https://iai.tv/articles/the-seduction-of-the-multiverse-auid-1806?_auid=2020

"Today, physicists still lack evidence of other universes, or even good ideas for obtaining evidence. Many nonetheless insist our cosmos really is just a mote of dust in a vast “multiverse.” One especially eloquent and passionate multiverse theorist is Sean Carroll. His faith in the multiverse stems from his faith in quantum mechanics, which he sees as our best account of reality.

In his book Something Deeply Hidden, Carroll asserts that quantum mechanics describes not just very small things but everything, including us. “As far as we currently know,” he writes, “quantum mechanics isn’t just an approximation to the truth; it is the truth.” And however preposterous it might seem, a multiverse, Carroll argues, is an inescapable consequence of quantum mechanics.

***

"This hypothesis, which came to be called the many-worlds theory, has been refined over the decades. It no longer entails acts of measurement, or consciousness (sorry New Agers). The universe supposedly splits, or branches, whenever one quantum particle jostles against another, making their wave functions collapse. This process, called “decoherence,” happens all the time, everywhere. It is happening to you right now. And now. And now. Yes, zillions of your doppelgangers are out there at this very moment, probably having more fun than you. Asked why we don’t feel ourselves splitting, Everett replied, “Do you feel the motion of the earth?” Carroll addresses the problem of evidence, sort of. He says philosopher Karl Popper, who popularized the notion that scientific theories should be precise enough to be testable, or falsifiable, “had good things to say about” Everett’s hypothesis, calling it “a completely objective discussion of quantum mechanics.” (Popper, I must add, had doubts about natural selection, so his taste wasn’t irreproachable.)

***

"Physicists have proposed even stranger multiverses, which science writer Tom Siegfried describes in his book The Number of the Heavens. String theory, which posits that all the forces of nature stem from stringy thingies wriggling in nine or more dimensions, implies that our cosmos is just a hillock in a sprawling “landscape” of universes, some with radically different laws and dimensions than ours. Chaotic inflation, a supercharged version of the big bang theory, suggests that our universe is a minuscule bubble in a boundless, frothy sea.

"In addition to describing these and other multiverses, Siegfried provides a history of the idea of other worlds, which goes back to the ancient Greeks. (Is there anything they didn’t think of first?) Acknowledging that “nobody can say for sure” whether other universes exist, Siegfried professes neutrality on their existence. But he goes on to construct an almost comically partisan defense of the multiverse, declaring that “it makes much more sense for a multiverse to exist than not."

***

"I am not a multiverse denier, any more than I am a God denier. Science cannot resolve the existence of either God or the multiverse, making agnosticism the only sensible position. I see some value in multiverse theories. Particularly when presented by a writer as gifted as Sean Carroll, they goad our imaginations and give us intimations of infinity. They make us feel really, really small—in a good way.

"But I’m less entertained by multiverse theories than I once was, for a couple of reasons. First, science is in a slump, for reasons both internal and external. Science is ill-served when prominent thinkers tout ideas that can never be tested and hence are, sorry, unscientific. Moreover, at a time when our world, the real world, faces serious problems, dwelling on multiverses strikes me as escapism—akin to billionaires fantasizing about colonizing Mars. Shouldn’t scientists do something more productive with their time?"

Comment: I'm with Horgan. Multiverse discussion is entertaining fluff, nothing more.

https://evolutionnews.org/2021/03/multiverse-myth-frees-atheists-from-real-science/

"If you’re hard-set at denying the existence of God, fine-tuning of the cosmos to allow the existence of man is not an easy observation to elide.

"Deniers of God’s existence have clung to one main gambit to avoid the design implications of the fine-tuning of the universe — the multiverse. The multiverse is a theoretical inference drawn from the mathematical description of the early moments of the Big Bang. The equations of relativity imply the possible existence of many companion “universes” to ours. It seems that we cannot observe them, which makes their status as scientific observations dubious. But the multiverse has, for atheists, played a much more important role than that ordinarily played by untestable inferences from equations.

"Atheists acknowledge the obvious: the likelihood that chance can account for the constellation of physical parameters that lead to the emergence man in our universe is vanishingly small. Instead, atheists argue that if the laws of physics differ slightly in each universe in the multiverse, then the probability across all of the universes — the multiverse — that the values of forces in one universe would permit life to arise becomes much higher.

