Probability of stars in a multiverse

[jimjohnson]

Having recently read two books (Just Six Numbers by Martin Rees and The Fallacy of Fine-Tuning by Victor Stenger) I am confused on one issue. Assuming a multiverse, what is the probability that stars and galaxies would form in a universe. Stenger would say it is high but Rees would say it is low. Based on the clarity of arguments, my vote would be with Rees. What do others think?

 

[Cybalicist]

In any system where the individual parts still act on each other with gravity it would only be a matter of time. Especially when you know how the early stars were formed.

 

[Chronos]

I'm no fan of multiverse theories, but, assuming it is correct, we still have no clue how probable structure formation [stars, galaxies, etc.] may be. Assuming the fundamental constants of nature are free to arbitrarily choose any value at the beginning of any given universe, I agree the probability appears vanishingly small. But, using the infinitude of alternate universes as an excuse to dismiss the odd coincidence our universe happens to be just right for structure formation sounds a little hand wavy to me.

 

[jimjohnson]

I agree with your comment but wanted to clarify the authors positions. Of the six numbers in Rees' book, all appear to be critical for the formation of stars and galaxies: N - the ratio of gravitation and electromagnetic forces (1039); ε -the percent of energy released in hydrogen to helium conversion (0.7%); Ω - the ratio of actual density to critical density (0.3); λ -the cosmological constant (0.7); Q - proportion of galaxy rest mass needed to disperse galaxies (10-5); and D - the number of dimensions (3). The first two are basic forces. The second two are relate to energy and expansion. The last two are properties of space. Rees says that changing anyone of these independently would not produce stars as we know them. Stenger says changing two or more may produce a stable environment because of the way they interact. Analysis appears to be very technical physics. Anyway, something to think about.

 

[Chronos]

My suspicion is the fundamental constants of nature are somehow intimately related, not free to arbitrarily assume random values. On that basis, I would hazard to guess structure formation is more likely than not in most 'multiverses'.

 

[Naty1]

Stenger says changing two or more may produce a stable environment because of the way they interact.

I have the Reese book. I have not seen Stenger's view...which seems interesting. Either our universe is 'one a kind never to be repeated' or we are in just one of perhaps an infinite number of universes, some habitable, some not. A related view which I have seen and find appealing is that from the universes which are born only those universes that can evolve do so, and of those, only the ones that can lead to new universes survive in the long run. If you can't have babies, your species dies out.

 

[Chalnoth]

My suspicion is the fundamental constants of nature are somehow intimately related, not free to arbitrarily assume random values. On that basis, I would hazard to guess structure formation is more likely than not in most 'multiverses'.

There's no real reason to suspect that. And everything we learn about the universe is pushing us in the other direction entirely. Though granted it is true that what we know now about the necessary physics is far too little to make a strong determination, what little we do know seems to be pushing in the direction of no such relationship that makes structure formation (or life) likely.

Also, we can infer nothing whatsoever about the likelihood of structure formation from the fact that we observe it: the probability that intelligent observers will observe structure formation is precisely equal to one, because without structure formation there can be no intelligent observers in the first place.

As far as what fraction of the universe beyond our cosmological horizon has structure formation? Well, we don't know. I suspect that fraction is very small indeed, based upon the very little that we do know about the topic.

 

[Naty1]

Chalnoth:

As far as what fraction of the universe beyond our cosmological horizon has structure formation? Well, we don't know. I suspect that fraction is very small indeed, based upon the very little that we do know about the topic.

I get the first two sentences, but not the last... Why might that be? Too young to have evolved much??

 

[Sayajin]

"Multiverse" theories are really speculative atm. There is no way to tell if something is going to happen when you don't know anything about it. Structure formulation would depend on the laws of physics.
If you believe that the laws of physics and all the constants except the cosmological constant are the same in the "multiverse" then our universe would be exception because if you change the cosmological constant by a little it affects the structure formulation in the universe by a lot.
However if you believe that some other constants or laws of physics are not the same then you can't say that because you can achieve other combination of values of the constants such that the universe has galaxies and stars even if it has much different cosmological constant.

 

[julcab12]

First, Let's put the speculation on one side and 'ASSUME' it is true. As per chaotic inflation theory. Multiverse tend to stop stretching in some region. Different bubbles may experience different spontaneous symmetry breaking resulting in different properties such as different physical constants. Acc. to WIKI. "Linde and Vanchurin calculated the number of these universes to be on the scale of 10^10^10,000,000. I don't know the probability of stars forming due to fact that we can't be sure of the variation of constants/factors for star formation as mentioned by Chronos.

 

[Chalnoth]

Chalnoth: I get the first two sentences, but not the last... Why might that be? Too young to have evolved much??

With slightly stronger gravity relative to the other forces, you get nothing but black holes. With slightly weaker gravity or a slightly larger cosmological constant no structures form at all. We don't know how likely these things are, but if these numbers vary much at all, star-bearing regions are probably extremely rare.

