According to Lucian, Archimedes invented a "death ray" by focusing sunlight with mirrors. In 212 BC, this ray was allegedly used to set fire to anchored Roman warships preparing to invade Greece. The existence and feasibility of the death ray have been heavily disputed.
The Archimedes death ray is generated by arranging mirrors or other reflective surfaces, such as polished shields, in a parabola so that sunlight is reflected to a single point. The process is mathematical and requires precise placement. In 2005, students at the Massachusetts Institute of Technology managed to use the sun in Boston Harbor to ignite a mock-up of a ship using an array of modern flat mirrors. However, because the mirrors available to Archimedes would have been much less reflective, less powerful and precise, it is likely that the death ray existed only in theory.