Archimedes of Syracuse was a Greek mathematician, physicist, engineer, inventor, and astronomer. The solar powered heat ray he is credited with inventing is thought by some to be a myth – but it may well have functioned based on the results of several experiments over the years.
Archimedes’ heat ray was supposedly used in the Siege of Syracuse to focus sunlight onto approaching Roman ships, causing them to catch fire. Some have theorised that highly polished shields may have been used to focus the sunlight, much in the same way modern solar thermal farms use parabolic collectors.
Parabolic mirrors were described and studied by one of Archimedes’ contemporaries, mathematician Diocles in his work “On Burning Mirrors”, so their existence and possible application was known in the same time period as the Siege of Syracuse.
Over the ensuing centuries, various parties have attempted to prove or disprove the existence of Archimedes’ heat ray using materials Archimedes would have had available to him at the time – and also with more modern materials.
A test in the 1970’s by Greek scientist Ioannis Sakkas using 70 mirrors measuring 1.5 metres by 1 metre set fire to a mock wooden ship at a distance of around 50 metres. In 2005, an experiment by students at Massachusetts Institute of Technology using 127 small mirror tiles at a distance of 30 metres from a wooden target resulted in a fire after 10 minutes of perfect conditions. A repeat of this experiment for the Myth Busters television series found Archimedes’ solar powered “death ray” was unlikely to have performed as reported and that other weaponry available at the time with the ability to set fire to ships, such as catapults, would have been far more effective and likely used.
More recently, the authors of Green Power Science have demonstrated the solar powered death ray was indeed possible. Using just 27 ordinary flat mirrors of various sizes, they were also able to set fire to a model wooden ship. Under ideal conditions, the mast of the model caught fire in under a minute. They believe Archimedes could have had access to many parabolic mirrors made of highly polished metal that would have provided a more focused reflection than flat glass mirrors; and also the necessary manpower for a substantial manual “solar tracking” system to keep sunlight focused on the ships for long enough to set them ablaze.
The video of Green Power Science’s version of Archimedes’ heat ray can be viewed here.
