How it began
The aeolipile was invented in the 1st century CE by Heron of Alexandria and described in his Pneumatica. Heron was a Greek geometer and inventor who flourished around 62 CE in Alexandria, Egypt, and was known as Mechanikos, the "machine man". The Pneumatica, in two books, describes a collection of mechanical devices that includes singing birds, coin-operated machines, a fire engine and a water organ. Britannica calls the aeolipile his most famous invention.
How it works
A cauldron was filled with water and heated over a fire. Steam rose through a pair of hollow tubes into a hollow sphere mounted so that it could turn on them. Pressure built up and pushed the steam out through narrow outlets at the ends of two or more bent tubes set around the sphere's equator. The outlets all pointed the same way around, so the escaping steam drove the sphere to spin rapidly.
What changed first
In antiquity the device was not used as a tool or a source of power. Like other machines of the time that demonstrated mechanical principles, it was regarded as a curiosity or a toy. Its purpose remains a matter of conjecture: some sources say Heron used it to show his understanding of physics, and others speculate that it helped stage seemingly miraculous effects for visitors to temples.
What lasted
Later centuries adapted the idea. Some records say that in 10th-century France it was used to make sounds in a hydraulic organ. By the 17th century it inspired blowing tools that sent jets of steam to turn roasting spits or to raise the heat of fires for melting glass and metal. In 1543 the Spanish naval officer Blasco de Garay is said to have built a modified aeolipile to drive wheels on a ship, a project abandoned as too costly and dangerous.
Where it stands today
The aeolipile is treated as the first recorded steam engine or reaction steam turbine. Wikipedia's account notes that it was neither a practical source of power nor a direct predecessor of the steam engines of the Industrial Revolution. Britannica describes it as the first known device to transform steam into rotary motion.
