## Probability of stars in a multiverse

 Quote by Chalnoth No, it actually does. For example, the reason why you don't get nothing but black holes now is not because of the absolute value of G, but rather of G's strength relative to the other forces: as long as gravity is weak enough that there is a regime where stable compact matter can exist without forming a black hole, we can have structure. Gravity's strength compared to the other forces is around $10^{-40}$. If it were around $10^{-39}$ or so weaker, it would overwhelm the other forces and we'd have nothing but black holes. Sure. The 0.7 number is based on convenience, and is particular to our period of time. A more sensible number is the one based on its ratio compared to the Planck scale, approximately $10^{-120}$. If the dark energy were much higher, around $10^{-119}$ or so, the universe would expand too rapidly and no structures could form.
i think actually we agree on substance and are differing with semantics.

i would say that there is no comparison of $G$ (or $c$ or $\hbar$ or $\epsilon_0$) to any other situation. they're all just 1. including $G$ (actually, i think it's $4 \pi G = 1$).

what makes gravity so much weaker, from the POV of subatomic particles, is that the electric charge of any of these particles (if charged) is in the ballpark of the Planck charge, or the rationalized Planck charge, where $e = \sqrt{4 \pi \alpha}$ while the masses of any of these particles is far, far less than the Planck mass, like something like 10-19 or something like that.

i do not believe that there is some intrinsic parameter of free space that is $G$. the parameter $G$ is only a manifestation of the units we choose to measure things.
 Recognitions: Gold Member Science Advisor I agree the weak anthropic principle is undeniably true - the universe cannot possess properties that forbid the existence of observers [i.e., us]. But, that does not explain why the measured properties of the universe possess the values they do. To wave it off as a statistical fluke in an infinite sea of alternative universes with different properties is just a little too convenient, IMO. In my mind, there are only four fundamental forces in the universe and all of existence is and was determined by these four forces. Presumably they were all combined as a single force in the beginning. That at least suggests the existence of some unknown principle that encourages the individual forces to emerge with well behaved values, or proportionality of values, similar to those we observe. The trick, obviously, is figuring out the interdependence between all the forces. Thus far we've only solved the puzzle for electromagnetism. Many scientists still hold out hope for a grand unified theory [EM, strong and weak force], and some ponder an even grander theory that includes the black sheep [gravity]. Armed with such a theory, I believe we could assert alternative universes substantially unlike our own demand a primordial unified force substantially unlike that from which our universe emerged.

Recognitions:
 Quote by Chronos I agree the weak anthropic principle is undeniably true - the universe cannot possess properties that forbid the existence of observers [i.e., us]. But, that does not explain why the measured properties of the universe possess the values they do. To wave it off as a statistical fluke in an infinite sea of alternative universes with different properties is just a little too convenient, IMO.
Why is it too convenient?

 Quote by Chronos In my mind, there are only four fundamental forces in the universe and all of existence is and was determined by these four forces. Presumably they were all combined as a single force in the beginning. That at least suggests the existence of some unknown principle that encourages the individual forces to emerge with well behaved values, or proportionality of values, similar to those we observe.
Many high-energy physicists have been going down this route for decades without success.

 Quote by Chronos I agree the weak anthropic principle is undeniably true - the universe cannot possess properties that forbid the existence of observers [i.e., us]. But, that does not explain why the measured properties of the universe possess the values they do. To wave it off as a statistical fluke in an infinite sea of alternative universes with different properties is just a little too convenient, IMO.
 Quote by Chalnoth Why is it too convenient?
perhaps because there is about as much evidence of the existence of these other universes as there is evidence of a transcendent God or of a flying spaghetti monster. no physical experiment is going to make a God-detecting device nor one that detects other universes.

fine-tuning of the universe begs the teleological question and i'm afraid that explaining it away with other universes that may or may not exist is just making a faith statement.

 Quote by Chronos In my mind, there are only four fundamental forces in the universe and all of existence is and was determined by these four forces.
there were forces and there was stuff. just having laws of interaction doesn't mean you have stuff to interact.

 Presumably they were all combined as a single force in the beginning.
some hope of that.

but i think there needed to be more than just the forces (or the big unified force), there had to be the physical quantities of stuff for the forces to act on. unless, i guess it all gets to pop into existence as a mondo "quantum fluctuation" which some might describe the big bang as. perhaps that's the reason that there is something rather than nothing.

i dunno.
 Recognitions: Gold Member Science Advisor The current idea of 'stuff' is that it was produced as a consequence of the big bang - i.e., a consequence of the initial, primordial energy state of the universe - thus, not fundamental.

