From Pythagoreans to Kepler. The contest between the Geocentric and Heliocentric System

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From Pythagoreans to Kepler: The Dispute
Between the Geocentric and the Heliocentric
System
E. Theodossiou, E. Danezis, V-N. Manimanis and Kalyva, E.-M.
Department of Astrophysics-Astronomy and Mechanics, School of Physics, University of Athens
Panepistimioupoli Zografu 157 84-GREECE
E-mail: etheodos@cc.uoa.gr
Presented in 9th Joint European and 5th National Euro-Asian Astronomical Meeting (JENAM
2000), Moscow, Russia, May 29-June 3, 2000.
Abstract
From the earliest years, ancient people considered Earth to be flat, floating on water, in the center of our
Solar System and of the Universe. These beliefs generated the so-called geocentric system and the ‘‘holy’’
circular orbits. However, the philosophical ruminations of the ancient Greek philosophers and thinkers
questioned the geocentric system and proposed instead the heliocentric. Main introducers of these,
‘‘heretic’’ for the times, views, are believed to be the Pythagoreans Philolaos, Heraclides, Hicetas,
Ecphantos, but mainly Aristarchos of Samos, who placed the Sun in the position of the ‘‘central fire’’ of the
Pythagoreans.
The geocentric system, reworked by Claudius Ptolemaeus (Ptolemy), was the dominant one for centuries,
mainly under the prestige of the Aristotelian views, and only during the 16th century the Polish monk-
astronomer Copernicus retrieved the heliocentric theories of the ancient Greeks from oblivion and became
the new introducer of the heliocentric theory which we today accept.
Key words: Pythagoreans, Aristarchos the Samian, geocentric, heliocentric
1 The Pythagorean School
The Pythagorean School considered the number as the essence of all beings; something
abstract, unreceivable by the senses, but only by the mind. Therefore, the nature of all beings is not
material, nor accessible to the senses. Only through abstract thought, according to the
Pythagoreans, can the essence be conceived. Thus, the philosophers of this School, reduced
infinity to a material element, which is beyond counting and definition. That is, they introduced
the notion of ‘‘matter’’ as an element that denies any definition, and as the source of ontological
and ethical imperfection.
For the Pythagoreans, the world is created after the initial ‘‘One’’ is formed. This entity, created
in the first beginning («το πρώτον αρμοσθέν») attracts the infinity and assigns to it the end.
The Pythagoreans considered an initial single element as the beginning of Creation, which
continuously expands and includes infinity.
This corresponds, in a certain sense, to the cosmological hypothesis of the Universe being a static
sphere, continuously expanding, that starts from an initial point.
The Pythagorean School stated that the Universe evolved from an infinitesimal nucleus, which was
expanding spherically upon the infinity.
As we know from Aristotle (Μetaphysics Book XIV, iii. 12-15, 1091a 15), the Pythagoreans: ‘‘for
they clearly state that when the One had been constituded –whether out of planets or seed or out
of something that they cannot explain– immediately the nearest part of the Infinite began to be
drawn in and limited by the Limit.’’[2].

2 The hypotheses of Philolaos of Croton
The Pythagorean hypotheses about the first beginning were made more widely known by
Philolaos of Croton (in South Italy) in the middle of 5th Century B.C., who was saved from the
revolt against the Pythagoreans along with Archippos, Lysis, et al.. Philolaos settled down in
Thebes, teaching Pythagorean philosophy and he wrote «Βάκχαι» (Bacchae) and «Περί φύσιος Α
Β Γ» (On Nature A B C). From the first book, the following passages were saved: ‘‘The world is
one, and it was created beginning from the middle, i.e. from the central point which is equidistant
from both the upper and the lower»” (Fragmente 17. [B. 90] Stob. Ecl. I 15, 7 [p. 148, 4W.] [16]
and “The initial one, consisting the beginning of the creation of the Universe, is called Hestia”
(Fragmente [B. 91] Stob. Ecl. I 21, 7 [p. 189, 17W.] [15].
