A temporal analysis really has to consider the impact the time traveler has on all of history.  Thus if in the first episode of the sixth season of Star Trek:  The Next Generation, Time's Arrow part II, several crew members travel to the nineteenth century, it is necessary for the analysis to consider what impact this has on their Encounter at Farpoint when the crew is just forming in season one, or on Guinan who joins the crew in the first episode of season two, The Child, but who apparently (we later learn) had previously met some of them in that past time--and on every other episode to that point.

Complicating it further, a television series that decides to include time travel will almost always do so more than once.  Time's Arrow was neither the first nor the last episode in which members of the crew of that ship traveled to the past, and each such trip has the potential to interact with the others.  It is entirely possible that at the end of the series, a final time travel episode would change events through its entire run.  That means you really cannot analyze the time travel in a television series without taking the series as a whole--potentially hundreds of hours of viewing, with which the reader might not be sufficiently familiar to follow the discussion.  Doing an analysis involves becoming familiar with the story in detail--the details are often critical, and no analysis has been published without reviewing the movie at least three times, sometimes as many as twenty, to confirm the minutia.  This would be impossible with a television series.  Besides, once the series has ended, interest lags significantly.  That is part of why most series end.

It is certainly true that movies also come in series, such as the Terminator collection, Back to the Future with its Part II and Part III, and the old Star Trek movies (along with the 2009 addition).  However, movies are released not closer than a year apart, are much shorter, and are frequently viewed on video and television for decades afterwards.  Even when they might impact events in previous movies (or in previous television episodes), they are generally much more self-contained as stories, and those impacts easier to untangle.

Additionally, television series have different writers at different times, and they often treat time travel differently from one episode to another.  Some episodes may be brilliant, while others might be disastrous, and if no effort is made to achieve consistency in the time travel rules, the analysis will be as inconsistent as the show itself.  That matters less with movies, which might treat time differently from one to the next, but are inherently more self-contained.

This is compounded to some degree by the difficulty for the reader to find the right episodes.  That is less of a problem today than it was when this effort started in 1997, but it is still more challenging for most of us to locate specific episodes of old television series than to get copies of most movies.  If the reader has not seen the show being discussed and cannot easily get it, the analysis has a very limited appeal.  This author first encountered time travel in the 1960's Time Tunnel television series and H. G. Wells' wonderful novel about English class stratification The Time Machine, but few readers of this site will be directly familiar with either of those.

Many of these problems apply as well to books, which although not usually serialized or episodic or inconsistent (although Poule Anderson's Time Patrol is all of these) are still more effort to read and so have a smaller audience; and to video games, which require effort to play so as to discover the story events, and comic books, which have a more limited audience.  There are, meanwhile, hundreds of movies with time travel elements in them, and thus plenty to analyze in the years ahead.

As always, the author welcomes questions by e-mail or in comment postings, and will offer opinions on any scenarios presented in such communications, as able.