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Excerpt from the introduction to "A History of Temporal Travel" third edition:
First of all, let me just get this out of the way, yes, time travel is possible.
Secondly, time travel is either extremely difficult or appallingly easy, depending on which way you do it.
Thirdly, and you probably already figured this out, but mistakes do happen.
We don't know when the technology to travel time was first invented, or discovered, as chronal navigation was subject to multiple thefts and subsequent anachronistic temporal inceptions. As a result we can only say that the technologies eventually came to crop up in the opening decades of the twenty second century at which point further anachronistic inceptions were impossible by virtue of lack of the fundamental prerequisite technologies.
More problematically there are unique people who, for reasons not well understood, find themselves no longer fully bound by time's flow, and exhibit strange abilities that seem supernatural to the unaware. A few of these rare individuals show evidence of being able to eschew the normal technological trappings normally required for chronal navigation.
With regard to the so-called "timeline," as you will learn time is not a line, but a woven tapestry of events with multiple outcomes. Many of the lesser inflection points create only minor disturbances that a quickly reintegrated to the "prime" sequence, while major events spur offshoot sequences that may take considerable time to converge, if indeed they ever do.