The doxographer (= writer that recorded the theories of older philosophers) Aetius writes in the
beginning of 2nd Century A.D.: “Philolaos held the view that in the middle of the world
approximately at the center lies the fire which he calls the hearth of the universe, the Jupiter’s
abode, the mother of Gods, the Altar and Unity and Messure of Nature. There is also another fire
in the upper part of the world which surrounds it. First come by nature the center around which
ten divine bodies revolve the heavens, the sphere of fixed stars, the five planets, then the Sun under
which the Moon, the Earth and the Counter-Earth (Antichthon) come in succession; at the very
end comes the fire which is the focus around the center” (Aetius II 7, 7). [1].
In another passage Aetius, getting his information from Theophrastus, writes: ‘‘Philolaos the
Pythagorean believed that the center of the world was occupied by the fire (because this is the
focus of the Universe), then came the Counter-Earth (Antichthon) and thirdly the inhabited Earth
which lies opposite the Counter-Earth and revolved around the center along with the Counter-
Earth; thus the inhabitants of the Counter-Earth are not visible to those who live on Earth…..’’
[Aet. III 11, 3 (D. 377 aus Theophrast.)] [1].
Philolaos, “On Nature A B C” –as mentioned by Diogenes Laertius– begins as follows: «Nature
in the ordered Universe was composed of unlimited and limited elements, and so was the whole
Universe and all that is therein’’ (Diog. VIII 85, chapter 7. [A1 I 398, 20]). [10].
Pythagoras laid the foundations of mathematical Philosophy and mathematical Physics, by
correlating the order and the harmony of the sounds with the order and the harmony of the
Universe. We must not forget of course that the great thinker believed the Earth was spherical: the
same that he believed about the World. Aristotle informs us in his work «On the Heavens» (II,
Chap. xiii, 293a, 293b) that the Pythagoreans were also supporting a pyrocentric theory of the
World, according to which Earth was revolving around a central fire, called «Διός Φυλακή»
(Watch-tower of Zeus). [3]. This theory, which as argued must rather be attributed to Philolaos,
did not yet place the Sun in the position of that central fire; this was done in the 3rd Century B.C.
by Aristarchos the Samian, who is also classified, as an astronomer and natural philosopher, to be
a Pythagorean.
Therefore, the Pythagoreans as a whole were who questioned for the first time the geocentric
theory of the Universe, and in doing this they opened the way for the (essentially Pythagorean)
heliocentric theory, made widely known after many centuries by Nicolaus Copernicus.
Cicero reports the following in his ‘‘Αcademica Priora’’ (II, xxxix, 123): “Hicetas Syracusius,
ut ait Theophrastus (Phys. Opin. Fr. 18, D. 492), caelum lunam stellas, supera denique omnia stare
censet neque praeter terram rem ullam in mundo moveri: quae cum circum axem se summa
celeritate convertat et torquerat, eadem effici omnia quae si stante terra caelum moveretur (Vgl.
Aet. III 13, 2 [s. Zeile 23]. Diog. VIII 85: 44 A1 [I 398, 12]). atque hoc etiam Platonem in Timaeo
dicere quidam arbitrantur, sed paulo obscurius”, which means: ‘‘The Syracusan Hicetas, as
Theophrastus asserts, holds the view that the heaven, the sun, the moon, the stars, and in short all
the things in hight are stationery, and that nothing in the world is in motion except the earth, which
by revolving and twisting round its axis with extreme velocity produces all the same result as
would be produced if the earth was stationery and the heaven in motion; and this is also in some
people’s opinion the doctrine stated by Plato in Timaeaus (40B) but a little more obscurely.’’ [5].
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3 Nicolaus Copernicus reads the ancient Greeks
We note that Nicolaus Copernicus in the Preface (Praefatio) of his work ‘‘De revolutionibus
orbium coelestium libri VI’’, which was addressed to the Pope Paul III (1534-1549), he refers to
both Hicetas and Ecphantos, writing the following: ‘‘For this reason I took the labor to search all
the books of the philosophers I could find easily, in order to ascertain whether someone was of the
opinion that the motions of the heavenly bodies are different than those being taught by the
teachers of mathematics in the Universities. And I found initially in Cicero that Nicetas 1 believed
that the Earth moves. Later I found in Plutarch that other philosophers too had the same opinion.
From them I took the motive and begun to think myself about the motion of the Earth.’’ [6].
4 Anaximander, Ecphantos and Heraclides of Pontus
Not only the Pythagoreans but also Anaximander (according to Theon of Smyrna who lived in
the times of Emperor Hadrian) considered the Earth as a moving body. It is very likely, that
Anaximander believed that the Earth, along with the Moon and the Sun, was performing a
revolving motion on a giant ring!
