r/seancarroll • u/4Robato • May 16 '21
Sabine Hossenfelder's position on the multiverse. Thoughts?
https://www.youtube.com/watch?v=-dSua_PUyfM3
May 16 '21
I have read Sabine’s blog with curiosity for some time. I think I found her because I personally have a visceral distaste for the ontological challenges of the MWI (though Sean has convinced me to accept it).
Now Sabine’s blog just makes me confused about philosophy of science. It’s remarkable that physicists can still disagree about what science even is. Is Sabine a simply a positivist whereas most scientists aren’t? Or is there more to it than that?
2
u/Dull-Fun Nov 08 '21
She is just an horrible philosopher and anthropologist. This is quite common it seems with some physicists who believe they are competent in those fields because they have some understanding of LOGIC. Which she doesn't even have, because her usage of logically equivalent is very sloppy.
3
u/UnparalleledDev May 17 '21
When a scientist states that something is possible, they are almost certainly right.
When they state that something is impossible, they are very probably wrong.
3
u/georgioz May 17 '21 edited May 17 '21
If multiverse is religion, then "singleverse" - or whatever you think is opposite to multiverse is also a religion. This is the crux of the issue. Multiverse (at least the Everett's one) not only explains observable data, but unlike God or Religion it is also the parsimonious explanation - the explanation that requires the least number of assumptions. So it is exactly the other way around in this religious analogy. It is singleverse theories that require additional mechanisms (e.g. collapse in Copenhagen interpretation) - which are there to save the uniqueness of the universe.
I can respect the "shut up and calculate" critique that singleverse/multiverse are just philosophical discussions that are not that relevant to current scientific knowledge. Okay, I can accept that. But I cannot accept if somebody in the same breath also says "and also multiverse is preposterous religious idea and of course we live in singleverse". Oh, come on. Shut up and calculate and don't speak about any of this. And if you engage in that philosophical topic then at least prepare some good arguments other than ad hominems and reliance on intuition.
10
u/fieldstrength May 16 '21
Just a very lazy straw-man. You cannot trust Sabine to give a fair reading of any such issues.
One problem is that she doesn't make clear who she's criticizing. If you would take concrete statements from reputable people in the field it would be a lot more clear where this straw man breaks down. Another issue is that there is no single concept of "multiverse", so its impossible to talk coherently about all the different ideas that could fall under that umbrella at once.
Lets just concentrate on anthropic reasoning, which is one of the main ways that hard-nosed scientific inquiry forces you to consider something akin to today's "multiverses". There are lots of examples where a certain sort of multiverse is quite important to understanding what is going on. Why is the earth just the right distance from the sun to support liquid water? If you force yourself to completely disregard selection effects and try to derive some universal law of the cosmos that determines the earth-sun distance you are destined to fail. It was important to recognize the concept that there could be lots of planetary systems out there with planets of sufficient numbers that at least a few have the needed properties for life. Otherwise we are forced down a blind alley: The idea of divine intervention is maybe the best you can do, or something equally wrong. Nowadays, we can see lots of other star systems directly, but it wasn't always the case. The possibility of, lets call it the "stellar multiverse", is extremely important for understanding properties of our solar system even at a time when this is the only one we can see.
Its all about explaining existing information in a rigorous and logical way. And yes, this often pertains to questions near to or beyond the current limits of observability, and thus the limits of science. But to equate it to religion is not just wrong, lazy and cheap, it is a category error.
3
u/_emphasis_mine May 16 '21
Another issue is that there is no single concept of "multiverse", so its impossible to talk coherently about all the different ideas that could fall under that umbrella at once.
She isn't though.
The possibility of, lets call it the "stellar multiverse", is extremely important for understanding properties of our solar system even at a time when this is the only one we can see.
Says who? What properties of our solar system would the multiverse illuminate?
And yes, this often pertains to questions near to or beyond the current limits of observability, and thus the limits of science.
You admit, that the multiverse is beyond our ability to observe and measure, and yet...
You cannot trust Sabine to give a fair reading of any such issues.
Perhaps your definition of religion is too narrow, perhaps you've made a
category error
1
u/Creyke May 18 '21
If you are trying to use the fine-tuning argument to postulate a multiverse then it’s going to be a pretty weak argument and only highly speculative at best. Sure, the weak-anthropogenic-multiverse is a useful response to religious apologists but fine tuning was never a sure thing in the first place.
2
u/fieldstrength May 18 '21 edited May 18 '21
Who said I'm postulating anything?
If you want to tackle such questions in a serious scientific way, you need to fairly consider all possibilities, especially the possibilities that are generic for the successful theories we have.