***

"What atheists have done is invoke a concept of multiverse that is conceptually unintelligible and scientifically unobservable. This unintelligible unobservable probability landscape is convenient for atheists, who can merely assert that it accounts for fine-tuning without providing even a shred of evidence or logic. The “multiverse” theory frees atheists from real science, which is the only condition in which atheism can survive."

Comment: We've been over all of this before. The conjecture is unproveable and therefore worthless. We have Karl Popper's word.

https://www.math.columbia.edu/~woit/wordpress/?p=12161

"I’ve written extensively here and elsewhere about the real problem with all claims by theorists to be studying the multiverse: they’re Theorists Without a Theory, lacking any sort of viable theory which could make the usual sort of scientific predictions. The main problem with the Quanta article is at the beginning:

"What lies beyond all we can see? The question may seem unanswerable. Nevertheless, some cosmologists have a response: Our universe is a swelling bubble. Outside it, more bubble universes exist, all immersed in an eternally expanding and energized sea — the multiverse.

"The idea is polarizing. Some physicists embrace the multiverse to explain why our bubble looks so special (only certain bubbles can host life), while others reject the theory for making no testable predictions (since it predicts all conceivable universes). But some researchers expect that they just haven’t been clever enough to work out the precise consequences of the theory yet.

"Now, various teams are developing new ways to infer exactly how the multiverse bubbles and what happens when those bubble universes collide.

"The big problem is with:

they just haven’t been clever enough to work out the precise consequences of the theory yet.

"The reference to “precise consequences” is a common misleading rhetorical move, implying that there is no problem getting “imprecise consequences”, that the problem is just getting those extra digits of numerical precision. What’s really going on is that we know of no theoretical consequences of the multiverse, precise or imprecise, because there is no viable theory. The logic here is pretty much pure wishful thinking: if you look at colliding Bose-Einstein condensates and see a particular pattern, then if you saw a pattern like that in the CMB, you could try and infer something about your unknown multiverse theory. It’s not unusual for theorists to work on speculative ideas involving some degree of wishful thinking, but this is a case of taking that to an extreme."

Comment: If you are given enough grant money you can follow any daydream. Without any benefit

QUOTE: "To say that the universe is one of many parallel ones is just one of many possible explanations. Being confined to this point in time and space in a potentially infinite universe where we have only been observing its expansion for the last 100 years, we can hardly make such bold claims. The answer is neither “we are special” nor “many universes”, it is “we don’t know”.

dhw: An answer which of course extends to all the major questions we keep asking!

DAVID: We should not let our confusion about quantum reality to drive us to the nutty conclusion there are multiple parallel universes.

dhw: Perhaps we should not let our confusion about all aspects of reality drive us to any nutty conclusions at all!

Agreed.

An answer which of course extends to all the major questions we keep asking!

DAVID: We should not let our confusion about quantum reality to drive us to the nutty conclusion there are multiple parallel universes.

Perhaps we should not let our confusion about all aspects of reality drive us to any nutty conclusions at all!

https://medium.com/the-infinite-universe/i-do-not-believe-in-the-multiverse-the-case-fo...

"The problem with it is that it fails Ockham’s razor and rests on the most tenuous physical arguments. It tells us that not only are there an infinite number of alternate realities out there but that this must be so because it is the only way to explain quantum theory coherently. The latter statement is hardly true, and the strawman argument that its only rival is something called “wavefunction collapse” is also false.

***

"To say that the universe is one of many parallel ones is just one of many possible explanations. Being confined to this point in time and space in a potentially infinite universe where we have only been observing its expansion for the last 100 years, we can hardly make such bold claims. The answer is neither “we are special” nor “many universes”, it is “we don’t know”.

"I’m not going to beat around the bush here: I don’t believe in the multiverse. Not only is it scientifically premature, I think it is logically weak too, on par with the simulation hypothesis in terms of philosophical merit.

***

"While Bohmian mechanics has some issues with relativity (which I have written about extensively elsewhere) as well as how to interpret particle creation and annhilation, it reestablishes realism and does away with the notion that how we choose to observe the universe changes reality itself.

"In the double slit experiment, unlike the multiverse, Bohmian mechanics says the photon goes through one slit or the other, not both, but that the wavefunction guides it into a wave interference pattern anyway. When you try to observe which slit it went through you are interfering with the wavefunction and particle and so you no longer get the pattern. It is very straightforward.

***

"Far from refuting Bohr, it upholds his interpretation on the whole because it says that experimenters are just viewing different aspects of reality through their experimental setups, not changing it. How they look at reality changes how they see it, but the underlying state is definite. While experiments destroy or alter the state of the particles under observation, they do not fundamentally change what is real for the observer. That is relativism not subjectivism.

