The history of science in early cultures covers protoscience in ancient history to Islamic science. In these times, advice and knowledge was passed from generation to generation in an oral tradition. The development of writing enabled knowledge to be stored and communicated across generations with much greater fidelity. Combined with the development of agriculture, which allowed for a surplus of food, it became possible for early civilizations to develop and spend more of their time devoted to tasks other than survival, such as the search for knowledge for knowledge's sake. Ancient Near East Mesopotamia From their beginnings in Sumer (now Iraq) around 3500 BC, the Mesopotamian peoples began to attempt to record some observations of the world with extremely thorough numerical data. A concrete instance of Pythagoras' law was recorded as early as the 18th century BC—the Mesopotamian cuneiform tablet Plimpton 322 records a number of Pythagorean triplets (3,4,5) (5,12,13) ..., dated to approx. 1800 BC, over a millennium before Pythagoras, —but an abstract formulation of the Pythagorean theorem this was not. Astronomy is a science that lends itself to the recording and study of observations: the rigorous notings of the motions of the stars, planets, and the moon are left on thousands of clay tablets created by scribes. Even today, astronomical periods identified by Mesopotamian scientists are still widely used in Western calendars: the solar year, the lunar month, the seven-day week. Using these data they developed arithmetical methods to compute the changing length of daylight in the course of the year and to predict the appearances and disappearances of the Moon and planets and eclipses of the Sun and Moon. Only a few astronomers' names are known, such as that of Kidinnu, a Chaldean astronomer and mathematician who was contemporary with the Greek astronomers. Kiddinu's value for the solar year is in use for today's calendars. Astronomy and astrology were considered to be the same thing, as evidenced by the practice of this science in Babylonia by priests. Indeed, rather than following the modern trend towards rational science, moving away from superstition and belief, the Mesopotamian astronomy conversely became more astrology-based later in the civilisation - studying the stars in terms of horoscopes and omens, which might explain the popularity of the clay tablets. Hipparchus was to use this data to calculate the precession of the Earth's axis. Fifteen hundred years after Kiddinu, Al-Batani, born in what is