For what it's worth from Wikipedia

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"They reasoned that an object situated at the center and related equally to the extremes in every direction can have no impulse to move in any specific direction. In fact, they compared the situation of such an object with that of a man violently but equally hungry and thirsty, standing at the same distance from food and drink and unable to decide in which direction to move." - Aristotle

And don't forget, Tegmark gave us the "quantum suicide" thought experiment (google it or see the thread in General Science). Personally I think it's pretty sad if 60% of scientists in theoretical physics think many worlds is "true", in the absence of even a single observational fact that distinguishes it. But I submit you will not find that among all practicing physicists-- only those "leading ones" who I submit have a pretty good dose of hubris to go with their brilliance. Of course we'll take the former to get the latter...

But the multi-worlds model in interpreting quantum mechanics isn't the same as the multiverse model in quantum cosmology, is it?

You're right, many worlds is the idea that because quantum mechanics involves a particular mathematical way of evolving wave functions in time, measurements "have to" yield all possible results and therefore spawn "many worlds". The multiverse is an idea that our universe is only one part of a larger one with statistically distributed values of the fundamental parameters. So that's not the same thing. But they do share a similar flavor, in that they are both efforts to "explain" without resorting to experiment. In that sense, they both treat an "explanation" as if its job was to generate a sense of cognitive resonance, rather than as a way of organizing data in a way that could lead to predictions for new experiments. In short, they are both efforts to insert what we might call "reality" into a larger milieu that is unconstrained and untested, just to resolve certain "pesky issues" about the reality we find. To me, it makes a lot more sense to simply recognize the pesky issues, than to think of them as in need of resolution using the information we have at hand. Why change reality just to make our minds like it better? It doesn't seem very scientific at all.

The discovery of a Multiverse or layered universes would still only make 1 single entity if tested and shown to be true.

The unification theory by name itself would explain EVERYTHING, which in turn would just make our universe different, but complete. Still JUST ONE.

One of something more than we had observed up to now.

Wonderful thread. I just saw Universe (Multiverse stuff) on the history channel and thought of y'all. They seemed so sure of themselves. I would guess it isn't the fame factor, but that they have been this scientigous for quite some time.

I agree. Ug. Is this what becomes of corn when converted to high octane? There best fight is with recondite!

What a great analogy! Tycho had to rely on Kepler to do the very difficult calculations of his unique and accurate data. [Kepler had refused to work under Tycho, insisting to only work with him.] Kepler loved his polygons, but he stuck with the data. The worst variance in the data from a circular orbit for Mars was 8 arcminutes, IIRC. He stuck with the data, and won the honors.

Even the Church was interested in observations to support their religious views! The Jesuits were some of Kepler's best friends, and he was Lutheran.

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Lighten up! This is a stellar board! Author: duh.

"The Sun, with all the planets revolving around it, and depending on it, can still ripen a bunch of grapes as though it had nothing else in the universe to do..." Author: Galileo supposedly.

But we know we can't observe the multiverse, our instruments could not even function in an environment with those parameters. There is no way we could ever "discover" the multiverse, its existence will always be like Shangri-La. A nice place to imagine exists if not knowing why our universe has its parameters is keeping you up at night.

I really don't see how anything has changed. It's good for us, since we like to exist, but this universe, as it is, is not objectively any better, any more special, than any other conceivable universe. It's only because we value the process called life that this universe is special to us at all.

If the universe had difference constants, perhaps other forms of life would exist, and they'd be thinking, "Hey, if the physical constants were just a little different, we couldn't exist. There would be no electromagnetic tendrils for us to live around and attract our magnetic monopole food. There'd be no quark-gluon plasma to swim through. Pshaw! Life couldn't exist without quark-gluon plasma!"

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If we don't play god, who will?-James Watson
I never think of the future, it comes soon enough.-Albert Einstein
The large print giveth and the small print taketh away.-Tom Waits

Yes, for all those reasons, I think the multiverse idea is scientifically sterile, and still await a shred of evidence to the contrary.

I don't know....We'd really like to understand what becomes of the matter and energy that find themselves inside the event horizons of black holes (assuming that such horizons do actually form, but that's another question.). Such an understanding would likely (being optimistic) have profound implications on what we can actually observe on this side of the event horizon (but I forget what the status is of the bet/debate between Thorne and Hawking re. information loss in black holes). Doesn't even the mere existence of black holes have something to say about the universe we live in? Is the multiverse concept so much further removed from that of black holes in at least this sense?

Your views on what science is, and is not, should be critical to all of science. Much is at stake in allowing pseudoscience residence in the objective realm.

Yet, there does not seem to be much of an appropriate term that identifies and puts conjecture in its place. "Theory" should be reserved term. I can see why everyone wants to use it as a tag to their ideas, but if another term were well established to qualify these incipient theories, then they should be less prone to try to abuse the "theory" term. [Added: I entered "Multiverse Theory" in Google and got 25,000 hits.]

