So, You’re Lost in the Space-Time Continuum? A Pop Culturist’s Guide to Time Travel
(TL;DR - Time travel is a very complicated bit of scientific gobbeldygook -- the technical term is Seriously FUBAR -- but, with the help of pop culture entertainment, you may be possible to survive and not be a mass murderer -- emphasis on "mass". Also, despite their inclusion in the header, neither Bill nor Ted are mentioned below -- because those two totally excellent dudes never met a rule they couldn't break!)
So, you're lost in the space-time continuum, huh? Don't panic, it happens to the best of us.
One minute you're minding your own business, listening to a pod cast you downloaded from iTunes onto your MP3 player or watching a streaming movie from any number of websites on your TV or reading a book on your tablet computer -- you know, something obviously indicative of our modern age. The next minute you find yourself in the same balcony box at Ford's Theater with President Lincoln or riding atop one of the many armored elephants crossing the Alps with Hannibal Barca's Carthaginian army or hunting dinosaurs with Cro-Magnon men led by Moses and Hercules -- you know, something that reeks of the ancient or prehistoric past, and most likely literally. It doesn't matter how you got there, or then, you're there then and you need to know what to do next, or if you can do anything at all, much less should. This guide is meant to help you navigate the confusing rapids of the time stream with little to no Universal destruction.
First things first: Do you still have access to the time machine that enabled you to make this temporal jaunt to begin with? If yes, stay perfectly still for a second and don't touch a damn thing. If no, then welcome to a consequence free existence! Any of the following rules of time travel are still likely true for you but, since you're trapped there and then with no hope of ever returning to your own time, you may as well do whatever you want since you have no way of testing these rules empirically. "Whatever happens, happened" is a phrase we're going to come back to, but in you're case it's 100% literal. So, go nuts, time traveler, you may as well enjoy yourself whenever you are. Because no matter what happens, you're probably going to bed dead soon -- whether from being considered a witch or because you can't eat the local delicacies dripping with bacteria that your precious stomach can't handle. The past is a very dangerous place to go.
If you're still reading this, then you still have the capability of returning to your own time, at least theoretically for now. Before you start experimenting with the fabric of existence, be sure to mark the exact moments and places of both your departure from the present and your arrival in the past. You're going to need to return to these exact points in space and time for every future trip, so we can narrow down exactly your quantum and physical limitations. Ignore what Bruce Willis said in Looper, the ramifications of your continued presence in the past is pretty important and worth some level of healthy scrutiny.
With your chrono-coordinates are set, you're ready to start messing with history!
According to leading chaoticians like Drs. Ian Malcolm and Ashton Kutcher, there's a very good chance that simply traversing backward through time and arriving at a date on Earth prior to the one you left means that you have already altered history sufficiently to never return home. This is most often regard to as "chaos theory" or "the butterfly effect" but can also be referred to as Chaotic Time, and it means that you're probably screwed if you wanted to humblebrag about your time travails when your sexy office mate is within earshot. However, if you have no loyalties in your present-day life, then Chaotic Time is the perfect way to change, well, everything with very little effort. Originally fictionalized by Ray Bradbury's A Sound of Thunder (movie adaptation starring Ed Burns and Ben Kinglsey to be avoided at all costs, no matter when you are), the "Time and Punishment" segment from "Treehouse of Horror V" of the Fox animated hitcom, "The Simpsons," illustrates perfectly what may be about to happen to you.
Immediately, prior to doing a damn thing besides breathing, go back to the present you left behind. When you've returned: go about some of your every day chores, check the news, check your Facebook, call mom, anything that can help you verify if you are indeed "home." Certainly, if you find your previously just-above-poverty living situation has been relocated to a McMansion, or John McCain is beginning his second term as Lord Comandante of the United Columbian Colonies, your mere presence in the past inarguably altered all of human history from then on. Even if everything else is the same but the world merely rains donuts, or everyone eats with their now snake-like tongues, you did it. You changed the past!
However, if nothing seems out of place or out of the ordinary, it's extremely likely that simply travling back in time changed nothing. At this point it's reasonable to assume that if you can change the past, then it's going to take an act on a far larger scale than just existing or stepping on an insect to make any difference. (Assuming, still, that you can make any difference at all, ever.) If that's the case, there are still many possibilities for what might occur and you're just getting warmed up. Since breathing in the past seems perfectly safe, let's return there now.
