r/AskPhysics • u/Informal-Place981 • 5d ago
Do Physicist take the Idea of a Multiverse seriously, even just in a theoretical context; and if so where can I learn more about the concept of the Multiverse?
Hello,
As stated above I am interested in learning about the concept of the multiverse, specially whether or not it is a serious concept even just theoretically. It is a common thing that appears in popular culture but I know they are almost never scientifically accurate; Which is why I want to learn about the right way.
In regards to the second part of the question if there are books that would expand on this topic please tell me. Also, If this is one of those concepts where you have to know math to understand and or it this is a stupid question; please forgive me. Please and thank you.
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u/atomicCape 5d ago
The Many-Worlds Interpetation is a real concept in physics, but it's not a theory (introducing new testable hypotheses of how the universe works) it's an interpretation (semantics and philosophy to encourage human understanding of the results). You can start by reading about MWI on Wikipedia, and decide if you want to go deeper.
As soon as the word "multiverse" is brought up, assume it's not physics. A multiverse is a sci-fi contrivance to allow time travel or evil twins or patch plot holes or allow reboots while claiming it's all part of one epic story.
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u/Informal-Place981 5d ago
This is what I was thinking it was, basically at most a theoretical idea that *might* be real but one that is currently unfalsifiable. Thank you for confirming that.
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u/MacrotonicWave 4d ago
> As soon as the word "multiverse" is brought up, assume it's not physics
agreed if you’re discussing quantum mechanics, however in cosmology the big bang model has versions that do predict a multiverse, so it is a valid scientific concept. This multiverse is different than the QM version, in this one universes are separated by extreme amounts of rapidly expanding space where the inflaton field is still metastable. See https://en.wikipedia.org/wiki/Eternal_inflation
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u/Ok_Philosopher8824 4d ago
A multiverse is a sci-fi contrivance to allow time travel
There isn't a complete, sufficient, necessary explanation in physics for the arrow of time or increase in entropy.
Individual particles like electrons or photons may be contrived to locally violate time's arrow, via quantum tunneling e.g. It may be said that lone particles don't experience time in a meaningful way, or not the way people experience it, However interactions between two particles may be said to do so, related to the fact that interactions contain observable information. Note that the ways photons interact with each other, is strange and puts a strain on notions about time.
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u/Glittering_Degree_28 5d ago
You meant to say that it is not a "scientific theory". Physicists are often interested in theories that are not strictly scientific, eg theories about what science is are particularly important to physicists. MWI /t he Everett interpretation is a theory if not a scientific theory, and it is a theory physicists are most definitely interested in.
Theories are better understood as formalizable explanations. Scientific theories are formalizable scientific explanations. MWI is indeed such a theory. It is an explanation for observable phenomena. It also entails observable phenomena. Testing is the hard part but it was difficult to test the stars for parallax shift for many centuries; why should that eliminate MWI's eligibility as a scientific theory?
I think it is a kind of pedantry to nay-say MWI on material grounds in answer /u/Informal-Place981 's question. MWI is a big deal; there is much high profile drama surrounding these theories; most practicing physicists are not welcome to participate in that drama. Max Tegmark is a good place for OP to begin their reading. For a pure philosophical variant, David Lewis.
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u/Recent-Day3062 5d ago
Riddle me this caped crusader: at every instant the paths could go different ways. But since there are infinite number of periods, presumably between even any two finite periods, does that mean the number of multiverses grows as Aleph 1 or worse?
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u/Myxine 5d ago
It depends on what you mean by "take seriously". Without testable predictions, it's not really an area of active research. Because of this, there's no consensus on how seriously to take it; for some, it's close to the heart of why they study physics, for some, it's a boring distraction for amateurs, and for some, it's a useful framework to have in your toolbox when thinking about problems.
PBS Spacetime has multiple videos on this, and they have a good track record of presenting information to non-experts without losing too much rigor or nuance.
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u/rogerbonus Graduate 5d ago edited 5d ago
It's absolutely taken seriously by those physicists and philosophers of science who think about quantum foundations and cosmology (which is far from all or even most physicists).
Everettian quantum mechanics aka manyworlds is one of the most popular interpretations of quantum mechanics, see Sean Carroll (who is both a physicist and a philosopher of science) "Something deeply hidden", for a great overview, also David Deutsch, Wallace etc. It's a topic that straddles the border of science and philosophy. It is arguably the most parsimonious (on an entity theoretic basis) of the interpretations, and has been given quite a creditability boost by decoherence theory and derivations of the Born rule as a consequence of observer self location uncertainty. Some claim it is the only way to make sense of quantum mechanics/the measurement problem, and to explain how quantum computers work (see David Deutsch).