As far as Ecphantos is concerned, but also Heraclides of Pontus, Aetius informs us the
following: ‘‘Heraclides of Pontos and Ecphantos the Pythagorean think that the Earth moves not
being displaced from its position in space, but rotationally, as the wheel rotates around its axis,
from the west to the east around its center” [Aet. III, 13, 3 (D. 378)]. [1].
According to Simplicius: “…But Heraclides of Pontus, by supposing that the earth is in the
center and rotates, while the heaven is at rest, through in this way to save the phenomena”
(Simpl., on Arist. De Caelo, II, 13, 293 b 30; p 519, 9-11, Heib). [14].
According to the ancient doxographers, Heraclides2 (340 B.C.) , Ecphantos, but also other
Pythagoreans as well, accepted the notion that the Earth moves only rotationally, as a wheel, fixed
to an axis, from the west to the east. Moreover, they believed that the stars and the planets
Mercury and Venus were moving around the Sun.
Heraclides believed that the sphere of fixed stars was at rest. Heraclides proposed a model where
Earth was at the center of planetary motion but rotated on its axis daily.
5 Aristarchos the Samian
Circa 280 B.C. the eminent figure of Aristarchos the Samian (310-230 B.C.) appears; he
framed the hypothesis: “Assumed that the Sun is at rest, while the Earth revolves around the Sun
in a circular orbit”. This hypothesis of Aristarchos has been also written down by Archimedes in
his work ‘‘Psammites’’ (Arenarius or The Sand-reckoner): “Aristarchus uero Samius hypothesium
quarundam descriptiones edidit, in quibus ex iis, quae supponuntur, adraret, mundum multiplicem
esse, quam supra diximus. Supponit enim, stellas fixas solemque immobiles manere, terram uero
circum solem in medio cursu positum secundum circuli ambitum circummolui” (Arenarius, I. 8-
13) [4]. An English translation:“Aristarchos the Samian has published in outline certain
hypotheses from which it follows that the universe is greater than formely believed. He assumed
that the fixed stars and the Sun are at rest, while the Earth revolves in an orbit the center of which
is occupied by the Sun. On the other hand, the sphere of fixed stars, having the same center as the
Sun, is so large that the circular orbit of the Earth around the Sun has the same ratio to the
distance of the fixed stars, as that existing between the center of the sphere and its surface”.
It is also verified by Plutarch, who states in his book “De Placitis Philosophorum” that:
“Aristarchos Solem fixis stellis adjungit, terram [al. lunam] autem moveri ait circum Solis orbem,
et suis inclinationibus umbram disco inferre” (De Placitis Philosophorum-Liber Secundus, XXIV.
De Solis defectu, 6.). [16]. An English translation:“Aristarchos held the view that the Sun and the
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fixed stars are at rest while Earth is revolving around the solar circle; also that during the Earth’s
obliquely circular motion the Sun’s disc is shadowed (causing a solar eclipse)”. [20].
All these references of the ancient writers show that Aristarchos of Samos is the father and founder
of heliocentric theory, which is also also ascertained by Claudius Ptolemaeus (Ptolemy) in his
Great Mathematical Syntaxis (2nd Century A.D.). The important astronomer writes that
Aristarchοs of Samos asserted the heliocentric system, as Hicetas and Ecphantos did anyway.
Certainly, Aristarchus could not prove his hypothesis with the astronomical instruments of his
time. On the other side, for many centuries humans were proud to believe that the Earth is the
center of the Universe, and views like the one of Aristarchos, were, to say the least, disrespectful
to the heavenly divine order, while at the same time shocked the foundations of our geocentrically
and egocentrically founded Solar System.
Plutarch mentions that Aristarchos was accused for atheism. It seems that for exactly this reason
the great philosopher of Samos did not elaborate his hypothesis mathematically, nor did he create
some system of planetary orbits in order to support it, as he did in the case of the geocentric
system. Instead, of his treatises, saved under the title « Περί των μεγεθών και αποστημάτων Ηλίου
και Σελήνης» (On the sizes and Distances of the Sun and Moon) is based on the geocentric system.
[14].
