Some interpretations of quantum mechanics suggest that our entire universe is described by a single global wave function that is constantly splitting and multiplying, producing a new reality for every possible quantum interaction. This is a very bold statement. So how do we get there?

One of the earliest realizations in the history of quantum mechanics is that matter has a wave-like property. The first to suggest this was the French physicist Louis de Broglie, who argued that every subatomic particle has a wave associated with it, just like Light can act like a particle and a wave .

This extreme idea was quickly confirmed by other physicists, especially in the experiments in which it was conducted Electrons Scattered thin chips before landing on the target. The way the electrons scattered was more characteristic of the wave than the particle. But then a question arose: What exactly is a matter wave? How does it look?

Related: Do we live in a quantum world?

Early quantum theorists such as Erwin Schrödinger believed that the particles themselves were smeared into space in the form of a wave. He developed his famous equation to describe the behavior of those waves, which is still used today. But Schrödinger’s idea flew in the face of further experimental testing. For example, although the electron behaved like a mid-flight wave, when it reached the target, it descended as a single compressed particle, so it could not actually extend into space.

Instead, an alternative explanation began to emerge. Today, we call it the Copenhagen interpretation of quantum mechanics, and it is by far the most popular interpretation among physicists. In this model, the wave function—the name physicists give the wave-like property of matter—doesn’t really exist. Instead, it’s a mathematical way we use to describe a cloud of quantum mechanics possibilities where we might find a subatomic particle the next time we go looking for it.

tangle chains
But the Copenhagen interpretation suffers from several problems. As Schrödinger himself pointed out, it is unclear how the wave function goes from a cloud of possibilities before the measurement to the mere absence of the moment in which we observe.

So maybe there is something more important to the wave function. They may be as real as all the particles themselves. De Broglie was the first to suggest this idea, but eventually joined the Copenhagen camp. Subsequent physicists, such as Hugh Everett, looked at the problem again and came to the same conclusions.

Making the wave function real solves this scaling problem in the Copenhagen interpretation, because it stops the scaling from being this super-specific process that destroys the wave function. Instead, what we call a scaling is really just a long series of quantum particles and wave functions that interact with other quantum particles and wave functions.

If you build a detector and shoot electrons at it, say, at the subatomic level, the electron doesn’t know it’s being measured. It just hits the atoms on the screen, which sends an electrical signal (made of more electrons) through a wire, which interacts with a screen, which emits photons that collide with the particles in your eyes, and so on.

In this picture, each particle has its own wave function, and that’s it. All particles and all wave functions interact as they normally do, and we can use quantum mechanics tools (such as the Schrödinger equation) to make predictions about how they behave.

Cat image and Schrödinger wave equation. (Image source: VICTOR de SCHWANBERG / SCIENCE PHOTO LIBRARY / Getty Images)
global wave function
But quantum particles have a really interesting property because of their wave function. When two particles interact, not only does one collide with the other; For a brief period, their wave functions overlap. When that happens, you can’t have two separate wavefunctions anymore. Instead, you should have a single wave function that describes both particles simultaneously.

When the particles go their separate ways, they still maintain this uniform wave function. Physicists call this process Quantum entanglement – What or what Albert Einstein It’s referred to as “spooky action at a distance.”

When we retrace all the steps of the measurement, what comes out are a series of entanglements caused by the interference of the wave functions. The electron gets entangled with the atoms in the screen, which gets entangled with the electrons in the wire, and so on. Even the particles in our brain are entangled with it a land with all the light that comes and goes from our planet, down to every particle in the universe entangled with every other particle in the universe.

With each new entanglement, you have one wave function that describes all the particles assembled. So the obvious conclusion from making the wave function a reality is that there is only one wave function that describes the entire universe.

This is called the “many worlds” interpretation of quantum mechanics. It gets this name when we ask what happens during the monitoring process. In quantum mechanics, we’re never sure what a particle will do – sometimes it can go up, sometimes it can go down, etc. In this interpretation, every time a quantum particle interacts with another quantum particle, the global wave function splits into multiple sections, with different universes containing each of the different possible outcomes.

and that is How to get a multiverse . By simply working quantum particles entangled with each other, you get multiple copies of the universe forming over and over again all the time. Each one is identical, except for a tiny difference in some random quantum process. This means that there are multiple versions of you reading this article now, all quite similar except for some subtle quantitative details.

This interpretation also has difficulties – for example, how does this split in reality unfold? But it’s a radical way of seeing the universe and a demonstration of how powerful quantum mechanics is as a theory – what began as a way to understand the behavior of subatomic particles may control the properties of the entire universe.

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