Sunday, May 24, 2015

How the Discredited Geocentric Cosmos Was a Critical Component of the Scientific Revolution

How Ptolemy's Geocentric Astronomy
Helped Build the Modern World

(all images are from

If you took the standard required western history course in college as I did, you learned that about 400 years ago astronomers Copernicus,  Galileo and Kepler along with Isaac Newton were key players in the scientific revolution that overturned the cumbersome system of geocentric astronomy. In this outdated system the Sun, moon and stars went around the stationary Earth. Instead these early scientists proved that the Earth and the planets went around the Sun. Known as the Copernican Revolution, it is considered the beginning of the scientific revolution, a new way of thinking which continues to this day and has created our modern world and our modern hi-tech marvels.

Well, that story is sort of true, but in hindsight it greatly simplifies the complex path that the scientific revolution took, the path that ultimately led to today's scientific and technological wonders. Specifically it leaves out the fact that the geometry of a geocentric universe and its foremost astronomer, Ptolemy, who perfected the geocentric system, were key players in this new scientific outlook. In fact the discredited geocentric theory was, oddly, essential for building our new scientific/technological world.


Over hundreds of years the early ancient Greeks put together a concept of the Solar System as a coherent system of concentric circles -- which was a major advance for Western thought. Later in the 4th century BCE, Plato and then Aristotle decided that the Earth was stationary and at the center of the universe, while the Sun, moon, planets and stars moved in perfect circles -- thought of as concentric spheres -- around the Earth. In the ancient Greek view of the cosmos, the orbits had to be perfect circles since all things in Heaven were considered 'perfect'. Each heavenly object moved with its own uniform motion.

However, "the geocentric model of Plato could not explain the retrograde motion of the planets. Around 140 A.D. Ptolemy proposed his refined geocentric model. In the Ptolemaic universe, a planet moves in a small circle called an epicycle, and the center of the epicycle moves along a larger circle around the Earth."

"A simple illustration showing the basic elements of Ptolemaic astronomy.
It shows a planet rotating on an epicycle which is itself rotating around
a deferent inside a crystalline sphere." Quoted from:

Claudius Ptolemy in his book the Almagest (published around 150 CE) laid out his refined geometry for the movement of the heavenly bodies, based on earlier Greek science and the work of the Greek astronomer Hipparchus. His revised system was quite accurate and this view of the universe lasted for almost 1500 years.

Ptolemaic Model Of The Solar System
From NASA's Cosmos: By selecting suitable radii and speeds of motion, Ptolemy could use this system of uniform motion around two [ED: perfect] circles to reproduce the apparent motions of the planets with remarkable accuracy. He succeeded so well that his model was still being used to predict the locations of the planets in the sky more than a thousand years after his death.
The problem people had with Ptolemy's cosmology was that it was complicated:The resultant system...seems unwieldy to modern astronomers; each planet required an epicycle revolving on a deferent, offset by an equant which was different for each planet.
Eventually the new heliocentric science advanced by Copernicus, observed by Galileo, perfected by Kepler and then explained by Newton was easier to calculate. It was accepted in part because it was a more elegant and simpler mathematical solution and once refined was more accurate than the predictions of Ptolemy's system.

So what is my argument with all of this you might ask?


Ptolemy's system had a large but hidden benefit. The perfect circles that were the key component of his system meant that man-made machines -- first clocks and later engines -- could be easily constructed with circular gears.

Ptolemy's system mapped out how mechanical models could be made of the solar system and these machines eventually led to the building of clocks. Yet even before the first astronomical clock was made, the idea of a mechanical universe based on Ptolemy's ideas was widely known.

