Archimedes burning mirrors


Mario Bettini - CC1.0

According to tradition, burning mirrors are inextricably linked to the siege of Syracuse and the Euryalus castle.
Burning mirrors are one of the many inventions of the genius of Syracuse Archimedes.
It is said that during the siege of Syracuse, Archimedes from the castle Euryalus would have used burning mirrors to burn Roman ships.
They speak of this event. various authors: first Galen, then Cassius Dione Cocceiano and various other authors. They add details to the earliest tales, describing burning mirrors as composed of a series of suitably oriented flat mirrors. The sun's rays concentrated by the mirrors in a single point would have been able to burn the wood of Roman ships. The described structure consisted of at least 24 large flat mirrors, arranged in a hexagonal shape on a rotating trellis on a pole fixed to the ground: the central mirror was used to direct the solar beam reflected on the lens, while the side mirrors were made to converge with a system of belts.
In reality, the ancient war use of burning mirrors is not very credible. First of all, it arouses suspicion that only late authors speak of it and there is no trace of the episode in the most ancient texts. It is also considered highly unlikely to obtain from the mirrors temperatures such as to burn the wood of the ships (temperatures above 300 ° are necessary) and to be able to build a parabolic mirror with a fire as far away as the ships must have been from the walls of Syracuse.
From historical sources, however, it is known that Archimedes really managed to burn Roman ships and that he actually created the famous burning mirrors. It is therefore believed that Archimedes, on the occasion of the Roman siege, perfected jet weapons capable of launching incendiary substances, and that the legend was born by superimposing the memory of Roman ships on fire on the actual design of burning mirrors intended for more peaceful uses.

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