The Hellenistic science of astronomy was one aspect of a distinctive intellectual culture arising in the Near East and Western Mediterranean—indeed, in all three of the Antigonid, Seleucid, and Ptolemaic Empires in the geographical area briefly unified by the conquests of Alexander the Great—during a period roughly extending from the late fourth century bce to the rise of Arabic astronomy. As a result of cultural contacts, some of longstanding and even more ancient roots, the development of astronomy in this period came to bear the impress particularly of Babylonian knowledge and practices. The significance of Babylonian influence is a key feature of the development of astronomy in the Hellenistic Period; whereas, at the same time, the development of Babylonian astronomy itself reached its apex in Babylonia under Seleucid rule. The characteristic features of Hellenistic astronomy as manifested in the various parts of the Near Eastern and Mediterranean worlds during this period and the contexts within which it functioned and was further developed are the remit of this volume.

Of all the sciences created in Antiquity, astronomy is second in importance only to medicine in its impact on human lives. And, for this reason, like medicine, it achieved remarkable sophistication. The development of astronomy in Greco-Roman culture from a qualitative science in the late fourth century bce to a fully quantitative and predictive science in the second century ce that was the paradigm of human knowledge and a rival to philosophy is truly astounding. So there is no denying the historical importance of astronomy as a basis for insight into the Greek and Roman worlds of that time. But ancient astronomy also developed in other geo-cultural domains and their understandings of the heavens are also important and merit close attention because they influenced, and were influenced by, the Greco-Roman science. In effect, each of these cultures played a role in defining ancient astronomy as a set of historically interacting bodies of knowledge that lasted in various forms to the beginnings of Arabic astronomy in the latter half of the eighth century ce.

One of the fascinations of astronomy in the period from roughly 300 bce to 750 ce, which we call Hellenistic, is surely that its geographical range was vast, spanning regions that were, prior to Alexander’s unification, culturally distinct. Even before Alexander the Great briefly formed a single inhabited world (oikoumene), the layers of culture and language, especially in the eastern part of that conquered area, were many and already integrated with one another in various ways. Thus, for example, in Mesopotamia, the region of the Seleucid Empire, the ancient Sumerian and Akkadian traditions of the third millennium fused into a Babylonian tradition that was followed by an Assyro-Babylonian form in the first millennium that was replaced yet again by a Late Babylonian form (after ca 500 bce), within which mathematical astronomy first made its appearance.

The Persian Empire had its own impact on the cultures of its political domain, accounting for the rise of Aramaic as a learned language in many parts of the Near East in the sixth to fourth centuries bce. The Hellenistic Near East, however, ushered in an unprecedented culture of intellectual transmission and circulation of knowledge. The component of Hellenistic astronomy that we see in Judea [chs 13.1–2] is an important instance of the influence of the Babylonian astronomical tradition within the new Hellenistic world and its adaptation for local interests in the Eastern Mediterranean.

Pre-Hellenistic Egyptian knowledge of the heavens was also absorbed within new forms of Hellenistic Egyptian astronomy [chs 4.8 and 11.1]. The capital city of the Ptolemies, Alexandria, became a center for scientific activity and served under the Ptolemaic dynasts to foster intellectual culture and, with it, the combined astral sciences of astronomy and astrology. Some of the most significant Greek treatises, such as the Almagest and Tetrabiblos by Claudius Ptolemy, came from Alexandria during the second century of our era.

Needless to say, therefore, any historical analysis that does not account for the impact of the cultures of the eastern regions of the oikoumene will be inadequate for understanding the Hellenistic sciences, particularly astronomy and astrology, since the East is where these sciences originated. In much the same way, the Hellenistic traditions of medicine and magic and, indeed, the combinations of these with astronomy to produce new ideas and practices (such as astral medicine [ch. 9.3] or astral magic) were equally products of the circulation of knowledge and the remarkable intellectual transmission of ideas from the East that characterizes the Hellenistic world.

Just as the geographical domain for the study of astronomy in the Hellenistic Period is extensive, so too is the range of the sources to be considered. The textual evidence for Hellenistic astronomy stems from tablets and papyri (or artifacts and inscriptions) from Seleucid Babylonia, Ptolemaic Egypt, and Macedonian Greece, as well as from the Roman Near East, where it may be found, for example, in the astronomical texts of the Qumran community in the first century bce [chs 13.1–2]. In tracing the continuation of Hellenistic astronomy in even later periods, it is clear that the Late Antique heirs in both East and West carried on certain elements of Hellenistic astronomical culture. These late manifestations of the tradition, such as in Christianity [ch. 13.3], Stoic and Neoplatonic philosophy [chs 14.1–2], and Hermeticism [ch. 13.5], have a place in the history of Hellenistic astronomy, and consequently a place in the present volume.

In order to accommodate the different languages, cultures, religions, and intellectual traditions that supported astronomy and astrology, we have adopted what is perhaps an ultra-long Hellenistic Period for our chronological framework (ca 300 bce to 750 ce). Our chronological limits are determined not by singular political turning points but rather by developments within the science considered as a transcultural phenomenon of shared knowledge. We have not found the standard date-limits given for the ‘Hellenistic Period’ (323–31 bce), the ‘Greco-Roman Period’ (332–395 ce), the ‘Byzantine Period’ (330–1453 ce), or ‘Late Antiquity’ (third to eighth centuries ce in the West and third to mid-eighth ce in the East) to be appropriate or useful in delimiting chronologically the long period within which astronomy appeared and then persisted until the major shift that occurred in the development of the science as it entered the Islamicate world of the eighth century. Such transculturally shared and interactively created systems of knowledge demonstrate yet again greater staying power than kingdoms and empires. Astrology, after all, was one of the longest lasting sciences of all from Antiquity.

Apart from delimiting the geographical and chronological framework for studying Hellenistic astronomy, what is called for is a history that is ever mindful of the fact that its great success was due to the development of an impressive mathematical apparatus, yet aware as well that this very success entailed addressing needs and requirements deriving from the diverse contexts in which this science was pursued. Our goal, then, is to provide critical analyses that lay out the great success that astronomy enjoyed by addressing the complex interplay between these needs or requirements and the mathematical apparatus developed to meet them.

But there is a caveat. The present volume is only a first step toward the larger project of understanding astronomy as a scientific and social phenomenon of the Hellenistic world. Given that the ambit of Hellenistic astronomy as we conceive it is extremely wide, it should not come as a surprise that this volume is incomplete in both its temporal and geo-cultural coverage. Practical constraints have necessitated that our focus be on the Mediterranean and Near East and mainly in the interval from 300 bce to 300 ce . And so much remains to be said and much more to be done. But completeness can only be a goal in a project that proposes to set Hellenistic astronomy in its diverse cultural contexts in order to understand both why and how its ideas and practices developed.

We are mindful, of course, that the very features that made Hellenistic astronomy such a success in its time, its technical apparatus, can prove an impediment to readers today, even to the few who have some knowledge of the heavens. And so, astronomy, that magnificent science which afforded its results, insights, and authority to so many aspects of Hellenistic culture [e.g., ch. 10.2] is often not given its due in studies of the cultures to which it was once such an integral part. Thus, this volume strives to overcome our modern preference for compartmentalizing knowledge, particularly scientific knowledge, in order to understand the more complex processes by which Hellenistic astronomy came to be the paradigmatic science that it was, and came to represent, as against a number of alternative cosmological pictures, a basic geocentric, spherical construction of the universe that lasted until the Early Modern Period.

Accordingly, we have divided the volume into three parts:

1. Technical Requirements;

2. Observations, Instruments, and Issues; and

3. Contexts