New books mount aggressive but ultimately unpersuasive defenses of multiverses
blogs.scientificamerican.com
blogs.scientificamerican.com
In other leading theories (Roger Penrose's twistors| ima Arkani-Hamed's amplituhedrons; Lee Smolin's causal relations | views; ...) spacetime emerges, and issues of locality are "irrelevant."
Pushing MWI as the simplest explanation for nonlocality misses the point -- the need for deeper and more rational, unifying theories that better explain observed phenomena.
I frankly found the idea that any and every quantum collapse spawned a "new world" to be absurd, regardless of the arguments.
Appealing to human intuition may not be the best strategy either, as whatever the truth is need not conform to any ideas of human intuition or aesthetic.
I'd be more surprised if the answer is something we can easily make sense of.
I’m very tired of seeing pop science articles describe this so incorrectly. It’s a similar mistake as describing quantum computing as simultaneously trying a bunch of solution states “in parallel.”
The multiverse theory doesn’t imply any “splitting” action and certainly no such thing as special measurement or collapse.
If you make a measurement that distinguishes one universe from another, then “you” just discover which Everett branch you happened to have belonged to all along. It’s no different from observing outcomes of a random variable. Your mind is ignorant of a certain state of affairs, you measure something, now you’re slightly less ignorant of the state of affairs.
I am so sick of these articles. Multiverse QM is a settled debate. Move on.
I’ll try to explain why, using your random variable sampling analogy, which is telling. In the case of say, sampling from a coin toss random variable, there is indeed a more primitive explanation for why the coin comes up heads or tails, it’s just that it would be a much more complicated explanation involving knowledge of huge amounts of detail about the exact force applied to the coin, maybe air currents in the area where coin is being flipped, etc. But in principle that is all explainable.
With quantum measurement, there is no such explanation available, even in principle. We are told only that we will find ourselves in one of the possibilities admitted by the distribution predicted by QM. We have no further explanation for which one it will be. The QM multiverse folks then expect us to be okay with this as the end of the explanation. But notice this is a choice to adopt something as axiomatic. We could have done that at other points in the history of physics but didn’t.
That question does not really make sense. In every branch, there is 'you' asking about why is being in that particular branch.
With the coin flip, it’s understood that the probability distribution is not reality. It’s just a way of approximating reality without having to model all the things that would explain our observations.
With QM we have equations that predict probability distributions, and there is debate about whether reality is literally a distribution of possible states, or if it’s more like the coin flip random variable.
But you had just explained why:
> With quantum measurement, there is no such explanation available, even in principle.
That's ridiculous. The Copenhagen Interpretation is still the prevailing view, among MANY others: https://en.wikipedia.org/wiki/Interpretations_of_quantum_mec...
Further, the science is settled, so anyone who disagrees is a denier? Is that you, Mr. Carroll?
Wave function collapse is a purely unjustified extraneous detail that violates the scientific method to believe it without additional evidence.
MWI is by its own definition the choice of belief not requiring attaching vestigial extra details onto the theory, as far as any currently known experimental results go.
It's also a red herring. You stated that the science is settled. It is not. Not even close. "Settled" means that that there is a scientific consensus by all but a fringe, that MWI is the correct interpretation of QM. Of course, that is not the case, as should be blatantly obvious to you.
Besides which, nothing in science is ever "settled." It is always open to new interpretations when new data presents itself, or when a more persuasive theory is formulated. So on both counts your "settled" argument fails.
Furthermore, this statement is pretty bold, but let me re-write it, because it applies better to MWI than to the wave collapse function: "The Many Worlds conjecture is a purely unjustified extraneous detail that violates the scientific method to believe it without additional evidence."
The inability of the MWI to distinguish itself from the CI by any experiment, real or imagined, is the very reason why it has not gained traction.
no, science is not related to consensus. If it were, then religion would be a matter pf physics.
Science is unique in that only theories which hold up to the evidence matter, regardless of how many or few people (or experts) believe them.
In ~1800, the science against creationism was just as settled as it is today, despite the prevalence of that religious view, even among scientific authority, at that time.
What you are promoting is not science but philosophical posturing.
That suggests you badly misunderstand MWI or else have your own dogma in terms of how you’ll define it. Either way, comparing MWI to religious dogma is beyond ridiculous.
> “ For it to be remotely "settled," there actually has to be evidence. There is none.”
We have nearly a hundred years of quantum mechanical experimental evidence that supports MWI and doesn’t require no-evidence purely hypothetical extra things to be attached to the theory, like special collapse.
> “ What you are promoting is not science but philosophical posturing.”
Unless you can support this claim, it seems entirely disingenuous and it’s like you expect some purely rhetorical flair to make your point. Copenhagen is closer to your quote than MWI... it’s not even controversial to say so, purely definitional (as non-controversial as it can get).