"I would suggest that Bohmian mechanics accurately extends and reinterprets Bohr’s original ideas of complementarity, putting them on a more solid mathematical footing. It rejects subjectivism and positivism (anti-realism) and embraces relativism in a single universe. In addition, it mathematically refines quantum theory, opening the door to potential tests of its validity. So far, the multiverse invites no such tests. (my bold)

"As for the anthropic principle, like I said, it’s a big universe and we have really been looking at it for a short time. We don’t even know answers to questions like: what really happened at the Big Bang, what is time, and what is beyond the observable universe. We don’t know what happens inside black hole singularities where new laws of physics may exist. Do the same laws of physics apply in the parts of the universe we can’t see? It seems lazy to jump to the MWI to explain our own existence because we think it is too big a coincidence. We don’t even have the knowledge to say such a thing. While we have discovered in the past 100 years that the universe is vast with countless stars and planets, it may be vaster still and yet still be one universe."

Comment: We should not let our confusion about quantum reality to drive us to the nutty conclusion there are multiple parallel universes.

https://www.math.columbia.edu/~woit/wordpress/?p=11767

"I never thought I would see this happen: a university PR department correcting media hype about its research. You might have noticed this comment here a week ago, about a flurry of media hype about neutrinos and parallel universes. A new CNN story does a good job of explaining where the nonsense came from. The main offender was New Scientist, which got the parallel universe business somehow from Neil Turok

"The ANITA scientists and their institution’s PR people were not exactly blameless, having participated in a 2018 publicity campaign to promote the idea that they had discovered not a parallel universe, but supersymmetry. They reported an observation here, which led to lots of dubious speculative theory papers, ... The University of Hawaii in December 2018 put out a press release announcing that UH professor’s Antarctica discovery may herald new model of physics. One can find all sorts of stories from this period about how this was evidence for supersymmetry,

"It’s great to see that the University of Hawaii has tried to do something at least about the latest “parallel universe” nonsense, putting out last week a press release entitled Media incorrectly connects UH research to parallel universe theory. CNN quotes a statement from NASA (I haven’t seen a public source for this), which includes:

"Tabloids have misleadingly connected NASA and Gorham’s experimental work, which identified some anomalies in the data, to a theory proposed by outside physicists not connected to the work. Gorham believes there are more plausible, easier explanations to the anomalies.

"The public understanding of fundamental physics research and the credibility of the subject have suffered a huge amount of damage over the past few decades, due to the overwhelming amount of misleading, self-serving BS about parallel universes and failed speculative ideas put out by physicists, university PR departments and the journalists who mistakenly take them seriously. I hope this latest is the beginning of a new trend of people in all these categories starting to fight hype, not spread it."

Comment: Part of the problem is the vast number of news outlets need startling news to draw enough readers. Thanks to Woit and Hossenfelder who try to bring sanity to the news.

QUOTES: And, no matter how much we might want to believe that God designed all life on Earth, we must accept that intelligent design makes no testable predictions of its own. It is simply a conceptual alternative to evolution as the cause of life’s incredible complexity.

…is it asking too much that they make their assertions with some honesty? Instead of ‘the multiverse exists’ and ‘it might be true’, is it really so difficult to say something like ‘the multiverse has some philosophical attractions, but it is highly speculative and controversial, and there is no evidence for it’?

DAVID: well stated.

dhw: Again it's a pleasure to agree with you! Thank you for this excellent exposé of double standards. It’s good to have such balanced articles on the agnostic website.

Thank you. Agreed.

…is it asking too much that they make their assertions with some honesty? Instead of ‘the multiverse exists’ and ‘it might be true’, is it really so difficult to say something like ‘the multiverse has some philosophical attractions, but it is highly speculative and controversial, and there is no evidence for it’?

DAVID: well stated.

Again it's a pleasure to agree with you! Thank you for this excellent exposé of double standards. It’s good to have such balanced articles on the agnostic website.

https://aeon.co/essays/post-empirical-science-is-an-oxymoron-and-it-is-dangerous?utm_so...

"There is no agreed criterion to distinguish science from pseudoscience, or just plain ordinary bullshit, opening the door to all manner of metaphysics masquerading as science. This is ‘post-empirical’ science, where truth no longer matters, and it is potentially very dangerous.

"It’s not difficult to find recent examples. On 8 June 2019, the front cover of New Scientist magazine boldly declared that we’re ‘Inside the Mirrorverse’. Its editors bid us ‘Welcome to the parallel reality that’s hiding in plain sight’.

