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  • Parallel worlds are a topic of science fiction  that seem to come up over and over again. Lately,  

  • the number of shows and movies featuring branching  timelines and multiverses have been multiplying,  

  • and you may be low-key wondering just how  much of the fiction resembles reality

  • Scientists have been asking these same questions  for decades because from what we've seen,  

  • the future is far from certain. The idea of  multiple worlds is compelling because it solves a  

  • thorny issue that arises from quantum mechanics. Classical physics is typically thought to be  

  • deterministic: if you know the speed and position  of something like a ball flying through the air,  

  • then you can predict where  the ball is going to land

  • But in the quantum worldthings don't work like that.  

  • It is impossible to know the exact speed  and position of a particle like an electron,  

  • and so it is impossible to say for certain  what it will do, only the probabilities

  • The mathematical expression of all known  possibilities of a particle's location  

  • and characteristics is called its wave  function. Bizarrely, in the quantum  

  • realm particles appear to exist in multiple  states simultaneously, until something causes  

  • only one outcome to result, what's known in  science-y talk ascollapsing the wave function”.

  • The mechanism that causes wave functions  to collapse is still debated, but one of  

  • the most widely accepted is the Copenhagen  Interpretation. It states wave functions  

  • collapse when they are observed, measured, or  interact with the classical world in some way

  • It sounds bizarre but that's a conclusion the  evidence points to. It's beyond the scope of this  

  • video but if you want to know more about it, check  out this video on the double slit experiment here.

  • The Copenhagen interpretation comes with its own  issues, which physicist Edwin Shrodinger tried  

  • to point out when he devised a thought experiment  where a cat in a box could be both alive and dead  

  • at the same time so long as no one looked inside. But what if we're looking at this the wrong way,  

  • and the wave functions don't actually collapse? What if instead all possibilities continue  

  • to exist and our universe simply branches  off into separate worlds for each outcome?  

  • A mind-boggling number of worlds  could be constantly branching off for every  

  • single possible outcome in this vast universe. That was the idea put forward by Hugh Everett  

  • in 1957. It's an intriguing thought  but if the worlds are truly split,  

  • then there's no way to ever directly observe  them, let alone open a doorway between them

  • On the one hand, that's great news if you're  worried about some some  

  • parallel-world- hopping conqueror 

  • suddenly showing up. On the other hand, it's  frustrating if you're a scientist or if you have  

  • aspirations of inter-universe conquestor both.

  • Of course, the many-worlds interpretation just  

  • creates its own set of questions, fittinglyLike, what actually causes worlds to split?  

  • One possible mechanism is decoherence where  quantum states gradually unravel as a result  

  • of their interactions with their environmentIf that's the case, then worlds don't have hard  

  • splits, more like gradual separations until  they reach a point when they can no longer  

  • affect each other and are truly distinct. There are more issues with the many-worlds  

  • interpretation, some that are more in the  realm of philosophy than physics. Like,  

  • if worlds are constantly branching off creating  countless slightly different versions of you,  

  • then what does it mean to be you? Some versions  of you should be incredibly similar while a huge  

  • number of others are profoundly different. Which one is the real one? Some physicists  

  • might say that no single one is, but the real  you is the sum total of all versions of yourself.  

  • And other physicists might say that the  whole idea of many worlds is hogwash.  

  • The debate rages on and because there's no proof  

  • yet for one argument or the other, it could  very well continue for a long time to come

  • One thing I will confidently predict is that due  to its intriguing nature and the possibilities  

  • it opens up, the many-worlds interpretation of  quantum mechanics is definitely going to be a  

  • staple of science fiction until the end of time.

  • While we're still searching for branching worlds,

  • another universe may have bumped into ours.

  • Check out this video on that right here.

  • So, do you buy into the many worlds idea, and if so,

  • what do you think about all the other you's that could be running around

  • out there. Let us know in the comments,  

  • be sure to subscribe, and I or some version  of myself will see you next time on Seeker.

Parallel worlds are a topic of science fiction  that seem to come up over and over again. Lately,  

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Could Parallel Realities Really Exist?

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    Summer posted on 2021/09/10
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