So! Bring on the nerd-babble. Who understands the fundamental principles of time travel?
Harry Potter and the Prisoner of Azkaban. That's right, bitches: J. K. Rowling does. I would say "spoiler alert," but let's be real. If you haven't already read the book or seen the movie by this point, it's a statistical near-certainty that you don't give enough of a shit about Harry Potter to complain if I ruin an ending or two. Long story short: Hermione is a total nerd, she wants to be in two classes at once because she's lame, blah blah, oh shit magic hourglass, she can go back in time. She and Harry use the device to go back and save a couple innocent people/hippogriffs, and discover that several mysterious things that had happened over the course of the evening had actually been their own doing. Harry and Hermione don't actually change anything about they past; they just realize that they're the ones who threw the stones and made that howling noise and summoned that Patronus, and proceed to do all those things just as they happened. This is a large part of why I maintain that Azkaban was the best book in the series. Rowling got a lot of awesome-points for this, but she squandered them in the fifth book by making the title character act like a complete twat.
I could also complain that Hermione never makes use of the golden hourglass again for the rest of the series because that shit could come in handy and since she knows how the time travel thing works then she's not at all likely to kill a Future!Hermione if one shows up out of the blue and two Hermiones at once would
Right. Moving on.
Bill and Ted's Excellent Adventure. This is just a great movie. In fact, it's probably the best thing that Keanu Reeves has ever done (or ever will), but that's really not saying much. Now, it's been a while since I've seen it, so some of my details are a little fuzzy, but my favorite element is actually a relatively minor one (in comparison to the kidnapping of several historical figures, at least). When they need keys to break the aforementioned historical figures out of jail, the solution is simple: they have to remember to get in the time machine later so they can go back in time, steal the keys, and hide them in the bushes right next to where they're standing now, so the keys will already be there in the present when they're needed. And what do you know--it works! They haven't done it yet, but the knowledge that they will means that the keys are right where they need to be. It's so brilliant that only two morons could figure it out! That's some zen shit right there.
8-Bit Theater and Atomic Robo. While Brian Clevinger's work is best known for screwball dialogue and senseless cartoon violence, he actually has a damn fine grasp of space-time theory. This is evident near the end of his webcomic 8-Bit Theater, when the nigh-omnipotent sage Sarda explains to the
Things get substantially more complex in Atomic Robo and the Shadow from Beyond Time: the eponymous badass wisecracking robot (built by Nikola Tesla) has to face off against a (literally) Lovecraftian abomination that somehow exists outside of time. It intersects with our time-stream at several points in the twentieth century, and each time Atomic Robo fights it and ends up inside of it. But since it's just one creature and it's experiencing all of its intersections with our reality simultaneously, there are actually four Atomic Robos inside it at once (it's really only the one Robo, but at different points in his existence). They all work together to destroy the creature from the inside out, with the three older Robos telling the youngest Robo about all sorts of theoretical science that he has to invent so they'll know what to do in the future. It's not technically time travel, I suppose, but it's so full of wonderful temporal mind-fuckery that I can't not include it. But: though it might be confusing to some, it actually makes a whole lot of sense.
Doctor Who: "Blink" (S3 E10). Steven Moffat wrote this, and it's all the proof anyone should ever need that he's amazing. This episode will hurt your brain if you try to puzzle out the causality involved. It's circular, really: events get their catalyst at the end, after everything has already happened--but since the Doctor is a time traveler, none of it has actually happened to him yet. This episode is also terrifying and you will never be able to look at angel statues the same way again. Hell, I can barely look at Thayer paintings anymore. If you haven't seen it, you should watch it. NOW.
Welllllllllll that's enough for now. I'm sure you all get the general point of all this, unless you're morons. So, as a final illustration of my point, I will go back in time and sum up the essence of time travel in the first sentence of my previous post.
OH SHIT YOUR MINDS HAVE JUST BEEN BLOWN.