The general theory of wormholes is discussed by Visser in the book "Lorentzian Wormholes". Investigating another wormhole, Moya belonging to a race called Pathfinders, experts in wormholes. If traversable wormholes exist, they could allow time travel. The star systems can contain moons, planets, stations, wormholes, asteroid belts and complexes. Instead, interstellar travel is accomplished by travelling through wormholes, most commonly via a train. Both Cetaganda and Barrayar have empires, acquired by conquering other planets via neighboring wormholes. His thesis film, "Wormholes", is about the theory of relativity. This is now believed to be the general fate of wormholes in General Relativity. This system uses the network of wormholes to send data between Commonwealth planets. As a student, she was interested in wormholes and quantum cosmology. This features special effect sequences of wormholes, shuttlecraft, and an inhabited exoplanet. The unstable, fluctuating nature of the wormholes makes accurate long-term mapping of them difficult. Much of civilised space is connected by a network of wormholes. Closed-curve space-time effects would be part of a field generation system to generate wormholes. In Nova, wormholes or hypergates may also be utilized for instantaneous travel.