***

"as so often happens these days, a few physicists have suggested that this is a problem with ‘a very natural explanation’. They claim that the neutrons are actually flitting between parallel universes. They admit that the chances of proving this are ‘low’, or even ‘zero’, but it doesn’t really matter. When it comes to grabbing attention, inviting that all-important click, or purchase, speculative metaphysics wins hands down.

***

"I, for one, prefer a science that is rational and based on evidence, a science that is concerned with theories and empirical facts, a science that promotes the search for truth, no matter how transient or contingent. I prefer a science that does not readily admit theories so vague and slippery that empirical tests are either impossible or they mean absolutely nothing at all.

***

"The philosopher Karl Popper argued that what distinguishes a scientific theory from pseudoscience and pure metaphysics is the possibility that it might be falsified on exposure to empirical data. In other words, a theory is scientific if it has the potential to be proved wrong.

***

"And, no matter how much we might want to believe that God designed all life on Earth, we must accept that intelligent design makes no testable predictions of its own. It is simply a conceptual alternative to evolution as the cause of life’s incredible complexity. Intelligent design cannot be falsified, just as nobody can prove the existence or non-existence of a philosopher’s metaphysical God, or a God of religion that ‘moves in mysterious ways’. Intelligent design is not science: as a theory, it is simply overwhelmed by its metaphysical content.

***

"But, for me at least, there has to be a difference between science and pseudoscience; between science and pure metaphysics, or just plain ordinary bullshit.

***

"Today, we’re blessed with two extraordinary theories. The first is quantum mechanics. This is the basis for the so-called standard model of particle physics that describes the workings of all known elementary particles. It is our best theory of matter. The second is Einstein’s general theory of relativity that explains how gravity works, and is the basis for the so-called standard model of Big Bang cosmology. It is our best theory of space, time and the Universe.

***

"To work satisfactorily, Big Bang cosmology requires rather a lot of ‘dark matter’ and ‘dark energy’, such that ‘what we can see’ accounts for an embarrassingly small 5 per cent of everything we believe there is in the Universe. If dark matter is really matter of some kind, then it’s simply missing from our best theory of matter. Changing one or more of the constants that govern the physics of our Universe by even the smallest amount would render the Universe inhospitable to life, or even physically impossible. We have no explanation for why the laws and constants of physics appear so ‘fine-tuned’ to evolve a Goldilocks universe that is just right.

***

"it has been argued, intelligent design is hardly less testable than many multiverse theories. To dismiss intelligent design on the ground that it is untestable, and yet to accept the multiverse as an interesting scientific hypothesis, may come suspiciously close to applying double standards. As seen from the perspective of some creationists, and also by some non-creationists, their cause has received unintended methodological support from multiverse physics.

***

"is it asking too much that they make their assertions with some honesty? Instead of ‘the multiverse exists’ and ‘it might be true’, is it really so difficult to say something like ‘the multiverse has some philosophical attractions, but it is highly speculative and controversial, and there is no evidence for it’?"

Comment: well stated.

https://www.forbes.com/sites/startswithabang/2019/07/16/you-must-not-trust-experiments-...

"Most scenarios involving parallel Universes like this are untestable, as we're restricted to living in our own Universe, disconnected from any others. Yet if one particular idea is right, there might be an experimental signature awaiting our investigations. But even if it yields positive results, you shouldn't trust it. Here's why.

"Whenever you have an experimental or observational result you cannot explain with your current theories, you have to take note of it. Robust measurements that defy the expectations of our predictions might turn out to be nothing — they might go away with more, improved data — or they might simply be errors. This has famously been the case many times,

***

"However, sometimes there are results that really do appear to be puzzles: the experiments shouldn't turn out the way they did if the Universe works the way we think it does. These results often turn out to be omens that we're about to discover new physics, but they also frequently turn out to be red herrings that lead nowhere. Even worse, they can turn out to be duds, where they only appear to be interesting because someone, somewhere, made an error.

***

"In all of these cases, as well as many others, it's important to get both the theoretical and the experimental work right. From a theoretical point of view, that means having a strong quantitative understanding about the expected signal that your new theory predicts as compared to the background signal that the prevailing theory predicts. You must understand what signals should be generated by both your new theory and the one it's seeking to supersede.

