Multiverse theory incompatability

[Faradaympp]

I also have real problems accepting most of the things described under the rubric of 'multiverse' hypotheses (I won't dignify it with the word 'theory'), and especially those which have such features as the 'trousers of time'* in which each decision spawns a new 'universe', and such idiocy as Everett's 'many worlds' interpretation of quantum mechanics, along with the idea that there are a huge number of universes, each running with different physical constants. All of these ideas should get no further than Occam's Razor until such crap is supported by evidence.
...

Now, there are a few models for cosmic instantiation on the table that allow for multiple instantiation events, such as Guth's inflationary model, with bubble 'universes', and the Turok/Steinhardt 'brane-worlds' model, that give a plausible mechanism for instantiation under which more than one cosmic expansion is more parsimonious than only one. this would seem to violate Occam's Razor on the face of it, and many people actually think it does, but this arises from a misunderstanding of precisely what Occam's Razor deals with. Since we have evidence for the instantiation of at least one cosmic expansion, something would be required to act as a barrier to it happening again. It is this barrier that is a violation of Occam's Razor, because it constitutes a new kind of entity, and therefore an unnecessary multiplication of entities.

*© Terry Pratchett

 Yes I realize that this concept is lacking as far as theories go but for the purpose of discussion let's assume it is correct.

 Originally the purpose of this thread was to see if people might try to rationalize the existence of universes that would be impossible to verify or interact with(assuming multiverse theory is correct).

However Hackenslash and Droplogic's last comment have made this discussion more or less pointless so... .
I don't know does anyone have anything to add?

[Thumpalumpacus]

I don't see a problem with entertain conjectures on subjects currently beyond the grasp of our knowledge, so long as we understand that those conjectures don't represent anything other than a conjecture.

[Wilson]

On the subject of multiverses -

There's the theory that at every quantum event, a new universe branches out.  That came about because it seemed to be the only explanation physicists could come up with to explain some of the quantum weirdness.  But that idea sounds more unlikely than God's existence.

The kind of multiple universe theory that makes sense to me is that our universe could have any number of parallel universes, each of which sprung up from a massive quantum fluctuation or whatever the hell caused our big bang.  Think of a superuniverse where frequently or rarely (or only once or twice) big bangs occur and spawn new universes, which are isolated from each other - except that theoretically they could maybe come in contact with each other.  Possible, but it's doubtful that we'll ever know one way or the other.  As to whether the physical laws could be different in those other universes, I agree that there may be underlying constraints that don't allow variation.  Obviously they have to be finely tuned in order for a universe to survive.

[ablprop]

I'm very unhappy with the idea that some world exists for every quantum possibility. For instance, there is an extremely unlikely chance that all the air in the room I'm in will suddenly find itself in the upper southeast corner and I will asphyxiate.

OK, that didn't just happen.

But the reason it didn't happen is that there are 10^umpteenth (very scientific measurement) ways of arranging the air molecules so that this doesn't happen, and relatively many, many fewer ways that it does. Do we need a different universe for every one of these possibilities? Do we need a universe that is exactly like this one except that one molecule in this particular room is in a slightly different spot? And does that apply to every molecule everywhere? The whole thing just seems ludicrous.

[Inevitable Droid]

But the reason it didn't happen is that there are 10^umpteenth (very scientific measurement) ways of arranging the air molecules so that this doesn't happen, and relatively many, many fewer ways that it does. Do we need a different universe for every one of these possibilities? Do we need a universe that is exactly like this one except that one molecule in this particular room is in a slightly different spot? And does that apply to every molecule everywhere? The whole thing just seems ludicrous.

I agree.  What matters to me is that the hypothesis is unfalsifiable and so I reject it out of hand.  If we can posit multiple universes then what the heck, let's posit God instead.  Do we need multiple universes to make the math work?  Never mind that.  We'll let God's divine Providence fill any gaps in the math.

I also reject dark matter until somebody captures some in a jar.  If our math isn't working, we should simply bracket off the portion that requires multiple universes, or dark matter, or God, or leprechauns, and label the stuff inside the brackets, To Be Determined.

[hackenslash]

I agree.  What matters to me is that the hypothesis is unfalsifiable and so I reject it out of hand.  If we can posit multiple universes then what the heck, let's posit God instead.  Do we need multiple universes to make the math work?  Never mind that.  We'll let God's divine Providence fill any gaps in the math.

That's possibly going a little too far, with due reference to the points I made above, particularly with regard to use of the word 'universe'. Rejecting anything out of hand is unwise. The best approach is not to rule things out, but not to rule things in without good reason to do so.

