Scivillage.com Casual Discussion Science Forum
Article Why we probably live in a quantum multiverse? - Printable Version

+- Scivillage.com Casual Discussion Science Forum (https://www.scivillage.com)
+-- Forum: Science (https://www.scivillage.com/forum-61.html)
+--- Forum: Astrophysics, Cosmology & Astronomy (https://www.scivillage.com/forum-74.html)
+--- Thread: Article Why we probably live in a quantum multiverse? (/thread-21653.html)

Why we probably live in a quantum multiverse? - C C - Oct 23, 2026

https://www.yahoo.com/news/science/articles/why-probably-live-quantum-multiverse-100000787.html

EXCERPTS: Superposition is an uncanny aspect of quantum mechanics that allows particles to be in multiple states at once-such as literally here and there simultaneously [...] A key aspect is that if you start with a state in a superposition, it remains in a superposition for all time: superpositions cannot be destroyed.

To appreciate the consequences of superposition, we must understand how waves are added and subtracted. [...] Throw a stone into the pond ... Wait until the surface is still again, then throw in a second stone at another position ... If you watch carefully, you will find that the result is just the sum of the two patterns that each single stone created.

If a wave crest from the first stone meets a wave crest from the second, they will combine to form a bigger wave crest, but if a crest and a trough meet, they will cancel each other out. These processes are called constructive and destructive interference, respectively. In this way, multiple solutions to a wave equation can be added together, and the result will still be a solution of the same equation. And it doesn't stop with two solutions-if you want the wave pattern of three stones, you just combine the three patterns, and so on.

[...] We know that superpositions can't be destroyed because Schrödinger's equation obeys the superposition principle. ... There can be no collapse according to Schrödinger's equation. [It's a brute add-on.]

[...] Everett's proposal is known as the Many Worlds interpretation of quantum mechanics. It's confusing, however, to call it an "interpretation." The Many Worlds interpretation and the Copenhagen interpretation are not really two different interpretations but two different theories. The former predicts the existence of a multiverse as an inevitable consequence of the superposition principle of Schrödinger's equation. The latter predicts a single universe by denying the universal validity of Schrödinger's equation.

Which theory is right? Is Schrödinger's equation universally valid, or does it apply only to microscopic systems such as atoms? [...] experimental progress over the past few decades shows that Schrödinger's equation is not valid only for minuscule particles. ... Although the multiverse sounds like science fiction, it is a real scientific prediction...

[...] If everything is described by the wave equation, why do so many things behave like classical particles? Why can't we interact with other branches of the multiverse?

[...] The answer is somewhat counterintuitive at first: we actually do see interference effects all the time but only from destructive interference. This is what physicists call decoherence -- the inability of many waves to show strong constructive interference.

Note that decoherence is not a new, fundamental law that we add to Schrödinger's equation to obtain classical behavior. It is a consequence of Schrödinger's equation that arises naturally once there are many interfering waves. In fact, decoherence is a universal phenomenon that we're already familiar with.

[...] Another clue is the fact that the universe appears highly fine-tuned: a slight variation in its fundamental parameters, such as the precise charge of an electron, the mass of a proton or the strength of the gravitational constant, would make life as we know it impossible. How can we explain the fact that these values seem almost chosen for their convenience for life? A popular answer is known as the anthropic principle: the fact that we are alive means we must find ourselves in a version of the universe compatible with life. We have essentially selected this universe from the array of all possible universes, which may be mostly hostile to life. But what does "select" mean? From which "selection of universes" are we choosing? Here the answer strongly depends on whether there is only one unique universe or a vast collection of them.

[...] The Many Worlds interpretation is gaining momentum as a candidate to solve the quantum measurement problem. Despite its seemingly weird prediction that our world is just one part of a multiverse, because of destructive and constructive interference, it is perfectly compatible with our sensation of living in one classical universe. Moreover, it opens possibilities for addressing fundamentally and technologically relevant questions.