In any case, it is an indisputable fact that Aristarchos of Samos asserted the heliocentric theory,
which he combined with the rotation of the Earth around its own axis.
Thus, Aristarchos proposed a heliocentric (sun-centered) model where the Earth had a double
motion; it rotated on its axis daily and revolved around the central Sun annually.
6 Aristotle and Claudius Ptolemaeus
In that period, the geocentric system was the dominant one, since it ‘‘served’’ human vanity
wanting everything to revolve around and having in the center our small planet. Many astronomers
supported the theory of the geocentric system, but it was under the weight of the great Aristotle
that this system was maintained for many centuries in the West Europe.
According to Aristotle the visible «corporality» of the stars –of the divine bodies– was in a
continuous circular motion. The fixed stars and the planets were mixed together in a series of
hollow spheres, and moving in circles with various directions and velocities. There should be as
many spheres as needed to explain without leaving out their known complicated motions.
According to the more contemporary to Aristotle theories of Eudoxos of Knidos and of Callippos,
55 spheres were needed to attain that goal. Therefore, one should take into consideration 55
‘‘stellar gods’’, consisting of a ‘‘moving spirit’’ and of a body in circular motion. The Sun was
moving around the Earth normally, but at different distances, in order to explain summer and
winter.
The geocentric system became widly known as the Ptolemaic system, due to the fact that
Claudius Ptolemaeus or Ptolemy (2nd Century A.D.) was the one who worked out the planetary
orbits in detail and tried to explain them. In the first book of the ‘‘Great Mathematical Syntaxis’’
(The Almagest)3 Claudius Ptolemy gives an account of his arguments to support a motionless
Earth in the center of the Universe. He argued that, if the Earth was moving, then certain
phenomena should be observable as a result of its motion. For example, since all bodies tend to
fall towards the center of the Universe, the Earth should be motionless in this center. Otherwise,
the falling bodies should not move towards the center of the Earth as they do. Moreover, if the
Earth were rotating around its axis once every 24 hours, an object thrown vertically should not fall
in the same place, as it seemed to happen. [19].
7 The Ptolemaic system
Nevertheless, Hipparchos as well as older Greek astronomers knew that the irregularities
observed at the motion of the planets led to the need of introducing a system of deferents or a
system of epicycles, in order to be able to explain them. This was not invented by Ptolemy, but by
the great geometrist of antiquity Apollonios of Perge (262-190 B.C.). Apollonios introduced the
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systems of eccentric and epicyclical motion in order to explain the motions of the planets. Of
special interest is his work on the determination of the points where a given planet appears
motionless.
The ancient Greek astronomers considered the motions of the planets uniform and circular.
Thus, the deferents were the larger circles having Earth at their center, while the epicycles were
the smaller circles, the center of which was moving on the circumferences of the deferents. The
motion of the Sun, the Moon and of the known planets was taking place on the circumference of
their own epicycles. On the moving eccenter there was only one circle. This circle had as its center
a point outside Earth. The planet was moving on the circumference of this circle. Although these
two constructions were mathematically equivalent, it was impossible to explain all the
observations of the planetary phenomena.
Claudius Ptolemy expanded the conclusions of Hipparchos and, from references found in
Almagest, it seems that he was influenced considerably by the geometrical views of Apollonios of
Perge. Thus, he introduced one more concept. He supposed that the Earth was offset by a small
distance from the center of the deferent of each planet, and moreover that the center of the deferent
was moving with a uniform circular motion around a point. He called this point the equant; it was
a hypothetical point, placed by Ptolemy on the diameter of the deferent in such a way that it was
opposite the Earth in respect to the center of the deferent. In other words, the center of the deferent
was always between the Earth and the hypothetical equant, and the distance between Earth and the
center of the deferent was equal to the distance between the center of the deferent and the equant.
With all these conjectures and acceptan also ces, Ptolemy could at last explain satisfactorily many
of the observed planetary phenomena.
In general, the plane of the ecliptic in the Ptolemaic geocentric system was the one followed by
the Sun during its annual ‘‘apparent’’ motion amidst the fixed stars. The planes of the planetary
deferents were believed to intersect the plane of the ecliptic at a small angle, while the planes of
the planetary epicycles intersected at the same angle the planes of the deferents. As a result, the
planes of the epicycles were parallel to the ecliptic plane. For the planes of Mercury’s and Venus’s
deferents, they supposed that they were oscillating in both sides of the ecliptic plane, and that the
planes of their epicycles were oscillating in respect to the planes of their deferents.
