Time travel science

My personal favourite time travel theories are the branching timelines one (this avoids paradoxes), and Homestuck's version with stable timeloops and doomed timelines (basically what happens is that basically instead of time being in a single dimension, it can sort of be "wrapped back" and then a later future version of the time traveller coexists with the present version, who will later become the future version. Any deviation from this (for example, the "present self" doesn't travel back in time to become the future self) will result in a doomed timeline where all inhabitants are destined to die. (that was badly explained, but whatever)).