Recognitions:
 Quote by rbj perhaps because there is about as much evidence of the existence of these other universes as there is evidence of a transcendent God or of a flying spaghetti monster.
That is completely and utterly false. The evidence for the existence of regions of space-time with different physical laws is the fact that spontaneous symmetry breaking resulted in the precise low-energy physical laws that we experience. We don't yet know how much spontaneous symmetry breaking played a part, but we know it did play a part. Quantum mechanics guarantees that all possible spontaneous symmetry breaking results occurred.

So the evidence for some level of multiverse with different physical laws is pretty significant, based upon what we know of quantum mechanics. We don't know just how much physical laws vary, or what the distribution is. But we know that there is some variation.

If you want to try to get around this, you have to make additional unevidenced assumptions (e.g. some unknown potential drove the symmetry breaking to be precisely the one we see).

A multiverse includes fewer assumptions, and because of this should be the default unless some strong evidence pushes us in another direction.

 Quote by rbj ... there is about as much evidence of the existence of these other universes as there is evidence of a transcendent God or of a flying spaghetti monster.
 Quote by Chalnoth That is completely and utterly false.
and that is a matter of opinion. your opinion. and i am sure that it is an opinion shared by others.

 Quote by rbj there were forces and there was stuff. just having laws of interaction doesn't mean you have stuff to interact.
 Quote by Chronos The current idea of 'stuff' is that it was produced as a consequence of the big bang - i.e., a consequence of the initial, primordial energy state of the universe - thus, not fundamental.
well, the primordial energy of the universe at t=0 is not "stuff"?

Recognitions:
 Quote by rbj and that is a matter of opinion. your opinion. and i am sure that it is an opinion shared by others.
Hardly. There simply isn't any comparison. One is a solid conclusion based upon broadly-supported scientific theory (in this case the standard model of particle physics). The others are completely made-up with no connection to any scientific theory or evidence, or even any known way they could fit with current scientific theories.

 Quote by Chalnoth Hardly. There simply isn't any comparison. One is a solid conclusion based upon broadly-supported scientific theory (in this case the standard model of particle physics).
multiverse is a conjecture. there is no evidence for it, nor is there evidence that precludes it.

 The others are completely made-up with no connection to any scientific theory or evidence, or even any known way they could fit with current scientific theories.
never said there was a connection to any scientific theory. but there are those who have made such a connection, like Amit Goswami.

but, a safer philosophical ground to stand on is that science doesn't speak directly to the supernatural or non-materialistic notions, Gould's Non-overlapping magisteria. the theists have to admit that science does speak to the issue of the intersection of the supernatural with nature (these are sometimes called "miracles"). anyone who claims that some miraculous event they believe happened in reality is not disputed by science also has their head in the sand.

personally, i am more impressed by folks like John Polkinghorne or Freeman Dyson or Owen Gingerich than i am of Goswami. at least at present. Chalnoth, if you insist that your authority to the facts and the interpretation of the facts exceeds theirs, i just have to say, "sorry, it doesn't". (where is your wikipedia page?)

Chalnoth, i think that your error (just an error in my POV, it's very well if you don't see it as an error), is that you think that, in the sphere of philosophy, that the material and that physics trumps every other line of thinking and that's that. i consider it short-sighted (physics isn't everything), but i don't know everything. and because i don't know everything and i recognize it, i look at what other persons of recognized authority have to say, i try to learn from them, and i try to discern myself what to believe. just because they are a recognized authority doesn't mean that i take everything they say for granted. because you will find persons of credible authority on either side or of multiple sides with diametric or nearly diametrically opposite conclusions.

your simplistic categorization of the POV that is not your own is just that: simplistic. Dawkins makes the same mistake, so you have company.

Recognitions:
 Quote by rbj multiverse is a conjecture. there is no evidence for it, nor is there evidence that precludes it.
You keep saying that, but it just isn't true. As I've already pointed out, evidence for spontaneous symmetry breaking is evidence for a multiverse.

 Quote by rbj Chalnoth, if you insist that your authority to the facts and the interpretation of the facts exceeds theirs, i just have to say, "sorry, it doesn't". (where is your wikipedia page?)
I'm not insisting any authority on anything. I'm simply pointing out that a necessary conclusion of spontaneous symmetry breaking is a multiverse. Exactly how diverse that multiverse is we don't yet know. But it is quite clear that there is one.

 Quote by rbj Chalnoth, i think that your error (just an error in my POV, it's very well if you don't see it as an error), is that you think that, in the sphere of philosophy, that the material and that physics trumps every other line of thinking and that's that.
Uh, what? When it comes to questions like this, physics is the relevant field of study.

 Quote by rbj your simplistic categorization of the POV that is not your own is just that: simplistic.
Simple arguments are the best arguments. They are easier to analyze for fallacies and more difficult to brush aside when lacking said fallacies.

