The many worlds.

 The quantum version of entanglement is essentially the same phenomenon — that is, lack of independence. 

Think about the day you’ve had. The choices you’ve made. What time to get up. What to wear. Whether to say yes to that workout or no to that date. When you think about it, your day has been a series of tiny and not-so-tiny decisions. How many of them have altered the course of your existence? Would your whole life have changed if you’d just left for school five minutes earlier? It’s hard to know, since you only get to live this one version of things.

 In this interpretation, every time a "random" event takes place, the universe splits between the various options available. Each separate version of the universe contains a different outcome of that event. Instead of one continuous timeline, the universe under the many worlds interpretation looks more like a series of branches splitting off of a tree limb.
Let’s think about that version for a second. Your version. Is she the only version? Or is there a copy of you out there somewhere, a person who is not you, but who shares your DNA and lives on a planet that looks and feels just like yours. A person who, so far, has done everything that you’ve done.
 
It sounds like the stuff of sci-fi novels, and it is, But it’s also the stuff of modern science. There are plenty of physicists out there who would tell you that this parallel you is a real person, inhabiting a world that is no less real than ours.
 
There are a few different theories about the existence of these other worlds. Two that scientists talk about a lot. The first, set forth by a guy named Hugh Everett in the 1950s, is called the “Many-Worlds Interpretation of Quantum Mechanics” and essentially says that whenever there are multiple ways an event could turn out, the world “splits” into new worlds to accommodate each possible outcome. This has some pretty wacky implications. Take yourself, for example. Many-worlds theory says that you split like an amoeba every time a new world is created, allowing a carbon copy of you to go forward in the newly created parallel world while you remain in our world, unaware that a split has taken place. Ever see the movie Sliding Doors? I think this is pretty much what happens to Gwyneth Paltrow’s character, Helen, when she misses that train. Original Helen stands in the station while New Helen speeds off toward home.
 
Like the many-worlds theory, string theory says that parallel universes exist, but goes even further and says that it is possible for our world to come in contact with them. When that happens, the theory goes, a Big Bang like the one that created our universe occurs. (Why is it called string theory? Because the theory proposes that the smallest building blocks of our universe are tiny, vibrating, one-dimensional loops of string. The theory is waaaay more detailed and nuanced than that, but this is a beginner’s guide, after all).