See, no one disagrees about the evidence itself. That's why there is an "I" in "MWI." It is one of many possible interpretations of the evidence.
So that puts your whole "settled" nonsense into the category of philosophical posturing. You have a preference for the the MWI, but you have no scientific reason for it. That is why your reasons are entirely philosophical.
But you absolutely do not.
“Thing plus totally extraneous, unnecessary additional complicated hypotheses” is not equally as supported as just “thing”.
Science says let the simplest, most parsimonious explanation that survives contact with the data prevail.
There can be multiple hypotheses that are all congruent with the same experimental observations. That does not make each hypothesis equally valid.
Those hypotheses, like anything specifying needless extra collapse physics, that are not as slimmed down as they could be while maintaining congruence with the observations must be rejected in favor of those which make fewer unnecessary assumptions or invoke fewer unnecessary details.
The evidence is always for all theories that are congruent with it. That does not at all mean science equally supports all those theories.
Also, your assumption that there is no "collapse" is predicated on the notion that whatever wavefunction amplitude is modeling is a continuous variable, but IMO it is much more likely that it is discrete. If that thing is discrete, as the universe evolves, some states will cease to exist simply due to the fact that their measure will fall below the unit value. When the measure of all states but one fell below that unit, that would essentially be a collapse.
Likewise I think you are incorrect about your discreteness claim. I agree with you that QM suggests the nature of reality is fundamentally discrete, but that reality also places the Born rule as a continuous mixture model across discrete states, and this is specifically what allows there to be a continuum of universes of every measurement regardless of whether the outcome is continuous or discrete.. like reality’s own Lesbesgue-Stieltjes measure.
What people have trouble accepting is we may be in gross error about the fundamentals of things we think we understand, things like causality, chance and probability, the nature of consciousness to name a few.
Scientists long to believe they are this close to a full understanding of the universe and reality. The sad truth is, the actual nature of the universe may be such that we cannot grasp it with our brains in anyway, the same way a goldfish can't grasp particle theory.
If that's the case, does that suggest that rather than a neat tree of discrete universes that don't interact after they branch, the universe could be much fuzzier mess of conflicting realities that can intercommunicate?
"Rather than a neat tree of discrete universes that don't interact after they branch, the universe could be much fuzzier mess of conflicting realities that can intercommunicate".
Very well said and, in my opinion, this agrees most with my sense of how the world works.
In a way, reminds me of Rupert Sheldrake's work a bit, atleast in the sense that his biological work, despite mostly lacking known mechanisms, does seem to belong more to a universe that's a "fuzzier mess of conflicting realities that can intercommunicate".
Also, what you're describing sounds more like a multi-dimensional (above the ones we're aware of) universe rather than a multiverse.
> what you're describing sounds more like a multi-dimensional (above the ones we're aware of) universe rather than a multiverse.
I don’t know enough about physics to understand how a multi-dimensional (above 4D) universe is different than a multiverse. I assumed they were one and the same concept.
Imagine multiple copies of the same 4D universe.
How about that?
This parsimony question also overlaps the Simulation Hypothesis: the fact that most physical laws resolve at macro-scale, by aggregating probabilities, and only break down into odd behavior (where a particle seems to care whether or not you're looking), smells to this programmer like an optimization hack. :)
Just started reading Donald Hoffman's "The Case Against Reality", which posits some very bold answers to this question, theorizing that there is no reason to assume that base reality is anything like our perceptions (subjective or scientific), any more than there's a reason to assume the perception of a desktop icon has a direct relationship with its filesystem implementation. The implications of a "consciousness-first" rather than "matter-first" explanation of existence are staggering, and it isn't hard to set up a model in which that explanation is more parsimonious than Multiple Worlds.
I think the leap from A to B is unnecessary. "We don't know" is also an acceptable answer.
This idea of a multiverse is some metaphysics sprinkled in with the Copenhagen interpretation that boils down to something like this: the total probability of any observed outcome summed with the probability of all possible outcomes is, of course, one.
The metaphysics is this-- assuming that all the outcomes that did not occur did occur in some other unobservable and inaccessible universes.
This is essentially the meaning of the plus symbol in summing probabilities; it separates the observed wavefunction from every other possible wavefunction. It is absurd to draw such a mind-boggling conclusion from a plus sign.
Just because a theory makes correct predictions, does not mean, necessarily that those mechanisms exist in the actual physical universe. It is entirely possible to make correct predictions with incorrect models.
>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.
It is?? Does anyone know to what he's referring? From my un-scientific vantage point it seems to be thriving.
And string theory looks like it may have wasted a lot of people’s time with no result.
I’m not sure I agree... was just trying to explain why there is a perception of progress slowing down.
Until this is no longer true, I will view discussions of the multiverse as akin to medieval philosophers discussing how many angels can dance on the head of a pin.
One of the biggest lessons of the scientific revolution is that logic alone is a poor predictor of reality. We need at some point to go out and test our ideas in the real world.