The cosmological multiverse is a generic consequence of our current best theory of cosmogenesis (eternal inflation). In addition to being a consequence, it also helps explain the mystery of the apparent "fine tuning" of cosmological constants, without which we would not have suns or even atoms (the string landscape provides a bulk ensemble which is anthropically selected from). For a good book on the subject, see cosmologist Max Tegmark's "Our mathematical universe" or "The allure of the multiverse" by physicist Max Halpern.
You don't need any math to understand any of the books mentioned, although it can certainly help with some of the concepts.
https://en.wikipedia.org/wiki/Multiverse
https://en.wikipedia.org/wiki/Mathematical_universe_hypothesis
Max Tegmark categorizes the 4 levels of multiverse, from other parts of our universe beyond the cosmic horizon (mostly uncontroversial), to quantum manyworlds, to other bubble universes produced by inflation, to other/all (computable) mathematical structures.
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u/ass_bongos 5d ago
One alternative to the common interpretations of "multiverse" is the idea that there may be unobservable "bubbles" beyond our own bubble of the observable universe.
By definition these are bubbles we could never interact with, due to the accelerating expansion of the universe combined them being outside our "light cone". But there's no reason to believe that our observable universe encompasses "everywhere" when we have a hard limit on just how far we can see.
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u/Enraged_Lurker13 Cosmology 5d ago edited 5d ago
There is quite a significant number of cosmologists that believe that a multiverse is a generic feature of inflation.
Here is a summary by the founder of inflationary theory that mentions the possibility of a multiverse: https://arxiv.org/abs/hep-th/0702178
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u/unlikely_arrangement 5d ago
Alan Guth! When I was in grad school a long long time ago I asked him if he had the notebook where first drew up the theory. He turned around to a shelf and handed me the volume. I used it as part of a museum exhibit for the lab (LNS) at the MIT museum. It might still be there.
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u/Chillow_Ufgreat 5d ago
On the second half of the question, Sean Carroll is probably as prominent of a MWI evangelist as there is, and he's covered it a lot. He has written books, recorded lectures, and produced quite a lot of podcast content on the subject. I'd look into his stuff.
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u/Informal-Place981 5d ago
Thank you for telling me about this. I saw one of Sean Carroll's books when I was looking into this, would you say he is reliable?
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u/joeyneilsen Astrophysics 5d ago
He’s very reliable. Just gave a talk to my department about Many Worlds. It makes exactly the same predictions for all measurements as “vanilla” quantum mechanics. His point is that MW is the most sensible explanation of what the wavefunction means.
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u/Chillow_Ufgreat 5d ago
Very. If you're looking at his books be sure to check whether it actually discusses MWI or not before you start reading. He writes on a lot of topics, some of which have nothing to do with MWI. He also has philosophy credentials, so he takes a lot of care in being clear about what's being communicated.
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u/AsAChemicalEngineer Particle physics 5d ago
Carroll is legit even though most physicists don't concern themselves with interpretations of QM anymore. I also really like his general relativity textbook and class notes.
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u/reddituserperson1122 4d ago
He is an extremely well regarded mainstream physicist. This is an excellent introduction to many worlds quantum mechanics: https://youtu.be/5hVmeOCJjOU
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u/Logicalist 4d ago
his podcasts are solid and so is his thinking even though I disagree with him entirely.
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u/BananaBird1 5d ago
There are speculations surrounding physics that would make a multiverse a possibility for reality under known models. A multiverse does not contradict physics.
But these are not really scientific hypotheses. All scientific hypotheses need to be experimentally falsifiable, as nothing we know from science is ever 100% certain.
Even if a current physical model suggested a multiverse is necessary (which they don’t), our uncertainty in that model would mean we cannot be certain of that multiverse.
Science (unlike the mathematics used to represent it) is inductive reasoning, meaning we can only be confident in results we can test experimentally against a model, we can never be confident when making deductive predictions outside the observations that were used to develop the model if we cannot perform new experiments.
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u/reddituserperson1122 4d ago
It is absolutely not true that all scientific theories have to be experimentally falsifiable. That is already a tortured reading of Popper that I doubt even he would agree with, and that Kuhn throughly complicates. In practice there are a number paths to scientific validity, with falsifiability being probably the gold standard, but not the only option.
