How to Know if Part of You Is in a Parallel Universe

You probably live in a parallel universe. Hither'south why.

Multiverses are everywhere.

Movies, popular scientific discipline manufactures, philosophical debates, Family Guy episodes.

At 1 time or another, we've all been invited to imagine copies of ourselves running around in some other dimension, living out a life well-nigh but not quite identical to our ain.

Merely why practise people think multiverses exist in the first place?

Equally information technology happens, I spent the commencement half of my time in grad schoolhouse trying to effigy out the answer to this question — and the second half trying to figure out how to explicate it to people who don't have a physics degree.

And then without further delay, here'due south a 100% math-free walkthrough of the multiverse theory known as Many Worlds quantum mechanics.

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Quantum mechanics: a dingy footling secret

Physicists similar pictures. To be honest, 80% of quantum mechanics work just involves drawing a series of pictures that show how something we're interested in changes over fourth dimension.

Merely physicists have frail egos and don't desire you to know that. And then they put special boxes (called "kets") that look like this: ⎜ 〉effectually their pictures to make themselves remember that they're doing something more complicated than they actually are.

All the ket ways is that you're talking about the "quantum state" of whatever is drawn inside. And "quantum state" is just fancy talk for "state", which is just fancy talk for "the way a thing is".

Example:

The thing to continue in heed is that the primary departure between some idiot cartoon stick figures and a breakthrough theorist is the employ of the ket ⎜ 〉in the paradigm on the right. All the ket means is that we're talking about the object that we've fatigued in the context of quantum mechanics.

To alloy in, we'll use this fancy "ket" notation in what follows. But only keep in heed that what we're really doing is just cartoon pictures of stuff.

Run into the electron

In order to understand why there are probably copies of yous running around in countless parallel universes, nosotros'll take to start small.

You lot've probably heard of electrons. Electrons are tiny, sub-atomic particles. For our purposes, you can retrieve of an electron as a very, very small sphere.

Spheres can spin clockwise or counterclockwise. And electrons can too.

Here'southward what an electron might wait similar when drawn using our ket notation:

The ONLY weird matter about quantum mechanics

At that place's simply one weird matter about breakthrough mechanics.

Similar a baseball, electrons tin spin clockwise or counterclockwise. But quantum mechanics says that tiny particles like electrons take a superpower: they can also spin clockwise and counterclockwise at the same time.

Holy shit.

To imagine how this works, it helps to think about colours: if clockwise is "white", and counterclockwise is "black", and so what I'm saying is that electrons can be "gray".

This is obviously a disruptive concept for most of us to grasp, since we've never seen anything spin in two directions at once. Just the math says that's exactly what's going on.

Let's see how we tin draw this state of affairs out using our ket notation. We'll bespeak that our electron is doing two things at once by calculation together its ii kets using a plus sign:

Co-ordinate to quantum mechanics, these "gray" particles are everywhere, spinning in 2 directions at the aforementioned time.

"But hold on!" you say: If the globe is total of weird objects that are spinning clockwise and counterclockwise at the aforementioned time, why take I never in my entire life seen that happen??

That excellent question is at the heart of what has go known as the "quantum measurement paradox".

And the answer will atomic number 82 the states directly to the multiverse.

Telling stories with kets

Before we tin can introduce the multiverse, we need to have a second and talk about how to tell stories with kets.

Imagine you had an electron in a closed box. In that location's a special detector next to the electron that will go "click" if the electron is spinning clockwise, and won't do anything if information technology'southward spinning counterclockwise.

If this "spin detector" clicks, it will send a signal to a gun, which will then burn down, and impale a true cat (besides in the box).

Let's draw out this scenario with our ket notation. If our electron is spinning clockwise, here'south how things will wait before the detector has been turned on:

A minute later, we turn on the detector. Because the electron is spinning clockwise, the detector goes "click". Nosotros'll bespeak that with a piffling checkmark (✓):

The detector at present sends its signal to the gun, which goes off a fraction of a 2nd later, at which betoken our box looks similar this:

The bullet flies through the air, and a moment later, it reaches our true cat, which becomes the sorry victim of our experiment:

Compared to this, the instance where the electron is spinning in the other direction is very straightforward.

Because the electron is spinning the wrong style, it won't trigger the detector, and nothing will happen:

These two stories — 1 where the true cat lives, and ane where it dies — seem to brand perfect sense so far.

But what if our electron doesn't simply offset off spinning 1 way or the other, merely instead spins in both directions at the same time?

Two words: zombie cat.

Breakthrough zombie cats

Let's tell a new story. This time, our electron starts in its simultaneous clockwise and counterclockwise spinning country.

Hither'southward what this will look like when drawn using kets:

Now the million dollar question: what happens when we turn our electron spin detector? Volition it click, or not click?

According to quantum mechanics, it does both. Function of it will see a clockwise spin, and part of it will see a counterclockwise spin; it's nigh as if the detector is beingness separate in two by our electron.

Again, using kets:

Notice that we accept two different "mini-stories" forming inside the red brackets: in one, the electron was spinning clockwise and the detector clicked, and in the other, the electron was spinning counterclockwise and the detector didn't budge.

Next, we wait for the signal to propagate from the detector to the gun. Volition the gun go off, or will the bullet stay in the chamber?

The reply is the same as for the detector: it will do both.

The gun will be split in two, one version of information technology having gone off, the other never having fired:

…which brings usa to our true cat.

By at present, you tin probably guess what its fate will be: the true cat, just like the spin detector and the gun, will exist split in 2: one version volition exist killed by the bullet, and the other will go on to exercise smashing true cat things.

