Disclaimer: I am an aeronautical engineer with a background in fluids. My knowledge of cosmology only extends to articles and things I read before I go to sleep. So, here is my question: I have though about time travel, as many other people have. Currently we think it may not be possible, as it would require moving faster than the speed of light. But what if we could travel "backward" in time with a manipulation of the geometry of space? The weird part. Imagine we are in a universe where spacetime is shaped like a cylinder...more specifically a coffee cup. Imagine the z axis represents time, while the radial axis represents space. The future is in the direction of positive Z. If we were to imagine time flowing such that along the main cylinder (the "cup" part of this strange geometry) it is advancing into the future, but when it goes into the handle part, time still advances forward, but in the opposite direction. That is to say, if we were to "travel" through the handle in our coffee cup universe, advancement in our future would result in us ending up in the past. Imagine a sequence of events representing time as a fluid flowing through the cup and recirculating in the handle. Maybe a more concise question will help: Can spacetime be flat, but have closed loops which would bring you into another part of space and time. Could "time" in these loops travel in a different direction than the main part of space, but still be advancing into the future? In these sense one could time travel without actually ageing or moving faster than the speed of light, or relying on any other crazy physics except a coffee cup shaped universe. If this question isn't clear I can draw a sketch and upload it.