"From an experimental point of view, this translates into understanding your backgrounds/noise, and looking for an excess signal superimposed atop that background. Only by comparing your observed signal with the anticipated background and seeing a clear excess can you ever hope to have a robust detection. It was only when the evidence for the Higgs boson passed a certain significance that we could claim a definitive detection.

***

"Any time you get a positive signal from an experiment, you cannot simply take that signal at face value. Signals can only be understood in relation to the noise background of the experiment, which is a combination of every other physical process that contributes to the result. Unless you quantify that background and understand the source of everything that your final signal is composed of, you cannot hope to conclude you've discovered a new phenomenon in nature.

"Science progresses one experiment at a time, and it's always the full suite of evidence that must be considered in evaluating our theories at any given time. But there is no greater false flag than an experiment pointing to a new signal extracted against a poorly understood background. In the endeavor of pushing our scientific frontiers, this is the one area that demands the highest level of skeptical scrutiny. Mirror matter and even a mirror Universe might be real, but if you want to make that extraordinary claim, you'd better make sure your evidence is equally extraordinary."

Comment: We live in this universe. How do we look out? The theory currently in vogue is if an other universe bumped into ours there should be a telltale circle in the CMB. There isn't. All the attempts are is to get rid of the appearance that the universe had a starting point and looks created.

DAVID: Sabine Hossenfelder again:

http://backreaction.blogspot.com/2019/07/why-multiverse-is-religion-not-science.html

QUOTE: "Universes besides our own are logically equivalent to gods. They are unobservable by assumption, hence they can exist only in a religious sense. You can believe in them if you want to, but they are not part of science.”

DAVID: 'nuff said

dhw: Thank you for this absolutely brilliant article.

She is the most clear-thinking theoretical physicist I know.

http://backreaction.blogspot.com/2019/07/why-multiverse-is-religion-not-science.html

QUOTE: "Universes besides our own are logically equivalent to gods. They are unobservable by assumption, hence they can exist only in a religious sense. You can believe in them if you want to, but they are not part of science.”

DAVID: 'nuff said

Thank you for this absolutely brilliant article.

http://backreaction.blogspot.com/2019/07/why-multiverse-is-religion-not-science.html

"Universes besides our own are logically equivalent to gods. They are unobservable by assumption, hence they can exist only in a religious sense. You can believe in them if you want to, but they are not part of science.

"I know that this is not a particularly remarkable argument. But physicists seem to have a hard time following it, especially those who happen to work on the multiverse. Therefore, let me sort out some common misunderstandings.

"First. The major misunderstanding is that I am saying the multiverse does not exist. But this is not what I am saying. I am saying science does not tell us anything about universes we cannot observe, therefore claiming they exist is not science.

"Second. They will argue the multiverse is simple. Most physicists who are in favor of the multiverse say it’s scientific because it’s simpler to assume that all universes of a certain type exist than it is to assume that only one of them exist.

"That’s a questionable claim. But more importantly, it’s beside the point. The simplest assumption is no assumption. And you do not need to make any statement about the existence of the multiverse to explain our observations. Therefore, science says, you should not. As I said, it’s the same with the multiverse as with god. It’s an unnecessary assumption. Not wrong, but superfluous.

"Third. They’ll claim the existence of the multiverse is a prediction of their theory.

It’s not. That’s just wrong. Just because you can write down a theory for something, doesn’t mean it exists*. We determine that something exists, in the scientific sense, if it is useful to describe observation. That’s exactly what the multiverse is not.

"Fourth. But then you are saying that discussing what’s inside a black hole is also not science

"That’s equally wrong. Other universes are not science because you cannot observe them. But you can totally observe what’s inside a black hole. You just cannot come back and tell us about it. Besides, no one really thinks that the inside of a black hole will remain inaccessible forever. For these reasons, the situation is entirely different for black holes. If it was correct that the inside of black holes cannot be observed, this would indeed mean that postulating its existence is not scientific.

"Fifth. But there are types of multiverses that have observable consequences.

"That’s right. Physicists have come up with certain types of multiverses that can be falsified. The problem with these ideas is conceptually entirely different. It’s that there is no reason to think we live in such multiverses to begin with. The requirement that a hypothesis must be falsifiable is certainly necessary to make the hypothesis scientific, but not sufficient.

"To sum it up. The multiverse is certainly an interesting idea and it attracts a lot of public attention. There is nothing wrong with that in principle. Entertainment has a value and so has thought-stimulating discussion. But do not confuse the multiverse with science, because it is not. "

comment: 'nuff said

https://www.forbes.com/sites/startswithabang/2018/07/17/what-is-and-isnt-scientific-abo...