Before you start mercilessly slaughtering every butterfly you see, take a look at your surroundings. If there are people near you, like, say, an about-to-be-dead Great Emancipator or the Carthaginian scourge of the Roman Republic, be sure to note how they are reacting to your sudden appearances out of seemingly thin air. If you arrived at a spot without any people, the same test can be achieved with any other living creature provided you try to make yourself known. Are the people/animals shocked and appalled by your presence, not to mention your curiously comfortable clothing, or have they noticed you at all? If you haven't been noticed, try poking someone in the eye. If you still aren't noticed or your hand passes right through said person's retina like a hot ghost through butter, then you have successfully demonstrated an aspect of the Novikov Self-Consistency Principle. The principle states that in order to avert a Universe-destroying paradox, time travelers can not change the past. Here, as illustrated in Charles Dickens' holiday classic, A Christmas Carol, your atoms have been fundamentally altered so that you're more akin to consciencious energy than a human-like object with actual mass. Neat, huh?
Yes, it turns out Dickens was better at science than even he probably realized. It should be noted, of course, that the "A Christmas Carol" episode of "Doctor Who" (shown above) is perhaps the worst example of this principle, as those who time travel can and do interact with the world of the past.* But this is the only mention of that long-lived British sci-fi show in this entire guide, and woe be to the person who discusses time travel without at least mentioning the good Doctor once. If you find yourself little more than apparition in the past, well, your plan to stop Lincoln and save Hitler (or whatever) will never come to pass. But you can still navigate history to your liking without worrying about your own death, or the deaths of billions of humans who have ever lived on this planet. You can also witness your own past, fill in those nostalgiac holes in your heart far better than that one time you rediscovered your favorite middle school mix tape after coming home for Thanksgiving your freshman year of college.
Now that we know you are, in fact, still of a corporeal nature, there's still the matter of precisely how much control over past events you actually wield. By now, surely somebody has noticed your presence, since you've just appeared and re-appeared from nowhere three simultaneous times, so it's best to proceed with caution. As mentioned earlier, the phrase "whatever happens, happened," which was made famous by Daniel Faraday on "LOST" and refers to another, separate aspect of Novikov's principle, could very well still be at play. Essentially, it means that whatever you do next is the way things were always done, so you have always traveled to this point in time and committed the act you're about to commit. Weed smoking philosophers call this Eternalism, but it's perhaps more easily understood as the Predestination Paradox and both theories could very well determine what you do or do not do next. So, hopefully you're somewhen in a situation of which you know the final outcome.
Let's check our moral compasses at the time-door and stay with the Lincoln analogy, just so we have clearly defined parameters for our measurement. You need to shoot that President, or try to. (By the way, you really should have a weapon with you every step of the way as your time travel, because safety is absolutely not guaranteed.) So what happens when you try to shoot old Abraham? If your gun jams or you're prevented from getting a clear shot by the wily Mrs. Todd Lincoln tackling you to the ground -- anything at all that stops your bullets from riddling our 16th President -- then that means Novikov is still in effect and the Universe is now actively working against you. This would also be a good time to make your escape. It's highly doubtful that the Secret Service are going to cotton to a crazed weirdo dressed like a clown and who tried to assassinate the President of the United States of America remaining in his seat to enjoy the show. It's okay, though, Our American Cousin can't be better than the 1985 Canadian film reboot. Not to worry: Since you have a time machine you can always return to the point just before you whipped out your gun.
Unless, of course, you were actually able to shoot President Lincoln. Were you? If so, then it still behooves you to make a quick getaway because -- congratulations? -- you're John Wilkes Booth! At least, you are if Novikov is still in effect. Do you have a beard and a waistcoat where suddenly you didn't before? It's also possible that the identity of Lincoln's assassin was moot and you're still you, just a you who senselessly murdered the greatest President ever. The only way to be sure is to return "home" and check Wikipedia's entry on the topic. Suffice to say, whatever happened, it's best to just go with it because it always meant to be.
