Astronomical measurement began before recorded history. Early astronomy was concerned mainly with establishing the calendar, which was of great importance to the first agricultural societies, who needed to accurately predict when to plant and harvest crops. The earliest collection of astronomical data that has been found dates from the Babylonian Empire of the fifth century B.C.E. Astronomical records were kept on clay tablets and consisted of intricate sequences of numbers that were used to calculate the daily positions of the planets.

Much of what is known of early Greek mathematics was written almost a thousand years after the events occurred. A work known as the Summary of Proclus, written in the fifth century, refers to a lost history of geometry that was written around 350 B.C.E. by Eudemus, a pupil of Aristotle. Eudemus credited Thales with being the first geometer. According...