Thunder house

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A thunder house in Museo Galileo. Casa del fulmine inv 1545 IF 41785.jpg
A thunder house in Museo Galileo.

The thunder house is a scientific model which gives a spectacular demonstration of the destructive effect of a lightning bolt striking a house with an imperfect lightning conductor.

Lightning Atmospheric discharge of electricity

Lightning is a naturally occurring electrostatic discharge during which two electrically charged regions in the atmosphere or ground temporarily equalize themselves, causing the instantaneous release of as much as one billion joules of energy. This discharge may produce a wide range of electromagnetic radiation, from very hot plasma created by the rapid movement of electrons to brilliant flashes of visible light in the form of black-body radiation. Lightning is often followed by thunder, an audible sound caused by the shock wave which develops as gases in the vicinity of the discharge experience a sudden increase in pressure. It occurs commonly during thunderstorms and other types of energetic weather systems.

The small wooden house has hinged walls and carries a brass rod representing a lightning rod. A section of the conductor runs along a piece of wood placed on the façade. Inside the house is a spark gap housed in a small brass cylinder containing a small quantity of gunpowder.

Gunpowder explosive most commonly used as propellant in firearms

Gunpowder, also known as black powder to distinguish it from modern smokeless powder, is the earliest known chemical explosive. It consists of a mixture of sulfur (S), charcoal (C), and potassium nitrate (saltpeter, KNO3). The sulfur and charcoal act as fuels while the saltpeter is an oxidizer. Because of its incendiary properties and the amount of heat and gas volume that it generates, gunpowder has been widely used as a propellant in firearms, artillery, rockets, and fireworks, and as a blasting powder in quarrying, mining, and road building.

When the piece of wood is removed, the lightning-conductor circuit is broken. The lightning bolt, simulated by a spark generated by a Leyden jar, ignites the powder, whose explosion causes the house to collapse. If, instead, the piece of wood is positioned correctly, the electricity will be discharged to the ground, leaving the house intact. Filippo Lucci depicted a similar device in the Stanzino of the Matematiche of the Uffizi Gallery in 1780—clear evidence of the popularity of such demonstrations in the late eighteenth century. The same phenomenon is also visible through the use of a similar instrument called Thunder Obelisk [1]

Leyden jar device that "stores" static electricity

A Leyden jar is an antique electrical component which stores a high-voltage electric charge between electrical conductors on the inside and outside of a glass jar. It typically consists of a glass jar with metal foil cemented to the inside and the outside surfaces, and a metal terminal projecting vertically through the jar lid to make contact with the inner foil. It was the original form of the capacitor.


Miniati, Mara, ed. (1991). Museo di storia della scienza: catalogo (in Italian). Firenze: Giunti. p. 248, board n. 50. ISBN   88-09-20036-5.

International Standard Book Number Unique numeric book identifier

The International Standard Book Number (ISBN) is a numeric commercial book identifier which is intended to be unique. Publishers purchase ISBNs from an affiliate of the International ISBN Agency.

Willem D. Hackmann, ed. (1995). Catalogue of pneumatical, magnetical and electrical instruments (in Italian). Firenze: Giunti. p. 140, board n. 163. ISBN   88-09-20732-7.

"Museo Galileo - object description".

  1. "Thunder obelisk". 7 March 2012.

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