A multiverse or a god?
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24-11-2013, 05:18 AM
RE: A multiverse or a god?
(24-11-2013 12:12 AM)Paranoidsam Wrote:  There is already some significant evidence of a multi-verse... according to a new theory, the phenomenon of "dark flow" is the result of another universe's gravitational influence.


Quote:1.3 But is the multiverse science?

Despite the growing popularity of the multiverse proposal, it must be admitted that many physicists remain deeply uncomfortable with it. The reason is clear: the idea is highly speculative and, from both a cosmological and a particle physics perspective, the reality of a multiverse is currently untestable. Indeed, it may always remain so, in the sense that astronomers may never be able to observe the other universes with telescopes and particle physicists may never be able to observe the extra dimensions with their accelerators. The only way out would be if the effects of extra dimensions became ‘visible’ at the TeV [tera-electron volt] scale, in which case they might be detected when the Large Hadron Collider becomes operational in 2007. This would only be possible if the extra dimensions were as large as a millimetre. However, it would be very fortunate (almost anthropically so) if the scale of quantum gravity just happened to coincide with the largest currently accessible energy scale.

For these reasons, some physicists do not regard these ideas as coming under the purvey of science at all. Since our confidence in them is based on faith and aesthetic considerations (for example mathematical beauty) rather than experimental data, they regard them as having more in common with religion than science. This view has been expressed forcefully by commentators such as Sheldon Glashow [22], Martin Gardner [23] and George Ellis [24], with widely differing metaphysical outlooks. Indeed, Paul Davies [25] regards the concept of a multiverse as just as metaphysical as that of a Creator who fine-tuned a single universe for our existence. At the very least the notion of the multiverse requires us to extend our idea of what constitutes legitimate science.

Carr (2007) Universe or Multiverse? p.14
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24-11-2013, 07:47 AM
RE: A multiverse or a god?
Eh, Carroll is excellent, but a lot of the quoted physicists (like Davies) are perfect examples of how things can go badly when a physicist tries to do philosophy (there are of course very good examples too, like some of Einstein's more "meta" work). Davies and his interlocutors have a very strange understanding of the nature of science that is totally ignorant of the philosophy of science. I am in no position to decide whether multiverse proposals are "right" or not, that can only be answered by the hard scientific work.

But let's take Davies' contention that multiverse theories are "metaphysical," indeed "just as" metaphysical as a creator! This is strange. The reason we would believe in a multiverse is because it is a necessary postulate of an otherwise superbly explanatory theory. This sort of thing is totally uncontroversial; we routinely commit ourselves to the existence of theoretical entities which are not observed but play an indispensable role in otherwise extremely successful theories. Sometimes we eventually do observe these entities, sometimes not, but the point is that you can have evidence for the existence of an unobservable entity inasmuch as it is part of a theory that is observationally supported in a myriad of other ways. This is a totally routine part of science. The only reason some people seem not to think so is because some scientists to this day seem bizarrely entranced by a quasi-Machian positivism or trite instrumentalism, at least when their back is against the wall under public scrutiny. The people wondering about whether multiverse ideas are "really science" simply on the grounds that the other universes are not observable would've been the people rejecting Boltzmann's atomic theory of gases in the late 19th century.

That's not to say there aren't legitimate worries about whether a multiverse is genuinely explanatory. For example, there are some who argue that other universes have no explanatory value since they cannot interact causally with ours. Not because this means we couldn't detect them (again, this is not problematic if the hypothetical entity is a necessary postulate in an otherwise extremely successful theory), but because successful explanations are causal. And not only causal, but "causal all the way down" - every hypothetical entity must play a causal role on this view. Note the difference from, say, atomic theory back when atoms were undetectable; they may have been undetectable, but they had a causal role in the explanation. These sorts of worries depend on the nuances of causal explanation, and I won't pretend to resolve them here. But silly statements all too common in the pop-science literature and science jorunalism to the effect that such proposals are "as metaphysical as a creator" or are unscientific-cum-unobservable are two sides of the same stupid coin and are laughable to any philosopher of science.

I do agree though that multiverse proposals are a bit over-hyped. They are highly speculative. I think a lot of this hype is attributable to a mix of a journalistic/pop-science taste among much of the public for "weird" physics rather than our best physics - weird or not - on the one hand, and a totally misguided idea that multiverse ideas have significant bearing on the science-religion debate one way or the other, which I don't think they do, on the other.
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24-11-2013, 09:41 AM
RE: A multiverse or a god?
(24-11-2013 07:47 AM)Philo Wrote:  Eh, Carroll is excellent, but a lot of the quoted physicists (like Davies) are perfect examples of how things can go badly when a physicist tries to do philosophy (there are of course very good examples too, like some of Einstein's more "meta" work). Davies and his interlocutors have a very strange understanding of the nature of science that is totally ignorant of the philosophy of science. I am in no position to decide whether multiverse proposals are "right" or not, that can only be answered by the hard scientific work.

