Hello! Sorry, I'm not not exactly sure if this post is in the right thread. But I would just like to ask what time travel theory is appropriate, and hopefully much easier to use, for science fiction? I am planning to write a semi sci-fi short story, and it involves using time travel: to the past, then back to the present, and then also to the future. I want to have some sort of time machine or something that can be built in an underground facility, because it is set in today's present-day world (kind of like Michael Crichton's Timeline), not in some distant futuristic world, like in most popular sci-fi, that uses hyperspace technologies. I know that it involves ideas in SR and GR, involving FTL travels, and wormholes, and spacetime warps, but I'm not exactly sure how to integrate them well enough technically in the story (I care about details to make it realistic as possible). I've been reading around, and I've found that a lot of this scenarios, theories, and metrics each have their own problems and "unrealistic" possibilities (CTCs, traversable wormholes and exotic matter, Hawking's chronology protection mechanism, etc.). Are there also ideas in quantum theory that can be used? I think Crichton used "Quantum Foam" and "Quantum Entanglement" in his novel: A tech-company is trying to build a "3D fax" by using quantum computers to scan and process particle-encoding (and DNA streams for people) to deliver packages, but instead unlocked a wormhole that "delivers" things (and then later people) in Medieval France. Also, I've read that when he was writing "Contact", Carl Sagan asked Kip Thorne for help in creating a workable wormhole for his novel, and that Thorne actually worked out the maths. So what did Thorne come up with? So what are good time-travelling theories/concepts? What is the best one to use? Thanks in advance!