Multiverse theory with impossible universes?

  • #1
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I found an article written by physicist George Ellis that confused me a little.

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.498.4569&rep=rep1&type=pdf

At some part, he says:

3.2 Non-uniqueness:

Possibilities There is non-uniqueness at both steps. Stating “all that is possible, happens” does not resolve what is possible. The concept of multiverses is not well defined until the space of possible universes has been fully characterized; it is quite unclear how to do this uniquely. The issue of what is to be regarded as an ensemble of ‘all possible’ universes can be manipulated to produce any result you want, by redefining what is meant by this phrase — standard physics and logic have no necessary sway over them: what I envisage as ‘possible’ in such an ensemble may be denied by you. What super-ordinate principles are in operation to control the possibilities in the multiverse, and why? A key point here is that our understandings of the possibilities are always of necessity arrived at by extrapolation from what we know, and my imagination may be more fertile than yours, and neither need correspond to what really exists out there — if indeed there is anything there at all. Do we include only

• Weak variation: e.g. only the values of the constants of physics are allowed to vary? This is an interesting exercise but is certainly not an implementation of the idea ‘all that can happen, happens’. It is an extremely constrained set of variations.

• Moderate variation: different symmetry groups, or numbers of dimensions, etc. We might for example consider the possibility landscapes of string theory as realistic indications of what may rule multiverses. But that is very far indeed from ‘all that is possible’, for that should certainly include spacetimes not ruled by string theory.

• Strong variation: different numbers and kinds of forces, universes without quantum theory or in which relativity is untrue (e.g. there is an aether), some in which string theory is a good theory for quantum gravity and others where it is not, some with quite different bases for the laws of physics (e.g. no variational principles).

• Extreme variation: universes where physics is not well described by mathematics; with different logic; universes ruled by local deities; allowing magic as in the Harry Potter series of books; with no laws of physics at all? Without even mathematics or logic? Which is claimed to be the properties of the multiverse, and why? We can express our dilemma here through the paradoxical question: Are the laws of logic necessary in all possible universes?

So he is proposing a multiverse classification which includes illogical universes. But as all scientists I've talked with say, that's impossible.

I've contacted Ellis to ask him some questions about it (his answers are below each question):

1. Does your classification includes universes where things that do not/cannot exist like problems without a logic solution (like Russell's set solution) would actually exist? Would it include inconsistent universes too?

I had not thought of that as useful. But maybe it suseful

2. Every physicist I've talked with denies the possibility of an inconsistent set of laws of physics. Let alone an illogical universe. Even Clément Vidal says in his article (https://arxiv.org/pdf/1205.1407.pdf) "We need to have a logic which describes M (the set of possible universes)". So how can it be compatible with the "extreme variation" types of universes?

Well we have to have some basis for describing the universe if we are to say anything about it. Without some form of logic you can't describe it.

3. Do these variations and universes you describe have a physical/scientific background? I mean, is there any scientific/physical theory (not mere philosophy) that proposes such variations and universes? Or even if it is just philosophy, do you know if there is a scientific theory that supports this?

To some degree String Theory provides a basis for universes with alternative physics.

I replied to his answers:

"I had not thought of that as useful. But maybe it suseful"

Can you extend that a bit, please? What do you mean as "useful"? Are you saying that in your multiverse classification you didn't thought of this specific case (universes where things that do not/cannot exist like problems without a logic solution (like Russell's set solution) would actually exist, or inconsistent universes...) but that they could exist under in your theory?

"Well we have to have some basis for describing the universe if we are to say anything about it. Without some form of logic you can't describe it."

But then an illogical universe is impossible? But in your multiverse classification you say that there could be universes like that.

"To some degree String Theory provides a basis for universes with alternative physics. "

Yes, but as you said in your multiverse classification, string theory universes would belong to moderate variation universes. I'm asking for the universes included in the highest level (extreme variation). Is there any physical/scientific theory that could create these types of universes?

He said he had no time and we finished the conversation.

Can you help me with this?
 

Answers and Replies

  • #2
jambaugh
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My best advise is to not waste your time with this (except for entertainment purposes). There's little actual science involved.

My argument. When speaking of whether universes might be logically consistent or not, one is committing an egregious category error. Logic is an activity of a mind. It is our mental constructs used to describe a universe which are logically consistent or inconsistent. That's the mathematics behind them. Then there is there utility in predicting and describing the observed phenomena in a given piece of a given "universe" and that's the science behind them.

You may philosophize all day but you cannot speak scientifically about the probability of counterfactual universes. It's just meaningless gobbledy-gook in so far as it can be tested via empirical observations is concerned. Now one might speculate about the space-time extension of our universe being part of some larger, possibly higher dimensional structure. That's fine if you can formulate testable hypotheses. Kaluza-Klein models are a case in point. Everett's many worlds is however NOT a case in point.
 
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