Inventing the Solar System: 

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              Early Greek Scientists Struggle to Explain 

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                        How the Heavens Move

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                         Ellen N. Brundige

                      University of CA, Irvine

                         ebrundig@uci.edu



 

I. Introduction

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	Since the first Egyptian farmers discovered the annual reappearance of 

Sirius [(1)] just before dawn a few days before the yearly rising of the Nile, 

ancient civilizations around the Mediterranean have sought to explain the 

movements of the heavens as a sort of calendar to help guide them conduct 

earthly activities. Counting phases of the moon or observing the annual 

variations of daylength could, after many years' collection of observations, 

serve as vital indicators for planting and harvesting times, safe or stormy 

season for sailing, or time to bring the flocks from winter to summer 

pastures. With our millenia of such observation behind us, we sometimes forget 

that seeing and recording anything less obvious than the rough position of sun 

or nightly change of moonphase requires inventing both accurate observation 

tools (a stone circle, a gnomon used to indicate the sun's shadow, a means to 

measure the position of stars in the sky) and a system of recording that could 

be understood by others (how many fingers' width or degrees is that star from 

the horizon? Which direction is due north?).

 

	The ancient Greeks struggled with these problems too, using both 

native technology and inquiry, and drawing upon the large body of observations 

and theories gradually gleaned from their older neighbors across the sea, 

Egypt and Babylon. Gradually moving from a system of gods and divine powers 

ordering the world to a system of elements, mathematics, and physical laws, 

the Greeks slowly adapted old ideas to fit into a less supernatural, 

hyper-rational universe. This paper is a short survey of the Greeks' earliest 

attempts to explain why and how the sky changes.

 

II. Mythology

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As ancient peoples began to realize that sun, moon and stars follow certain 

rhythms in step with the seasons, they made the leap of thought to postulate 

that some conscious set of rules must be dictating these movements and 

seasonal changes which, for agrarian or pastoral societies, were a matter of 

life or starvation. Who or what could be causing these all-important changes 

to come about? Certainly nothing on earth, no beast or human, had the power. 

Thus gods were born.

 

	II.A. Homer and Hesiod: Chariots [(2)] of Fire in the Vault of Heaven

 

	There are hints of the Greek conception of the universe in Homer, who 

mentions many subjects on his two epics describing war and the perils of 

trying to come home after long absence. For Homer, heaven is a solid inverted 

bowl (Od. 15.329 sideron ouranon) straddling the earth, with fiery, gleaming 

aither above the cloud-bearing air. (Il. 14.288 `fir-tree reached through the 

aer to aither).[1] Homer mentions the movements of sun (Od. 4.404), moon, and 

many stars by name. The fact that Hades is on the underside of earth has an 

important impact on conceptions of heaven: it is unlit by the sun (in Homer 

and in Hesiod), therefore, the sun--and by extension, other heavenly bodies-- 

must sink only to the level of Ocean, which is conceived as a river circling 

earth's edge. From it the Sun must also rise--though how it gets back to the 

eastern bank of Ocean is never explained.

 

	These popular conceptions of sky are more fully explained in Hesiod, 

whose works on gods and on agriculture and animal-herding are more closely 

connected to the practical application of astronomy. He clocks spring, summer, 

and harvest by solstices and the rising and setting of certain stars, and 

notices that the sun migrates southwards in winter.[2] Night is a substance 

welling up from under the earth, as if it were a dark flowing mist (Hes. Th. 

726).[3]

 

	II.B. Other mythological schemes of the heaven

 

	One early and popular cult, that of Orpheus, developed its own of gods 

and universe-creation variant from those in Homer and Hesiod; there, a 

primeval egg is birthed by the early gods, and the upper half of its broken 

shell becomes heaven's vault.[4] Various cults, cities and tribes of Greeks 

(who were unified only by language and common culture, and both of these had 

regional variants) probably had different versions of cosmogony and slightly 

different gods in charge of astronomical movement, but the general physical 

conception of the sky is alluded to by many authors of plays and other popular 

works (Eur. Melanippe 484), and was probably held by the majority of people.