Here's the final state of everything in our box:

Find that we now have ii fully independent stories to tell most the contents of the box: in ane, the electron spin was clockwise, the gun went off and the cat died. In the other, the spin was counterclockwise, the gun didn't go off and the cat lived.

Both are true. Neither is more true than the other. They coexist within the box.

Is the electron spinning clockwise or counterclockwise? Both.

Has the detector clicked or not? Both.

Is the cat alive or dead? Both. #zombiecat

Quantum consciousness

Ok so yous're skeptical of the story I but told you. You've never seen a half-dead, half-living true cat.

You might even want to say, "well clearly breakthrough mechanics doesn't work because I've never seen a zombie cat, so let's throw out the whole matter."

But the trouble is that quantum mechanics makes the best predictions of whatever concrete theory of the universe we've e'er had (like, literally ever). So we can't throw the infant out with the bathwater.

Somehow, we're going to have to explain why breakthrough mechanics says at that place should exist zombie cats, when no one has ever seen one.

And that's what a guy chosen Niels Bohr wanted to figure out. He came up with the first real attempt at explaining the zombie true cat problem.

To paraphrase, Bohr was similar, "I've never seen a zombie cat, only the math says it's in that location. And then there must be something special almost me, that forces the cat to choose its state (either dead or alive) when I look at information technology. When I look at it, the true cat must be forced to collapse out of its simultaneous live/dead state and becomes either alive or dead (not both)."

He probably said information technology in Danish, only that was basically the gist.

Hither's what Bohr was suggesting:

Although this does explain why we never run into zombie cats, many people today see it equally an unnecessary bit of magic to introduce into our laws of nature.

At the time though, the physics community was pretty freaked out almost the zombie cat problem, and most jumped on Bohr's bandwaggon.

But Bohr's explanation had some holes in it that no one could quite plug:

1. What makes humans then special that they tin force a quantum system (like our electron/detector/gun/cat arrangement) to collapse into a single, well-divers state (similar "dead" or "live")?
2. Does the cat have the power to collapse the land of the electron/detector/gun combination? Would a monkey?
3. How almost the gun or the detector? Why can't they collapse the state of the electron?

Some people started throwing around some pretty New Agey terms in response to 1.

"Information technology'south human being consciousness that collapses the zombie cat into its alive or dead country!"

"The deed of ascertainment affects the quantum system, and induces it to collapse!"

Leaving aside the fact that it's totally unclear what anyone might hateful by "consciousness" or "observer", we nevertheless have issues 2. and iii. to deal with.

And so how do we get mind magic out of the equation?

One word:

The multiverse

Luckily for us, the story doesn't stop here. In the 1950s, a bloke called Hugh Everett 3 came up with an culling style of explaining why we don't encounter zombie cats all around usa.

Everett said: "Listen upwardly, y'all dickheads. What makes yous think yous're and so much improve than a freaking cat? You're not. You're just a bum with a chalkboard. Absolutely pathetic. Also your fly is undone. Dumbass."

It's not a direct quote, simply hey if yous wanted historical accuracy you'd become to Wikipedia.

What Everett was getting at was that we really shouldn't be thinking of humans or observers as beingness special in any manner. Instead, he suggested thinking of ourselves equally breakthrough objects, that nosotros could put in a ket, merely similar the true cat, the gun and the detector.

Let's see how that would play out. Nosotros'll take our zombie cat box, and explicitly add the experimenter/observer as another part of our system, in a ket similar everything else.

Before the experimenter looks within the box, here'due south how our arrangement will wait:

Now he looks inside. Just similar the true cat, the gun, and the detector, he too is split into ii distinct copies of himself:

Now imagine asking the experimenter — both versions of him — what the result of the experiment was.

Was the cat dead? One version will requite a definite "yes", and the other a definite "no".

Did you come across the true cat alive and dead simultaneously? They both give the obvious reply: "Of course not, what a stupid question."

In each example, the experimenter just e'er sees i result: the cat is either live or dead, simply never both, fifty-fifty though the laws of quantum mechanics say that both versions of the cat exercise exist.

The experimenter but doesn't find considering he'due south stuck in one of these two timelines, unable to see the other ane.

And that was Everett's indicate: the reason we've never seen zombie cats or one-half-fired, one-half-not fired guns is considering the moment we await at these objects, we ourselves are split into multiple timelines, where unlike versions of united states of america see different — but well-defined — outcomes.

Until now, I've been referring to the two groups of kets — one where the cat is alive, and the other where the true cat is dead — equally "stories" or "timelines", merely another word you might just as well use is "universe". That's because everything about the "alive" and "dead" timelines volition brainstorm to change dramatically from this signal on.

For example, the experimenter who sees the dead cat might be so saddened that he ends up quitting his job, and never inventing a fundamental technology that would otherwise have been used by millions of people.

It's interesting to note that this giant difference between the "alive" and "dead" universes all arose from the spin of a unmarried tiny electron.

And because electrons and other particles are leading parallel lives all around u.s.a., our multiverse is constantly splitting, spawning off new timelines or universes with every possible interaction outcome.

So that'due south all there is to it.

Well, non really — in that location'due south actually a lot more to say well-nigh multiverses. They may explain why nosotros haven't encountered aliens yet, and have been used to argue that humans may already be immortal, among other things. But that's for some other article, and another timeline.

*Side-note: I'm writing a book almost this stuff! If you'd like me to let y'all know when information technology's out, just get out me your name and email via this form 🙂

If you lot have a annotate or question, I'g e'er game to chat on Twitter at @jeremiecharris

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Source: https://medium.com/@JeremieHarris/why-do-physicists-believe-in-parallel-universes-e16aee491f42

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