Multiverse Evidence Explanation?

[DennisN]

Hi, I just read some things I thought I might share in this thread.

Frank Wilczek's paper "Multiversality" has caused some debate (abstract, paper):

• http://www.sciencenews.org/view/generic/id/352421/description/Belief_in_multiverse_requires_exceptional_vision (Tom Siegfried comments on Wilczek)
  
• "Belief in multiple universes requires exceptional vision. So does belief in telepathy." * (Ashutosh Jogalekar comments on Siegfried)
  
• "Belief in multiverse requires exceptional vision" (Peter Woit comments on Siegfried)
  
• "Multiversing around" (Sabine Hossenfelder's blog post, mentioned in the Woit comment thread)

(* the title made me laugh.)

After reading and thinking about this, I'm starting to realize that one of the main problems (perhaps the main problem at the moment) seems to be that people can't even agree on what multiverse means. So, in my view, the multiverse can't be considered a hypothesis - it is a set of hypotheses. So we've got ourselves a multitude of multiverses, oh dear.

I'm trying to sum up the main ideas as I understand them; multiverse can be

1. a set of universes that have different physics, and can not interact with each other
2. a set of universes that have the same physics, and can not interact with each other
3. a set of universes that have different physics, and can interact with each other
4. a set of universes that have the same physics, and can interact with each other

1 and 2 are versions that can not interact, so we will not get any observational support from them. 3 and 4 are versions that can interact, so this will boil down to what we mean by same/different physics - and - how we define a universe. Should a universe be defined as

1. everything that obeys the same set of physical laws and physical constants
2. everything that belongs to the same spacetime continuum
3. or both 1 and 2?

Of course, I don't expect any definite answers to this , since I don't believe there are any yet. I just wanted to share some of my frustration. I now think I understand the term multiverse mania. :tongue2:

 

[rbj]

I have to agree on that, I'm also one that prefers answers to our own universe. As opposed to quoting multiverse as an answer to questions we cannot yet answer.

Then how do you deal with the fact that if we do live in a multiverse, then certain features of our universe might only possibly make sense if understood in that context?

To take an example, consider the cosmological constant. If we live in a multiverse where an extremely large number of different values of the cosmological constant are realized in different contexts, then there is nothing to explain: we see the value we do simply because life requires a small cosmological constant.

Noth, i realize you might not like me pointing out the obvious, and i am not sure what Mordred's position is, but the nature of the question/challenge you make is a purely epistemological one, yet, similarly to the IDers, you begin with restrictions or axioms that support your worldview.

you're relying on the presumption of the multiverse to use selection bias to explain away anthropic coincidences. a sort of Multiverse-of-the-gaps theory.

an IDer could ask the same question within the domain of epistemology by use of substitution of a word or two. what might be different is that the IDer might admit that faith in the Undetectable and Unverifiable is necessary.

 

[Chalnoth]

Noth, i realize you might not like me pointing out the obvious, and i am not sure what Mordred's position is, but the nature of the question/challenge you make is a purely epistemological one, yet, similarly to the IDers, you begin with restrictions or axioms that support your worldview.

you're relying on the presumption of the multiverse to use selection bias to explain away anthropic coincidences. a sort of Multiverse-of-the-gaps theory.

There is absolutely no comparison. The designer of ID is, by definition, more complex than that which it purports to explain. It is more complex because it is fundamentally impossible to derive any specific observation from the nature of the designer: each specific observation must be independently assumed. The designer of ID is, therefore, to be considered highly unlikely by Occam's Razor.

By contrast, models which include a multiverse are inherently simpler than models which do not, because it requires additional assumptions to restrict the universe to one realization, in the same way that it requires more assumptions to fully-describe the set [1,2,3,4,5] than it does to describe the set of all integers.

Even more stark, the proponents of ID often rely upon designers which are in principle undetectably by any potential experiment. Sometimes they come up with designers that make testable claims, but those are trivially proven false through very simple observations.

By contrast, many multiverse models are very much testable. Sometimes those tests are extremely difficult to perform, but they are in principle possible. This is rooted in the fact that such models are by necessity mathematical in nature, and that nature allows one to produce very specific predictions of the model. Whether or not those predictions can be accessed by current observation shouldn't bias us for or against any particular theory.

The simple fact of the matter is that by excluding a priori models which you don't like, based upon nothing but your dislike for those models, you are biasing your potential answers for the nature of the universe. And no, there is absolutely no valid reason to exclude multiverse ideas a priori.

 

[rbj]

There is absolutely no comparison. The designer of ID is, by definition, more complex than that which it purports to explain.

according to the Prophet Dawkins, i s'pose. "by definition" here is quite dependent on who is defining.