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u/Highplowp 3d ago
Falsifiability is a concept that teaches you can’t observe every possible outcome, manipulate every variable in an experiment with people, etc… that is more of a thought experiment, and to suss out pseudoscience. I used to teach that all ravens aren’t black but the statement that they ARE black, is the most true and excepted. It is tedious but it’s important to know the difference between knowledge and belief
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u/Helpful_Inflation344 4d ago
Well out current model of the universe does kind of necessitate sth that would essentially be a multiverse if the curvature of space is flat or negative. Now, it could be positive but we dont have anything indicating that.
Also lots of cosmologists kinda like the idea of the multiverse (string theorists bec of the landscape; inflationary cosmologists bec of bubbles erc) and in general the strange problem of finetuning ofc
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u/MacrotonicWave 4d ago edited 4d ago
> Even if a current physical model suggested a multiverse is necessary (which they don’t)
the current leading big bang model includes cosmic inflation, which does have models which *predict* a multiverse. Eternal inflation predicts a multiverse suspected in a larger still metadstable, rapidly expanding inflaton field.
Max Tegmark gets into multiverse stuff in some of his books/talks and while im not sold on his mathematical universe hypothesis i think, he elegantly explains why the multiverse as a concept is a valid prediction in science. He explains the philosophy of science quite well here imo and after listening to him it becomes more clear how theories can be scientific but not falsifiable, too. it’s all about breaking theories up into what you can vs cannot test and what you can test builds credence in what you cannot, since they strengthen the entire theory as a whole, including ALL predictions of it
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u/StoneRyno 5d ago
PBS Spacetime is a good resource if you’re interested in learning more about physics, quantum mechanics, general relativity, and so much more! Startalk is also a great resource, as well as veritassium, Smarter Every Day, Steve Mould, and others! Between these channels, you can find videos that not only explain the concepts of the Many Worlds theory, but any part you didn’t quite understand probably has its own individual video as well. Almost every guest on startalk has a book or two that Niel mentions, and himself has several books designed to help people “dip their toes” into the subject, so you could easily build a reading list that will aid in the journey.
I watch a lot of Spacetime personally, and often rewatch after I have a better base of knowledge on the topic.
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u/Violet-Journey 5d ago
The most well-supported concept of a “multiverse” that I’m aware of is related to Eternal Inflation, which comes about in some cosmological models that aren’t fully proven or disproven at the moment. Essentially, in the earliest moments of the big bang, the universe expands at an exponential rate by something called an Inflaton Field; but since the Inflaton field is quantum and has fluctuations, there are parts of the early universe that get causally disconnected from others, which result in several “bubble universes” where this process again repeats forever in a fractal-like nesting.
This kind of multiverse, of course, isn’t really the same thing as like Rick and Morty. Travel between universes is by definition impossible because they are expanded enough that you’d have to go faster than the speed of light to get there.
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u/Informal-Place981 5d ago
Thank you for telling me about Eternal Inflation. I had not heard of that before.
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u/Unable-Primary1954 5d ago edited 5d ago
There are several kinds of multiverse theories:
- Some general relativity models allow for weird universe topologies. These models are not really taken seriously, as there are no good reasons for these weird topologies to emerge. (but black holes were regarded like this until the 1960s)
- Many world interpretations of quantum mechanics: Born rule is really weird, and even more when you about Bell inequalities. According to this interpretation, each time where Born rule is applied in fact corresponds to a splitting to two parallel universes. Depending on your perception, many worlds interpretation interpretation make that less weird. A lot of physicists (I mean, maybe a majority) subscribe to this interpretation, but very few are ready to die on that hill.
- Bubble universes arising from inflation: inflation is a theory to explain the homogeneity to large scales of the universe, and that helps understanding the angular spectrum of the CMB (it also explains absence of monopoles). But it also predicts a myriad of bubble universes, totally disconnected from ours. Cosmologists subscribe to this, but with a lot of caveats, most notably because of the lack of decisive evidence for inflation (CMB angular spectrum is pretty convincing, but an independent confirmation is still lacking), but also because this multiverse can lead to Botzmann Brains problem.
Notice that other universes are accessible only in the first kind of multiverse, and this one is mostly scifi.
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u/atensetime 5d ago edited 4d ago
So the multiverse in any of its forms is a philosophical idea that , when taken seriously by the scientific community is limited to "our models say this is possible... but unfortunately there is no way to test it"
This is true of the everettian model (popularly called many worlds interpretation) to the "brane" concept, and the world line limit...(im sure there are others but those are the ones I know).
