People are often confused by time-travel. They tend to think of time as a series of events. A progression from A to B to C and so on. But, in fiction, there is time-travel, which forces us to think of time in a more sophisticated way. Often however, the radical departure from the usual nature of chronology causes people to simply give-up and say “Oh well, it doesn't make any sense to me, but it's all nonsense anyway.” But that's simply not the case.
Time-travel is a trope used in fiction, but comprehending a more nuanced form of continuity is important. Not just because wrapping one's brain around something confusing makes us smarter, but because because of recent discoveries in quantum mechanics, it seems that time-travel has more legitimacy than was previously thought.
For the purposes of discussing time-travel, first, one must figure out what kind of universe one is talking about. There's your conventional universe, like the one we live in, where chaos theory reigns. There's your deterministic universe, where every event is quantifiable and every outcome predictable. That's the kind of universe people thought they were living in until last century, when scientists began discovering the bizarre world of wave-particle duality, and quantum interference patterns. Then you've got your magical universe, where the rules are only as consistent as an amulet's current owner.
Today we're going to be talking about time-travel in this universe. As this is still an untested technology, it's unclear what type of time-travel is allowed by the fundamental laws of the universe. But until many-worlds-theory is either proven or dis-proven, there are two basic categories of time-travel possible within our universe.
The first-type is “Solid-State Time-Travel” and the second is “Many Worlds Time-Travel”. In this explanatory piece, we'll be focusing on Solid-State. Many Worlds will have to wait.
In a solid-state timeline, every instance of time-travel must be considered to have already happened.
Let's pick a time-machine. You've got your steampunk spinny-wheel H.G. Wells type, you're Deloreans and your TARDISes. The simplest one here is the obvious choice for the purpose of explaining the nature of time-travel. So we're going with the TARDIS type.
One day, you find yourself in a bit of a jam. You're on your way to a date, when someone brushes up against you. You catch a brief glimpse of a flash of light reflecting off their sunglasses. While you didn't realize it at the time, that person was picking your pocket. Later, when you try to pay for a cab, you discover that you're wallet has been stolen. After the cab-driver yells at you for seven minutes, you head over to a friend's house on foot. On the way there, you see a big blue box, and as a science-fiction aficionado, you recognize that it is a TARDIS. Suddenly, it seems that you have a way of reclaiming your wallet. You just need to go back in time to yesterday, and take your wallet from the bedside table where you left it while you slept the night before.
You check the door of the TARDIS, and luckily, in yet another instance of irresponsibility, The Doctor has left it unlocked. So, you get in, use your phone to consult the Doctor Who Wiki for information on the TARDIS controls. Confident that you know what you're doing, you set the dial for yesterday, pull the requisite levers and after a brief sound-effect, you emerge from the TARDIS expecting to be where you entered, 24 hours earlier. But because the TARDIS is notoriously unreliable, it seems that it has moved to a hotel room several miles from where you entered, and only three hours in the past.
Without cash, you call a friend for a ride. Let's call this person Annie. She pulls up in front of the TARDIS and you hop in her car. A few minutes later, you pull up near the spot where you believe you were pick-pocketed. There, you see a suspicious-looking man, and figure that he's probably the guy that stole your wallet. But he hasn't done it yet. By your cell-phone's time, you've probably got twenty-minutes before he steals your wallet.
You hang around, waiting for the you of yesterday to come down the street. The suspicious-looking guy eyes you, and suddenly starts walking north. You look down the street to the south, and there you are, three hours younger, still with a wallet. You must have scared the thief off. Your loitering nearby probably spooked him, and now the event that started you on this venture will not occur. You figure you're screwed. Past you is going to walk into the restaurant and have his date, and you're going to be written out of existence. If your wallet was never stolen you would never have been walking past the TARDIS. So, you figure, you've got to steal your own wallet from yourself.
You pull up your collar and slip on your sunglasses. Surreptitiously, you sidle-up to the younger you, and with one deft move, you slip your wallet out of the pocket of younger you. Once you go around the corner, you make the realization that the person who stole your wallet was always you. You remember that brief flash of light reflecting off the thief's sunglasses. They were your sunglasses. The suspicious-looking guy was never involved.
The entire series of events had already been determined before you even woke-up that morning. In fact, it had already been pre-determined before you were even born. No matter what happened or ever would happen, the events of today were unavoidable. Everything from your erroneous assumption that you would be erased from existence to the suspicious-looking guy red-herring. It was all as immutable as gravity.
You peek around the corner and watch the younger you discover that his wallet is missing. He walks away, soon to find the TARDIS. Once he's out of sight, you head into the restaurant, and enjoy your date.
Now, you might be wondering, what if you walked up to the other you and punched him square in the face? That would mean you'd changed the past. But in a solid-state timeline, that's impossible. If you suddenly decided to head over and lay three-hours-younger-you out with a strong right hook, you wouldn't make it. Something would get in the way. Not because the universe couldn't allow it, but because it already happened. Not from a linear perspective, but from an objective non-linear perspective, it simply is.
That is solid-state. Many worlds, however, that's a different story. Which I'll be getting into tomorrow.