 

III. The Ionian Revolution: Fiery Clouds and Wheels of the Sky

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	Many Greeks settled on the coast of Turkey in the early migrations of 

the eleventh century BCE, and there enjoyed rich cultural mingling with their 

neighbors (and sometimes their conquerers) the Lydians and Persians, latest 

descendents of Mesopotamian civilization. (See Hdt.1.142 for a discussion of 

Ionia; Strab. 14.1.7 about famous Ionian scholars.) The freshwater conception 

of the Ocean river is seen by many scholars as a telltale sign of early 

adoptations from that ancient `between the rivers' people.[5] They kept in 

touch with their western cousins, who began a second wave of settling across 

the Aegean in the seventh century, as well as with other rich sea-faring 

cultures like Egypt. It is not surprising that, by the sixth century, these 

Ionian navigators of the sea began to develop new ideas about the sky they 

steered by. The most fundamental of these was that the universe might run, not 

only by the whim of gods, but by physical, mechanical rules and principles 

that might, through study, be understood and predicted.

 

	III.A. Thales of Miletus (c. 585 BCE): Eclipses and Stellar Studies

 

	Our sources for all early Greek astronomy are scant, none more so than 

for Thales, supposedly the first of the philosophers. Various inventions and 

discoveries are attributed to him, most famous of which is his prediction of 

an eclipse of 585 (Hdt. 1.74). Modern scholars are fairly sure he was able to 

do this by consulting known Babylonian eclipse and lunar observations going 

back about 150 years, long enough to notice that eclipses recur after about 18 

years[6]. His activities also seem to have included star-observations and 

trigonometry, which he is credited with having founded, but the details of his 

theories are either lost or obscured by later legends about this early thinker 

who left no written record. He seems to have conceived of earth as flat and 

water-borne, and to have postulated that there must have been some first 

substance out of which the world arose, which he guesses is water (Aristot. 

Met. 983b 6)[7].

 

	III.B. Anaximander of Miletus c. 550 BCE: Celestial Fire and Pipes

 

	The earth for Anaximander is still a cylinder circled by air and then 

fire "like the bark of a tree" (Ps-Plut. Strom. 2)[8], which separated off at 

an early stage. We still see echoes of the early cosmologies here, but an 

attempt is made to explain the scheme in purely physical--in fact, in 

mathematical--terms. The heavenly bodies are all described as wheels of fire 

(Homerically described as like chariot wheels) enclosed by are via a further 

separating-off. Their light which we actually see is only a part of them, 

described as an axle, pipe, vent, or bellows-nozzle, through which fire jets 

(Aetius 2.20-21).[9] Eclipses and lunar variations are accordingly caused by 

these vents opening or partially closing.

 

	All these ideas are attempt to explain the universe in physical terms, 

though as yet there is only the vaguest theory as to why these things are so. 

Anaximander seems to suggest a process of separation and "equilibrium", with 

the earth suspended in the middle and the various heavenly bodies "balanced" 

all around it by some unseen rule ( Aristot. de caelo. 295b 10). Here, as with 

all the early thinkers for whom direct quotes are almost non-existent, we must 

be cautious about later sources who tend to read later theories into earlier 

philosophers' ideas. Yet with that caution in mind, we can see by 

Anaximander's "equilibrium" (and the "condensation" of Anaximines and all his 

successors, next section) that the Greeks were beginning to be aware of 

gravity but still needed to put two and two together and recognize it 

explicitly.

 

	III.C Anaximines of Miletus (c. 525 BCE): Condensation of All From Air

 

The third of the Ionian thinkers refined the flat-earth idea, suggesting that 

all things are produced through a process of gradual condensation and 

"rarefication"[(3)]: earth condenses out of air, and fire is "exhaled" from 

the earth (Ps.-Plut. Strom. 3).[10] The earth and heavenly bodies are flat and 

loft on infinite air like a leaf (Aristot. de caelo. 294b 13).[11] Celestial 

bodies do not set beneath the earth, just as in mythology, but instead turn at 

an angle (the axis of rotation, after all, is visible to us in the northern 

part of the sky) so that many are obscured by the "higher" parts of earth to 

the north ( Aristot. Meteor. 354a 28).

