"Gravitation crystal detector"@en . "An Gravitation crystal detector was a type of device that could be used to measure gravitational waves. It was was used by the Urbankans and Trakenites, though the gravitation crystal detectors were replaced with the interferometer by the Trakenites. (PROSE: Four to Doomsday)"@en . "An Gravitation crystal detector was a type of device that could be used to measure gravitational waves. It was was used by the Urbankans and Trakenites, though the gravitation crystal detectors were replaced with the interferometer by the Trakenites. (PROSE: Four to Doomsday)"@en . .