A logic paradox I hear a lot is the time-traveler scenario, and it goes a little like this: “If time travel is possible within this universe and one can travel back to the past and potentially alter the future, why haven’t we seen any time travelers?” It’s a good question, seems to make sense on the surface, but, aside from the obvious explanation (time travel isn’t possible; nerds everywhere wail and gnash their teeth), I believe there’s another possibility that makes sense.
We haven’t seen any time travelers because we haven’t invented a time-travel method yet.
In order for time travelers to exist, they must have some way to reverse the normal causal chain of events (for example, a machine with wibbly-wobbly bits, or mysterious meditation techniques, or an eighteenth-dimension wormhole), and (here’s the important part) they cannot travel any farther back in time than the very first implementation of that method. We’ll call that Point Zero, mainly because it sounds pretty cool.
The reason they can’t go past Point Zero is that if they do, they change the circumstances leading up to the creation of that time-traveling method, thus preventing its existence, thus splattering themselves across the temporal boundary of nonexistence and dissipating into a fine mist that was never there. If you kill your grandfather when he’s a boy, then you never exist, and therefore the possibility of you killing your grandfather never exists (the normal paradox there continues with “but then your grandfather exists so you exist so you can still go back and kill him blah blah,” all of which is unimportant because it’s not dealing with the actual method of traveling back). The universe continues on its way sans one temporal wanderer.
Think of Point Zero as a lighthouse that’s also a wall—the window of events you can potentially travel back to grows wider and wider as time marches on, but you can’t go past that wall; you simply don’t exist once you get past it. Events may constantly change and fluctuate as travelers slip back and forth, but the existence of the method is the only solid constant in a sea of chaos.
So this is great news, right? All we have to do is actually invent a way to time-travel, and we can fix all our mistakes from that point forward. We’ll create a utopia, keep going back again and again to ensure the most desirable outcome until it’s all sugarplums and gumdrop fairies, blissful perfection. Anytime something bad happens, we’ll just rewind a little bit, reload that last save, and make it so it never occurred.
Not so fast.
You see, whenever someone travels back, he completely wipes out whatever happened in the universe from the point he traveled back all the way to the point he arrived at. Butterfly effect, chaos theory, fractal branching—a tiny change introduced into a complex equation (and what could possibly be more complex to us than the universe?) alters the outcome in a million billion tiny unforeseen ways, ripples propagating across an infinitely vast pond, and the more time that passes, the larger the divergence. A traveler from Imperialist Singapore looking to slightly alter the path of genetic research brings about the rise of the Fifth Sudanese Reich, crushing the nascent island empire before it can encompass the world; a Free Anarchy Moscow agent slips back to alter the marriage ceremony of the duke of America for tax-break purposes and plunges half the planet into nuclear winter that a Mutant Jesus Reborn cleric then prevents from ever happening; competing travelers all racing back earlier and earlier in order to wipe the others from existence by preventing them from ever being born; the one constant being the ability to travel back to when that first switch was flipped…
Unfortunately, the farther your timeline is from Point Zero, the more certain it will be erased in less than an instant when someone travels back to change things for his own interests, and only one person will ever know you existed (until that person too is negated by someone who arrived a picosecond earlier) (who will be obliterated in return) (and so on and so forth). Traveling back a small distance produces small changes; traveling back a large distance produces impossible changes, and trillions of possibilities will occur and disappear without any sign of their passing. Countless loves will never be consummated, countless wars will never raze countless hopes and dreams, countless scenarios will never resolve—because someone will always be heading back to Point Zero to rebuild the world the way he thinks it should’ve originally been.
In fact, once time travel is invented, the only actual outcome anyone will ever see is the incomprehensively brief instant that is the smallest unit of time possible in this universe before the method is destroyed—by either the massive influx of would-be alchemists fighting over who gets ultimate control, or whoever finally figures out that the only way to create a stable future is to blow up any possibility of rewriting it. All it takes is one person in the infinitely large realm of timelines to go back to Point Zero and shut the whole thing down, and we’ll never even know what led him to do so.
We can only hope the explosion isn’t too big.