"According to the leading ideas of theoretical physics, however, our Universe may be just one minuscule region of a much larger multiverse, within which many Universes, perhaps even an infinite number, are contained. Some of this is actual science, but some is nothing more than speculative, wishful thinking. Here's how to tell which is which.

"In the 1980s, a large number of theoretical consequences of inflation were worked out, including:
what the seeds for large-scale structure should look like,
that temperature and density fluctuations should exist on scales larger than the cosmic horizon,
that all regions of space, even with fluctuations, should have constant entropy,
and that there should be a maximum temperature achieved by the hot Big Bang.
In the 1990s, 2000s and 2010s, these four predictions were observationally confirmed to great precision. Cosmic inflation is a winner.

"Inflation tells us that, prior to the Big Bang, the Universe wasn't filled with particles, antiparticles and radiation. Instead, it was filled with energy inherent to space itself, and that energy caused space to expand at a rapid, relentless, and exponential rate. At some point, inflation ends, and all (or almost all) of that energy gets converted into matter and energy, giving rise to the hot Big Bang. The end of inflation, and what's known as the reheating of our Universe, marks the start of the hot Big Bang. The Big Bang still happens, but it isn't the very beginning. (my bold)

***

"If you then require inflation to have the properties that all quantum fields have:
that its properties have uncertainties inherent to them,
that the field is described by a wavefunction,
and the values of that field can spread out over time,
you reach a surprising conclusion.

***

"Inflation doesn't end everywhere at once, but rather in select, disconnected locations at any given time, while the space between those locations continues to inflate. There should be multiple, enormous regions of space where inflation ends and a hot Big Bang begins, but they can never encounter one another, as they're separated by regions of inflating space. Wherever inflation begins, it is all but guaranteed to continue for an eternity, at least in places.

"Where inflation ends for us, we get a hot Big Bang. The part of the Universe we observe is just one part of this region where inflation ended, with more unobservable Universe beyond that. But there are countlessly many regions, all disconnected from one another, with the same exact story.

"That's the idea of the multiverse. As you can see, it's based on two independent, well-established, and widely-accepted aspects of theoretical physics: the quantum nature of everything and the properties of cosmic inflation. There's no known way to measure it, just as there's no way to measure the unobservable part of our Universe. But the two theories that underlie it, inflation and quantum physics, have been demonstrated to be valid. If they're right, then the multiverse is an inescapable consequence of that, and we're living in it.

"So what? That's not a whole lot, is it? There are plenty of theoretical consequences that are inevitable, but that we cannot know about for certain because we can't test them. The multiverse is one in a long line of those. It's not particularly a useful realization, just an interesting prediction that falls out of these theories.

"So why do so many theoretical physicists write papers about the multiverse? About parallel Universes and their connection to our own through this multiverse? Why do they claim that the multiverse is connected to the string landscape, the cosmological constant, and even to the fact that our Universe is finely-tuned for life?

***

"As I've explained before, the Multiverse is not a scientific theory on its own. Rather, it’s a theoretical consequence of the laws of physics as they’re best understood today. It’s perhaps even an inevitable consequence of those laws: if you have an inflationary Universe governed by quantum physics, this is something you’re pretty much bound to wind up with. But — much like String Theory — it has some big problems: it doesn't predict anything we either have observed and can't explain without it, and it doesn't predict anything definitive we can go and look for.

"Because even though it's obviously a bad idea, they don't have any better ones.

***

"But when people then contend that they can draw conclusions about fundamental constants, the laws of physics, or the values of string vacua, they're no longer doing science; they're speculating. Wishful thinking is no substitute for data, experiments, or observables. Until we have those, be aware that the multiverse is a consequence of the best science we have available today, but it doesn't make any scientific predictions we can put to the test."

Comment: Multiverse may be worthless, but the article is a great review of what we know.

https://www.npr.org/sections/13.7/2018/01/22/579666359/scientific-theory-and-the-multiv...

"Today, the idea that we live in a multiverse has become popular in the foundations of physics. The multiverse collects all universes in which the constants of nature — Newton's constant and about two dozen more — can take on any value. Each combination of constants is realized in infinitely many universes.

"And not only the constants can change from one universe to another, the locations of particles relative to each other can also be different. Since there are infinitely many universes in which to arrange the particles, some of these universes will be very similar to our own, just that eventually some initially tiny deviation will lead to an alternative history. Thus, somewhere in the multiverse our lives play out in any which way you can imagine.

