Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

New books mount aggressive but ultimately unpersuasive defenses of multiverses

blogs.scientificamerican.com

Post reply on HN
Print view View original

41–50 of 72 posts

Re: New books mount aggressive but ultimately unpersuasive defenses of multiverses

#41

Post by bawolff »

archgoon wrote: post #39
bawolff wrote: post #36

Earlier quoted context omitted.

Similarly, how many actual physicists actually seriously argue about interpretations of quantum mechanics? I'm not a physicist but i'm pretty sure its a thing more talked about by philosophers and the popular press than actual physicists. Not that there is anything wrong with philosophizing and inquiring into metaphysical questions.

Sufficiently few that it is beginning to be said by a small number of physicists that it is a point of embarrassment that the Measurement Problem is about as unresolved as when it first came up a hundred years ago. https://www.nytimes.com/2019/09/07/opinion/sunday/quantum-ph...

The nytimes article you linked has the quote:

> 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.

Re: New books mount aggressive but ultimately unpersuasive defenses of multiverses

#42

Post by charlesism »

yoz-y wrote: post #21
charlesism wrote: post #8

Shouldn’t the default position be that a multiverse exist? A multiverse is what logic suggests (starting with “a point in motion is a line” and moving up to higher dimensions)

I don't think there should be any _default_ position before we can even think of an experiment to prove or disprove it.

Why isn’t the Schrödinger's cat thing sufficient? I don’t know much about quantum physics, but if we find situations where matter has odds of behaving a certain way, that seems like evidence. How do we explain events not always having a predictable outcome unless all possible outcomes occur somewhere?

Re: New books mount aggressive but ultimately unpersuasive defenses of multiverses

#43

Post by maroonblazer »

From the final paragraph:

>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.

Re: New books mount aggressive but ultimately unpersuasive defenses of multiverses

#44

Post by noneqwerty »

The implications of a non multiverse universe sort out to some sort of conscious design. Obviously religious types will jump all over this but religion X is not the only way to think about a designer.

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.

Re: New books mount aggressive but ultimately unpersuasive defenses of multiverses

#45

Post by analog31 »

RcouF1uZ4gsC wrote: post #9

> Today, physicists still lack evidence of other universes, or even good ideas for obtaining evidence. 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…

Virtually every physicist is painfully aware of this. The lack of testable theories is not for lack of trying. The search for a theory is precisely the search for a testable theory.

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.

Re: New books mount aggressive but ultimately unpersuasive defenses of multiverses

#46

Post by pchiusano »

zajio1am wrote: post #27
pchiusano wrote: post #15

Earlier quoted context omitted.

The thing missing is an explanation for why we find ourselves in a particular branch. Insisting that this doesn’t require an explanation is never going to be satisfying for some people. 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 tai…

> The thing missing is an explanation for why we find ourselves in a particular branch. That question does not really make sense. In every branch, there is 'you' asking about why is being in that particular branch.

I think you are making a hidden assumption. Here is a good question to tease it out: why does it make sense to ask why a coin flip came up heads but not make sense to ask why we observe one QM outcome?

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.

Re: New books mount aggressive but ultimately unpersuasive defenses of multiverses

#47

Post by fourthark »

maroonblazer wrote: post #43

From the final paragraph: >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.

Probably stuff like, we still don’t have any new particles despite spending a lot of money smashing stuff.

And string theory looks like it may have wasted a lot of people’s time with no result.

Re: New books mount aggressive but ultimately unpersuasive defenses of multiverses

#48

Post by vstuart »

The many worlds interpretation (MWI) as an explanation for nonlocality ("spooky action" ...) avoids more complete interpretations that avoid locality (spacetime) altogether as fundamental properties of the universe.

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.

Re: New books mount aggressive but ultimately unpersuasive defenses of multiverses

#50

Post by mlthoughts2018 »

teilo wrote: post #16
mlthoughts2018 wrote: post #6

> “ The universe supposedly splits, or branches, whenever one quantum particle jostles against another, making their wave functions collapse.” 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 suc…

> Multiverse QM is a settled debate. Move on. 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?

Why do you think a poll among certain people adds credulity to one or the other? Many Worlds allows purely unitary wave function evolution while explaining all known experimental and observational results with no less fidelity than any alternative. It’s solely a matter of Occam’s Razor that, until there is experimental evidence to the contrary, MWI is the solely most parsimonious available explanation.

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.

Post reply on HN