 

IV. Ionic thought's Influence: Wheels and Bowls of Fire

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	Xenophanes of Colophon (c. 570-490 BCE) migrated from Ionia to Italy 

fleeing the Medes' takeover, bringing Milesian theory with him. Although 

largely concerned with de-anthrophomorphizing god to make it infinite and 

all-encompassing, he propagates the view of heavenly bodies condensing into 

fiery clouds from earth's exhalations (Aetius 2.20.3). His heavenly bodies, 

like Anaximines', follow circular courses (conceived as bands or zones) and 

are obscured behind high parts of the earth.

 

	Heraclitus of Ephesus (c. 500 BCE), though criticizing his 

predecessors' work as data, not understanding, continues the idea of creation 

through balance of different substances and the process of condensation, this 

time, from fire. Night is formed of murkier exhalations from earth (as from 

Tartaros in Hesiod above) and day from exhalations ignited by the sun. Sun, 

moon, and stars ae fire caught in bowls, which tip away to cause eclipses and 

lunar phases. The moon travels through the less purified air close to earth, 

so is dim, and the sun is the closest and thus brightest and hottest of stars 

(Diog. Laert. 9.8-11).[12]

 

V. Parmenides, Empedocles, and Pythagoreans: Paradoxes, Spheres, and Cycles

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	The later of these "Presocratic" philosophers began to specialize, 

develop, and apply the systems of empirical observation and deduction which 

their predecessors had invented. Some, like Parmenides and Zeno, concentrated 

on exposing the fallacies and logical traps to which the first uses of 

analytical thinking often fell prey. Others, like followers of the 

semi-legendary Pythagoras, used their theories about how the universe worked 

to develop new ideas of divinity, astronomy, universal harmony, and 

mathematics, and extended these ideas to dictate a proper, "harmonious" 

lifestyle. All these continued to refine and argue over the basic precepts put 

forth by the Milesian thinkers.

 

	V.A. Parmenides (c 450 BCE): The Sphere of All, Wreaths of Fire

 

	Parmenides of Elea, in Italy, manages to demolish all physics by his 

proof that neither motion, change, nor differences in matter can exist (quoted 

by Simplicius in Phys. 146.5).[13] Having done this, he coyly outlines the 

"beliefs of mortals", which must in fact be his view of the"deceitful" 

physical world, a sort of Greek version of the Buddhists' maya. His heavenly 

bodies, separating out with the heaviest matter towards the center, are again 

concentrations of fire-vapor, here regulated by "Necessity" to move them 

between an inner "wreath" of fire and an outer solid sphere (Aetius 2.7.1). It 

sounds like he conceived of the "wreath" as a belt like an asteroid belt, and 

the outer shell as a true sphere; whether or not his earth was flat is 

difficult to tell.[14]

 

	V.B. Empedocles and Anaxagoras: Reflections of Light

 

	Empedocles of Acragas (mid 5th cent. BCE) works on a system to 

reconcile the "unchanging" universe of Parmenides' sphere with chaotic, 

differentiated matter by having the universe in a state of flux (as in 

Heraclitus) between harmony and strife. Along the way, he propounds an outer, 

hard universal sphere upon which the stars are fixed, and an inner sphere of 

double hemispheres, one of lighter fire for day, one of darker for night. The 

sun and moon are not physical bodies but concentrated, polished spots on this 

inner surface which reflect the outer fire (Eusebium P.E. 1.8.10).[15]

 

	Anaxagoras, friend of the Athenian statesmen Perikles and thus 

slightly younger than Empedocles, follows the usual theory of separation and 

condensation, but his heavenly bodies are again solid objects (Plat. Apol. 

26D). His most important contribution to astronomy was the claim that the 

moon's light is a reflection of the sun (Plat. Crat. 409b),[16] and that 

eclipses of the moon were caused by earth's shadow, eclipses of the sun by the 

moon passing before it (Aetius 2.29.6).

 

	V.C. Pythagoreans: The Hearth of the Universe

 

	The Pythagoreans first proposed a non-geocentric system, perhaps 

partly on the basis of moral and religious grounds: to them, humanity and 

earth were imperfect, and only by sacrifice and a strict regimen of personal 

conduct could one strive to reach the divine. Accordingly, they placed the 

divine, poetically called the "Hearth of the Universe" or "Throne of Zeus", at 

the center of a finite, spherical universe (Aristot. de. caelo B13, 293a-b30). 