Ptolemy believed that the planets were much closer to the Earth than the fixed stars. However,
he apparently believed in the existence of crystal spheres upon which, the fixed stars were
attached. Beyond the sphere of the immovable fixed stars there were other spheres and ultimately,
as he proposed, the ‘‘first cause of moving’’, the force causing the motion of the other spheres in
his perception for the Universe. Probably, Claudius Ptolemaeus was feeling intuitively the
incorrectness of the geocentric theory; but he remained faithful to his terrestrial standards. He tried
to be thoroughly geocentric and static, avoiding any theories that could shake his world-image.
Thus, he spent a lot of time trying to prove that space could not have more than three dimensions!
Later on, the geocentric system became accepted by the Christian Church as a dogma and in
spite of its shortcomings it was almost impossible to replace it. It withstood the astronomers’
criticism until the 16th Century, when more detailed observations of the planetary orbits and of
other heavenly bodies complicated it so much (epicycles over epicycles had to be created in order
to explain the observations), that its validity was seriously disputed.
8 The Emperor Julian
In the meantime, we should not assume that the faith in the heliocentric system had died off
completely. The Emperor Julian (336-363 A.D.) was deeply affected by his knowledge, respect
and admiration for the ancient greek civilization. Strongly influenced by the Neoplatonic
philosophers, he believe in the right of the individually carved path towards the truth. The
Emperor-philosopher thought it was an unalienable right of each person to search and doubt, while
at the same time he was afraid of that this right could be lost forever with prevailing a religion
which characterized any doubter as a heretic. He became known in History as Parabates or
Renegade, two high-handed surnames since he never became a Christian, so he never reneged on
something. History and the Church nevertheless branded him even after his death. He was a
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passionate idealist and envisioner of the revival of the ancient greek spirit and values, which he
wrongly combined with the revival of the ancient greek religion, a religion having irrevocably
declined. The Oracle of Delphi answered when the Emperor asked: “Tell the Emperor everything
is destroyed, Apollo has no roof over his head, Pythia has no bay leaf, not even mountain spring to
speak, even the water stopped its voice’’.
Julian himself studied the ancient wisdom at the philosophical schools of Athens. Captured by
the beauty of the ancient greek spirit he wished to revitalize it. He became interested in Philosophy
as well as in Astronomy, and he warmly supported the heliocentric system. In his treatise ‘‘Hymn
to King Helios dedicated to Sallust’’ he states: ‘‘For that the planets dance about him as their
king, in certain intervals, fixed in relation to him, and revolve in a circle with the perfect accord,
making certain halts, and pursuing to and fro their orbit [i.e. the stationary positions and the
direct and retrograde movements of the planets], as those who are learned in the study of the
spheres call their visible motion” (The Orations of Julian, IV. Vol. I., 31, 135 B, p. 366). [22].
This passage shows that the theory of Aristarchos of Samos not only had not been forgotten, but in
the 4th Century A.D. it had several supporters.
9 The prevalence of the heliocentric system
The geocentric system that was dominant could not explain the retrograde motions of the
planets on their orbits. At the same time, the heliocentric system was still alive in the memory of
astronomers and the writings of the ancient Greek Pythagorean philosophers. However, it was only
during the Sixteenth Century, an era of intense scientific investigation, that the Polish astronomer
Nicolaus Copernicus (Mikolaj Kopernik, 1473-1543) reintroduced the heliocentric theory, which
is from then on accepted by the scientists. The hypotheses of Aristarchos and the faith of the
Pythagoreans in the heliocentric theory formed the basis of the thoughts of the great Polish
astronomer.
The original geocentric system, under the label ‘‘Ptolemaic’’, remained unaltered and
indisputed for more than 14 centuries. Still, despite its originality, it was complicated enough.
Mikolaj Kopernik, based on the ideas and the hypotheses of the Greek philosophers, and after his
attentive and long studies, concluded that some of the difficulties with the Ptolemaic system could
be superseded if the Sun was placed at the center of the planetary system instead of the Earth.