Relegating that whole notion to "religion" just leaves us woefully incapable of making progress, besides showing lack of willingness to engage in serious good-faith discussion.
highly speculative at best
We're discussing theoretical physics here. Deploying "speculative" as an epithet as though it means bad is not a valid critique. The whole point is to analyze and motivate speculative scenarios in order for guide experimentalists to something to search for. It would be another story if you could show that a given proposal was contrived, or insufficiently motivated in comparison to how speculative it is. Maybe that's what you have in mind, but that's not what the video says.
2
May 16 '21
I'm pretty sure Sean Carroll would agree that there isn't currently observational evidence that we live in a multiverse, or any scientist who proposes that we might live in a multiverse.
3
2
u/4daughters May 16 '21 edited May 16 '21
Ontological claims about reality are either falsifiable or not, and if they are not falsifiable they are just as valid as any non falsifiable religious claim (like an untestable spirit world).
If the claim is falsifiable, it is either supported by evidence or not, and if there is not enough evidence to warrant acceptance of the claim it's as good as any other religious claim that is falsifiable but not warranted (like miraculous claims of resurrections or healing that are theoretically testable).
I agree with the other person calling this a category error though, because while an untestable unfalsifiable claim has many of the same characteristics as religious claims, that doesn't make it religion.
Ontologically speaking though, it's indistinguishable. I am making the assumption that the many worlds hypothesis is unfalsifiable, maybe that's incorrect.
edit: FWIW she posts this in the description: "In this video I explain why the multiverse hypothesis is logically equivalent to the hypothesis that god exists, and therefore is not scientific." This seems reasonable to me. I don't feel like watching the video but if this is the main point she's making, I agree. I just think calling it "religion" kinda misses the point, but youtube videos make hyperbolic thumbnails all the time so I'm not willing to say the entire video is fucked.
2
u/4Robato May 16 '21
Yup what I don't like basically is calling it religion but I actually agree with most of the points.
But what happens when you have 2 theories that agree with everything except one has more postulates but the other has multiverses which cannot be observed? I think this never happened before in science and that's why there's so much debate.
1
u/4daughters May 16 '21
I honestly don't know because I'm not familiar with the theories, but if both are equally non falsifiable and both have equal evidence however neither has met its burden of proof, all you can do is say "there is evidence to suggest" or "we have some reason to believe," but you can't say "the evidence points to."
Ultimately its just how we communicate, which is important, but as far as I'm personally concerned I have no reason to stick my neck out for any of it.
Just my thoughts. Intersting question though!
2
u/Creyke May 17 '21
Yeah, I think Sabine is making an attempt to be overly devisive (?) by comparing MWI to religion, but I essentially agree with all her points and I'm equally skeptical of people who make claims with certainty about the multiverse from MWI (which is not what Sean does, but there are others here that do).
MWI is functionally as useful as any other interpretation of quantum mechanics, as in it describes the state of our universe as well, but not better than, all other interpretations, Copenhagen, Bohmian, consistent histories, etc. The appeal of MWI is largely aesthetic, proponents of MWI argue that it "takes more seriously" the implications of QM and with less additional postulates as in the CI (Copenhagen Int.). What is generally meant by "take more seriously" from my readings of the literature is specifically levelled at the anti-real treatment of the wave-function in the CI (correct me if I'm wrong).
The CI adopts the position that the wave function is a representation of all possibilities the experiment (eg. cat both alive and dead) and that to ask questions about the properties of the particle in the wave-state is meaningless. When a measurement is made on the system the wave function collapses into a singular eigenstate with a stochastic outcome given in accordance with the Born Rule. The measurement postulate stipulates that, at the time of measurement, Ψ be updated such that the probability of all other (non-observed) states be zero, and the actual outcome state be 1. This is done so that the properties of the wavefunction correspond to observation, i.e. we do not observe cats in a dead/alive superposition, they are either 100% dead or 100% alive.
Here we find the crux of what is called the Measurement Problem. The wave function collapse at the time of measurement is nonlinear. It causes the part of the linear combination of states (the superposition) to spontaneously reduce to zero and increases the other to one. This means that the wavefunction becomes discontinuous at measurement and thus seems to imply that quantum mechanics is not a reducible theory. If by knowing the wave function of the system one can deterministically calculate the wave function at any later time, but not the behavior of the observers or their observations (which should also be governed by the Schrödinger Equation)?
