The true nature of reality is currently unknown. Ever heard of Quantum Mechanics? Everything exist in wave patterns unless it is observed, measured.

Like Schrodinger's Cat, we never know which state the cat is, dead or alive, unless we reveal and measure. Our measurement affects the waves and it collapses into a particle. The amazing part is that the cat is both dead and alive.

Quantum computing on the other hand computes all the possible configurations of any given state. If there's two bits of information, quantum computer can compute all possible combinations at the same time. Which means two bits can hold {00, 01, 10, 11}. And what's fascinating is that even there is two bits, the four possible outcomes EXIST.

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Electrons observe wave-particle duality. Also photons, and all matter in the universe. Even you, are a product of quantum mechanics. We all are waves.

We exist as waves, but we are now particles because we are measured. Isn't it? Wrong. We are never measured. Let me explain.

Let's have a thought experiment.

We have a two bits of quantum computer, like the example earlier.

There are only four sates of outcome: 00, 01, 10, 11

But only 1 outcome will emerge from the two bits, not all four.

How do we solve that?

We can solve it my measuring, in other words, collapse the wave function.

But you said earlier that all the possible outcomes exist, why there is only 1 outcome not all four?

All four outcomes EXIST, but they are on a copy of our own universe. For every possible outcome, our universe makes a copy of itself and changes it slightly.

There are a universe that the outcome is 00. At the same time there is a universe that the outcome is 01. There is also the universe that the outcome is 10. And I'm pretty sure that there exist a universe where 11 is an outcome. In this case, all the possible outcomes simultaneously exist at the same time.

Same also with Schrodinger's Cat. There is a universe where the cat is dead. And there's a universe where the cat is alive.

This also means that, every change of state in this universe. Every particle outcome is getting split. Which also means that every slight possible change of the universe, from slight change in the digits of speed of light, from humans never existed, all of the possible universe EXIST simultaneously.

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Why do we feel that there is only ONE REALITY where there are lots of them?

Well, using the example above, the Schrodinger's Cat.

If the outcome of the cat is dead, you will ask yourself, "Why the cat is dead, but not alive?"

If the outcome of the cat is alive, you will ask, "Why the cat is alive, but not dead?"

Well more accurately, both copies of yourself could ask, "Why did the cat died/alive in my reality?"

Both copies of you asked almost the same thing, even if they are in the separate universe. They asked why the outcome is this, not the other way around. The reality we're experiencing is just an illusion.