 Quote by rbj Chalnoth, i think that your error (just an error in my POV, it's very well if you don't see it as an error), is that you think that, in the sphere of philosophy, that the material and that physics trumps every other line of thinking and that's that.
 Quote by Chalnoth Uh, what? When it comes to questions like this, physics is the relevant field of study.
just confirming what i said.

 Simple arguments are the best arguments. They are easier to analyze for fallacies and more difficult to brush aside when lacking said fallacies.
"simplistic" is not the same as "simple". the latter might mean that there's some elegance or profundity in it.
 Recognitions: Gold Member Science Advisor I think we are all on the same page here, guys, so let's play nice. I agree with Chalnoth to the extent there is theoretical support for the multiverse idea. I also question if it is possible to observationally confirm or reject. That provokes me to great cynicism.
 Recognitions: Gold Member I wanted to add Brian Greene's perspective from The Hidden Reality. Quoting from pages 8/9: "So my point in writing this book is not to convince you that we're part of a multiverse. I'm not convinced- and, speaking generally, no one should be convinced - of anything not supported by hard data. That said, I find it both curious and compelling that numerous developments in physics, if followed sufficiently far, bump into some variation on the parallel-universe theme…. all of the parallel-universe proposals that we take seriously emerge unbidden from the mathematics of theories developed to explain conventional data and observations."

Recognitions:
 Quote by jimjohnson I wanted to add Brian Greene's perspective from The Hidden Reality. Quoting from pages 8/9: "So my point in writing this book is not to convince you that we're part of a multiverse. I'm not convinced- and, speaking generally, no one should be convinced - of anything not supported by hard data. That said, I find it both curious and compelling that numerous developments in physics, if followed sufficiently far, bump into some variation on the parallel-universe theme…. all of the parallel-universe proposals that we take seriously emerge unbidden from the mathematics of theories developed to explain conventional data and observations."
Honestly, I think he's hedging way too much.

Given what we know of physics, what has been tested, a multiverse should be the default assumption because it requires fewer assumptions.

 Quote by Chalnoth Honestly, I think he's hedging way too much.
and you have every right to think that.

 Given what we know of physics, what has been tested,
so what properties or any physical manifestation of a universe other than the one we exist in has been tested? how did that experiment turn out?

i'll tell you about my God-measuring experiment after you settle that.

 a multiverse should be the default assumption because it requires fewer assumptions.
"should" is a value judgment. you are welcome to have your own values, Noth.

what requires whatever assumptions is, again, a matter of opinion. and how to value and count the assumptions is, also, a matter of opinion.

Chalnoth, you just seem to not be able to understand that just because you believe something or believe in something that others might have very good reason to believe otherwise. you seem to insist that your sensibilities are the only sensible sensibilities; that everyone in the world should believe exactly as you do. ain't that a bit presumptuous?

i mean, if i read someone else insist that everyone else accept his or her faith-statement in what is not seen, nor measured, nor even possibly measured, i would call that person to task also. but you seem to think you are immune to that.

it might not be the case, but i would associate that with a hard-core fundamentalist of the faith of Materialism or Physicalism. you're certainly free to adhere to such a faith, but to insist that every thinking person, whether a scholar or not, adhere to the same is, to say the least, a bit pushy.

 Quote by Chalnoth You keep saying that, but it just isn't true. As I've already pointed out, evidence for spontaneous symmetry breaking is evidence for a multiverse. .
I'll keep an open view on the matter. We have to be careful. I'm not keen to say that multiverse is the only interpretation for SSB. It's somewhat simple, slightly convincing notion. Simple in a sense that it is viewed directly as a possible outcome and often ignores some other basic possibilities not to mention the less unfounded nature of that idea. It 'can' be just a effect of radiative correction found in massless gauge theories were it can induce spontaneous symmetry breaking as a consequence of relationship between the masses of the scalar and vector mesons, predicting (for small coupling constants) that the scalar mesons are much lighter. (http://arxiv.org/abs/hep-th/0507214).

 Quote by rbj Chalnoth, you just seem to not be able to understand that just because you believe something or believe in something that others might have very good reason to believe otherwise. you seem to insist that your sensibilities are the only sensible sensibilities; that everyone in the world should believe exactly as you do. ain't that a bit presumptuous? it might not be the case, but i would associate that with a hard-core fundamentalist of the faith of Materialism or Physicalism. you're certainly free to adhere to such a faith, but to insist that every thinking person, whether a scholar or not, adhere to the same is, to say the least, a bit pushy.
Lets keep it clean guys. I believe point is already taken. No more rendundant 'god and spaghettis (I'm beginning to feel hungry). Needs attenuation and be more direct. hehe

 Tags galaxies, multiverse, stars