"But before you pack your bags and search for a universe more to your liking, let me add there's no way to cross over into another universe or even interact with one. This only works in science fiction. Indeed, to my taste, the multiverse itself is already too close to fiction.
Many theoretical physicists have argued the conclusion that we live in a multiverse is based on sound scientific reasoning. But that isn't so — and I will tell you why.

***

"If Ockham could see what physicists are doing here, he'd pray for God to bring reason back to Earth. You should remove unnecessary assumptions, alright. But certainly you shouldn't remove assumptions that you need to describe observations. If you do, you'll just get a useless theory, equations from which you can't calculate anything.

"These useless theories which lack assumptions necessary to describe observations are what we now call a multiverse. And they're about as useful as Ockham's prayers.

"Since you cannot calculate anything in the multiverse, the assumptions which physicists removed must then be replaced with something else. That "something else" is a probability distribution on the multiverse, which tells you not what we do observe, but what we are likely to observe. But it is simpler to assume a constant than an infinite number of universes with a probability distribution over them. Therefore, Ockham's razor should shave off the multiverse. It's superfluous. Unfortunately, this argument carries little weight among many of today's theoretical physicists who value the multiverse because it excuses boundless speculation.

***

"Let me also add that these examples of "predictive" multiverses are ad hoc constructs invented for the very reason of convincing skeptics that some types of multiverses can have observable consequences. Don't fall for it. Just because a theory is falsifiable doesn't mean it's scientific. For a theory to be scientific its predictions must also have a reasonable chance to accurately describe reality. Construing up one of an infinite number of multiverse variants has no reasonable chance.

***

"Why then has the idea become popular? A cynic may argue it's because the multiverse offers infinitely many new opportunities for paper writing. But I don't want to feign hypotheses.
Let me thus stick to the facts: To our best knowledge, assuming the existence of any universe besides our own is unnecessary to explain anything we have ever observed. In the best case, then, the multiverse is an interpretation.

"You can believe that the seeming arbitrariness of the constants of nature is due to an infinite number of other universes. You can believe that, but you don't have to. Science cannot confirm that the other universes exist, but it also cannot rule them out. Just like science cannot rule out the gods and angels."

Comment: Sabine Hossenfelder at her best. Like string theory theory not likely to be of any help in understanding the universe.

DAVID: I'm glad you like my thoughts about loneliness. It does offer a different approach about God's possible personality. If He is all-knowing, then this discussion is a n on-starter. He knows all about emotions and relationships without experiencing them. But since I try not to use Biblical impressions of God, He may have to experience relating to us, His creations.

I do like this approach, and I think it is one element of so-called process theology: that God is not immutable and all-knowing but is involved, like ourselves, in a process of “becoming”. In other words, he learns and experiences as he goes along. Needless to say, you can apply this to evolution – he learns as he goes along (or, if my autonomous inventive mechanism hypothesis is correct, he learns as it goes along).

DAVID: As for the diversity, it is balance of nature/energy supply, nothing more. As for making no sense, I like my sensible answers to the questions.[/i]

dhw: There is no misunderstanding, unless you are backtracking on your original agreement with me, which I have now quoted several times, that it does not make sense if an all-powerful God sets out with the intention of producing humans, but first produces the weaverbird’s nest, the monarch’s lifestyle (plus all the other natural wonders extant and extinct) in order to keep life going until humans appear. The only explanation you could offer was that your God might be limited, i.e. not all-powerful. I have offered alternatives to your two hypotheses, and you have agreed they fit in with the history of life as we know it.

There is no disagreement between us on the proposal that diversity is the result of the changing balance of nature, as caused by the changing energy supply. We have agreed that this has nothing whatsoever to do with humans being the “endpoint” of evolution.

Thank you. We agree.

I do like this approach, and I think it is one element of so-called process theology: that God is not immutable and all-knowing but is involved, like ourselves, in a process of “becoming”. In other words, he learns and experiences as he goes along. Needless to say, you can apply this to evolution – he learns as he goes along (or, if my autonomous inventive mechanism hypothesis is correct, he learns as it goes along).

DAVID: However, you finished your reasonable paragraph with a note about life's diversity and the length of time for evolution of humans with total misunderstanding, as usual.
We do not know if God is limited in any way in explaining the length of time for human evolution. If He is control of the rate of evolution, as I believe, then the rapid appearance of life earlier on Earth and the sudden appearance of the Cambrian Explosion, tells us He can move quickly when He wants to. Look at how quickly human development occurred in the past eight million years. As for the diversity, it is balance of nature/energy supply, nothing more. As for making no sense, I like my sensible answers to the questions.