The same cannot be said, however, if when you failed to kill Lincoln you also lost your gun in the ensuing fracas and then that gun was used by the original assassin to do the deed. Derringers are frowned upon for many reasons, and this is merely the most obvious one. If this happened, then you have suddenly found yourself committing an Ontological, or "Bootstrap," Paradox, so named for the Robert Heinlein short story By His Bootstraps. It is perhaps most easily understood by way of James Cameron's Terminator films, wherein the time traveling robots (T-800s) and the program that gives them artificial intelligence (Skynet) were created by the remains of the first time traveling robot sent back in time by that same future artificial intelligence.
Basically, this means that if you hadn't traveled back in time with the exact object required for a specific task or outcome to be achieved, that task or outcome may not have happened at all, and because the object is from a different time it shouldn't theoretically exist. That it does is the paradox. However! Because the object, e.g. your President shooting pistol, exists within it's own time loop, then Novikov hasn't been violated. You haven't necessarily changed anything, and time is passing as it did before and the Universe isn't about to implode. But it still means President Lincoln's assassination on April 14, 1865 was entirely your fault. Don't blame this guide for telling you to pull that trigger or bring that gun with you, clearly you would have done so anyway. You monster.
If murdering beloved historical figures is less to your liking, there is another way to test Novikov's principle that is somewhat less morally repugnant. Normally referred to as the Grandfather Paradox, what this theory lacks in political assassinations it makes up for in good, old fashioned patricide. Basically, instead of traveling to the past to witness great historical moments, you've traveled back in time to murder your own grandpa. Who knows why? Because he called you "dumber than dirt" your entire childhood and died before you could ever get your sweet, sweet revenge? To really see how much you can effect the time stream, you'll need to travel back in time to kill Peepaw before you or your parents were born. If Novikov was right, you will find this just as impossible a task as killing Lincoln was had you gone that route. If Novikov was wrong, your mission may be a success but you've just killed yourself, poindexter, because now gramps can't spread his seed down to you. Good job!
Then again, since you no longer exist that means you never traveled back in time, and so your grandfather is still alive to hate you in 50 years' time. That Novikov is an even wilier sonovagun than the lady Lincoln. However, there is a cleaner, if morally ambiguouser, option as seen in the "Futurama" episode, "Roswell That Ends Well." You can call it the Grandmother Paradox, though matricide may or may not be necessary. If you impregnate your Gam-gam first (gross, but necessary), or if you're a woman you'll need old Peepaw to impregnate you (also gross, also necessary), then in nine months you will have become your own grandfather or grandmother. Should this succeed, Novikov hasn't been violated and you now know that the past can change so long as the basic outcomes stay the same. Since you are also your own bootstrap at this point, feel free to take out that young/old bastard who will wrong you in the future. As far as the Universe is concerned, gramps's life is now forfeit. How does dad's dad like you know, eh?
Now that you have successfully determined your impact, or lack thereof, on the past, it's a good to determine exactly what your actions are doing to the Universe's timeline(s). There's no need to discuss Immutable Timelines because that just means that Novikov was proven correct throughout and you can't really affect anything substantially, so you may as well go back to the present and play some XBox. However, Mutable Timelines are still on the table if you managed to affect any historical changes at all in your prior tests. There a three distinct variations on this theme, the first of which involves Plastic Time , which was rather expertly showcased in the Back to the Future trilogy.
As Marty McFly and Doc Brown race through the past, they are doing so on a single timeline in a single Universe. So every with every new iteration of the timeline, every change they or Biff Tannen make (now there's a grandpa who deserves to be paradox'd) their entire history and the memories of those still living within the time stream are completely altered to reflect those changes. Sure, it adds drama to the movies, but that really means all of existence is constantly being rewritten from numerous divergent points, and there must eventually be diminishing returns when you make copies of the Universe based on copies of copies of copies. Keep that in mind as you jump back and forth through history, okay? You could be slowly unraveling the fabric of space-time and there's nothing even the wildest, silver haired genius can do to fix that.
