2

In discussions around multiverse hypotheses, what is the extent and current state of conversation around why the multiverse configuration (whether one or many multiverses, etc.) is one which generates/includes universes such as ours?

That is to say, consider that a multiverse could exist in any number of forms. Perhaps that's not the case. Or, perhaps it only contains two lifeless universes, for example. Or it contains an infinite number of universes, all alike. Or it contains a large or infinite number of universes, varying in nature. Or perhaps there are an infinite number of multiverses, making it inevitable for some of the multiverses to contain universes such as ours.

Further, if there's only one multiverse, is there discussion regarding the particular attributes it has, and why it has those? Or contrariwise, if more than one multiverse is needed to give a reason why we exist in one such as ours, what contains them, and what precludes an infinite regression of multi-multi-...multiverses?

Don Branson
  • 164
  • 8
  • There are too many possible answers. There are infinitely many approaches but an interesting one might be the one that makes the smallest number of assumptions. Also, you should gives us the distinction between universe and multiverse since both can be numerous according to you. – rus9384 Nov 16 '18 at 16:50
  • @rus9384 I was supposing that there were a couple predominant areas of thought - but perhaps at this stage there are too many schools of thought to summarize trends in thinking. – Don Branson Nov 16 '18 at 18:35
  • And "numerous according to" me? No, that's not a claim I'm making in the least, but ideas of others that I'm seeking to understand. – Don Branson Nov 16 '18 at 18:37
  • 1
    This is ironic. Multiverse was introduced partly to explain how our universe is not special but just one among many that happens to be this way. Now we are talking about multiplicity of multiverses with the same question being raised. I suppose one can make the same move, introduce multimultiverse of multiverses, and dismiss such questions. But it is less headache inducing to stick to a single multiverse (or universe). – Conifold Nov 18 '18 at 22:19
  • @Conifold - "But it is less headache inducing to stick to a single multiverse (or universe)." I'm in favor of fewer headaches. :) For those who are advocating the single-multiverse view, are there discussions about why a single multiverse would have the "right" attributes? – Don Branson Nov 19 '18 at 00:03
  • The point is that once this digression is followed it becomes clear that the question of why a verse has the "right" attributes is completely vacuous. One can always embed it into a verse of verses and answer "why not?" – Conifold Nov 19 '18 at 00:09
  • @Conifold - Ah, okay. Is it so obviously vacuous that there's no discussion around that consideration? Or is there discussion that puts the question to bed? – Don Branson Nov 19 '18 at 00:17
  • There is no putting philosophical questions to bed, I am afraid, people always find a way to discuss them some more. But the substance of this discussion is exhausted already at the first level, universes in a multiverse, the "upgrade" adds nothing new. You can look up the neverending (and nowheregoing) discussions of the [anthropic principle](https://en.wikipedia.org/wiki/Anthropic_principle#Reception_and_controversies). – Conifold Nov 19 '18 at 00:24
  • "There is no putting philosophical questions to bed." Heh. I have no doubt. Or human ideas in many contexts. :) I am familiar (at a layperson's level) of the anthropic principle. If I understand correctly, the multiverse idea addresses this issue because the multiverse contains enough (perhaps an infinite number) of universes, right? But if that's the right understanding, why would the multiverse be one that contains a sufficient number? Anyway, if there's discussion going on wrt that topic, I'd like a summary that lays it out for the commoner. – Don Branson Nov 19 '18 at 00:40
  • Because we can stuff as much as needed into a single multiverse, for that matter, we can stuff enough causally isolated regions even into a single universe (Vilenkin made proposals along these lines using eternal inflation). I looked, and it appears that multiple multiverses are mostly discussed by gamers and ufologists (search with key word "omniverse"), so there is nothing to summarize. Physicists stick to multiverse for now, and many are skeptical even of that. Here is [Linde's recent review](https://notendur.hi.is/~einar/Heimsfraedi/Linde_multiverse.pdf) – Conifold Nov 19 '18 at 00:54
  • @Conifold - Thanks. Seems like you have enough to assemble an upvotable answer. – Don Branson Nov 19 '18 at 01:10
  • 1
    Thanks, but writing an answer would require me to be more thorough than I have time for right now :) – Conifold Nov 19 '18 at 01:18
  • @Conifold I get that. Thanks for the chat. – Don Branson Nov 19 '18 at 01:26

0 Answers0