The practice or art of using sunlight reflected by mirrors to transmit signals or create images, or the technique and science behind such methods.
From Greek 'helios' (sun) + 'graphia' (writing/recording). The broader term encompasses the entire field of sun-based signal and image transmission developed in the 19th century.
Heliography sits at the intersection of physics, engineering, and military strategy—understanding it teaches you how geometry, light, and human ingenuity solved communication problems before electronics!
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