The sun is a glass sphere (Aetius 20.12) which catches and reflects this 

hearth-light. A counter-earth, the "antichthon", had to be invented, 

supposedly to make the number of planetary spheres ten. These include the five 

visible planets out through Saturn, earth, the moon, the sun, and the heavenly 

sphere on which were the stars.(Aetius 2.7.7,Aristot. Met. A5,986a1). Heath, 

in outlining this system, suggests that the counter-earth was invented to 

account for the frequency of lunar eclipses [17]. The counter-earth also 

solves a major problem in this view, serving to eclipse the Hearth-Fire so 

that we never look God in the face, so to speak. The concepts of number, 

harmony, and music all influenced the Pythagoreans to invent this 

fully-realized version of the concentric celestial orbits, which resonate with 

"the music of the spheres" .[18]

 

VI. The Socratics and Beyond: A Geocentric System

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	The atomists Leucippus and Democritus in the generation preceding 

Socrates refined the various pre-Pythagorean views of space: there is a 

drum-shaped earth (in Leucippus), condensation is the falling-together of 

atoms, and centrifugal force helps keep the earth and bodies of fire in place 

(Diog. Laert. 9.30ff).[19] Leucippus was probably from Miletus, and Democritus 

from Abdera; their development of atomic theory was a refinement of two 

centuries of Ionian scholarship.

 

	After them, however, Socrates' pupil Plato and Plato's pupil Aristotle 

would espouse Pythagorean harmony and spheres and a geocentric system. Their 

many works analyze, refute, discuss, and expand on their successors; two of 

the passages representative of their views on astronomy are found in Plato's 

Timaeus 37dff and Aristotle's De Caelo 2,289a 11-291b 23. In keeping with 

these theories now becoming prevelant, the early fourth century mathematician 

Eudoxis of Knidos mathematically described the idea of concentric spheres 

(Aristot. Met. 1073b 17-1074 a 15)[20], anticipated by the "wreaths" and 

"zones" of many earlier scientists and probably assumed by the Pythagoreans.

 

	Having discovered a theory of the solar, or rather, geo- system which 

accounted for all visible phenomenon (and was, moreover, aesthetically 

pleasing), subsequent astronomers and philosophers fine-tuned the idea for 

their particular fields. The philosophers dwelt on harmony, cycle, and a new 

scheme of the divine; the mathematicians, a description of heaven in the 

marvelous language of geometry which was nowhere else in the physical world 

more eloquently expressed. Sophisticated three-dimensional moving systems were 

worked out by various geometers to account for observed inconsistencies in 

their basic theory. It would take many centuries before anyone had accurate 

enough observations to realize that the theory could not account for all data. 

By then, people would have even more difficulty letting go of their clockwork, 

geocentric, "divinely subsidized" [21] universe than the Greeks, who had 

placed their version of a Bible, the Homeric and Hesiodic myth-cycle, into the 

realm of metaphor after executing only one gadfly of a philosopher.

 

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Endnotes

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[(1)] 	Sepdet, or Sothis  - A summary of info about the star Sirius and 

sky-myths

 

	Sepdet is the Ancient Egyptians' goddess who appeared to them each 

year as the dog-star, Sirius, brightest star in the sky. She disappeared from 

the sky for several months of summer, when the Nile was at low ebb, and 

hopeful Egyptian farmers planted seeds in the fields along the banks of their 

irrigation ditches. She reappeared just before dawn at the end of our July 

(Hom. Il. 5.5), and a few days later, the Nile would begin to rise too, so 

that she was thought to be a herald calling the life-giving waters back to the 

fields. Naturally, the star came to be revered for this.

 

	The Egyptian New Year began on the first day whose dawn saw Sirius 

rise just before the sun, nowadays close to August 1st, a harvest holiday for 

many cultures coming as it does midway between the summer solstice and 

autumnal equinox. She was sometimes called Wep-renpet for that reason, which 

means, "Opener of the Year", and the month that followed her rising was often 

called this too.

 

	Sepdet's symbolism and meaning were absorbed into the well-known 

national goddess, Isis, due to another legend about the star. Sirius happens 

to travel the sky just ahead of the large constellation of Orion. (His belt of 

three stars serves as an easy pointer towards Sirius, the unmistakable bright 

star that is one of the few visible even in city lights' glare). Orion was 

identified with the dying-and-resurrected god Osiris, in Egyptian mythology, 

who was one of the most well-known gods of the pantheon. His wife and sister 

Isis was Lady of Magic, who brought her husband back to life, and the bright 

star his constellation followed naturally came to be associated with her. The 

function of Sirius as herald of the life-giving inundation of the Nile added 

another layer of metaphor to this age-old story.

