Astronomy has often been called the oldest science, and some ancient Greek authors acknowledged a debt to Babylonian predecessors. Many of the earliest Greek philosophers are credited with astronomical observations, predictions, explanations, and discoveries. Yet, throughout much of Greco-Roman antiquity – and later – astronomy was regarded as a branch of mathematics, along with arithmetic, geometry, and harmonics. This view of astronomy – as a branch of mathematics – raises questions about what constituted astronomy, as well as its relationship to philosophy.