Multiverse has different approaches to be described.
The general concept, it exists, according to the GR math model with some equations extremes. The multiverses are theoretical in this case and so tiny that we cannot observe them
Another case is macro-scale. Schrödinger's cat. A speculative experiment made by Schrödinger when the deterministic model of the universe came to some probabilistic equation solutions. He ‘created’ the cat who is alive and dead at the same time, while the box is closed. That means that the observer himself is in the two states: the one who will open the box and see a dead cat and the one who will see it alive.

In theory and the scale, which we are not able to observe, there are multiverses. But as soon as we cannot observe them, we cannot tell what it is.

What is still hypothetical about quantum mechanics is gravity. Physics could quantize everything, except gravity, it just doesn’t fit the model. There are hypothetical graviton particles. Detecting gravitons, the hypothetical quanta of gravity, would prove gravity is quantum.
In 2012 CERN confirmed the existence of the Higgs boson, so that almost nothing to add to the physics of elementary particles (as far as we targeted)
Now there is dark energy, dark matter and gravity are in the spotlight.
‘Removing gravity’ for physiological tests or adding artificial gravity for future ‘colonized’ planets and the Moon - are both scientific and engineering tasks.
You may check a digest on Skyrora site: https://www.skyrora.com/

Weird thread lol..
Btw, Ars Technica posted a series of articles about quantum mechanics some time ago:
https://arstechnica.com/series/exploring-the-quantum-world/

Yeah, you disagree with what I say, but then you agree with what I say. Let me say it that you have no idea about subject, about scientific model and fail to understand me, I call this discussion pointless and leave it. Best to you.

In closed systems yes, but there are no 100% (pun) closed systems.

sigh
Please, I beg all of you, just let this thread die, as it's a complete abomination and has nothing to do with logical thinking or science.

And no, they were talking about sigmas, in that context there is exactly 100% and nothing more. Sigma, the standard deviation, is calculated from all of your data, and only from your data. The more sigmas, standard deviations, the more of that data is within the range of expected / average value. Sort of a measure of how much of your data is within expected values. So when somebody says 5sigma means probability of something is higher than 100%, they simply have no bloody idea what they're talking about.


*A disclaimer: I know only basic stuff regarding statistics, but that's enough to see through OP's nonsense.