It is more complex because it is fundamentally impossible to derive any specific observation from the nature of the designer: each specific observation must be independently assumed. The designer of ID is, therefore, to be considered highly unlikely by Occam's Razor.

right outa Chapter 3.

By contrast, models which include a multiverse are inherently simpler than models which do not, because it requires additional assumptions to restrict the universe to one realization,

just because an equation that describes reality has many solutions, does not mean that every solution exists in reality. it only means (if such equation really does describe reality) that the solution we observe in reality must be one of those many solutions. in a simple sense, it's like the 4 modes of the solution of a 4th-order diff eq. the solution can be any of the 4 (or any linear combination, if the diff eq is homogeneous) but, say it's waves on a string, it doesn't mean that if there are 3 other strings.

in the same way that it requires more assumptions to fully-describe the set [1,2,3,4,5] than it does to describe the set of all integers.

concepts (like whole numbers) are not physical things. maybe there's an infinite amount of physical stuff out there, or maybe it's finite (and much bigger than you and me). we don't know. still doesn't tell us diddley about whether or not there are other universes (that we can't measure).

Even more stark, the proponents of ID often rely upon designers which are in principle undetectably by any potential experiment. Sometimes they come up with designers that make testable claims, but those are trivially proven false through very simple observations.

By contrast, many multiverse models are very much testable. Sometimes those tests are extremely difficult to perform, but they are in principle possible.

so in principle, it's possible to test the state of something outside of the observable universe? even just the existence of the thing with the state?

This is rooted in the fact that such models are by necessity mathematical in nature, and that nature allows one to produce very specific predictions of the model. Whether or not those predictions can be accessed by current observation shouldn't bias us for or against any particular theory.

The simple fact of the matter is that by excluding a priori models which you don't like, based upon nothing but your dislike for those models, you are biasing your potential answers for the nature of the universe. And no, there is absolutely no valid reason to exclude multiverse ideas a priori.

i am not excluding models. i don't really like or dislike any of these different cosmological models. some components of some models are testable and potentially falsifiable. yea!

still doesn't clue us in on a falsifiable reality of universes outside our own.

Noth, i sort of like multiverse theories. i think, for as little as we know and can know, that the existence of other universes is as plausible as the lack of such existence. but i don't need that imagined reality to be true (it might be true, for all we know) to make some sense of the reality that i do observe myself in.

but if you're going to use selection bias to write off some otherwise difficult to explain anthropic coincidences regarding some critical universal constants, there isn't a causal logic to get you there without first the assumption of many "experiments" (universes), most of which fail (to be observed by anyone) but we (by definition) can only observe an "experiment" that succeeds. the "substance of things hoped for, the conviction of things not seen." the nasty 5-letter F-word.

 

[Chalnoth]

just because an equation that describes reality has many solutions, does not mean that every solution exists in reality.

Sure. But you have to add additional, unevidenced assumptions to the theory to make it so that those solutions don't exist.

so in principle, it's possible to test the state of something outside of the observable universe? even just the existence of the thing with the state?

It's often possible to test a model which unambiguously predicts a multiverse only by reference to its effects in our own observable universe. The thing which is being tested is not the multiverse directly, but the model which underlies it.

i am not excluding models. i don't really like or dislike any of these different cosmological models.

You clearly do, or you wouldn't be trying to tar some models with associations to creationism.

 

[skydivephil]

Noth, i realize you might not like me pointing out the obvious, and i am not sure what Mordred's position is, but the nature of the question/challenge you make is a purely epistemological one, yet, similarly to the IDers, you begin with restrictions or axioms that support your worldview.

you're relying on the presumption of the multiverse to use selection bias to explain away anthropic coincidences. a sort of Multiverse-of-the-gaps theory.

an IDer could ask the same question within the domain of epistemology by use of substitution of a word or two. what might be different is that the IDer might admit that faith in the Undetectable and Unverifiable is necessary.

The comparison between the multiverse and ID is not a good one.
Unlike ID , the multiverse is well motivated in contemporary cosmology.
Read Alan Guth's paper here:
http://arxiv.org/abs/hep-th/0702178
He gives a very reasonable argument for a mutiverse in my opinion.
Moreover inflationary cosmology has strong evidence in favour of it.
According to the leading inflationary theorists inflation has to be eternal therefore there is multiverse.
Guth gave a talk about that here at the British Institue of Physics:
www.youtube.com/watch?v=eQxa911BYBA
There is nothing like this for ID, there is no seriosus debate in biology as to whether ID or evolution is right. But there is a serious debate in cosmology about eternal inflation and hence the multiverse. If people only thought there was a multiverse for anthropic purposes then maybe you have a point, but that just isn't the case.
Of course whilst the evidence for inflation is good, there is still room for doubt. Similarly its always possible that inflation is right but Guth has it wrong on the way the inflaton field evolves.
For this reason the mutliverse is not a fact and could be wrong. But it is a serious scientific proposal unlike iD.

