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One theory holds the distinction of being the most incredible idea in all of science.

It’s not proven but it is consistent with what scientists knowย about the universe, and if this theory were true, it would answer many long-standing and difficult questions in physics.

It’s called the ‘multiverse’.

It’s an idea that has been borrowed a thousand times in comics, books, and TV. It is the idea that there are alternative universes to the one we’re living in. We’re going to look at what these questions are, how the multiverse might answer them, and what it means if there are entire universes other than our own.

One of the biggest questions in quantum mechanics right now is how something called the ‘wave function collapse’ happens.

You know that everything is made up of atoms, and atoms are made up of protons, neutrons

are made up of protons and neutrons, which are made up of even smaller particles like quarks and photons. It’s the job of quantum mechanics to explain how these particles behave. So far it has done a really good job. It’s given us a whole new version of the periodic table, and has unified most of the fundamental forces into one theory. It’s a pretty spectacular achievement.

But it made a startling discovery.

Quantum mechanical particles, like quarks and photons, behave in a really strange way. It comes from the fact that they are so small. Because they’re so tiny, they spend a lot of their time not interacting with any other particles. Compare that to objects at our scale, like tennis balls and sky scrapers, which are constantly bumping into atoms in the air, the ground, and their own internal atoms.

When tiny quantum mechanical particles aren’t interacting with anything,ย they stop acting like particles. You can’t track their position or movement. Instead, they start to act likeย waves. We don’t know how, but they seem to spread out into a wave-like shape and move like a wave would.

As soon as they hit another particle, like the atoms on one of our detectors, the detector registers a single point, like a particle.ย But if you let lots of particles through, the pattern that they make is one that can only be made by a wave.

This is a pretty difficult concept and is more fully explained in the article on quantum mechanics and the double slit experiment. But if you don’t get it, don’t worry. All that you have to know is that tiny particles sometimes act like waves, and that when they hit something they act like a particle again.

One of the big mysteries is, where within this wave pattern is any one particle going to appear? On the left? The right? Dead center? The best that we’ve been able to do is to create a set of probable places that it will appear. I.e. A 40% chance of appearing on the left or right, and 20% chance of the center. This set is called the particle’s ‘wave function’.

//We don’t quite know how the wave function comes about, because to find out would mean interacting with the particles. And as soon as that happens, the wave function collapses.

//One of the big questions is, why did the wave function collapse at this one point? Why not somewhere else along the shape of the wave?

This is where the many worlds hypothesis comes in. When it was first presented in a lecture by physicist Erwin Schrรถdinger, he warned his audience that it “may seem lunatic”.

Tiny particles, like electrons and quarks, will have phases where they are not interacting with any other particles. During this phase, they take on the very strange property of seemingly existing in many places at once. This is called the wave function of particles.

But there is another, much more wild explanation. It proposes that the wave function never collapses. Instead, for every possibility of the particle’s state in the wave function, a new universe branches off the current one. So if there are two possible positions for a particle according to its wave function, then two universes branch off from the ‘current’ universe, each one identical except for the position of that one particle.

This leads to an infinite amount of universes, all existing in parallel, each one representing a slightly different version of reality where a single particle went a different way, since the big bang. The crazy thing is, the mathematics of this idea makes sense. It is truly possible.

When we look back at history, we see a single past. Humanity invented farming, Napoleon was defeated at the Battle of Waterloo, and Archduke Ferdinand was assassinated which led to the two world wars.

Our history is a timeline that stretches back to include all of these events.

But the many worlds hypothesis says that this is a serious lack of imagination.

What if that first crop was never planted? Or that a stray bullet hit the Duke of Wellington and won the battle for Napoleon? Or that the Archduke was never assassinated and the world wars never happened?

Each of these events was surely a turning point in history. It feels like

car went left, resulted in ____. Car went right, and ____.

But what if, and this is pretty out there, at each major turning pointย a new universe was created?


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Ben McCarthy

Ben McCarthy

Ben is the Founder of Discover Earth and the author of the Big Ideas Network.