 

[(2)]  	While popular conception of Greek myths paints a quaint picture 

of the solar chariot riding across the sky, a search for "sun", "Helios", 

"Apollo", and his son "Phaethon" yielded only one instance of this motif in 

Homer or in Hesiod, although all are mentioned many times. Various gods do 

employ chariots to travel the sky throughout Homer, Poseidon more often than 

Apollo. Later authors and Greek art begin to use this scene more explicitly and 

frequently.

 

[(3)] 	Many of the Greek thinkers had earth condensing from water, or 

earth exhaling watery mist which condensed through "rarefication" into fire. 

Anaximenes started with earth condensing from air, which seems even more 

counter-intuitive to us, but we can understand it better if we consider the 

following.

 

	Perhaps Anaximenes was observing the way dust precipitates out of the 

air onto tables, chairs, and any surface. The bright sky was often thought by 

the ancients to be a bowl or curtain of "shining" air, which they often 

assumed was smoke or mist refined one step further. Although we find these 

laughable concepts in the way the Greeks expressed them, we do in fact believe 

something of the same thing: the gas giants Jupiter and Saturn glow with heat 

of their own like stars, but are not large enough to collapse, ignite, and 

form suns. Similarly, we know that compressed gas makes heat, and that the 

difference between solid, liquid, and gas is that solid matter has the atoms 

packed closely together so that they cannot move freely, whereas in liquids or 

gases the atoms are looser.

 

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References

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Heath--Heath, Sir Thomas L., "Greek Astronomy.", 

	New York: Dover Publications, 1991.



KRS--Kirk, G.S., Raven, J.E., and Schofield, M., 

	"The Presocratic Philosophers."

	Cambridge University Press,1957.



[1] KRS. p. 9

[2] Heath. p. xii.

[3] KRS. p. 726.

[4] KRS. p. 25. Aristophanes spoofs this in The Birds.

[5] KRS. p. 11.

[6] Heath. p. xvi.

[7] KRS. p. 88.

[8] KRS. p. 131.

[9] KRS. p. 135.

[10] KRS. p. 151.

[11] KRS. p. 153.

[12] Heath. p. 15.

[13] KRS. p. 252.

[14] KRS. p. 258

[15] Heath. p. xxxvii, KRS. p. 300.

[16] Heath. p. 27.

[17] Heath. p. xxxvi-xxxvii.

[18] Heath. p. 34.

[19] Heath. p. xxxviii.

[20] Heath. p. xliv.

[21] Christopher Fry, The Lady's not for Burning. Second Edition. 1950. A 

skeptic chastises a fellow rationalist for waxing poetic about the moon: "The 

moon is nothing but a circumambulating aphrodisiac, divinely subsidized to 

promote a rising birthrate, a veneer of sheerest Venus upon the planks of 

time, which may fool the Ocean, but which fools not me."

 

 

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Related web sites of interest

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	Mythology

	_________

 

	JM Hunt's overview of Greek Cosmogony, mostly taken from Hesiod 

		http://info.desy.de/gna/interpedia/greek_myth/creation.html

 

	MythText,an amateur scholar's website of world mythologies, fun to browse 	

		http://www.the-wire.com/culture/mythology/mythtext.html

 

	Modern Astronomy

	________________

 

	W3 Virtual Library of Astronomy and Astrophysics on the Web

		http://www.w3.org/hypertext/DataSources

			/bySubject/astro/astro.html

 

	Bill Arnett's Multimedia Masterpiece: The Nine Planets 	

		http://seds.lpl.arizona.edu/nineplanets

			/nineplanets/nineplanets.html

 

	JPL's new guide to the solar system 	

		http://stardust.jpl.nasa.gov/planets/

 

	3000 years of research: Fourmilab's Orrery (an animated schematic of 

		the solar system) 	

		http://www.fourmilab.ch/solar/solar.html

 

		Current phase of moon (against map of earth) 	

			http://www.fourmilab.ch/homeplanet/samples/help2.gif