-centered reference makes more sense in terms of meaning. It uses as a point of reference the time and place on Earth of the thing being commented upon itself, such as the time and place of the person’s birth
An astronomer may give observational coordinates for observing something from your backyard. That does not entail that they reject heliocentric planetary motion. Similarly, An astrologer mapping signs from a similar vantage point need not reject centuries of astronomical progress to do so.
Is Heliocentric Astrology More Scientific?
Heliocentric astrology is not more scientific in any way. The difference lies in its claims as to what constitutes a meaningful astrological sign. As with any astrology, its evaluation rests on the ability of its signs to say something relevant. In other words, how well do established interpretations of its conventionalized signs accord with the realities they comment upon?
Heliocentric astrology seeks to assign meanings to new types of phenomena. These are things that were not traditional sings, such as angular aspects to the Sun from the Sun’s perspective. For this reason, it is actually most natural to treat it with greater suspicion than traditional astrology. After all, traditional astrology uses conventionalized celestial signs used over a couple thousand years. Those signs were traditionally judged relative to the time and place of the matter they comment upon.
Rethinking the Geocentric and Heliocentric Astrology Dichotomy
As astrologers, we should probably be more careful throwing around terms like geocentric and heliocentric without clarification. I don’t advocate policing anyone, just greater awareness. The terminology is confusing to the general public and many astrologers. Astrologers insist that celestial phenomena can serve as signs. That’s a big stretch in thinking for many people. Add the word geocentric into the mix and it sounds like astrology requires the rejection of modern science as well.
The truth is that astrology is not dependent on a specific scientific model of celestial motion. It does not depend upon Aristotelianism. Even traditional astrology does not even rely on the Ptolemaic model. In fact, there were key Hellenistic astrologers (such as Dorotheus and Vettius Valens) before Ptolemy ever proposed his model. The Copernican Revolution was largely spearheaded by astrologers, such as Tycho Brahe and Johannes Kepler. They continued doing astrology based on earthly points of reference while advocating heliocentric models of planetary motion – without contradiction.
So, is astrology geocentric? In the informal sense of using the Earth as the central reference point, it is. It is in the same sense that the astronomy website, EarthSky.org is geocentric. It’s concerned with celestial happenings from an earthly vantage point. However, in the more narrow astronomical sense pertaining to models of planetary motion, astrology is not at all geocentric. Astrology is not dependent upon any single specific theory of planetary motion. Astrologers probably accept the superiority of the heliocentric model of planetary motion just as readily as anyone else.
Thurston, H. (2012). Early Astronomy. Springer New York.
The featured image is an illustration of the comet of 1577 which was seen by Brahe. It was clipped from the title page from Cometographia quaedam lampadis aeriae que 10. die Novemb. apparuit, anno a Virginto partu, 1577, London: 1578, by Laurence Johnson. STC 1416, Houghton Library, Harvard University (public domain)
Cellarius’s 1661 chart illustrating Copernicus’s heliocentric model of the Universe is in the public domain.