Heron's fountain is a hydraulic machine invented by the 1st century inventor, mathematician, and physicist Heron, also known as Hero of Alexandria

Hero of Alexandria

Hero of Alexandria was an ancient Greek mathematician and engineerEnc. Britannica 2007, "Heron of Alexandria" who was active in his native city of Alexandria, Roman Egypt...

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Heron studied the pressure of air and steam, described the first

Aeolipile

An aeolipile , also known as a Hero engine, is a rocket style jet engine which spins when heated. In the 1st century AD, Hero of Alexandria described the device, and many sources give him the credit for its invention.The aeolipile Hero described is considered to be the first recorded steam engine...

 steam engine

Steam engine

A steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...

, and built toys that would spurt water, one of them known as Heron's fountain. Various versions of Heron's Fountain are used today in physics

Physics

Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...

 classes as a demonstration of principles of hydraulics

Hydraulics

Hydraulics is a topic in applied science and engineering dealing with the mechanical properties of liquids. Fluid mechanics provides the theoretical foundation for hydraulics, which focuses on the engineering uses of fluid properties. In fluid power, hydraulics is used for the generation, control,...

 and pneumatics

Pneumatics

Pneumatics is a branch of technology, which deals with the study and application of use of pressurized gas to effect mechanical motion.Pneumatic systems are extensively used in industry, where factories are commonly plumbed with compressed air or compressed inert gases...

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Construction

Heron's fountain is built as follows:

• Start with a basin, open to the air. Run a pipe from a hole in the bottom of that basin to an airtight air supply container. (Glass flasks are shown here, and serve the purpose well. Cans with airtight lids may also be used.) The air supply container stands significantly below the basin.
• Run another pipe from the top of that container up to the top of the airtight fountain supply container, which is filled with water.
• From the fountain supply container, have a pipe that reaches nearly to the bottom of the container, through the top up to the spout of the fountain. A refinement is to have the spout coming up through the centre of the basin, and the containers may be concealed in a column supporting the basin, as long as the air supply container is lower than the fountain supply container.
• Fill the basin with water.
• The water from the basin flows by gravity into the air supply container. It fills the container, displacing the air.
• The air flows into the fountain supply container, displacing the water, which shoots out higher than the original basin.
• The flow will stop when the water supply container is empty (i.e. when the water level drops below the lower end of the outlet pipe).

Motion

Heron's fountain is not a perpetual motion machine. If the nozzle of the spout is narrow, it may play for several minutes, but it eventually comes to a stop. The water coming out of the tube may go higher than the level in any container, but the net flow of water is downward.

Its action may seem less paradoxical if it considered as a siphon

Siphon

The word siphon is sometimes used to refer to a wide variety of devices that involve the flow of liquids through tubes. But in the English language today, the word siphon usually refers to a tube in an inverted U shape which causes a liquid to flow uphill, above the surface of the reservoir,...

, but with the upper arch of the tube removed, and the air pressure between the two lower containers providing the positive pressure to lift the water over the arch. The device is also known as Heron's siphon.

The gravitational potential energy of the water which falls a long way from the basin into the lower container is transferred by pneumatic pressure tube (only air is moved upwards at this stage) to push the water from the upper container a short way above the basin.

The fountain can spout (almost) as high above the upper container as the water falls from the basin into the lower container. For maximum effect, place the upper container as closely beneath the basin as possible and place the lower container a long way beneath both.

As soon as the water level in the upper container has dropped so low that the water bearing tube no longer touches the water surface, the fountain stops. In order to make the fountain play again, the air supply container is emptied of water, and the fountain supply container and the basin are refilled. Lifting the water provides the energy

Potential energy

In physics, potential energy is the energy stored in a body or in a system due to its position in a force field or due to its configuration. The SI unit of measure for energy and work is the Joule...

 required.

In popular culture

An example of Heron's fountain, built by Larry Fleinhardt

Larry Fleinhardt

Larry Fleinhardt PhD is a fictional character in the television show Numb3rs, played by Peter MacNicol.Dr. Lawrence Fleinhardt is a professor of physics at CalSci and best friend and colleague of Charlie Eppes...

, was featured in the 8th episode (titled "Tabu") of the 4th season of the television show Numb3rs

NUMB3RS

Numb3rs is an American television drama which premiered on CBS on January 23, 2005, and concluded on March 12, 2010. The series was created by Nicolas Falacci and Cheryl Heuton, and follows FBI Special Agent Don Eppes and his mathematical genius brother, Charlie Eppes , who helps Don solve crimes...

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External links

• R.Ya.Kezerashvili, A.Sapozhnikov. "Magic Fountain", at arxiv.org