The authors, Michael S. Morris, Kip S. Thorne, and Ulvi Yurtsever, explore the possibility of advanced civilizations creating and maintaining wormholes for interstellar travel, and the potential for these wormholes to be converted into time machines. They argue that if such wormholes can be created, they might violate causality by allowing time travel. The paper discusses the deep issues surrounding cosmic censorship, quantum gravity, and quantum field theory, including whether field theory enforces an averaged version of the weak energy condition (AWEC). The authors begin by examining the creation of wormholes, which requires the violation of the weak energy condition and the presence of closed timelike curves. They then consider the maintenance of wormholes using quantum field theory stress-energy tensors, which must also violate the AWEC. The paper delves into the conversion of wormholes into time machines, where an advanced civilization can manipulate the motion of one wormhole mouth to create a closed timelike curve, potentially violating causality. The authors also explore the stability of the Cauchy horizon, a boundary between regions with and without closed timelike curves, and suggest that it may be stable, challenging the strong cosmic censorship hypothesis. They propose that physical fields, both quantum and classical, evolve uniquely through this horizon, and discuss the implications for causality and free will. Overall, the paper raises intriguing questions about the constraints imposed by the laws of physics on advanced civilizations and the nature of time and causality.The authors, Michael S. Morris, Kip S. Thorne, and Ulvi Yurtsever, explore the possibility of advanced civilizations creating and maintaining wormholes for interstellar travel, and the potential for these wormholes to be converted into time machines. They argue that if such wormholes can be created, they might violate causality by allowing time travel. The paper discusses the deep issues surrounding cosmic censorship, quantum gravity, and quantum field theory, including whether field theory enforces an averaged version of the weak energy condition (AWEC). The authors begin by examining the creation of wormholes, which requires the violation of the weak energy condition and the presence of closed timelike curves. They then consider the maintenance of wormholes using quantum field theory stress-energy tensors, which must also violate the AWEC. The paper delves into the conversion of wormholes into time machines, where an advanced civilization can manipulate the motion of one wormhole mouth to create a closed timelike curve, potentially violating causality. The authors also explore the stability of the Cauchy horizon, a boundary between regions with and without closed timelike curves, and suggest that it may be stable, challenging the strong cosmic censorship hypothesis. They propose that physical fields, both quantum and classical, evolve uniquely through this horizon, and discuss the implications for causality and free will. Overall, the paper raises intriguing questions about the constraints imposed by the laws of physics on advanced civilizations and the nature of time and causality.