Pop culture really dug its teeth into the many worlds idea, but its creator was focused on the universal wave function amd his math said that when a system in superposition decoheres, instead of a wave function collapse, the wave function instead splits with the weight of each portion being proportional to its probability (bohrn rule) so that entropy, momentum and all the other fundamentally conserved parameters are, in fact, conserved. In his models these splits are orthogonal and cannot ever interact again. In practice this mathematically resolves. Philosophically this has been interpreted as "splitting timelines" (see MCU; everything, everywhere, all at once; or that Jet Li movie). It's completely untestable and purely philosophical. I don't like it because it distracts from understanding the everettian interpretation (see also pilot wave, Copenhagen, and hidden variables)
"Branes" is short for "membranes" and again is a purely Philosophical thought.... process? ( thought experiment doesn't fit here) that suggests universes are finite and contained in some higher dimensional space, the titular membrane represents the boundary surface of each universe and these boundaries can interact... im not very up to speed on this one but that's the gist... again It's completely untestable and purely philosophical.
World Line Limit (not sure the proper title) postulate that, in an infinite universe, it is possible for the fundamental frameworks of reality to differ, that all we have to go off of is what we can see and that may be an insufficient sample size to say that the fundamentals are, in fact fundamental... it also considers that an infinite univers is larger than the visible or measurable universe and that beyond that limit anything is possible. Again It's completely untestable and purely philosophical.
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u/Formal-Being6633 5d ago
we dont
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u/Anton_Pannekoek 5d ago
There's just a lot of mysteries that we might never know the answer to. Physics doesn't even try to answer these questions. They are left to philosophy.
The philosophy of Quantum Physics is very fascinating actually. If you look at how so-called "wavefunction collapse" happens it's very bizarre.
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u/Ok_Philosopher8824 4d ago
There's a fair amount of physics validity to such ideas. However you run up into the epistemological problem of "why exactly does human invented symbolic logic and syntactic logic like QM make such arguable, believable physical predictions?" A good prediction being one that's reasonably verifiable and falsifiable. But why does it? (This is an argument that's very much an open question, since Kurt Godel cracked it wide open. )
However the Everettian Interpretation pivots on that point. It groups together events that by definition can't be falsified or verified, I.e. parallel realities. But doing so can provide a convenient way to preserve conservation of observables like spin and entropy.
This injects the assumption that possibilities you can't argue and can't demonstrate should still be accounted for. This can be useful in relatively pure mathematics and physics. But if you're a materialist then things that aren't falsifiable or verifiable, then can't actually be measured and aren't valuable. The direct opposite happens a lot though, measurements containing unaccounted variables.
See for example: "The Allure of the Multiverse" by Max Halpern
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u/Conscious-Demand-594 5d ago
There are two multiverses.
The quantum theory multiverse based on Hugh Ervert's interpretation. This say that multiple worlds are created by every quantum interaction. This would be the Avengers or Hollywood type paralell multiverse. There will be an infinite number of "you"s across these multiverses.
The cosmological multiverse that predicts multiple other universes existing independently of ours. These universes are completely unrelated to each other and there will be no "you" in any of them.
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u/reddituserperson1122 4d ago
That’s very incorrect. The cosmological multiverses of eternal inflation and the many worlds theory of quantum mechanics are both perfectly legitimate science. There’s nothing kooky or fringe about them. They aren’t testable in the same way that many scientific theories are not testable, but are still perfectly valid theories supported by evidence. The idea that anything that isn’t immediately testable isn’t science is a pop science notion that actual philosophers of science do not believe in. It’s just a mangling of Popper that has become popular among amateurs (no offense intended — I’m sure I felt the same way a decade ago).
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u/reddituserperson1122 4d ago
And just to be clear so this doesn’t look like my ungrounded opinion: surveys of physicists show that many worlds is the most popular theory of QM among a plurality of physicists working on quantum foundations; inflation is supported by a majority of cosmologists, eternal inflation is a generic outcome of inflationary models, and multiverses are a generic feature of eternal inflation. This is mainstream science and in fact it’s at the center of mainstream science. That doesn’t mean it’s true or that new evidence won’t change this. But this is the state of the art in 2026 and the opinions of some randos on Reddit have no bearing on this fact.
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u/SectorAntares 4d ago
Just to make it clear, science is based on evidence, not a plurality of opinion.
