12
$\begingroup$

Hipparchus applied Apollonius's epicycle/eccenter construction to the motion of the Sun and the Moon, but not to the planets. There are speculations about epicyclic gears for planets in the Antikythera mechanism, but apparently they did not survive. On the other hand, a few centuries later Ptolemy had well advanced models for all the planets, and even introduced equant to make them more accurate. What happened in between? Who first applied epicycles to planetary motions?

Lucio Russo even speculated about dynamical ideas from this time period concerning celestial motions based on some passages from Plutarch and Strabo. What is the consensus on that?

Improve this question
$\endgroup$
3
$\begingroup$

Actually, I've found some sources that suggest that Apollonius applied epicycles to planetary motion:

From here:

Apollonius also was an important person in founding Greek mathematical astronomy. He used geometrical models to explain planetary theory. He introduced systems of eccentric and epicyclic motion to explain the motion of the planets.

From here:

Apollonius was also an important founder of Greek mathematical astronomy, which used geometrical models to explain planetary theory. Ptolemy in his book Syntaxis says Apollonius introduced systems of eccentric and epicyclic motion to explain the apparent motion of the planets across the sky. This is not strictly true since the theory of epicycles certainly predates Apollonius. Nevertheless, Apollonius did make substantial contributions particularly using his great geometric skills. In particular, he made a study of the points where a planet appears stationary, namely the points where the forward motion changes to a retrograde motion or the converse.

From here:

Lastly, from references in Ptolemy’s Almagest, it is known that Apollonius introduced the systems of eccentric and epicyclic motion to explain planetary motion. Of particular interest was his determination of the points where a planet appears stationary.

And Wikipedia, by the way, uses the slightly dubious phrasing:

The hypothesis of eccentric orbits, or equivalently, deferent and epicycles, to explain the apparent motion of the planets and the varying speed of the Moon, is also attributed to him.

This last passage, of course, does not state outright that he applied the theory to planetary orbits.

Improve this answer
$\endgroup$
5
  • 1
    $\begingroup$ Sorry, what I meant by "applied" is used it to fit actual observations. Apollonius did some theoretical analysis of the epicycle construction, but Wikipedia says "all this was theory and had not been put to practice" before Hipparchus.en.wikipedia.org/wiki/Hipparchus#Orbit_of_the_Moon $\endgroup$
    – Conifold
    Oct 30 '14 at 23:58
  • $\begingroup$ Ahh, that makes a bit of a difference. Thanks. $\endgroup$
    – HDE 226868 ♦
    Oct 31 '14 at 0:04
  • $\begingroup$ Apollonius (of Perga) was a contemporary of Hypparchus. $\endgroup$
    – Alexandre Eremenko
    Nov 3 '14 at 20:46
  • 1
    $\begingroup$ It looks as though these "sources" are all copied from one another. $\endgroup$
    – fdb
    Jan 5 '15 at 15:53
  • $\begingroup$ And all of them are based on Ptolemy. $\endgroup$
    – Alexandre Eremenko
    Mar 7 '15 at 13:55
2
$\begingroup$

You can look in Wikipedia for the list of astronomers between Hipparchus and Ptolemy, or for more detail consult Neugebauer. (Or Ptolemy himself:-)

The problem is that 90% of our knowledge about astronomy before Ptolemy (except Babylonian for which we have an independent source) is based on Ptolemy books, and this is not an exaggeration. An evidence of this is Neugebauer's History of Ancient Mathematical astronomy. The first volume is an analysis of Ptolemy, the second of EVERYTHING else (Including Hipparchus, Babylonians, Egyptians, and everything in between), and the 3-d volume is Appendixes, tables plates etc.

EDIT. Wikipedia lists the following astronomers in the period between Hipparchus and Ptolemy: Aglaonice, Agrippa, Andronicus of Cyrrhus, Hypcicles, Geminus, Menelaus and Theon of Smyrna (these two are contemporaries of Ptolemy), Posidonius, Seleucus of Seleucia, Theodosius of Bythinia.

Of these, Ptolemy mentions: Agrippa, Theon of Smyrna and Menelaus. One book of Geminus still exists. All others are just mentioned somewhere in other sources.

EDIT 2. There is no consensus about Russo's speculations. The fact is that most of the Greek pre-Ptolemy astronomy is lost. (Including almost everything that Hipparchus wrote. Only one minor work of Hipparchus survives.) I am inclined to think that Russo is right in his general conclusions.

Improve this answer
$\endgroup$
2
  • $\begingroup$ Is it known what those astronomers did? I remember from reading Ptolemy's passages that he only compares himself to Hipparchus and nobody else, maybe to make his own work look more substantial. $\endgroup$
    – Conifold
    Nov 3 '14 at 23:39
  • $\begingroup$ Ptolemy credits those he cites with some observations. (Menelaus with a theorem). As I said, the problem is that Ptolemy is the only important source that survived. Even what Hypparchus did we mainly know from Ptolemy. $\endgroup$
    – Alexandre Eremenko
    Nov 4 '14 at 0:17

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.