A Universally safer theory is the possibility of Alternate Timelines , which means that rather than rewriting the timeline, you have actually been creating new timelines that branch off of your original timeline. Confusing? Not really, Einstein. Basically, whereas with Plastic Time your experiments were disassembling and reassmebling existence with every trip, this theory states that you were simply assembling new Universes that exist concurrently with the old. The 2009 reboot of Star Trek shows this working in both literal and meta senses. As far as the characters are concerned, they know there's another reality out there; and the fans' memories weren't wiped out in the process. Isn't that comforting, knowing you have God-like powers minust the destructive capacity?
When Spock and his Romulan enemies enter the black hole, they are creating a new timeline but not destroying the one they came from just by the mere fact of doing so. Since the trip through time was induced by a cosmic phenomenon, there is very little chance that Spock could ever return to a Universe where his home planet of Vulcan was never destroyed. That's sad, but at least you still have the DVDs of Star Treks II, IV, VI, and First Contact. (Coincidence that half of those deal with this very topic? Not likely.) However, because you got there manually -- remember, that's how you managed to test these hypotheses earlier, with your handy-dandy time machine -- you might very well be able return to your own timeline, should you get tired of the Lens Flare Blindness common in this one. Bonus: All without continuously destroying time and space. Then again, that whole law of conservation of matter probably means that something isn't surviving the of all these burgeoning Universes...
Unless, that is, the Many-Worlds Interpretation is actually the correct one. This means that rather than creating or destroying anything when you killed Lincoln or your grandfather, you were simply traveling to timelines in Universes that already existed concurrently with your own. Rather than making changes or fulfilling predestined history, then, you were setting the not-inevitable paths of these totally standalone worlds. Just about the only thing that Fox's mercifully canceled
time travel family drama "Terra Nova" had going for it was its depiction of the Multiverse. You remember that show, right? The one about time and dinosaurs that wasn't remotely entertaining? Now that's a paradox.
Granted, only two 'Verses were shown in the series, but having those future scientists discover that the cosmic phemonenon allowed for timeline travel was the absolute only conceit that could make the show's premise logically sustainable. Similarly, knowing that you are not the Angel of Death for countless lives in all the histories across innumerable timelines will probably help you sleep at night. Many-Worlds and the Multiverse means you are not responsible for the fate of hundreds of trillions of lives, which would be enough to drive one mad, wouldn't it? And that explains the barely-contained murderous rage of Mister Peabody. Of course, you still killed Lincoln. He wasn't your Lincoln from Earth Prime, but that's still a terrible thing that you did. You really should apologize to the peoples of Earth-2 before your name becomes synonymous with Benedict Arnold and Judas Iscariot.
Or not? There is a final theory on the natures of time and space, one that promotes the possibility of a Universe that endlessly renews itself in cycles of birth and destruction. You probably like the sound of that, huh? The concept in mathematics is called Eternal Return, but a more affectionate name only found in this guide is Ouroboros Universe. If true, this means the Big Bang was just one of many birthings of the Universe, possibly the first but probably not the last, and now you've got your moral relativism needed to justify all that time-blood on your hands. What does destroying a few Universes mean if they're just going to get recycled anyway, right? Of course, the only way to prove that this is true would be to go as far into the future as physically possible, like in another "Futurama" episode, "The Late Philip J. Fry." Professor Farnsworth manufactured a future-only time machine, which means he took the scientifically easy way out as usual, so when he, Fry, and Bender accidentally travel 1000 years into their own future they've only way to get back to their own time and place...
By traveling trillions of years into the future until the Universe decompresses and blows up all over again, expanding like a mirror of the original, finally settling at the exact moment they left. You could attempt going backward again, but if you're wrong, you'll join non-existence in a singularity with the rest of matter in space. Going forward, if true, the same thing will happen but you'll come out the other side intact. Either way, witnessing the birth or re-birth of the Universe would be an awfully beautiful sight. Was murdering Abraham Lincoln in cold blood and becoming history's greatest monster worth that view?
Sorry, that's a question this guide can't answer. But, hopefully after reading, you are now more prepared when you pull the trigger this time.
* Though having the elder Scrooge-like character only able to watch the adventures via video diary is an inspired choice to maintain the original narrative's sense of historical helplessness.
Rob Payne also writes the comic The Unstoppable Force, tweets on the Twitter, tumbls on the Tumblr, and his wares can be purchased here. He's given this topic a lot of thought over the years, yet Timecop still confuses him.