Astronomy is probably the oldest of the natural sciences. Since prehistoric times, humans have looked at the sky and observed the motions of the Sun, Moon, planets, and stars. As humans began to develop the first applied sciences, such as agriculture and architecture, they were already well aware of the celestial objects above them. Astronomy was used by ancient humans to help them keep time and to maximize agricultural production; it probably played an important role in the development of mythology and religion, too.