hi all, im realy so interest in time travel. but there is something that i couldnt understand: What is time lines, world lines and cosmic lines? how can someone travel through time using different time lines? i realy would like to understand this with details because if it is possible to travel through time and that anyone can do it ,, i would like to know how. is it this just a theory as the relativity of Einstein which cannot happen untill now?? or it is a theory that can be achieved as experiences?? anyway, waiting for replies. thank u Hadeka.