Indeed, the retrograde motion of the planets could be explained without the epicycles, since the
inferior planets were moving faster than the superior, which are much farther from the Sun. As a
result he was convinced for the correctness of the heliocentric system. Nevertheless, althought his
detailed study must have been finished in 1515, he did not dare to publish it under the fear of the
Inquisition. As the Earth was then considered the center of the Universe with everything in the
Universe revolving around it, any theory questioning this belief (turned into a Church dogma)
automatically set its inspirator in a difficult situation. Therefore, although the Austrian
mathematician Georg Joachim (1514-1574), more widely known as Rheticus, who was a disciple
of Copernicus, exhorted his teacher to publish the theory, the eminent Polish astronomer decided it
in Nurnberg in 1543, just before his death. The editor Andreas Osiander wrote a preface where it
was stressed that the Copernican system was nothing more than a model, and not necessarily the
true representation of the planetary system. In any case, the immortal work of Copernicus under
the title ‘‘De revolutionibus Orbium Coelestium libri VI’’ was dedicated to Pope Paul III.
Let it be noted, though, something that is not widely known: Eventually, Copernicus did not
manage to remove the epicycles, nor was he able to predict the positions of the planets with any
greater accuracy than the Ptolemaic system.
10 The system of Tycho Brahe and Johannes Kepler
Therefore, a generation after Copernicus, the great Danish observer of the sky Tycho Brahe
(1546-1601) proposed, in 1583, his own system for the description of the planetary motions in the
Solar System. The effort of Tycho Brahe (Tychonic system), a combination of the Ptolemaic and
the Copernican systems, adopts the Ptolemaic idea that the Earth is the stable center of the
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Universe around which the Sun and the Moon revolve; but it also accepts that all the rest planets
were revolve around the Sun, according to the new system of Copernicus.
Both the Ptolemaic and the Tychonic systems predicted the existence of an external sphere, the
one with the fixed stars, executing a certain daily revolution around the Earth. The theory of Tycho
allowed the explanation of the observed changes in the phases of Venus, impossible to explain
within the frames of the Ptolemaic system. In fact, a system analogous to the Tychonic had been
proposed, as we have already mentioned, by the Greek philosopher Heraclides of Pontos, who
considered that at least Mercury and Venus were revolving around the Sun.
The system of Tycho Brahe became better known from the book ‘‘Astronomica Danica’’,
written in 1622 by his student Christian Longomontanus (1562-1647). Tycho Brahe himself,
though, appreciated greatly the astronomical insights of the German astronomer Johannes Kepler
(1571-1630), to whom he offered, in 1599, a position of assistant in Prague. Kepler accepted,
because he wanted to cooperate with the great Danish astronomer, who had accumulated an
amazing quantity of data from many years of accurate observations. Unfortunately, each one of
them wanted to take the maximum possible advantage of the other. Tycho wanted to justify his
system through Kepler’s genius, while Kepler wanted to prove the validity of the Copernican
system through Tycho’s observations. Indeed, Kepler was an ardent supporter of Copernicus; he
had heard of his theory from Michael Maestlin (1550-1631), professor of mathematics and
Astronomy at the University of Tubingen, when, in 1590, he studied at that University. Studying
the Copernican system, Kepler saw its virtues and he wanted, by improving it, to make it
acceptable to the astronomical circles.
The cooperation of the two men was difficult; Kepler had no access to Tycho’s data. This only
became possible after Tycho’s death, in 1601. Then Kepler, by inheriting his teacher’s data and
after many years of hard work, succeeded in discovering exactly the imperfections of the
Copernican system. Although Copernicus had correctly placed the Sun at the center of the Solar
System, he had retained the circular orbits. Moreover, he supposed that the planets were moving
with constant velocity, forcing him to retain the epicycles in his system.
Kepler, the real founder of the new heliocentric system, formulated his three laws, which proved
to be catalytic to the study of the Solar System and the explanation of the motions of the planets.
He stated that the planets do not describe circular orbits, but elliptical. This was a new heretic
belief, since from the beginning the astronomers and philosophers were believing in the divine
sanctity of the circular orbits. He also realized that the planets do not move with constant velocity;
instead, the line connecting the Sun with the respective planet describes equal areas in equal times.
