Hero of Alexandria, a renowned mathematician, engineer, and inventor, is widely regarded as the greatest experimenter of his time. Among his numerous inventions, the windwheel stands out, showcasing his innovative prowess. One of his most notable creations is the ‘aeolipile,’ also known as ‘Hero’s engine,’ a steam-powered instrument that he meticulously described in his publications. Influenced by the works of Greek inventor and mathematician Ctesibius, Hero’s designs and writings have unfortunately been mostly lost, with only a few manuscripts surviving. Nevertheless, his mathematical contributions endure, including an iterative method for calculating square roots and the famous ‘Heron’s formula’ for computing triangle areas, which bears his name.

## Quick Facts

- Died At Age: 60
- Died on: 70
- Place of death: Alexandria, Egypt
- Engineers
- Mathematicians

## Childhood & Early Life

Hero of Alexandria was born in 10 AD. While growing up, he spent most of his time in the library of ‘University of Alexandria.’ After completing his education, he went on to teach at the ‘Mouseion at Alexandria’ (Musaeum), an educational institution which housed the famous ‘Library of Alexandria.’ Based on his writings, historians have concluded that he taught at the ‘Musaeum.’ His writings are in the form of lecture notes for courses in physics, pneumatics, mathematics, and mechanics.

## Inventions and Contributions

Hero became famous for the inventions of his automated devices. Some of his devices represent the first formal research into cybernetics. Interestingly, ‘Cybernetics’ was not formalized as a field of study until the 20th century.

Hero is best remembered for his description of a steam-powered appliance called an ‘aeolipile.’ He described the device in Roman Egypt in the 1st century AD. His description of the aeolipile is considered to be the first recorded description of a steam turbine and steam engine. A similar device was described by Vitruvius in the 1st century BC. However, unlike Hero, Vitruvius does not mention rotating parts in his description. Ctesibius (285–222 BC) who first wrote the uses of compressed air is said to have inspired the works of both Vitruvius and Hero. In 1979, an animated short film portrayed Hero as a craftsman who invents the turbine accidentally (as aeolipile).

Another important invention of Hero was a windwheel. His invention became the first machine in history to harness wind energy. His windwheel used the wind energy to play one of the oldest musical instruments, – the organ. Hero’s invention is considered as the foundation of modern-day windmills.

Though the modern vending machine was invented in 1883 by Percival Everitt, Hero is credited for the construction of the earliest known vending machine. His vending machine was constructed to perform the task of dispensing holy water. The machine had a slot to deposit a coin. Once deposited, the coin would fall on a pan which was attached to a lever. The weight of the coin would tilt the pan and the holy water continued to flow until the coin rolled off the pan.

Hero’s contribution to the field of optics is invaluable. He was the first to formulate ‘principle of least time,’ which is widely known as ‘Fermat’s principle,’ named after French mathematician Pierre de Fermat. However, ‘Fermat’s principle’ was based on Alhacen’s works on reflection and refraction, which were, in turn, based on Hero’s ‘principle of the shortest path of light.’

The famous Greek theater, which mesmerized the audience in the ancient past, was elevated to a whole new level by Hero. He used the laws of mechanics to orchestrate an entire play of almost ten minutes in length. The ‘mechanical play’ was powered by a binary-like system of ropes and simple machines. Since the mechanics involved was concealed behind the stage, the entire play had a magical effect to it.

He also invented a hydraulic machine, commonly known as ‘Heron’s fountain.’ To demonstrate the principles of pneumatics and hydraulics, different versions of the machine are used in modern-day physics classes. Heron’s fountain was featured in the fourth season of the popular TV series ‘Numb3rs.’ It was also featured in Guy Martin’s television show ‘How Britain Worked.’

## Contribution to Mathematics

‘Heron’s formula,’ which is widely used to calculate the area of a triangle, is named after him. The description of the formula is found in Hero’s book ‘Metrica,’ so the formula is credited to him. However, it is believed that the formula predates Hero’s time as ‘Metrica’ is a mere collection of the knowledge available at the time. It is also said that Archimedes of Syracuse knew the formula two centuries earlier.

Hero came up with an iterative method for calculating the square root of a number. The iterative method was first described in ‘Metrica.’ In modern-day mathematics, the method is known as the ‘Babylonian method’ or ‘Heron’s method.’ He also came up with a method to calculate the cube root of a number.

He often used his knowledge to calculate the seating capacity of a huge stadium and to estimate the number of jars that could be stored in containers and ships. He also coined many geometrical terms and pioneered geometrical symbols. He mastered a branch of mathematics called ‘geodesy,’ which is now used to measure and understand the Earth’s geometric shape, gravitational field, and orientation in space.

## Written Works

Hero is credited with writing many books that describe several of his inventions and works. A book titled ‘Pneumatica’ describes the operation of mechanical devices and toys, such as aeolipile, water organ, coin-operated machines, puppets, and singing birds. The book is basically a description of machines that harness the power of air, steam, and water.

Hero’s book ‘Mechanica’ presents a wide range of principles, including a method to lift and transport heavy objects, theory of motion, and method to calculate the centre of gravity for simple shapes. Though the original texts have been lost, an Arabic translation of the book has been preserved.

A book titled ‘Automata’ gives a description of machines that were invented to create magical effects in temples. Some of these machines enabled the automatic closing and opening of doors. The book also gives a detailed description of mechanical statues that poured wine.

Hero’s ‘Metrica’ is a series of three books. They were found by R. Schone in 1896, in Istanbul. In the book, Hero focuses on calculating volumes and surface areas of diverse objects, such as cones, cylinders, pyramids, and prisms. Another book titled ‘Geometrica’ was a collection of equations that were based on Metrica’s first chapter.