There is no misunderstanding, unless you are backtracking on your original agreement with me, which I have now quoted several times, that it does not make sense if an all-powerful God sets out with the intention of producing humans, but first produces the weaverbird’s nest, the monarch’s lifestyle (plus all the other natural wonders extant and extinct) in order to keep life going until humans appear. The only explanation you could offer was that your God might be limited, i.e. not all-powerful. I have offered alternatives to your two hypotheses, and you have agreed they fit in with the history of life as we know it.

There is no disagreement between us on the proposal that diversity is the result of the changing balance of nature, as caused by the changing energy supply. We have agreed that this has nothing whatsoever to do with humans being the “endpoint” of evolution.

dhw: We are making progress.[/i]

DAVID: Not much progress. If God is all alone, to whom does He relate to have all the emotional feelings you ascribe to Him? He might have created humans so that we could relate to him so He could observe our feelings and find out what emotions are like. That could be it. He's lonely and needed us to relate to!

Thank you for a brilliant answer. We are making huge progress! Let us substitute your humanized “lonely” for my humanized “bored”, if that is what you prefer. It gives us a very logical reason for his creating life. And indeed one can well imagine him designing all sorts of creatures, or creating a mechanism which would do its own designing, so that he could find some diversion to relieve the burden of his loneliness. He might possibly have wanted to create a mind like his own, and experimented. Or he might possibly have had the idea of designing a mind like his own during the course of his experiments. (I link experimentation to dabbling.) Or he might have been delighted to find that the mechanism he had designed to do its own designing actually came up with a mind like his own without him dabbling. All of these hypotheses fit in perfectly, not only with the history of life on Earth but also with the hypothesis that God may have been lonely and required some relief from his loneliness. Wouldn’t you say they are just as likely as your God saying to himself at the very beginning: “I’ll relieve my loneliness by creating humans that I can relate to, but first I shall have to design the weaverbird’s nest, the monarch’s lifestyle, the fly’s compound eye because…” either for the next 3.X billion years he is incapable of getting what he wants, or he just wants to do it that way for reasons you and I can’t even guess at, because such a decision makes no sense to either of us?

I'm glad you like my thoughts about loneliness. It does offer a different approach about God's possible personality. If He is all-knowing, then this discussion is a n on-starter. He knows all about emotions and relationships without experiencing them. But since I try not to use Biblical impressions of God, He may have to experience relating to us, His creations.

However, you finished your reasonable paragraph with a note about life's diversity and the length of time for evolution of humans with total misunderstanding, as usual.
We do not know if God is limited in any way in explaining the length of time for human evolution. If He is control of the rate of evolution, as I believe, then the rapid appearance of life earlier on Earth and the sudden appearance of the Cambrian Explosion, tells us He can move quickly when He wants to. Look at how quickly human development occurred in the past eight million years. As for the diversity, it is balance of nature/energy supply, nothing more. As for making no sense, I like my sensible answers to the questions.

DAVID: Not much progress. If God is all alone, to whom does He relate to have all the emotional feelings you ascribe to Him? He might have created humans so that we could relate to him so He could observe our feelings and find out what emotions are like. That could be it. He's lonely and needed us to relate to!

Thank you for a brilliant answer. We are making huge progress! Let us substitute your humanized “lonely” for my humanized “bored”, if that is what you prefer. It gives us a very logical reason for his creating life. And indeed one can well imagine him designing all sorts of creatures, or creating a mechanism which would do its own designing, so that he could find some diversion to relieve the burden of his loneliness. He might possibly have wanted to create a mind like his own, and experimented. Or he might possibly have had the idea of designing a mind like his own during the course of his experiments. (I link experimentation to dabbling.) Or he might have been delighted to find that the mechanism he had designed to do its own designing actually came up with a mind like his own without him dabbling. All of these hypotheses fit in perfectly, not only with the history of life on Earth but also with the hypothesis that God may have been lonely and required some relief from his loneliness. Wouldn’t you say they are just as likely as your God saying to himself at the very beginning: “I’ll relieve my loneliness by creating humans that I can relate to, but first I shall have to design the weaverbird’s nest, the monarch’s lifestyle, the fly’s compound eye because…” either for the next 3.X billion years he is incapable of getting what he wants, or he just wants to do it that way for reasons you and I can’t even guess at, because such a decision makes no sense to either of us?