**The universe is so vast that the existence or non-existence of a Multiverse can never be fully proved or disproved** - The universe is vast and [expanding](https://www.nasa.gov/feature/goddard/2019/mystery-of-the-universe-s-expansion-rate-widens-with-new-hubble-data), we don't even [understand how big it is](https://www.bbc.com/future/article/20210326-the-mystery-of-our-expanding-universe) - Quantum physics is full of [conflicting](https://www.forbes.com/sites/startswithabang/2019/03/15/this-is-why-the-multiverse-must-exist/?sh=1b80d10d6d08) [theories](https://www.forbes.com/sites/startswithabang/2018/07/17/what-is-and-isnt-scientific-about-the-multiverse/?sh=3b1f30c25c46) and [evidence](https://astronomy.com/news/2020/12/is-the-multiverse-theory-science-fiction-or-science-fact), including about Multiverses - String Theory suggests the [existence of multiple universes](https://www.newscientist.com/question/are-there-multiple-universes/) - [Everett's Quantum Multiverse](https://www.newscientist.com/question/are-there-multiple-universes/) theory suggests that "that quantum effects cause the universe to constantly split" , this means that every decision that is or is not made creates a new parallel universe with endless possibilities, if this existed by design would we even be able to be conscious of the existence of this and by design by becoming conscious of parallel universes in themselves would create new parallel universes - I recommend [Nick Payne's play 'Constellations'](https://royalcourttheatre.com/whats-on/constellations-2/) for its exploration of Multiverses - Overall the universe is so vast that we will never know whether multiverse's exist or don't

**The multiverse is an as yet, and perhaps forever, unfalsifiable idea of there being multiple-to-infinite other universes besides our own.** - The constantly-splitting, forking-paths conception of the multiverse is typically referred to as the Everett interpretation of quantum mechanics, after [Hugh Everett](https://plus.maths.org/content/many-lives-hugh-everett-iii). Also known as the many-worlds interpretation, it's not really a definite theory so much as a way to contextualize the wavefunction collapse described by quantum mechanics: Instead of the hyper-set of all possibilities (the wavefunction) collapsing into a singular "choice"/a singular reality every moment, the hyper-set of all possibilities _itself_ is the objective reality, meaning there's a new universe being spawned with each collapse. - Physicist Max Tegmark [conceptualizes](https://space.mit.edu/home/tegmark/crazy.html) several "levels" of the multiverse, one of which is the Everettian quantum mechanics interpretation above. Another is simply "regions beyond our cosmic horizon", where, if the universe is indeed infinite, there will exist, given enough expanse, a repeat of everything eventually. Others involve purely-mathematical-multiverse conceptions and other imaginings of "many-worlds" based on abstract forms of numeration purported to exist. - Here's a curiosity: The many-worlds interpretation of quantum mechanics makes some people question whether ["quantum immortality"](https://iopscience.iop.org/article/10.1088/1742-6596/1936/1/012015/pdf) is possible. Effectively, if there's always a chance for your consciousness to exist in some form, you'll "always" be alive. Whether it's a smoothly-transitioned continuity of the same consciousness that feels like "you" right now, no one knows. It very well could not be, if any of this were even true, though it's likewise possible you might just keep living forever with each split of the wavefunction in which your survival has a probability greater than zero. - Thinkers have devised methods for "testing" [quantum immortality](https://interestingengineering.com/a-theory-of-quantum-mechanics-that-suggests-everyone-is-immortal), but none of them has ever been found to make a difference in our certainty one way or another. (And they involve quantum suicide, which not only would _only_ prove the theory to the person undergoing it but is also, it must be said, not something anyone should ever attempt, given the stakes.) Additionally, there are some requirements for the idea of quantum immortality in the first place, anyway: 1)The multiverse theory does not have to mean that absolutely anything that can happen will happen; there could very easily and likely be limits to occurrences, whereby only things that follow the chain of events happen. 2) Ruling out the universes where our existence turns to potential oblivion when we die is not necessarily something we have to do. In these cases, especially where 1 and 2 might be combined, we would, indeed, eventually die. And, of course---the many-worlds interpretation of quantum mechanics is, and may forever remain, simply one unfalsifiable possibility for reality.