Red and green traffic lights have been around since the 1800s, when British traffic officers used to rotate gas lamps that burned red and green to control the movement of mostly horse-drawn vehicles.

Traffic lights have been with us since 1868, when the first gas-powered set was switched on in London. These lights used a semaphore system similar to those used by the railways of the day and ...

The most important thing to know about Fresnel lenses, before casually attempting to drop them into conversation, has to do with phonetics: "Fresnel" is pronounced "Fruh-NEL." If the silent "S" makes ...