Archimedes' heat ray

Device purported to be used by Archimedes to burn Roman ships

Archimedes is purported to have invented a large scale solar furnace, sometimes described as a heat ray, and used it to burn attacking Roman ships during the Siege of Syracuse. It does not appear in the surviving works of Archimedes and there is no contemporary evidence for it, leading to modern scholars doubting its existence. It was an established story about Archimedes by around 500 AD, when Anthemius described a reconstruction, and it has become the subject of speculation about its plausibility.

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