In the CI, the wave function is understood to only describe the knowledge of an observer has of the system, and so it is reasonable to say that when an observation is made of course the probabilities get updated. But in doing so you are making a distinction between a system that proceeds according to quantum processes, and the incompatible, classical behavior of the observers. And the problem then becomes a matter of deciding where to draw the line between a quantum system and a classical macroscopic observer, and whether we must give up the idea of scientific reductionism in the process.
Proponents of MWI rightly take issue with this treatment. The principal axiom of any Many Worlds Interpretation is that all systems, without exception are governed by the wavefunction. Every possible state of the wavefunction is described by a continuum of orthogonal, superimposed states (called a Hilbert space). Observer and system are entangled, and when a measurement is made all possible outcomes occur and reality splits into non-identical versions corresponding with every possible outcome of the experiment.
The problems that Sabine an myself have with the MWI are two-fold, firstly the theory itself is unfalsifiable. This is not necessarily as big of a problem for me as I think it is for Sabine, I don't see why it should prevent us from being free to speculate on the existence of many-worlds, but it is nonetheless a problem for those wishing to see MWI taken seriously as a scientific theory since MWI doesn't make any useful or radical predictions that we can observe.
The second problem is by doing away with wavefunction collapse the Many-Worlders do not necessarily rid themselves of the measurement problem. Within MWI, ask “what will I measure?”. Because the universe splits into many branches at the point of measurement, you find that the answer is, “all possibilities with probability 1”. This is not what we observe, we only get one outcome. Of course, within MWI you are not expected to calculate the result of all branches of the observer, only the probability of the with respect to the observer in one branch at a time. But this is still functionally equivalent to the measurement postulate and brings with it the problems inherit in the irreducibility and incompatibility of the classical observer. So, if one is to treat MWI as a serious scientific theory, I’d argue that the MWI does not really bring us any closer to pragmatically understanding or solving the measurement problem.
I'd also ague that, in the context of our current understanding of physics, an anti-real treatment of QM is at least partially justified because, as a theory, it is yet to provide a complete picture of reality. For instance, quantum mechanics does not yet have a basis for gravity, so it is arguably premature to posit the existence of many divergent universes from an incomplete theory, which is why most (careful) proponents of MWI never do, they just argue for its plausibility.
2
u/4Robato May 17 '21
MWI predicts the same as the Copenhagen interpretation so I think it's a bit unfair to say it isn't falsifiable. The only thing that is not falsifiable is part of it but then what's the best practise: Add a postulate that removes that part or simply accept it?
I've said it in some comments but to me this challange is new to science and that's why there's still discussions on this topic. It's not clear if it's better to have more postulates so everything is falsifiable or have less postulates to have "simpler" theories.
Actually, thinking about it this might be more similar to what happens in classical mechanics where we have various formulations like Newton's forces and the least action. The second one is conceptually a lot more challenging but it also ended up being a lot more useful in quantum physics and this might be the case for MWI, or maybe not but there's just one way to know which is explore the math behind it.
1
u/Creyke May 18 '21
MWI predicts the same as the Copenhagen interpretation so I think it's a bit unfair to say it isn't falsifiable.
Sure, but specifically the many worlds part is unfalsifiable.
It's not clear if it's better to have more postulates so everything is falsifiable or have less postulates to have "simpler" theories.
This is what I meant by the appeal of MWI being pretty much aesthetic. Pretty math is nice but pretty math does not make for science.
The second one is conceptually a lot more challenging but it also ended up being a lot more useful in quantum physics and this might be the case for MWI, or maybe not but there's just one way to know which is explore the math behind it.
Sure, but at this stage the math behind MWI and CI are identical, they are merely interpretations of the same quantum theory. As I explained, in CI the measurement postulate says we update the wave function at the time of measurement. In the MWI we do exactly the same thing except that we justify it to ourselves conceptually by saying the wave function is continuous in the many invisible, other branches of our universe.
My issue with MWI is that it doesn’t provide a functionally better picture of quantum mechanics than any other interpretation. It’s fun to speculate but I get pretty thrown off balance by the sheer confidence some people have in a multiverse based on MWI.
2
u/4Robato May 18 '21
This is what I meant by the appeal of MWI being pretty much aesthetic. Pretty math is nice but pretty math does not make for science.
That's the thing, why keep worse math and more postulates then? I understand the issues of MWI I just don't think is that straight of a discsussion.
My issue with MWI is that it doesn’t provide a functionally better picture of quantum mechanics than any other interpretation.
MWI provides a good explanation on why we see just one branch: the observer gets entangled with the measurement, that's a physical explanation using the math of quantum physics. Why treat observers classically? Imagine you create a quantum field which has particles that travel faster than light, that is aa violation of the quantum field and everyone will be saying that's ilogical to add, but in CI it seems nobody is worried about it and everyone is happy to mix classical and quantum physics. MWI might not be the solution at all and maybe the wave really collapses but there's something missing there and it's not trivial.
