Astronomical and astrological knowledge circulated in many ways in the an-cient world: in the form of written texts and through oral communication, and by the conscious assimilation of sought-after knowledge and the uncon- scious absorption of ideas to which scholars were exposed. The circulation of knowledge happened both between cultures, for example the transmis-sion of astronomical texts, theories or parameters from one culture to another, and within cultures, both spatially, for example, between scholars in different cities, between “elite” and “popular” astronomical traditions, and between dif-

ferent genres of scholarship, and temporally, for example later interpretations of and reaction to earlier works. I use the term “circulation” deliberately here to emphasize that the transmission of knowledge is not a unidirectional process: astronomical knowledge from one group is not imposed upon another group; rather the process is one of negotiation between the two parties. Furthermore,

the act of receiving knowledge almost always involves a process of adaptation of that knowledge to make it relevant to and compatible with the existing schol-arly practices of the recipients.