Finally, his third law, the harmonic law, states that the square of the time of revolution around the
Sun for any planet is proportional to the cube of the semimajor axis of its orbit. The harmonic law
was probably the starting point and the decisive factor for the subsequent formulation of the
gravity law by Newton, a law which was probably (as many who have studied Kepler’s work
maintain) discovered by the great German astronomer, but not analyzed in detail. In any case, it is
indisputable that the formulation of the pioneering, for their era, laws of Kepler paved the way for
Isaac Newton, who as a mathematician created and formulated his majestic work.
Nevertheless, the prevalence of the heliocentric system was not an easy affair. The case of the
well-known French astronomer Jean-Baptiste Morin (1583-1656), professor of mathematics at the
College de France (1630), is typical: Morin, an exceptionally good observer of the sky, was the
first astronomer who had the idea to attach a graded circle on the astronomical telescope
(refractors). But in spite of all his high-quality observations, he was an ardent supporter of the
geocentric theory. More than a century after Copernicus there were known astronomers who were
trying to prove that the Earth was motionless at the center of our Solar System.
11 The complete acceptance and justification
The indisputable superiority of the heliocentric system lead finally to its full acceptance, at least
by the astronomical community. However, Vatican included Copernicus’ book in its Index
Librorum Prohibitorum, from 1616 until 1822.
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Nevertheless, in June 1999, the current Pope John-Paul II, who is of Polish origin, during his
visit to Torun, birthplace of Copernicus, he delivered a speech at the city’s University in which he
restored and justified, indirectly but clearly, the great Polish astronomer. The Pope stated that the
discoveries and conceptions of Copernicus strengthened the confidence for the wisdom of the
Creator and at the same time they exhibited the power of the human logic.
12 Notes
1 Copernicus, as did the Greek scholar Regas Velenstiles (18th-19th century) [19] after him,
followed an altered writing of the manuscripts and he refers to Hicetas as Nicetas.
2 As far as the composition of the material of the Universe is concerned, Heraclides of Pontus
(Heraclides Ponticus, from the city Heraclea of Pontus or Heraclea Pontica) conceded that it was
made of small molecules of matter not connected with each other. It seems that he had modified
the theory of Democritus and he thought that the first element that existed in the world were not
the atoms, but the molecules which these atoms constituted.
3 Claudius Ptolemy wrote at the middle of the 2nd Century his opus: Great Mathematical Syntaxis
(= ordering, system) of Astronomy” [17]. The Arab astronomers translated it in 827 A.D.. Through
the Arabs it became known to the Western Europe as Almagest (Al+Megisti). The Almagest, a
collection of 18 Books, formed the basis of every astronomical study up to the years of
Copernicus.
13 REFERENCES
1. Aetius: Aetii Placitorum Compositione (De Vestutis Placitis) in “Diels, Hermann: Doxographi
Graeci. Berolini. Apud Walter De Gruyter et Socios, Editio Quarta, 1879 (reprinted 1965)”.
2. Aristotle: “The Metaphysics”. The Loeb Classical Library. Βook XIV with an English
Translation by Hugh Tredennick, M.A. London. William Heinemann Ltd. Cambridge,
Massachusetts Harvard University Press, MCMLVIII (First printed 1939, reprinted 1945, 1953).
3. Aristotle: “On the Heavens”. The Loeb Classical Library, with an English Translation by
W.K.C. Guthrie, M.A. London William Heinemann Ltd. Cambridge, Massachusetts Harvard
University Press, MCMLIII (First printed 1933, reprinted 1936, 1947, 1956).
4. Archimedes: «Ψαμμίτης» “Arenarius or The Sand-reckoner” in Opera Omnia. Bibliotheca
Scriptorum Graecorum et Romanorum Teubneriana. Edidit J.L.Heiberg, Vol. II corrigena Adiedit
E.S. Stamatis. Stutgardiae in Aedibus MCMLXXII.
5. Cicero: Academica Priora, with an English Translation by H. Rackham, M.A. London. William
Heinemann Ltd. Cambridge, Massachusetts Harvard University Press, MCMLXI (First printed
1933, reprinted 1951, 1956 and 1961).
6. Copernicus, Nicolaus: De Revolutionibus Orbium Coelestium libri VI. On the Revolution of
Heavenly Spheres. Trans. Ch. C. Wallis. Prometheus Books, 1995.
7. Die Fragmente der Vorsokratiker von Hermann Diels, Herausgegeben von Walter Kranz. Erster
Band, Weidmann, Zurich, 1996.
