Time travel is impossible. That said, I still love the way that time travel is treated in the Terminator series. SkyNet, the evil computer that causes mankind's nuclear holocaust, sends Terminators back in time to kill the mother of it's fiercest opponent. Never mind that doing so creates a separate timeline, and SkyNet remains unaffected in its own time. In fact, in this new timeline, the alternate SkyNet does one better by sending another Terminator (the T-1000: you know, the liquid guy from the second movie) back to kill the future leader of mankind, and creates yet another timeline.

Then we get the decently made (I can't say "excellent", not yet) TV series Terminator: The Sarah Connor Chronicles. To complicate things further (and provide enough plot elements to last 5 seasons), the good guys and the bad robots are sending many Terminators/people to many different points in time, making a chronology too twisted to explain properly in text.

So I made a handy chart.

Fortunately, the producers of the show declared that Terminator 3: Rise of the Machines is NOT canon for the TV series, which simplifies things greatly. I made an earlier chart, trying to reconcile the discrepancy between T3 and the show, and it gives me a headache.

But Time Travel Is Impossible!

Yes, it is, but it's fun to think about. Or consider this:

Given a multiverse of infinite alternate realities, there must be some reality that is exactly like ours, except that there it's 30 years ago. By traveling to this alternate universe, it's like you're traveling back in time, but you really aren't. To see the results of your meddling, you can either wait 30 years, or go to yet another alternate reality which resembles our universe exactly, except that a person who was exactly like you appeared there 30 years ago and interacted with it. Okay, so it's not exactly time travel, just a really complicated way of navigating alternate universes. It also solves the whole "Earth is moving so time travel would send you into space" problem.

Thinking about infinite alternate realities is not fun, however. You can just say, "well, there's a reality out there for every possibility, so everything's been done." Not so great for storytelling. For the Terminator TV series to go on, the characters have to be grounded in a single reality that they must cope with. Even if their reality is a byproduct of altered timestreams of other realities, it is still where they exist and cannot escape from (unless they travel in time yet again).

We have to stick with one set of characters, too, because otherwise they become immortals and godlike - which only works in fiction as a joke. For a serious drama, which TSCC is attempting to be, it requires dutiful attention to the mortality and vulnerability of the characters, otherwise they become as soulless as the machines they fight.