Page from De sphaera mundi
The Sphere of the Cosmos (De sphaera mundi) is a medieval introduction to the basic elements of astronomy written by Johannes de Sacrobosco (John of Holywood) [ED: publication date] c. 1230. Based heavily on Ptolemy's Almagest, and drawing additional ideas from Islamic astronomy, it was one of the most influential works of pre-Copernican astronomy in Europe. Sacrobosco's De sphaera mundi was the most successful of several competing thirteenth-century textbooks on this topic. It was used in universities for hundreds of years. Sacrobosco spoke of the universe as the machina mundi, the machine of the world... This concept is similar to the clockwork universe analogy that became very popular centuries later, during the Enlightenment. [ED: my emphasis]
Around 1264 Campanus of Novara, an Italian astronomer, "wrote a Theorica Planetarum [which] ... included instructions on building a planetary equatorium as well as its geometrical description. The data on planets are drawn from the Almagest [by Ptolemy] and the Toledan Tables of the Arab astronomer Arzachel. Campanus gave precise instructions on using the tables, and made detailed calculations of the distances to the planets and their sizes."
The Theorica Planetarum has been called "the first detailed account of the Ptolemaic astronomical system... to be written in the Latin-speaking West."
Benjamin, Francis Seymour; Toomer, G. J. (1971). Campanus of Novara and medieval planetary theory: Theorica planetarum. 
Thus, the ancestors of Western clocks were early planetaria, and forerunners of what later became known as astronomical clocks.
Fraser, J.T. (1978). Time as Conflict: A Scientific and Humanistic Study.
In the middle ages starting in 1364 CE, many astronomical clocks were made throughout Europe. They were both timekeeping instruments and devices that showed the movement of the Sun, moon, planets and the zodiac.
See a list here:
Most of the first clocks were not so much chronometers as exhibitions of the pattern of the cosmos ... Clearly the origins of the mechanical clock lie in a complex realm of monumental planetariums...   
White, Lynn Jr. (1966). Medieval Technology and Social Change.
The first documented astrarium clock was completed in 1364 by Giovanni de' Dondi (1318–1388)... The original clock, consisting of 107 wheels and pinions, was lost..., but de' Dondi left detailed descriptions which have survived, enabling the reconstruction of the clock. It displays the mean time, sidereal, or star, time and the motions of the Sun, moon and the five then known planets Venus, Mars, Saturn, Mercury, and Jupiter. It was conceived according to a Ptolemaic conception of the solar system.[ED: my emphasis]

"The Prague astronomical clock [above] was installed in 1410...and is the oldest functioning Astronomical clock in the world." Quoted from:

The Prague clock was built more than 130 years before Copernicus published On the Revolutions of the Celestial Spheres in 1543. The publication of Copernicus' book is considered by some to be the beginning of the modern age, yet was preceded by astronomical clocks starting in 1364 (see above) -- almost 180 years earlier.

Explanation of the information on the Prague astronomical clock.

The design of these mechanical clocks, a huge technological advance for the age, was largely based on Ptolemy's geometry. Clocks eventually became the symbol for the Newtonian age -- the age of the scientific revolution. They helped spawn the idea that God was the great watchmaker.
In the history of science, the clockwork universe compares the universe to a mechanical clock. It continues ticking along, as a perfect machine, with its gears governed by the laws of physics, making every aspect of the machine predictable.
René Descartes saw "the cosmos as a great time machine operating according to fixed laws, a watch created and wound up by the great watchmaker."

Gears in a pocket watch.

So the idea of a mechanical universe -- a central idea to this new scientific revolution -- was derived from the discredited geocentric astronomy. In addition the building of geared clockwork machines was also due to the geocentric model, showing the importance of this system to the manufacture of practical technological devices.
Clocks were the "key machine of the modern industrial age."
Strandh, Sigvard (1979). A History of the Machine.
This was the ultimate irony: The central image for the new scientific mechanical age was a watch which was created with the discredited geometry and physics that the scientific revolution had overturned.


Yet the story does not end here -- it continues today. In fact you probably use geocentric physics everyday. For example, much of the gearing in automatic transmissions in cars and other vehicles is based on a geocentric design. Let me explain.

