Within the "Stargate" fictional universe, Stargates are large metal rings with nine "chevrons" spaced equally around their circumference. Pairs of Stargates function by generating an artificial stable wormhole between them, allowing one-way travel through. The symbols on the inner ring of the Stargate correspond to constellations and serve to map out coordinates for various destination planets and other locations in space. A typical Stargate measures in diameter, weighs , and is made of the fictional heavy mineral "naqahdah". The Stargates were created millions of years ago by an alien race known as the Ancients; their modern history begins when Egyptologist Daniel Jackson deciphers their workings in the "Stargate" film.