Every dog wants in the house when it's raining, but build them a dog house and they can stay out where they belong.

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Lighten up! This is a stellar board! Author: duh.

"The Sun, with all the planets revolving around it, and depending on it, can still ripen a bunch of grapes as though it had nothing else in the universe to do..." Author: Galileo supposedly.

A fair question, but I would say that everything we know about black holes, everything, comes from extrapolating the equations of physics as found through experiments on this side of the event horizon. That is the natural logic-- we do experiments here, develop theories, the theories make predictions, and the predictions have their own consequences here. If in the process, we create an image of something on the "other side" that helps us organize the data over here, that's fine-- but we don't need to say that our picture of what is going on inside a black hole is real, beyond its impact over here.

I would use the example of "image charges" here. We know that if you put a charge near a conductor, the conductor will impose a boundary condition that lets you figure out the electric field near the charge. This you can determine without knowing what is actually happening inside the conductor, and indeed you can model it by replacing the conductor with an "image charge" that serves to create the same boundary condition. If you never do observations inside the conductor, the image charge approach is a fully successful model of the reality where you do the experiments, and your scientists would never be the wiser that conductors do anything different. If you do experiments inside the conductor, you find it is not a sufficient model. But with black holes, the latter never happens, so we need not distinguish what is "really happening" inside a black hole from the image it leaves on the outside.

The connection to multiverses is that there we have the worst of both worlds-- we never do the observations on the "other side", but they also don't establish any conditions that are relevant here. They don't help us calculate or predict anything happening here, they don't put any constraints on the physics here. They are purely a philosophical tool to give a sense that there is not a mystery where there in fact is a mystery. It's classic magical thinking-- the inclusion of an untestable mechanism to replace our discomfort and powerlessness about mystery. That's a valid approach for some things that humans do, but science was expressly designed to get us away from that-- how ironic the ways it tries to sneak back in, like a wolf in sheep's clothing.

Excellent point. Say what you will about multiverses, but we should at least be able to agree it is not a "scientific theory" in the same way that evolution is, because if it is, then all the complaints about evolution would actually be correct. Concepts like that dilute the meaning of a scientific theory, and instill confusion about what scientists actually do and what their claim on the truth actually is. That's the harm in it, I agree with you.
Yes, the trouble is, everyone wants to eat at the captain's table-- no one wants to be "in the doghouse"!

To the extent that what you describe is and always will be true about "multiverses", then I'd agree. Certainly, any idea that exists solely (and so untestable for any conceivable length of time) to address the anthropic (or some other philosophical) principle is pretty useless from science's point of view. However, I am uncertain that even at the present time this is entirely the case for the multiverse "model" (but I'll leave that to Linde et al.), and if you had asked physicists in Mr. Karl Schwarzschild's day whether black holes had a snowball's chance in to exist in this reality outside of the mathematics of GR or that we could ever study them even if they did, I doubt you'd find many takers.

I was hoping for a snappy new term for a "want-a-be" theory; an antidote for the anecdotal.

An incipient theory could stumble into something that would validate it as a legitimate theory, but [until then] some special term should exist to minimize the confussion or expectations.

That's kinda snappy! But a little restrictive to the corn field, of which I'm often fond.

Here is one suggestion for an incipient theory.... Thark. It is a theory that is just bark, thus no bite. "The multiverse thark", hmmm, maybe not.

"The Mulitiverse Theific". Theific -- if it were a theory, we'd call it theory. IOW, too ify to qualify as a theory for now.

"The Multiverse Theison". Theison -- You can go ahead and do a thesis on it, just don't call it a theory.

My usual fee for this effort applies, of course.

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Lighten up! This is a stellar board! Author: duh.

"The Sun, with all the planets revolving around it, and depending on it, can still ripen a bunch of grapes as though it had nothing else in the universe to do..." Author: Galileo supposedly.

Don't sugar coat it, Ken, tell it like it is.

By the way, I agree whole heartedly with everything you've said on this thread.

Thanks, John M.

But black hole models make specific predictions. It has nothing at all to do with my feeling like something is "unphysical", I would not impose my philosophy. Indeed, my whole point is that there is no need to invoke philosophy at all-- we find the truth by looking. It is clear enough to me what we are looking at when we talk about black holes-- what are we "looking at" when it comes to multiverses? My problem is not that they make predictions that I find unlikely, my problem is that they don't make predictions at all. And if they do, they are sure doing a far worse job of publicizing those predictions than they are of weaving semi-scientific parables to convince others of the absence of mystery here.

Maybe something along the lines of "parable" works here. I don't want to suggest there's not a value to making pictures about how we understand things, I just don't think people should think it is science or that the way to establish its validity is to consider how it alleviates anxiety.