 

[Tanelorn]

Intelligent Design, in which certain initial conditions and Physical Constants are intelligently predetermined is an interesting idea, rather like setting the oven temperature for a specific cake recipe. Perhaps our reality and our existence are all the result of some very large science experiment. However, I believe that specific results or details of "the Universe experiment" are indeterminate and also non repeatable. I have been searching for opinions whether the Universe is indeterminate or if we could have all been intended, designed or planned in some way here:

https://www.physicsforums.com/showthread.php?t=706541&page=4Another remote possibility, either ID or not, is that our top level, largest scale Universe and Physical reality could be following, through some mechanism, a predetermined or preset trajectory, like the predetermined trajectory of a river from its simple beginnings in the hills, flowing down valleys, on its way to the ocean. The river's course is preset by Physical geography, but relatively small scale details, perhaps equivalent to features in our Universe up to at least the size of Galaxies remain completely random and indeterminate. Could something like this for example explain why the expansion rate of the Universe has been observed to change over time?

I am not saying I agree with ID, it is just an interesting possibility which probably cannot be proven one way or the other. However as I say in the thread above, I believe that even with a complete understanding of all the Physics and QM in the Universe, the detailed features of our Universe, up to at least the size of Galaxies are completely indeterminate. Anything smaller than a Galaxy, and probably features even bigger, have all happened solely as a result of random chance, and therefore not designed and not likely to ever happen again.

 

[rbj]

The comparison between the multiverse and ID is not a good one.
Unlike ID , the multiverse is well motivated in contemporary cosmology.

there are other disciplines of thought and study (than astrophysics) that have a "contemporary cosmology".

For this reason the mutliverse is not a fact and could be wrong. But it is a serious scientific proposal unlike ID.

ID is not a serious scientific proposal. it is an epistemological proposal. it's at a philosophical level below science, if you're visualizing causality as concepts being built "on top" of other concepts. epistemology is foundational. "science" and "religion" and perhaps other disciplines of thought rest on that foundation.

science, as best as i can tell, is an epistemological branch that is axiomatically materialistic.

religion, as best as i can tell, is an epistemological branch that is axiomatically extra-materialistic.

the only part of ID that may have anything to do with science (and it isn't particularly good science, IMO) is about the question of whether some observed order in nature has its root in design or undirected process. those IDers are trying to make a case (and not succeeding, IMO) that there are scientific reasons to believe that this apparent order cannot be the result of undirected processes or, is not likely to be the result of undirected processes.

i, personally, disagree with Gould about non-overlapping magisteria. i think that it is clear that many or most religions make fact claims that overlap in the domain of science. (e.g. we better the hell not ever see a reference to resurrection in a physiology textbook.) cosmology is an overlapping area, also.

now science has no choice in what to do about unanswered (and possibly unanswerable) questions. perhaps we can label these questions as "mysteries". science cannot be science and appeal to or look for non-material causes of mysteries. so it must look somewhere else (essentially, it must look only in the material).

but religion can and often does look outside of the material, and it is still legitimate epistemology. just not science.

the issue for me, is whether or not either branch (or other fundamental branches, say about art or sociology or ethics) has sufficient humility to embrace mysteries, rather than to make unfalsifiable claims to dispel them. in that, hardcore materialists make the same mistake that IDers do (and i don't see much willingness to own up to that).

 

[Chalnoth]

Intelligent Design, in which certain initial conditions and Physical Constants are intelligently predetermined is an interesting idea, rather like setting the oven temperature for a specific cake recipe. Perhaps our reality and our existence are all the result of a very large science experiment.

Interesting in terms of interesting to chat with somebody over a beer with. Not interesting in the sense of being able to do any real theoretical or scientific work with the idea.

I'd also point out that Intelligent Design as a concept is purely a rebranding of creationism, one that coincided with a court case that ruled that creationism cannot be taught in public school classrooms. This was uncovered to great effect in the recent Dover trial, where the main textbook put out by ID proponents, "Of Pandas and People," had all of its revisions subpoenaed. They found that the revision immediately before Edwards v. Aguillard and the immediately following revision essentially consisted of a search-and-replace of references to "creationism" with "intelligent design" (as well as changing other related terms). There was even a mistake in this initial revision, with "creationists" changed to "cdesign proponentsists".

 

[Tanelorn]

Interesting in terms of interesting to chat with somebody over a beer with. Not interesting in the sense of being able to do any real theoretical or scientific work with the idea.