Still, many challenging open questions must be answered before the Many Worlds interpretation can be accepted as our best explanation for the measurement problem..... (MORE - missing details)

RE: Why we probably live in a quantum multiverse? - Syne - Oct 23, 2026

(Yesterday 05:38 AM)C C Wrote: A key aspect is that if you start with a state in a superposition, it remains in a superposition for all time: superpositions cannot be destroyed.
Except:
Quote:[...] If everything is described by the wave equation, why do so many things behave like classical particles? Why can't we interact with other branches of the multiverse?

[...] The answer is somewhat counterintuitive at first: we actually do see interference effects all the time but only from destructive interference. This is what physicists call decoherence -- the inability of many waves to show strong constructive interference.
Undetectable superposition, through decoherence, is destroyed for all practical purposes. Nothing is ever considered "destroyed" in the universal wave function, but that's begging the question when talking about a multiverse.

Quote: To appreciate the consequences of superposition, we must understand how waves are added and subtracted. [...] Throw a stone into the pond ... Wait until the surface is still again, then throw in a second stone at another position ... If you watch carefully, you will find that the result is just the sum of the two patterns that each single stone created.

If a wave crest from the first stone meets a wave crest from the second,...
I'm assuming something got lost in translation from this author's native language, since there are not two sets of waves if you "wait until the surface is still again" between throwing stones.

Quote:[...] We know that superpositions can't be destroyed because Schrödinger's equation obeys the superposition principle. ... There can be no collapse according to Schrödinger's equation. [It's a brute add-on.]
More begging the question, by simply presuming the many-worlds interpretation.

Quote:[...] Everett's proposal is known as the Many Worlds interpretation of quantum mechanics. It's confusing, however, to call it an "interpretation." The Many Worlds interpretation and the Copenhagen interpretation are not really two different interpretations but two different theories. The former predicts the existence of a multiverse as an inevitable consequence of the superposition principle of Schrödinger's equation. The latter predicts a single universe by denying the universal validity of Schrödinger's equation.

Which theory is right? Is Schrödinger's equation universally valid, or does it apply only to microscopic systems such as atoms? [...] experimental progress over the past few decades shows that Schrödinger's equation is not valid only for minuscule particles. ... Although the multiverse sounds like science fiction, it is a real scientific prediction...
No, it's really not that cut and dried. Violating parsimony, by introducing an infinity of unobservable universes, is not justified by wanting the Schrödinger equation to be universal, at all scales. IMO, that sounds like the lazy way to approach a TOE.

Quote:We have essentially selected this universe from the array of all possible universes, which may be mostly hostile to life. But what does "select" mean? From which "selection of universes" are we choosing? Here the answer strongly depends on whether there is only one unique universe or a vast collection of them.
Well, if you're not using a lot of motivated reasoning, the selection is among all possible universes, not of all actually existing universe... which again, we cannot observe in any way.

Quote:[...] The Many Worlds interpretation is gaining momentum as a candidate to solve the quantum measurement problem.
Really? I'll believe it when you actually manage to:
Quote:[open] possibilities for addressing fundamentally and technologically relevant questions.

So far, many-worlds is still experimentally equivalent to Copenhagen.

RE: Why we probably live in a quantum multiverse? - confused2 - Oct 23, 2026

All this (that^^) is increasingly convincing me there is no such thing as a particle. The only time you see a particle is when a field changes state .. and that is (probably) instantaneous. So a 'particle' is just a summary of field as it changes state. Classically a field can change state gradually .. in quantum mechanics it's all or nothing. The position of a particle isn't 'indeterminate' .. there's no particle position to be determined because there is no particle.

RE: Why we probably live in a quantum multiverse? - Syne - Oct 23, 2026

Someone's still butthurt about something. 9_9

RE: Why we probably live in a quantum multiverse? - confused2 - Oct 23, 2026

(11 hours ago)Syne Wrote: Someone's still butthurt about something. 9_9

Have a nice day.