What Ptolemy achieved with his circles within circles was an advanced design of gears and gearing -- gearing that worked well and was quite reliable -- as had been shown in the creation of clocks. The ability to create such gears was not only critical to the construction of clocks but later to the design of engines and machines such as the early Watt steam engine -- the mechanical device that kick started the industrial age and the Industrial Revolution.

About the Watt steam engine in 1785:
"The firm's [ED: Watt's company] fourth innovation [was] Sun and planet gearing...
As Boulton and Watt engines were prime movers in the Industrial Revolution, this very significant engine represents not just invention and entrepreneurship, but also wealth creation, mass consumerism, great changes in working life, a massive shift in the use of resources, and consequent damage to the natural environment."
While it was called a Sun and planet gear with the Sun in the middle, in fact the gearing was based on the geocentric geometry of Ptolemy with his understanding of perfect circles, epicycles and uniform motion.

Sun and planet gearing. "This particular [Watt steam] engine was installed in
Whitbread's brewery in 1785, 
and clocked up 102 years' work." Quoted from:

Early locomotive gearing due in part to the geocentric system of interrelated circles.

Today epicycle gears, also known as planetary gears, are used in a wide range of machines including automatic transmissions for automobiles and bicycle gearing.

About modern epicycle gears from Wikipedia:
Epicyclic gears get their name from their earliest application, which was the modeling of the movements of the planets in the heavens. Believing the planets, as everything in the heavens, to be perfect, they could only travel in perfect circles, but their motions as viewed from Earth could not be reconciled with circular motion. At around 500 BC, the Greeks invented the idea of epicycles, of circles traveling on the circular orbits.With this theory Claudius Ptolemy in the Almagest in 148 AD was able to predict planetary orbital paths.

 A modern epicycle gear train or planetary gear train.


One of the reasons Ptolemy's science has gotten such bad press and even been labeled bad astronomy was due to the trial of Galileo by the Catholic Church which prevented him from criticizing this geocentric system. This was seen later as a huge impediment to the advance of science, when the new ideas of Copernicus, Kepler and Newton won out. As a result the Ptolemaic system itself took part of the blame for standing in the way of scientific investigation. Yet it is important to note that the cosmology of Copernicus was initially not as accurate as that of Ptolemy and even more complicated -- although it did solve a number of nagging problems.
However, Copernicus, like Ptolemy, also used circular orbits and had to resort to epicycles and deferents to explain retrograde motions. In fact, Copernicus was forced to use more epicycles than Ptolemy, i.e. a more complicated system of circles on circles. Thus, Copernicus' model would have failed our modern criteria that a scientific model be as simple as possible.
Yet, as we know, history is written by the victors and in this case, the science of Newton et al was the victor, so the previous science was discredited.

Stephan Jay Gould in his book Time's Arrow And Time's Cycle pointed out that something of a similar nature occurred in the science of geology. It would seem that this attitude of denigrating and distorting past thinkers is also true in just about every branch of science.
Gould, Stephan Jay (1987). Time's Arrow, Time's Cycle: Myth and Metaphor in the Discovery of Geological Time.

Perhaps Albert Einstein understood the process of theorizing better than anyone and understood how one theory builds on another -- which does not mean that the earlier theory was in error, but rather that it was a necessary step in the process.
Physical concepts are free creations of the human mind, and are not, however it may seem, uniquely determined by the external world. In our endeavour to understand reality we are somewhat like a man trying to understand the mechanism of a closed watch. He sees the face and the moving hands, even hears its ticking, but he has no way of opening the case. If he is ingenious he may form some picture of a mechanism which could be responsible for all the things he observes, but he may never be quite sure his picture is the only one which could explain his observations. He will never be able to compare his picture with the real mechanism...But he certainly believes that, as his knowledge increases, his picture of reality will become simpler and simpler and will explain a wider and wider range of his sensuous impressions.
Albert Einstein

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