Many of the greatest scientific discoveries were not testable until decades later.
Would you also have viewed Einstein as just a medieval philosopher back in his day ?
Einstein's theories were a response to experiments and known facts of the day, that didn't fit the current theoretical models. Sure plenty of it was difficult to test at the time (and still is in some ways when it comes to human scale. How many people do you know that have actually experianced human scale time dialation?) but its not like it was some castle in the sky totally divorced from the observable reality of the day.
Additionally even for predictions that weren't practically testable immediately, they were still testable theoretically given enough engineering effort. There is a big difference between not yet knowing how to test something, and not even knowing what you would test if resources/effort were no issue.
Interestingly, this is almost certainly anti-catholic protestant agitprop that lost context.
As such, the question never seems to have been asked; similar questions of extreme minutae were widely parodied but were probably never a matter of actual debate or discussion by scholastics.
Not that there is anything wrong with philosophizing and inquiring into metaphysical questions.
https://www.nytimes.com/2019/09/07/opinion/sunday/quantum-ph...
> But what is the wave function? Is it a complete and comprehensive representation of the world? Or do we need additional physical quantities to fully capture reality, as Albert Einstein and others suspected? Or does the wave function have no direct connection with reality at all, merely characterizing our personal ignorance about what we will eventually measure in our experiments?
Isn't this really just asking about scientific realism? Couldnt you say the same thing about any scientific concept? Instead of "what is the wave function", why not "what is an atom". I suspect the main difference is that earlier physical theories had a direct analogy to real life events. We could tell a story about the billard ball model of atoms and we can imagine that in our heads. I have no idea how to imagine a superposition of states. Without the ability to analogize it, i suspect humans intuitively assume its wrong. But lack of imagination hardly seems like a logical reason to reject something.
On the other hand, the question of how/when/why (non-metaphysically) a superposition collapses into a single state, seem much more scientific, and that part of the measurement problem seems like a worthy target of scientific investigation.
Disclaimer: iana physicist nor really know anything beyond basics about quatum mechanics.
Right, hence the popular aphorism (among physicists): "Shut up and calculate."
But it appears to be a hard problem, and a couple centuries of remarkable progress at solving problems is no predictor that the next problem will be easy.
Science cannot resolve the existence of either God or the multiverse, making agnosticism the only sensible position.
Science also can't refute me being a brain in the vat, or the universe having been created last thursday with the appearance of age. It's not only ok to commit to beliefs that cannot be proven scientifically, it is necessary.
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?
Why stop at the natural sciences? Let's get rid of all the useless parts of mathematics - or art and music, for that matter...
If you restricted human endeavours to the utilitarian, the world would be poorer for it.
Exactly, most people never realize this because they're so used to nonsense like gods and such. There is an infinite number of assertions that cannot be proved or disproved, it doesn't mean that I have any reason to be agnostic about them.
Couldn't you say the same about the author of the article himself? Why is he whining about scientists investigating the multiverse theory rather than doing something more productive with his time? What real world problem was solved with his article? If multiverse theory is escapism, then what the author is doing is a worse form of escapism.
Imagine there was a group of people who liked to meditate all day, every day (preferably at the beach, with a cold beer). Would you seriously argue that society should support these people in that, rather than push them to do something else to earn their keep? Note that meditating wouldn't be illegal, so they could still do it on their own time, they'd just need to have a day job.
I know nothing at all about multiverses beyond what I read in articles though, so I don't know if my idea would even be possible.
As light or matter approaches a Black Hole's event horizon, to the outside observer it takes an infinite amount of time to actually enter the black hole, but aside from being ripped apart on the way in, it seems we don't know what happens after that.
Within this event horizon, this time we can call "now" exists forever to the outside observer, as we add matter to the black hole we continue to add it to "now". So in essence the size of the inside of black hole grows inside as we add matter from the outside, but the inside has "always" had this amount of matter, yes?
The big bang is often thought to be an explosion, but as you read about it, there really was no center, rather there was a rapid expansion of space, not matter. It is the space between the matter that "exploded".
It seems to me there may be the potential for our known universe to be the result of a massive blackhole that took "forever" to create, so lots of time to create what we, being inside, see as a massive universe.
Because there may be material still be added from outside the blackhole, our space-time may be distorted with expansion and dark matter, but that part is hard to grasp. I suppose there could be blackholes inside of blackholes. If new material was added inside a blackhole, would we be able to observe that? Probably not now.
Our observations do indicate some uniformity to the known universe, the way galaxies are spread out relatively evenly, indicating some sort of law or tendency.
Continuing to keep in mind there is no center to the big bang, and matter may be continuing to be added, this may be a possibility of why our universe is is in a sort of continuous expansion, and in it exists dark matter.
Interesting stuff, but of course no way to know right now, unless of course now is forever, in which case I either forever don't know, or at some point will have always known.