New Inventions. The Banu Musa (Sons of Moses), whose books on geometry aroused so much interest in the ninth century, also wrote extensively on the relationship between physics and mechanics. Mechanics so fascinated people that this field of study became known in Arabic as Urn al-hiyal (knowledge of the ruse, or deception)— expressing the wonder people felt at new inventions that seemed impossible to explain during that time. Many of these mechanical objects were made for the entertainment of the wealthy, including mechanical servants that poured drinks for guests and mechanical musicians that entertained people while they dined.

Water Clocks. Some of the earliest mechanical clocks used water to measure the passage of time. The simplest water clock is thought to be an Egyptian invention dated around 1500 B.C.E. This cone-shaped vessel narrowed toward the base, and a hole at the...