I also reject dark matter until somebody captures some in a jar.  If our math isn't working, we should simply bracket off the portion that requires multiple universes, or dark matter, or God, or leprechauns, and label the stuff inside the brackets, To Be Determined.

And that's definitely unwise. You might want to read this thread, particularly my posts, which deal with precisely what dark matter is and what it isn't, in scientific parlance. It's important to know just what it is you are dismissing out of hand, because it may be that your understanding of it, or lack thereof, is what causes you to reject it. I'm happy to clarify anything that crops up in that thread that gives you pause, but I can tell you categorically that dark matter is real. That's not to say that what most people think of as dark matter, namely some kind of exotic 'stuff' is real, but the thing which we label dark matter most certainly is real, even if that thing is only a gap in our understanding of something else. Something is causing the effects we observe, and it is that which we label 'dark matter'. Thus, dark matter is real, and indisputable.

[Inevitable Droid]

That's not to say that what most people think of as dark matter, namely some kind of exotic 'stuff' is real, but the thing which we label dark matter most certainly is real, even if that thing is only a gap in our understanding of something else. Something is causing the effects we observe, and it is that which we label 'dark matter'. Thus, dark matter is real, and indisputable.

If it's a gap in our understanding, then in my opinion we should call it a gap in our understanding.  To apply Rumsfeldian epistemology, this would be a "known unknown."  

[hackenslash]

That's not to say that what most people think of as dark matter, namely some kind of exotic 'stuff' is real, but the thing which we label dark matter most certainly is real, even if that thing is only a gap in our understanding of something else. Something is causing the effects we observe, and it is that which we label 'dark matter'. Thus, dark matter is real, and indisputable.

If it's a gap in our understanding, then in my opinion we should call it a gap in our understanding.  To apply Rumsfeldian epistemology, this would be a "known unknown."  

We do call it a gap in our understanding. However, we also call it dark matter, for reasons detailed in the thread I linked to. In brief, it is matter that is postulated to exist to account for particular gravitational effects, but we can't see it, so it is clear that it doesn't reflect or emit electromagnetic energy, hence it's dark. Given that the only thing we have yet elucidated that has gravitational effects is matter, we call it matter. Given that it doesn't reflect or emit electromagnetic energy, we call it dark. Thus, dark matter exists, regardless of whether we understand it or not.

By your logic, we should call gravity a gap in our understanding, rather than calling it gravity, because we don't know what it actually is. Again, all of this is dealt with in that thread, so perhaps a read of the thread may be in order.

[Davin]

That's not to say that what most people think of as dark matter, namely some kind of exotic 'stuff' is real, but the thing which we label dark matter most certainly is real, even if that thing is only a gap in our understanding of something else. Something is causing the effects we observe, and it is that which we label 'dark matter'. Thus, dark matter is real, and indisputable.

If it's a gap in our understanding, then in my opinion we should call it a gap in our understanding.  To apply Rumsfeldian epistemology, this would be a "known unknown."  

It's difficult to work that way. It's better to name something and work with it knowing that you don't know exactly what it is than to try to work without naming things.

[Inevitable Droid]

Given that the only thing we have yet elucidated that has gravitational effects is matter, we call it matter. Given that it doesn't reflect or emit electromagnetic energy, we call it dark. Thus, dark matter exists, regardless of whether we understand it or not.

First, let me say that in addition to reading the thread you pointed us to, I had previously read a variety of articles discussing dark matter.  Two that suggest alternative hypotheses, albeit to the enduring skepticism of critics thus far, are these:

Scalar-tensor-vector gravity (STVG) - http://www.newscientist.com/article/dn8631-gravity-theory-dispenses-with-dark-matter.html

Modified Gravity (MOG) - http://www.space.com/scienceastronomy/071029-mm-mog-theory.html
 
My previously noted discomfort is partly semantic, but moreso it's psychological.  Logically there are two possibilities that automatically get ruled out if we populate our brains with this dark matter concept.  One, perhaps something else, in addition to matter, can affect this thing we call gravity.  Two, perhaps under certain conditions, for example when operating across astronomical distances, this thing we call gravity behaves differently than we think it should.  Talking about dark matter pushes both of these possibilities out of our brains.  Or at least it does for me.  Maybe my brain is odd in that respect.

By your logic, we should call gravity a gap in our understanding, rather than calling it gravity, because we don't know what it actually is.

