Does a multiverse appear likely?

It is the basis for some really good science fiction…and some abstruse theology, too… Larry Niven’s “All the Myriad Ways” got the ball rolling. Jack Vance refined it in “Rumfuddle.” Someone else wrote “The Ultimate Anthropic Principle.” (Well, okay, I did…)

The key insight, I think, is in what obfusciatrist said: the idea eliminates the concept of free will. I would say, more subtly, it changes the concept of free will, broadening it, applying it across all possibilities.

For instance, what if God, on judgement day, judges us, not by what we did, but by the total sum envelope of all the things we could have done? Larry Niven basically implied that all possibilities were equal, but what if our possibilities are weighted? What if the branching tree follows rules of “probability density?” Some people might have extended trees with more good branches than bad…and others might not.

Extravagant? Heck, it’s luscious!

I took Czarcasm’s question to be asking if there were evidence either way.

The flip side of the question you answered is “Is there any evidence we live in a singleverse?”

Direct evidence that absolutely no other universes exist? Surely there is none.

However, in the absence of any direct evidence for the existence of other universes, I think it makes more sense to adopt the less ontological bloated proposition.

There is some mathmatical evidence that additional dimensions or parallel universes could exist. As many as eleven to 26 according to various string theory shit. However, I’m not sure what that actually means as anything other than artifacts of some theoretical mathmatical equations.

For example, I can push a tennis ball along it’s x,y and z axis. Why can’t I push it into some sort of 8th dimension, Buckaroo Banzai style?

The conventional explanation is that some of the extra dimensions are localized, or “curled up” and don’t have the same kind of extent as our familiar x, y, z, and t dimensions.

Some writers have used the image of an ant on a string. The ant can, of course, go forwards and backwards along the string, and that is an “ordinary” dimension.

The ant can also go sideways, but all he ends up doing is putting himself on the other side of the string. He can circle it all he wants, but never really gets anywhere. He has a freedom of movement in that sideways direction – it really is a direction – but it doesn’t take him very far. It doesn’t have unlimited extension.

Apparently, though, it makes the math come out pretty!

Nothing solid. There is some far-out speculation that the “dark flow” of galactic clusters might be caused by another universe impinging on our own, but that’s as far as it goes as far as I know.

You are working from the erroneous premise that other universes add ontological bloat.

The same researcher – Laura Mersini-Houghton – has also predicted the existence of the CMB cold spot prior to its discovery based on her theory of the selection of the initial conditions of the universe through the evolution of a quantum wave function on the string-theoretical landscape (of possible universes).

And of course, there’s David Deutsch with his claims that the quantum speedup (i.e. the performance advantage quantum computers have over classical ones) is only explainable through interaction with parallel universes… He manages to make this sound not quite so ludicrous in his book The Fabric of Reality, but still, I never found it convincing.

I see nothing erroneous about that. This notion requires postulating the existence of a multitude of universes, not just one. That sounds like a pretty bloated proposition to me.

Now if there were some actual evidence for the existence of these universes, that would be another matter. As I said, the extravagant nature of this proposition doesn’t necessarily make it wrong. It does require postulating the existence of objects – or worse, entire universes! – that are far in excess of what we have any actual evidence for.

msmith537 mentioned that based on certain mathematics, these universes could exist. That only means that they’re possible, though. It doesn’t constitute any evidence for their actual existence.

On the other hand, assuming that there’s only one universe adds the assumption that whatever process resulted in our universe being born stopped. That it was unique, special. That seems like a species that evolved on a system inside a dust cloud assuming that there’s only one star in the universe. It also adds the assumption that some unknown process fine-tuned the various laws of physics to make life and so forth possible.

Unintuitive as it may be, assuming that “more” implies “more bloated” or “more complex”, is a logical fallacy. Here this point is nicely addressed by physicist Max Tegmark:

Tegmark’s comment is disingenuous. He’s likening the existence of universe to the existence of numbers? That’s just pure sophistry.

Numbers are mere concepts, and they only “exist” as such. They are completely unlike the universe in that regard. Moreover, we have plenty of reason to believe that multiple numbers exist – at least, insofar as they exist at all. The same can not be said of physical universes beyond our own.