As badly as when philosophers try to do science?
Tongue

(24-11-2013 07:47 AM)Philo Wrote:  But let's take Davies' contention that multiverse theories are "metaphysical," indeed "just as" metaphysical as a creator! This is strange. The reason we would believe in a multiverse is because it is a necessary postulate of an otherwise superbly explanatory theory. This sort of thing is totally uncontroversial; we routinely commit ourselves to the existence of theoretical entities which are not observed but play an indispensable role in otherwise extremely successful theories. Sometimes we eventually do observe these entities, sometimes not, but the point is that you can have evidence for the existence of an unobservable entity inasmuch as it is part of a theory that is observationally supported in a myriad of other ways. This is a totally routine part of science. The only reason some people seem not to think so is because some scientists to this day seem bizarrely entranced by a quasi-Machian positivism or trite instrumentalism, at least when their back is against the wall under public scrutiny. The people wondering about whether multiverse ideas are "really science" simply on the grounds that the other universes are not observable would've been the people rejecting Boltzmann's atomic theory of gases in the late 19th century.

I'm not sure that's quite the best way to put things; certainly Boltzmann's statistical mechanics was chock-full of testable predictions.

String theory, itself at times called quasi-science, is at least in principle quite testable. A multiverse (and there are a very many different multiverse ideas), not so much.

(24-11-2013 07:47 AM)Philo Wrote:  That's not to say there aren't legitimate worries about whether a multiverse is genuinely explanatory. For example, there are some who argue that other universes have no explanatory value since they cannot interact causally with ours. Not because this means we couldn't detect them (again, this is not problematic if the hypothetical entity is a necessary postulate in an otherwise extremely successful theory), but because successful explanations are causal. And not only causal, but "causal all the way down" - every hypothetical entity must play a causal role on this view. Note the difference from, say, atomic theory back when atoms were undetectable; they may have been undetectable, but they had a causal role in the explanation. These sorts of worries depend on the nuances of causal explanation, and I won't pretend to resolve them here.

Big Grin

(24-11-2013 07:47 AM)Philo Wrote:  But silly statements all too common in the pop-science literature and science jorunalism to the effect that such proposals are "as metaphysical as a creator" or are unscientific-cum-unobservable are two sides of the same stupid coin and are laughable to any philosopher of science.

Yes. Equivocating untestable positions. Notwithstanding that they spring from very different sources. And notwithstanding that any more-than-deistic god (as posited by the vast majority of religion) is eminently testable.

I really don't like that word, metaphysical. Is it even possible to define coherently?

(24-11-2013 07:47 AM)Philo Wrote:  I do agree though that multiverse proposals are a bit over-hyped. They are highly speculative. I think a lot of this hype is attributable to a mix of a journalistic/pop-science taste among much of the public for "weird" physics rather than our best physics - weird or not - on the one hand, and a totally misguided idea that multiverse ideas have significant bearing on the science-religion debate one way or the other, which I don't think they do, on the other.

True and true.

People take science - or the vaguely scientific sounding - to justify whatever kooky woo they were already leaning towards.

Because quantum. It's like magic, but real!

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24-11-2013, 10:22 AM
RE: A multiverse or a god?
(24-11-2013 09:41 AM)cjlr Wrote:  As badly as when philosophers try to do science?
Tongue

Pretty much. Just look at Thomas Nagel, or 90% of the work in "analytic metaphysics," or basically any theistic philosophers no matter how prestigious.

Quote:I'm not sure that's quite the best way to put things; certainly Boltzmann's statistical mechanics was chock-full of testable predictions.

Sure. I only meant it as an example of how theoretical entities which are not presently, and may never be (who knows?) directly observable are a legitimate part of science. So other universes could in themselves be unobservable, but be an integral part of a theory that does provide testable predictions. Obviously if multiverse theories don't provide any testable predictions, that's a problem. But there are indeed a lot of people out there who reject multiverse theories simply because other universes are unobservable entities, which is who I'm criticizing.

Quote:String theory, itself at times called quasi-science, is at least in principle quite testable. A multiverse (and there are a very many different multiverse ideas), not so much.

Why not? This isn't a rhetorical question by the way, I'm genuinely curious since this is not my field.

Quote:Yes. Equivocating untestable positions. Notwithstanding that they spring from very different sources. And notwithstanding that any more-than-deistic god (as posited by the vast majority of religion) is eminently testable.

Yup, God fails pretty miserably as an explanation.

Quote:I really don't like that word, metaphysical. Is it even possible to define coherently?

Like most interesting concepts, I think "metaphysics" is more of a family resemblance term than a word that admits strict definition in terms of necessary and sufficient conditions. By "metaphysics," I mean the idea of supposed inquiry into the fundamental structure/nature of reality, and which sees it as necessary to go "beyond" the particular ontological commitments of our best scientific theories. This "beyond" is usually in the sense of either a supposed need to "interpret" scientific theories, or in the form of purely "conceptual" inquiry into the necessary (as opposed to "merely contingent") nature of reality. And by "fundamental" in this context, I mean the idea of a "God's-eye point of view," or a view from nowhere. This is usually coupled with an intuition insisting on how things "really" are, "behind" the merely empirical found in science.