I'd also point out that Intelligent Design as a concept is purely a rebranding of creationism, one that coincided with a court case that ruled that creationism cannot be taught in public school classrooms. This was uncovered to great effect in the recent Dover trial, where the main textbook put out by ID proponents, "Of Pandas and People," had all of its revisions subpoenaed. They found that the revision immediately before Edwards v. Aguillard and the immediately following revision essentially consisted of a search-and-replace of references to "creationism" with "intelligent design" (as well as changing other related terms). There was even a mistake in this initial revision, with "creationists" changed to "cdesign proponentsists".

I totally distance myself from that nonsense, I am surprised that you even brought that up. I am just talking about this from the angle that the Physical constants appear fine tuned to allow complexity, which obviously proves nothing.

 

[Chalnoth]

I totally distance myself from that nonsense, I am surprised you even brought that up.

I don't think it's possible to meaningfully disassociate Intelligent Design from its creationist roots.

 

[Tanelorn]

I don't think it's possible to meaningfully disassociate Intelligent Design from its creationist roots.

Well its not what I was talking about. I am not even saying I agree with what I was discussing, I am just saying that it is an interesting remote possibility which can never be proven. It is like trying to prove or disprove a theory with only a single measurement, since this is the only Universe that we have ever observed. Here it is again:

http://en.wikipedia.org/wiki/Fine-tuned_Universe

 

[skydivephil]

there are other disciplines of thought and study (than astrophysics) that have a "contemporary cosmology".



ID is not a serious scientific proposal. it is an epistemological proposal. it's at a philosophical level below science, if you're visualizing causality as concepts being built "on top" of other concepts. epistemology is foundational. "science" and "religion" and perhaps other disciplines of thought rest on that foundation.

science, as best as i can tell, is an epistemological branch that is axiomatically materialistic.

religion, as best as i can tell, is an epistemological branch that is axiomatically extra-materialistic.

the only part of ID that may have anything to do with science (and it isn't particularly good science, IMO) is about the question of whether some observed order in nature has its root in design or undirected process. those IDers are trying to make a case (and not succeeding, IMO) that there are scientific reasons to believe that this apparent order cannot be the result of undirected processes or, is not likely to be the result of undirected processes.

i, personally, disagree with Gould about non-overlapping magisteria. i think that it is clear that many or most religions make fact claims that overlap in the domain of science. (e.g. we better the hell not ever see a reference to resurrection in a physiology textbook.) cosmology is an overlapping area, also.

now science has no choice in what to do about unanswered (and possibly unanswerable) questions. perhaps we can label these questions as "mysteries". science cannot be science and appeal to or look for non-material causes of mysteries. so it must look somewhere else (essentially, it must look only in the material).

but religion can and often does look outside of the material, and it is still legitimate epistemology. just not science.

the issue for me, is whether or not either branch (or other fundamental branches, say about art or sociology or ethics) has sufficient humility to embrace mysteries, rather than to make unfalsifiable claims to dispel them. in that, hardcore materialists make the same mistake that IDers do (and i don't see much willingness to own up to that).

Of ocurse science allows for mysteries, if we knew everything why do any more research?
I don't agree religioon is looking anyhwehre, it just assumes. How do you look for the non material?
We both agree ID does not succeed in making a good case for a designer, so the question is do Guth and freinds make a good case for the multiverse? I think he does, not a slam dunk, he might be wrong. But I think there's a clear difference .
The controversey over ID a social controversey, its manufactured to look like a scientific contrvoersey. But when you read through the biological liteature there is no controversey over Id, its just nto taken seriously in biology, it is not discussed, its ot part of the scienitifc dialogue.
The same is not true for the multiverse, here there is a very real scientific controversey with communtiies of scientists making good argument on both sides. So people should not put the two on the same footing at all.

 

[DennisN]

So people should not put the two on the same footing at all.

I agree with this. ID is creationism; creationists tried to smuggle it into mainstream science by giving it a new name. And there is no serious creator hypothesis in physics/cosmology nor biology AFAIK. And I have no ID why this discussion turned into this, shouldn't we be talking multiverse hypotheses instead of polytheism?

 

[Tanelorn]

I also agree that ID should not be taught in schools. It is one very small non provable possibility in a very large number of possibilities. I didn't get taught any Cosmology at all in school, so if Cosmology is being taught now ID should probably not take up any more than 0.1% of the time spent on Cosmology. Which probably amounts to no more than the first paragraph here:

http://en.wikipedia.org/wiki/Fine-tuned_Universe

Anyone who disagrees with this is clearly heavily biased and wants to distort children's knowledge for their own agenda. Hardly a "good" motive for anything.

 

[George Jones]

Posters have not been able to take DennisN's hint:

And I have no ID why this discussion turned into this, shouldn't we be talking multiverse hypotheses instead of polytheism?

Consequently, I have closed the the thread. This is a cosmology forum. Any further transgressions (by anyone) will result in infractions.