Clearly, Tegmark is overly infatuated with the notion of multiple universes if he thinks that such an analogy holds water.

Der Trihs is right on here: it’s explanatory entities that matter, not existing ones; so to the extent that a multiverse may have a simpler explanation than a single, unique, fine-tuned universe, it’s what parsimony should prefer (in this case, the existence of the universe would be evidence for the existence of the multiverse).

For instance, the complexity of the set of all binary strings is less than the complexity of any (typical) binary string – a very short program prints out all binary strings in succession, but for most binary strings, there does not exist a program much shorter than the string itself that outputs it. I’ve made this point more at length in this post.

Edit: iamnotbatman’s comment wasn’t there when I started writing this post, so to not receive the ‘Award for Redundancy by the Department of Redundancy Department Award’, let me address briefly Jragon’s worry: it’s true that the universe is not a number, or a binary string in my case, but the concept applies more generally; and besides, you can ‘code’ the universe into a number (or a binary string), simply by indexing all events, effectively ‘Gödel-numbering’ it. This number (string) would contain all the information contained in the universe, and thus, be equivalent in that sense (if you had a universe building kit, you could reconstruct the universe just from knowing that number). So the conclusion holds no matter what.

Tegmark is alluding to a rigorous sense in which a multitude can be less complex than its parts. It is an example proving that what I said earlier was not mere speculation but a fact, namely that unintuitive as it may be, assuming that “more” implies “more bloated” or “more complex”, is a logical fallacy.

The logic of complexity theory has more general applicability than Tegmark’s example of numbers (which you did not seem to understand, as he was not arguing anything about the existence of numbers) or field equations (which you did not address), and in the text I quoted he gives explicit examples (similar to what Der Trihs said earlier) of how a single universe requires a more bloated description than many.

Like Michio Kaku, Carl Sagan has both been on television and written several books, as has Neil DeGrasse Tyson. How is Kaku any different than those two men?

iamnotbatman: one interesting way in which a multiverse is “simpler” as an explanation has to do with the classic conundrum of the “perfect balance” of the physical forces in our universe that make higher chemistry (and thus life) possible. It is a standard of creationists to say that this proves a higher design. But if there was a vast multiverse, with all sorts of different values for the physical forces, then the matter devolves to an example of the weak anthropic principle.

In a caricature of this (don’t take this one too seriously!) I like to say that the outcome of the Cuban Missile Crisis suggests a branching-history multiverse. Everyone who has studied the crisis says how very, very, VERY close the world came to nuclear war. It has been called “miraculous” that we were able to pull back without going hot.

Well…in a multiverse, we simply happen to exist in one of the very small minority of worlds where it didn’t happen – since if we had been in one of the other worlds, we (or our parents…sigh…I’m showing my age) would have been fried! Not a matter of luck, simply of “pruning the tree.” Again, an “anthropic principle” argument.

Yeah, anthropic arguments are pretty much the cornerstone of multiverse/many-worlds theories. Your Cuban Missile example is a variant on the “quantum immortality” concept.

Well, it’s one of them. There’s also the question of if there’s only one universe, what is stopping more universes from being born? If a process exists that can do so once, why wouldn’t it do so many times? Multiverse theories also seem more in line with the Copernican Principle; asserting that we live in the one and only universe is an assertion that we are special; unique. Rather like the historical practice of cultures claiming they lay at the center of the world.

You expletive deleted I thought I finally had an original idea but you’ve come up with the same thing!

Well I’ll just claim I thought of it first (I did mull over the idea several years ago). :wink:

It seems like a more fair way to determine someones ultimate fate (though I’m not a big fan of punishment in the afterlife, reward for the ‘good guys’ sure but simple non-existence for the ‘bad guys’). You’d have to sort of merge all the different alternate lives together for the final judgement though, maybe purgatory is the ‘holding pattern’ till all the alternate versions of an individual are finally deceased.

I’m fairly sure we can expand this idea into a new religion…

I’ve already begun it; I call it Niventology. I now live a life of hedonism and debauchery, forcing the other zillion versions of myself to “choose” a path of righteousness.

Come with me, my brethren… to the darker side of the collapsed wave function…