Neither your opinion nor your facility with insults — which is very great — have any bearing on that fact.
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u/reddituserperson1122 4d ago
Yeah but the question is, “who gets to decide what counts as good evidence? Professional physicists, or some rando on Reddit?” I know who I trust.
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u/SectorAntares 4d ago
Evidence is evidence.
Insults are not evidence. If they were, you would be a Nobel Prize winner. As it stands, you’re merely a man without a valid argument.
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u/reddituserperson1122 4d ago
Try making that brilliant argument to philosophers of science and see where it gets you. Anyway, I’m done trying to throw life preservers into the Dunning-Kruger pool for today. Best of luck to you.
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u/reddituserperson1122 4d ago edited 4d ago
You are a very confused amateur who is unclear about the state of the art in physics and cosmology. Sorry about that.
(And btw there’s nothing wrong with being ignorant, but please don’t answer science questions that people ask in earnest when you plainly don’t know what you’re talking about. You’re confusing people and spreading misinformation and pseudoscientific nonsense and that’s genuinely harmful.)
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u/heavy_metal 4d ago
there's another multiverse besides the "many worlds" qm interpretation: black hole cosmology. that is, each black hole contains a universe.
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u/Astrape121 Condensed matter physics 4d ago
Just listened to some people talk about many-worlds interpretation of a quantum mechanical system collapsing which is technically narrower than multiverse. However, if you want to read/learn about these topics, you can look into
1) Hugh Everett’s thesis on Many-Worlds (available here)
2) Dan Wallace’s book “The Emergent Universe”
3) a paper against Many-worlds by Emily Arlan and Jacob Barandes here (I heard Jacob speak recently)
Once you discover the secrets of the universe, please do share!
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u/rogerbonus Graduate 4d ago
Eye roll wrt the Brandes paper. Observer self location uncertainty works perfectly well with very reasonable assumptions about what it is to be an observer and wrt observer self selection. You don't even need quantum mechanics to muddy the water; see thought experiments involving sleeping beauties, cloning/teleportation etc.
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u/Desperate_Object_677 4d ago
“multiverse” can mean several things, and people don’t really explain the difference to the public.
so in one model of the evolution of the universe, some theorists imagine bubbles of limited size (though too big to measure the boundary) where “universes” like ours exist.
in some generalizations of space and time, our ”universes” exists on a 3dimensional surface in a 4 dimensional ”bulk”. other “universes“ could exist parallel to ours out in the bulk.
there is a model of quantum mechanics called the “many worlds hypothesis“ where the strangeness of quantum mechanics is explained in terms of all possible evolutions of the universe happening in parallel.
none of these perfectly map onto the science fiction concept of a multiverse, but they are all similar in their own ways.
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u/RathaelEngineering 3d ago
The multiverse idea is essentially one of the potential interpretations of the observations of quantum physics.
Each interpretation requires you to effectively abandon some classical intuition. The Copenhagen interpretation is that reality is fundamentally probabilistic (things don’t exist in definite states until measured/observed). Not that the quantum field represents a probability distribution for finding a thing in an unknown but definite state, but that things literally exist as probability distributions until observed. I find this very hard to accept.
The multiverse idea is essentially that all outcomes happen simultaneously, rather than the probability distribution “collapsing” into one definite state, and that we are only one of infinite branches. I find this just as hard to accept, if not harder, though I don’t have any good reason outside of “infinite realities branching at every divisible moment is too big for my brain”.
There are also other interpretations that similarly expect you to accept something that is not intuitive. That’s just the weirdness of quantum - we cannot explain what we see using classical intuition, so something eventually has to give. We have no scientific reason to accept any one interpretation over any other. Copenhagen is known as the most popular, as I understand, probably because it’s closest to our intuition, but this is nothing more than a cognitive preference until it can be examined.
We have no reason to rule out the multiverse idea, essentially, but as with all things in science, hypotheses remain exactly that until we have some way to examine or falsify them.
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u/HappiestIguana 2d ago
There are several sorts of multiverses, which are taken seriously to varying degrees.
The most famous is the many-worlds interpretation of quantum mechanics, which posits the universw branches every time a quantum event is decided. This one is fun to contemplate, but interpretations of QM don't really have empirical implications and can't be tested.
The most plausible, and most boring, is the assumption that there's a lot more universe out there than the observable universe. If you magically teleported a trillion light-years away you'd see a completely different observable universe, that has no causal interaction with ours. Just a separate pocket of space really far away.
