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Seleucus (or Seleukos) of Seleucia (born c. 190 BC, fl. 150s BC) was a hellenized Babylonian astronomer and philosopher who stood in the tradition of Greek astronomy.[1][2][3] Coming from Seleucia on the Tigris, the capital of the Seleucid empire, or, alternatively, Seleukia on the Red Sea,[4] he is most known as a proponent of heliocentrism[5][6][7] and for his theory of the origin of tides.


Heliocentric theory

Teaching around 150 BC, he is known to have been a follower of the heliocentric theory of Aristarchus of Samos, which stated that the Earth rotated around its own axis which in turn revolved around the Sun.[8][9] According to Plutarch, Seleucus was the first to prove the heliocentric system through reasoning, but it is not known what arguments he used.[10] According to Bartel Leendert van der Waerden, Seleucus may have proved the heliocentric theory by determining the constants of a geometric model for the heliocentric theory and by developing methods to compute planetary positions using this model, as Nicolaus Copernicus later did in the 16th century. He may have used trigonometric methods that were available in his time, as he was a contemporary of Hipparchus.[11]

Since the time of Heraclides Ponticus (387 BC-312 BC), the inferior planets Mercury and Venus are named at times solar planets, as their positions diverge from the Sun by only a small angle.

According to the Greek geographer Strabo, Seleucus was also the first to assume the universe to be infinite.[12] None of his original writings or Greek translations have survived, though a fragment of his work has survived only in Arabic translation, which was later referred to by the Persian philosopher Muhammad ibn Zakariya al-Razi (865-925).[13]


According to Lucio Russo, Seleucus' arguments for a heliocentric theory were probably related to the phenomenon of tides.[14] Seleucus correctly theorized that tides were caused by the Moon, although he believed that the interaction was mediated by the pneuma. He noted that the tides varied in time and strength in different parts of the world.

According to Strabo (1.1.9), Seleucus was the first to state that the tides are due to the attraction of the Moon, and that the height of the tides depends on the Moon's position relative to the Sun.[12]

Seleucus in Strabo

Seleucus is known from the writings of Plutarch, Aetius, Strabo (all Greeks) and the Persian Muhammad ibn Zakariya al-Razi. Strabo lists Seleucus as one of the four most influential "Chaldean" astronomers:

In Chapter XVI of his Geographia, Strabo mentions several "Chaldaen" astronomers. At the end he adds: "Seleukios of Seleukia was a Chaldaean too." ... Babylonian astrologers and astronomers were often called "Chaldaeans." Strabo calls them "the so-called Chaldaeans". Their writings were translated into Greek and used by later authors like Geminos. The "Chaldaean" astronomers mentioned by Strabo are Kidenas, Naburianos, Sudines, and Seleukos. The first two are also known from astronomical cuneiform texts under their Akkadian names Nabu-Rimannu and Kidinnu.[12]


  1. ^ Chaldaean/Babylonian astronomer:
    William P. D. Wightman (1951, 1953), The Growth of Scientific Ideas, Yale University Press p. 38, where Wightman calls him "Seleukos the Chaldean"; Neugebauer 1945, p. 25:
    On what background can we understand, for example, the report that the "Chaldaean" Seleucus from Seleucia on the Tigris, completed the heliocentric theory, ...
  2. ^ Greek astronomer:
    The SAO/NASA Astrophysics Data System (ADS):
    Greek philosopher, born in Seleucia, ...
    Greek philosopher who was the one astronomer of note who championed Aristarchus's heliocentric theory.
  3. ^ Greek astronomical tradition: Sarton 1955, p. 169:
    During the last three centuries B.C., three different kinds of astronomy were cultivated simultaneously within a relatively small area, the Near East, (1) the heliocentrical astronomy invented by Aristarchos of Samos (III B.C.) and still defended a century later by Seleucos the Babylonian, (2) the geocentrical astronomy which thanks to Hipparchos (II B.C.) became the leading astronomy of the Greeks, (3) the Chaldaean astronomy, concerned exclusively with ephemerides, not with theory. The first two were essentially of the same kind, and hence the discussion might be restricted to two terms. (1) and (2) represent Greek astronomy, and our own astronomy is derived from both, (3) is Chaldaean and as we shall see presently very different in purpose and methods.
  4. ^ Neugebauer 1945, pp. 39–42:
    Among several cities named Seleukia, the best known is Seleukia on the Tigris, the capital of the Seleucid kingdom. It is possible that the astronomer Seleukos lived or was born in this city, but it is also possible that his native town was Seleukia on the Erythrean Sea.
  5. ^ Index of Ancient Greek Philosophers-Scientists
  6. ^ Seleucus of Seleucia (c. 190 BC-?), The SAO/NASA Astrophysics Data System (ADS)
  7. ^ Seleucus of Seleucia (ca. 190-unknown BC), ScienceWorld
  8. ^ Russell, Bertrand — History of Western Philosophy (2004)‎ - p.215
  9. ^ We do not know other names of ancient astronomers or scientists who supported the heliocentric system: Hipparchus and later Ptolemy contributed to the success of the geocentric system; however, in the writings of Plutarch and Sextus Empiricus we read of "the followers of Aristarchus", thus it is probable that other people we do not know of adhered to the heliocentric view.
  10. ^ Van der Waerden 1987, p. 528
  11. ^ Van der Waerden 1987, pp. 527−529
  12. ^ a b c Van der Waerden 1987, p. 527
  13. ^ Shlomo Pines (1986), Studies in Arabic versions of Greek texts and in mediaeval science, 2, Brill Publishers, pp. viii & 201-17, ISBN 9652236268 
  14. ^ Lucio Russo, Flussi e riflussi, Feltrinelli, Milano, 2003, ISBN 88-07-10349-4.


  • Neugebauer, O. (1945), "The History of Ancient Astronomy. Problems and Methods", Journal of Near Eastern Studies 4 (1): 1–38 
  • Sarton, George (1955), "Chaldaean Astronomy of the Last Three Centuries B. C.", Journal of the American Oriental Society 75 (3): 166–173 
  • Van der Waerden, B. L. (1987), "The Heliocentric System in Greek, Persian and Hindu Astronomy", Annals of the New York Academy of Sciences 500: 525–545 

See also



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