 

[Chalnoth]

"Multiverse" theories are really speculative atm. There is no way to tell if something is going to happen when you don't know anything about it. Structure formulation would depend on the laws of physics.
If you believe that the laws of physics and all the constants except the cosmological constant are the same in the "multiverse" then our universe would be exception because if you change the cosmological constant by a little it affects the structure formulation in the universe by a lot.
However if you believe that some other constants or laws of physics are not the same then you can't say that because you can achieve other combination of values of the constants such that the universe has galaxies and stars even if it has much different cosmological constant.

This is why proper comparisons use only dimensionless numbers that aren't prone to these problems.

 

[rbj]

"Multiverse" theories are really speculative atm. There is no way to tell if something is going to happen when you don't know anything about it. Structure formulation would depend on the laws of physics.
If you believe that the laws of physics and all the constants except the cosmological constant are the same in the "multiverse" then our universe would be exception because if you change the cosmological constant by a little it affects the structure formulation in the universe by a lot.
However if you believe that some other constants or laws of physics are not the same then you can't say that because you can achieve other combination of values of the constants such that the universe has galaxies and stars even if it has much different cosmological constant.

This is why proper comparisons use only dimensionless numbers that aren't prone to these problems.

i realize why we need to consider only dimensionless values for the fundamental constants of the universe to compare to other possibilities. but i do not understand why the need to consider dimensionless numbers has anything to do with what Sayajin wrote. he/she said nothing about units or the like.

but i do sort of object to saying that the Cosmological Constant is 0.7 . it is not 0.7 .

also, i thought that the whole idea of the concept of multiple universes is so that even if it is unlikely for some universal parameter to take on some necessary value for structure to form and eventually life that is intelligent enough to behold that structure, even if that is highly unlikely, it is not remarkable that we see such structure and such values for those universal parameters in the universe we behold. it's called selection bias, or specifically in this case, the Anthropic principle.

 

[Chronos]

Im no more a fan of the anthropic principle than the multiverse conjecture. Both go to great [and rather fantastic] lengths to explain the universe we observe - and resist any observational constraints. I think there must be a simpler, less 'finely tuned' expanation.

 

[jimjohnson]

I found two references addressing opposite views on the probability that stars/galaxies form. In the first, page 151 in The Hidden Realities, Greene quotes Weinberg on his argument for galaxy formation based on the value of the cosmological constant. His conclusion is that if it were a few hundred times larger there would be no galaxies. Using analogy he concludes that if E124 universes existed in a multiverse, then one like ours would be likely. The second reference is from Stenger's book page 227 and is based on the Principle of Mediocrity: " This implies that when we use physics to compute the possible range of a parameter, the value of that parameter should not be at the edges of that range but somewhere in the mediocre in-between." Not sure we will ever know.

 

[Chalnoth]

Im no more a fan of the anthropic principle than the multiverse conjecture. Both go to great [and rather fantastic] lengths to explain the universe we observe - and resist any observational constraints.

The weak anthropic principle is necessarily true. It makes as much sense to object to it as to object to the statement that 2+2=4. To not take it into account when considering questions of, "Why these laws?" is foolish: it's a selection effect that must be considered to have a chance at arriving at the correct answer.

I think there must be a simpler, less 'finely tuned' expanation.

Why?

 

[Chalnoth]

i realize why we need to consider only dimensionless values for the fundamental constants of the universe to compare to other possibilities. but i do not understand why the need to consider dimensionless numbers has anything to do with what Sayajin wrote. he/she said nothing about units or the like.

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.

but i do sort of object to saying that the Cosmological Constant is 0.7 . it is not 0.7 .

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.

Anyway, my point is that if we take the space of all possible laws that we know of, the space in which structures can form only comprises a teeny, tiny subset of that space. Now, it is possible that there are details of the universe that we don't know which disallow or disfavor certain parts of the whole space. It's also possible that the fundamental laws of physics are richer and more varied than we currently imagine, leading to a much larger parameter space than a naive analysis based on the standard model would predict. Either way, work in high energy physics seems to be pushing that there probably isn't anything that really makes the low-energy laws we see the preferred ones in any sense.

 

[rbj]

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.

 

[Chronos]

I agree the weak anthropic principle is undeniably true - the universe cannot possesses properties that forbid the existence of observers [i.e., us]. But, that does not explain why the measured properties of the universe possesses 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.

 

[Chalnoth]

I agree the weak anthropic principle is undeniably true - the universe cannot possesses properties that forbid the existence of observers [i.e., us]. But, that does not explain why the measured properties of the universe possesses 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?

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.

 

[rbj]

I agree the weak anthropic principle is undeniably true - the universe cannot possesses properties that forbid the existence of observers [i.e., us]. But, that does not explain why the measured properties of the universe possesses 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?

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.

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.

 

[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.

 

[Chalnoth]

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.

 

[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.

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.

there were forces and there was stuff. just having laws of interaction doesn't mean you have stuff to interact.

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"?

 

[Chalnoth]

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.

 

[rbj]

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.

 

[Chalnoth]

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.

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.

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.

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.

 

[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.

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.

 

[Chronos]

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.

 

[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."