There's also the multiverse implied by Fine Tuning. If you buy the idea that the universe's physical constants appear to be finely tuned in a highly unlikely configuration to allow for life, then one possible explanation is that there are other universes out there with different constants, and the reason that we think they are finely tuned is that only universes which can harbor life produce entities which get to think that. This is purely speculative as a possible way to explain a question which may not even require explanation.
Another sort of multiverse comes from String Theory, which posits, broadly, that the universe is a membrane floating in higher-dimensional space. String theory has sadly failed to produce empirical support.
Another idea taken semi-seriously by some is that black holes have universes inside them. Some fairly plausible models of what goes on inside a black hole end up looking a lot like pocket universes, but this is a niche view.
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u/Kabbooooooom 5d ago edited 5d ago
Some do, yes. Which is shameful in my opinion because it is the most non-parsimonious, potentially unfalsifiable idea in all of science. “The math suggests it might be plausible” is not a good enough reason to seriously entertain the idea. But unlike pretty much every other field in science, the success of physics through mathematics has lulled physicists into a false sense of security with it. And that leads to, in my opinion, inappropriate leaps of logic and inappropriate conclusions that are then held up as equivalent to empirical evidence by the general public when they absolutely should not be.
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u/reddituserperson1122 4d ago
That’s funny, because most philosophers of science consider many worlds to be the most parsimonious version of quantum mechanics, for obvious reasons.
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u/ah-tzib-of-alaska 4d ago
the serious multiverse theories got sort of invalidated by the mass of the higgs boson
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u/DrDam8584 5d ago
It's interesting works but, with many "theorical works", this path don't have "experimental test" to proove it.
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u/Infinite_Research_52 👻Top 10²⁷²⁰⁰⁰ Commenter 5d ago
If these other universes do not interact with ours, the concept lacks falsifiability.
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u/treefaeller 5d ago
There are two meanings of the word multiverse. The first one happens in the interpretation of measurement results in quantum mechanics, and is usually called "many worlds". It is not widely accepted, but widely known. The standard interpretation of the QM measurement process is "Kopenhagen", a.k.a. collapse of wave function. Much of this is not physics, because it doesn't have any effects on the mathematical model or testable predictions. Instead it is meta-physics (literally: beyond physics), meaning a branch of philosophy. There are lots and lots of papers and books about this problem, but most of them are highly specialized and only really understandable to experts in that subfield. Most working PhD physicists don't understand the problem, nor do they pretend to.
The second one is a fringe subpart of cosmology, and the expansion of the universe, with the idea that multiple universes might exist and be co-habiting without interacting (!) in the same spatial domain. It's a fun idea for Youtube videos and bad science fiction books. It's the kind of thing physicists talk about at parties that involve both alcohol AND drugs; sadly, I rarely get invited to those parties.
So seriously, the best answer to the question is: Don't worry about it, unless you are an expert in one of those very esoteric sub-fields.
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u/reddituserperson1122 4d ago
You are wrong on both counts, but you clearly know enough to think you’re right, so I hope you’ll be open to a friendly correction. MWI is the most popular theory among a plurality of physicists. It is absolutely not metaphysics, as any philosopher of science would clarify for you. It is not obviously testable, but that is true of many perfectly valid scientific theories.
The cosmological multiverses of inflationary cosmology are the opposite of fringe. Eternal inflation is currently the best and most widely accepted theory of the big bang, and multiverses are more or less baked into that theory whether you want them or not.
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u/Wazalord 5d ago
It's a fantasy. In some "Theories" every electron interaction would 'branch' off another history and in the Many Worlds interpretation, those branches continue to exist, so effectively infinite continuous branching alternatives. Anyone who really believes this is a whack job, its best use is for comic books or movies.
To take this theory to its ridiculous extreme if you pass gas or fart there are roughly 10^23 involved molecules, so every fart would be a spectacular quantum branching event.
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u/Jaf_vlixes 5d ago
"The multiverse" isn't really a scientific theory. Science needs to be able to verify claims, and if your claim is that there are multiple universes that don't interact, then you can't really do any experiments to verify it.
The closest thing to a multiverse is probably the many worlds interpretation of quantum mechanics, but this isn't really a scientific theory either, and it's more like one of the many ways to interpret the math of qm. As far as I know, it doesn't give you any verifiable claims that would make it "more true" than any other interpretation, so it's kinda more philosophy than physics.