8. Die Fragmente der Vorsokratiker von Hermann Diels, Herausgegeben von Walter Kranz.
Zweiter Band, Weidmann, Zurich, 1996.
9. Diels, Hermann: Doxographi Graeci. Berolini. Apud Walter De Gruyter et Socios, Editio
Quarta, 1879 (reprinted 1965).
10. Diogenes Laertius: Lives of Eminent Philosophers, with an English Translation by R.D. Hicks,
M.A., In two volumes. Vol. II. Book VIII, chapter 7, 85, p. 400. William Heinemann LTD
Cambridge, Massachusetts. Harvard Uninersity Press MCMLVIII. (First printed 1925, reprinted
1931, 1937, 1950, 1958).
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11. Dreyer, John L.E.: A History of Astronomy from Thales to Kepler. Dover Publications Inc.
New York, 2nd edition 1953.
12. Heath, Thomas L.: A History of Greek Mathematics. From Aristarchus to Diophantus, vol. 2.
Dover Publications Inc. New York (first publising in 1931, reprinted 1963).
13. Heath, Thomas L.: Aristarchus of Samos the ancient Copernicus. Part II: «Αριστάρχου Σαμίου:
Περί των μεγεθών και των αποστημάτων Ηλίου και Σελήνης»-“On the sizes and Distances of the
Sun and Moon”. Dover Publications Inc. New York (first publising in 1981).
14. Heath, Thomas L.: Greek Astronomy. Perpint. Originally published: London: Dent, 1932.
Dover Publications Inc. New York (February 1991).
15. Philolaos of Croton: «Βάκχαι» and «Περί φύσιος Α Β Γ» in Die Fragmente der Vorsokratiker
von Hermann Diels, Herausgegeben von Walter Kranz. Zweiter Band, Weidmann, Zurich, 1996.
16. Plutarch Chaeronensis Scripta Moralia. Graece et Latine. Tomus Secundus. De Placitis
Philosophorum-Libri quinque. II, KΔ΄, Dox. 355. I. Parisiis Editore Ambrosio Firmin Didot,
MDCCCXLI.
17. Ptolemaeus Claudius: «Σύνταξις Μαθηματική» (Almagest) (ed) J.L. Heiberg, Part I 1898 and
Part ΙΙ 1903, Lipsiae, Teubner.
18. Ptolemy’s Almagest. Translated by G.J. Toomer. British Library Cataloguing in Publication
Data. Ptolemaeus Claudius, First published in 1984. Duckworth.
19. Regas Velestinles: Φυσικής Απάνθισμα (Physics Selection), Wien 1790. (National Greek
Library, No. 1288).
20. Stamatis, E.S.: The Heliocentric System of Greeks, Contributions from the Research Center for
Astronomy and Applied Mathematics. Academy of Athens. Ser. I (Astronomy), No.32. 3. p.32-44.
21. Theon of Smyrna: (Theonis Smyrnaei Philos. Platonici Lipsiae 1878, p. 198, 14-19, Hiller).
22. Τhe works of the Emperor Julian (The Orations of Julian, IV). Vol. I ‘‘Hymn to King Helios
dedicated to Sallust’’. The Loeb Classical Library. With an English Translation by Wilmer Cave
Wright, Ph.D. William Heinemann Ltd. Cambridge, Massachusetts Harvard University Press,
MCMLIV (First printed 1913, reprinted 1930, 1954).
Short C.V. of the authors
Dr. Efstratios Theodossiou and Dr. Emmanuel Danezis are assistant Professors of Astrophysics at the
University of Athens (School of Physics, Department of Astronomy-Astrophysics and Mechanics). Their
scientific interests included observational astronomy and astrophysics, satellite spectrophotometry in UV of
Be stars, variable stars and history and philosophy of astronomy. They have published in excess 40 scientific
papers in international journals and proceedings of astronomical conferences, more than 150 scientific
articles in Greek newspapers and journals, and eight books on his scientific subjects.
Mr. Vasilios Manimanis, Master of Sciences in Astrophysics, he is doing now his Ph. D. Thesis on Double
and Variable stars in our Department.
Miss Kalyva Euanthia-Maria is student of the School of Physics and he is doing her diploma dissertation on
the “Cosmological ideas of Pythagoreans”.
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