It's a contested notion, but I think that captures the activities of those philosophers who call themselves "metaphysicians" or self-identify as doing "metaphysics" pretty well. The confusion I think comes because when challenged by more strictly scientific thinkers on this, they fall back onto this idea that metaphysics is just a "very general inquiry into how things are." Of course, I'd say we have a name for that: science.
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24-11-2013, 12:08 PM
RE: A multiverse or a god?
(24-11-2013 10:22 AM)Philo Wrote:  
Quote:I'm not sure that's quite the best way to put things; certainly Boltzmann's statistical mechanics was chock-full of testable predictions.

Sure. I only meant it as an example of how theoretical entities which are not presently, and may never be (who knows?) directly observable are a legitimate part of science. So other universes could in themselves be unobservable, but be an integral part of a theory that does provide testable predictions. Obviously if multiverse theories don't provide any testable predictions, that's a problem. But there are indeed a lot of people out there who reject multiverse theories simply because other universes are unobservable entities, which is who I'm criticizing.

Oh, indeed. If multiple universes are a consequence of some explicative theory which is otherwise of some testable validity...

But I'm not sure that the distinction of directly observable is one with any scientific merit. Observing consequences of interaction is for all intents and purposes the same thing, and arguably all we can ever do. But then we get into the nature of just what sensory experience itself is... Tongue

(24-11-2013 07:47 AM)Philo Wrote:  
Quote:String theory, itself at times called quasi-science, is at least in principle quite testable. A multiverse (and there are a very many different multiverse ideas), not so much.

Why not? This isn't a rhetorical question by the way, I'm genuinely curious since this is not my field.

A lot of formulations end up with something that doesn't particularly interact with us in any way. Even when posited to explain something we can interact with.

Contrast string theory, where we know exactly how we could test some of its predictions, but the technical ability is beyond us. For a lot of multiverse concepts there isn't even a way in which we might theoretically test the idea - let alone practically!

(24-11-2013 07:47 AM)Philo Wrote:  
Quote:I really don't like that word, metaphysical. Is it even possible to define coherently?

Like most interesting concepts, I think "metaphysics" is more of a family resemblance term than a word that admits strict definition in terms of necessary and sufficient conditions. By "metaphysics," I mean the idea of supposed inquiry into the fundamental structure/nature of reality, and which sees it as necessary to go "beyond" the particular ontological commitments of our best scientific theories. This "beyond" is usually in the sense of either a supposed need to "interpret" scientific theories, or in the form of purely "conceptual" inquiry into the necessary (as opposed to "merely contingent") nature of reality. And by "fundamental" in this context, I mean the idea of a "God's-eye point of view," or a view from nowhere. This is usually coupled with an intuition insisting on how things "really" are, "behind" the merely empirical found in science.

That's reasonable. "Beyond" scientific theories is necessarily beyond current scientific theories, no? And the purview of the metaphysical must change with time. Historically speaking science is the metaphysics which became empirical.

A view from nowhere may be well and good as a thought exercise, but it is also physically completely untenable...

(24-11-2013 07:47 AM)Philo Wrote:  It's a contested notion, but I think that captures the activities of those philosophers who call themselves "metaphysicians" or self-identify as doing "metaphysics" pretty well. The confusion I think comes because when challenged by more strictly scientific thinkers on this, they fall back onto this idea that metaphysics is just a "very general inquiry into how things are." Of course, I'd say we have a name for that: science.

Fair enough.

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24-11-2013, 04:23 PM
RE: A multiverse or a god?
(24-11-2013 04:41 AM)houseofcantor Wrote:  
(24-11-2013 12:12 AM)Paranoidsam Wrote:  ...significant evidence of a multi-verse... full of arty-farty metaphors and bullshit camera angles...

fix't.

There ain't no significant evidence of jack shit. Angel

Well, perhaps significant isn't the right word... But certainly interesting and exciting findings suggest the possibility.

http://www.dailygalaxy.com/my_weblog/201...dence.html

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But I would slave to learn the way to sink your ship of fools
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24-11-2013, 05:05 PM (This post was last modified: 24-11-2013 05:34 PM by houseofcantor.)
RE: A multiverse or a god?
(24-11-2013 04:23 PM)Paranoidsam Wrote:  
(24-11-2013 04:41 AM)houseofcantor Wrote:  fix't.

There ain't no significant evidence of jack shit. Angel

Well, perhaps significant isn't the right word... But certainly interesting and exciting findings suggest the possibility.

http://www.dailygalaxy.com/my_weblog/201...dence.html

From Peter Woit's blog -

Quote: In both cases, you have press stories promoting things which have very little support from experts, and this is something to be legitimately concerned about. In these two cases, I think one of the two is far more damaging: it simply is not true that the Planck satellite data gives “hard evidence” for the existence of a multiverse, and the press is being used to mislead the public on a central issue of what we have scientific evidence for and what we don’t.
- http://www.math.columbia.edu/~woit/wordpress/?p=5966

From the physics forums... http://www.physicsforums.com/showthread.php?t=694919

I actually remember reading about this stuff earlier, 'cause multi goes with stringy and susy, and them are things I don't like. Big Grin

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