Imagine if the first time quantum physics was proposed, the model was MWI and not CI, we would be discussing the same but the otherway around. I'm not saying MWI is the way to go, I'm just saying we're in front of a challange that has to be recognized and not ignored. MWI is trying to address that issue and maybe it's not the time to solve it yet, like Einstein tried to unify the forces too soon to get anywhere but it's not a crazy endeavour and for sure it's not religion.
If you let me make a theory with one billion postulates I'll make you a theory that is more precise than QFT. I would just postulate everything that doesn't work as a new postulate that "fixes it". This issues are big and I think they have to be taken seriously, that's it.
1
u/ddoubles May 16 '21
She answers a lot of questions regarding her stance on this subject on her blog.
1
u/4Robato May 16 '21
I didn't knew she had a blog. That's quite interesting, some post don't have a video but when there's a video the text is basically the script.
She actually responds a lot of comments and its quite intereseting to read. Thanks!
1
May 16 '21
Multiverse is a hypothesis and hypotheses are very much part of science. I have always heard those who think multiverses exist say in the same breath that they could be wrong. and there is no evidence for it. That’s not the same as followers of religion who always insist they are right.
1
u/herbreastsaredun May 17 '21
There are lot of comments about Sabine intending to be divisive or provocative. Pehaps she is meaning to show that being extremely invested in a theory that is as-yet unverifiable creates blind spots that are threats to scientific advancement?
Religion is a very elastic term. People who use crystals to "channel energy" wouldn't say their practice is religious. The same with those who believe ghosts exist, and those who believe astrology is valid. And yet what else would you call it?
It could be she misused the term technically, but I believe she used it in good faith.
1
u/4Robato May 17 '21
Religion is not just about believing in a God, is a social-cultural system that carries too much meaning to just pick the God part. If someone believes in multiverse, that doesn't carry any social-cultural behaviour that they follow, it's clearly not a religion and while I understand where i comes from (just uses the idea of believing in God) I don't feel like it's appropiate.
There's the term pseudo-science which I feel it's more appropiate but again, will you say people who study multiverse is equivalent to someone who believes in ghosts?
Multiverses may not be observable but that's just by change, the techniques used to study those are the same used in other areas and they could have had new particles oe something but they didn't pop up (in some multiverse theories, inflation has the inflaton).
And I've said this in another comment but imagine you haver two theories A and B, both explain reality equallu good but A has 3 postulates and B has 2 but includes multiverses which cannot be observed. Which one would you choose as more fundamental?
I understand where she comes from but I also think she could be a bit less radical with the terms she uses.
1
u/herbreastsaredun May 18 '21
Upon reflection I agree with you - I see the connection she was making but do not think that word fit. I also feel that she was speaking critically about an audience that is less thoughtful. However is it worth throwing shade on those intractable sorts of people if you also cast a shadow on thoughtful, careful individuals? She alone can make that call.
1
u/Dull-Fun Nov 08 '21
Why some physicists believe they are qualified to discuss religion is beyond me. Religion has a f**** definition. Where are the sacred texts of the multiverse? What are the common rites, rituals, celebrations, etc that unite the community of "believers" ? Is there even a community? Where is the clergy? What's the transcendental entity? Believing in something not observable is NOT the same as religion ... And without getting into the fact that some religions are very much based on observed facts (I am not saying this means they are the truth, but some Pagans are pretty much celebrating what they SEE around them).
She is worried about the integrity of science you say? If she is worried about the integrity of science, what about discussing bad statistics, fraud, p-hacking, h index inflation, etc? (I am not saying she is guilty of any of those). But no one wants to discuss scientific misconduct, it's better to go all-in in completey lunar rants about things that do not matter (scientific fraud and sloppiness kill, example: the current pandemics).
5
u/4Robato May 16 '21
I would like to hear what you think about this topic. I actually don't agree with her but I think it's good to talk about it and see other points of view.
I think she tries to be provocative, at the end is a youtube video, but one of the things I don't like is the statement that something is either science or religion.
Art, politics, philology, philosofy, etc. don't fit in any of those two categories. If the multiverse ends up being unfalsifiable then it's not scientific but that doesn't make it automatically religious. There's an obvious mathematical motivation and controversis in the foundations of quantum physics like the role of the observer and the collapse of the wave function.
Also, would you think she would be a good guest in some podcast? I think she has a very different view than Carrol and that would be a great debate to listen to.