Since gravity simply means, "mass pulling mass," denoting nothing of substance beyond those three words, I would actually be happier if we talked instead about mass pulling mass, and dropped the word gravity.  All we know is that mass pulls mass; therefore, in my opinion, all we should talk about is mass pulling mass.  If four syllables are too many, we can shorten it to just pull.  Then we could call the factor that does weird things to how mass pulls mass, weird pull factor, or WPF.  I wish "pull" started with a "T" as that would be amusing, but never mind that.

[Ihateyoumike]

Then we could call the factor that does weird things to how mass pulls mass, weird pull factor, or WPF. I wish "pull" started with a "T" as that would be amusing, but never mind that.

Would "Weird Tugging Factor" work for you?  

[Inevitable Droid]

Then we could call the factor that does weird things to how mass pulls mass, weird pull factor, or WPF. I wish "pull" started with a "T" as that would be amusing, but never mind that.

Would "Weird Tugging Factor" work for you?  

[Faradaympp]

Well since the discussion seems to have turned to dark matter I might as well point this  out.
 John Moffat wrote a book about the MOG theory (interesting read). It explains the universe just as well as relativity accompaniied with dark matter, the most noteable differences are the abscence of dark matter and the speed of light is not treated as a constant. (on a purely non-scientific basis I think this theory is worthy of attention because the trend in scientific revolutions seems to point to a removal of constants)

 Also, Hackenslash, your views about the universe and the theories we use to explain it seem very absolute. You seem very quick to dismiss any theory or thought you seem to think implausible or unfounded, I could be wrong, but given the length of your responses I can only conclude that you give such matters much thought. But what I would like to know is; how difficult do you think it would be for you to accept a theory you don't agree with, such as multiverse theory. And what kind of "evidence" might you want to see?

[Davin]

But what I would like to know is; how difficult do you think it would be for you to accept a theory you don't agree with, such as multiverse theory. And what kind of "evidence" might you want to see?

I think this is a loaded question. For instance, I will agree with anything that has sufficient reasonable evidence and follows logically, and not accept that which doesn't. This doesn't mean that I deny anything that doesn't fit that, the rest just sits on neutral ground (and a few things which are too unreasonable go into the denied bucket). So if I were answering the question I would say that I would not accept anything that I don't agree with. However I don't find that unreasonable as I think my criteria for agreeing with something is reasonable.

I don't have a preference on what reality should be, my preference is that I should understand reality.

[hackenslash]

Well since the discussion seems to have turned to dark matter I might as well point this  out.
 John Moffat wrote a book about the MOG theory (interesting read). It explains the universe just as well as relativity accompaniied with dark matter, the most noteable differences are the abscence of dark matter and the speed of light is not treated as a constant. (on a purely non-scientific basis I think this theory is worthy of attention because the trend in scientific revolutions seems to point to a removal of constants)

I'll give it a read, although I think your last point is misplaced. In reality, constants are the axioms upon which scientific understanding is rooted. Indeed, most physicists would argue that only constants are remotely interesting, because they provide the benchmarks against which all things are measured.

As for c being a constant (you'll note that I don't use 'the speed of light', which is a red herring), there is a wealth of empirical support for that, and for other features of Minkowski spacetime. What any new hypothesis must do is to explain all that the current paradigm explains along with some things that it doesn't. It may well turn out that relativity is a mere approximation, and indeed this has been the way of all our models preceding relativity and QM (and of course we know it to be incomplete at best, since it can't yet be married with QM). However, I haven't come across anything that so completely covers its remit as relativity as yet.

Also, Hackenslash, your views about the universe and the theories we use to explain it seem very absolute. You seem very quick to dismiss any theory or thought you seem to think implausible or unfounded,

Dismiss? No. What I do is not to accept that which does not conform to my understanding. I hope you'll note the distinction. If I can raise objections to a model based on what we know to be supported, then I will raise them. That's not the same as dismissing them, it's simply pointing out a problem to be overcome if the model is correct. This is the way of scientific peer-review, and is the proper way to assess any model.

I could be wrong, but given the length of your responses I can only conclude that you give such matters much thought.

I certainly have, and much study besides.

But what I would like to know is; how difficult do you think it would be for you to accept a theory you don't agree with, such as multiverse theory. And what kind of "evidence" might you want to see?

Which multiverse theory? I've already gone over this ground, and detailed my response to several of those models, yet you still cite 'multiverse theory' as if that explains what you're talking about. Further, as Davin has noted, this is a loaded question, so my response should really be limited to 'have you stopped beating your wife?'

In any event, what it would take for me to accept any theory, regardless of my agreement or not, which is irrelevant, because my personal feelings have no bearing on reality, is evidential support for the postulates and predictions of the model. This is always the case, and it was the case with Relativity and QM. Difficulty is not, in and of itself, a factor. Only evidential support.