posted 01-28-2006 01:14 PM            

Hero (or Heron) of Alexandria (c. 10–c. 70) was a Greek engineer and geometer. His most famous invention was the first documented steam engine, the aeolipile. He is said to have been a follower of the Atomists. Some of his ideas were derived from the works of Ctesibius.

A number of references mention dates around 150 BC, but these are inconsistent with the dates of his publications and inventions. This may be due to a misinterpretation of the phrase "first century" or a confusion of this Hero with other Heros- Hero was not an uncommon name.

Publications
The complete surviving works are

Pneumatica (Greek, c. 60),
Automata (Greek),
Mechanics (Arabic),
Metrics (Arabic),
Dioptra (Arabic).
In optics, Hero proposed that light travels along the shortest geometric path. This view is no longer accepted, having been replaced by the least-time principle.

In geometry, he stated and proved the result now known as Hero's or Heron's formula, which expresses the area of any triangle in terms of the lengths of its sides:

where s is the triangle's semiperimeter:

He also came up with an iterative process for calculating square roots of numbers.

Hero is credited with inventing many feedback control devices using water, fire and compressed air in various combinations, and the first type of analogue computer programming via intricate systems of geared spindles studded with pegs and wound with ropes connected to weights (trays of sand emptying over time) used to operate his automatic theaters that included automatic doors and multiple changing scenes of moving figures accompanied by lighting and sound effects.

Projects
steam turbine (50/62/70) (Aeolipile) - the first recorded steam engine, which was created almost two millennia before the industrial revolution, which was powered by steam engines. Apparently Hero's steam engine was taken to be no more than a toy, and thus its full potential not realized for quite some time.
automatic temple doors - controlled by the temple priest lighting an altar outside of the temple, which heated water beneath it, which then moved counterweights which would open the doors. When the fire was extinguished, the water would cool and thus return the counterweights to their original position, which closed the temple doors.
First automated, coin operated Vending Machine called Pneumatica- to vend holy water for temple worshipper to cleanse their hands
Machine gun (which fired arrows), mechanical bow (which could fire arrows with great strength), and hand-powered catapult - these were designed but not realized because the needed materials were not yet available.
water organ or hydraulic organ
Automated puppet theatres using a complicated series gears, rods, and rope to move small wooden figures on a "stage". Rope was wrapped around wooden rods with carefully placed pegs. As the rods rotated, the rope would unwrap accordingly, and this initiated gears and other mechanisms to move, thus putting the figures in motion. This was a primitive but effective form of computer programming.
omen machine - temple patrons asked a simple yes or no question, and by descretion of the priest, the answer was yes or no depending on whether the mechanical bird sitting on the top of the box would sing and twirl or not
water-powered mechanical birds - this was used in Hero's omen machine as well as entire flocks of mechanical birds. Realistic chirping sound effects also produced by a water device.
compressed-air fountain (see Heron's fountain)
siphons - this powered many of Hero's projects
machine for threading wooden screws
automated machine for moving full-scale theater set pieces
density of air
odometer
naval log, a variation of the odometer to be used at sea
Deep study (if not invention) of the dioptra, a surveying device similar to the theodolite, sophisticated enough to, for example, construct a tunnel through two opposite points in a mountain..
http://en.wikipedia.org/wiki/Hero_of_Alexandria