I wonder if would be right to say that while most ancient astronomical activities, such as building and improvement of observational structures, had a strong astrological component, the Greek philosopher’s or mathematiscians' deduction of the spherical shape of the moon, the Earth and the calculation of the Earth’s dimensions constitutes what we might call basic astronomical research, in that the endpoint was not related to the ability to make horoscopes or to any other astrological activity?

Is it therefore right to call these activities - in the above sense - one of the first purely astronomical research activities?

  • 3
    $\begingroup$ The link between astronomy and astrology was strong also in Greek science; see Ptolemy. $\endgroup$ Jan 24, 2021 at 18:20
  • $\begingroup$ In a sense, astrology was "applied astronomy": astrology was based on computations, and astronomical techniques of computations was developed by... astronomy. $\endgroup$ Jan 25, 2021 at 7:35
  • $\begingroup$ One form of it. The other application of astronomy was calendars. $\endgroup$
    – Mary
    Jan 27, 2021 at 0:53

1 Answer 1


There was a link between astronomy and astrology, as @Mauro Allegranza notes but the two things were strictly separated. Ptolemy's Almagest (and his many other scientific books) contains no single word, not even a hint of astrology. On astrology he wrote a separate book, Tetrabiblos. Same applies to other Greek writers on astronomy. No one mixed the two subjects.

To a lesser extent this applies to Muslim astronomers, Brahe and Kepler, but still the two things were usually strictly separated. When one compares "Astronomia Nova" with astrological writings of Kepler, one has a strong impression that these are works of different authors. Same applies to Ptolemy's books.

I suppose, an explanation of occupation of astronomers by astrology lies in their need to make a living somehow. There was little public demand for pure astronomy, and very few or no positions where you could earn your living by practicing pure science. For the same reason, many mathematicians and astronomers until 17 century practiced medicine (or law). This is my own conjecture, please do not ask for confirming references.

One confirmation of this is an inspection of the web site which is called Math genealogy You see a lot of people whom we remember as scientists and mathematicians, and who obtained their degree in medicine.

Edit. There is a strong indication, that some of the astronomy and all astrology came to the Greeks from Babylon, after Macedonian conquests. (Astrology did not exist in Greece before that, and astronomy was rudimentary). How well they were separated in Babylonia, is not clear. But it seems that they were. At least modern scientists are able to make a clear distinction between astronomical and astrological texts that survive.

Edit 2. In the late Roman empire, public interest to science vanished almost completely and the word "mathematicus" at that time meant "astrologer". Eventually this occupation was simply prohibited by the ban of the Emperor.

  • $\begingroup$ @Eremenco Accepting the two points of view presented I would like to persevere by concluding that “i) taking into account the coexistence of astronomy and astrology ii) with a marked then-perceived difference between the two disciplines, astronomical progress – such as calculation of dimensions of the Earth and the moon - were included in the Greek culture that we must now see as considerable astronomical advances unheard of in earlier eras”. $\endgroup$ Jan 26, 2021 at 15:27
  • 1
    $\begingroup$ Re: edit - a quote from a recognized expert, Rochberg-Halton "The direct and absolutely determinative influence of the motions of the celestial bodies upon the earth is therefore understandably a Greek, or Hellenistic, concept, one which has no parallel in Babylonian omen texts." ‘New Evidence for the History of Astrology’, J. of Near Eastern Studies, 43, 2(1984), p. 117" $\endgroup$
    – sand1
    Jan 26, 2021 at 22:22
  • $\begingroup$ @sand 1: thanks for an interesting reference. Yes, the Hellenistic Greeks not only adopted astrology, they developed it:-) $\endgroup$ Jan 26, 2021 at 22:25
  • $\begingroup$ Re: edit2 The banning of astrologers from Rome seems a neat story but see Ripat P., Expelling Misconceptions, Class. Phil. 2011 (106) p. 115 winnspace.uwinnipeg.ca/bitstream/handle/10680/1231/… $\endgroup$
    – sand1
    Jan 27, 2021 at 10:09
  • $\begingroup$ @sand I am writing an essay on physicalism and models of reality, using the development of our models for the Solar system as an example. I am very satisfied by all the answers and comments here. $\endgroup$ Jan 27, 2021 at 10:50

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

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