Cyclic Universe

[Bettina]

I just received the latest copy of New Scientist and they had an article on the cyclic universe model (my favorite model). What I want to know is the percentage of scientists who believe in that model vs the other models.

 

I've been reading about branes that collide every trillion years too and got to wondering about who believes in what....

 

Thanks

 

Bettina

[CanadaAotS]

I like the cyclic universe model as well. big bang in general rubs me the wrong way, since no one knows why there was a bang, what happened during the bang, what is banging etc. lol.

 

I also like the nice round number of every trillion years lol

[Martin]

Bee, do you have the New Scientist issue #2564 that has this editorial?

I only can get a sample of it on the web

 

"Editorial: Loop quantum gravity increases its pull

12 August 2006

Magazine issue 2564

String theory's main rival has earned the right to be taken seriously - it could be the most profound scientific generalisation of all time

THE accepted idea of matter is that it is made up of minuscule particles guided by quantum force fields. This is already far removed from the common-sense view that matter is, well, just chunks of stuff. If that seems hard enough to take, then brace yourself for another step away from common sense.

 

Theoretical physicists working in the rarefied field of loop quantum gravity have developed a way to describe elementary particles as merely tangles in space (see "Out of the void"). If they are right, it could be the most profound scientific generalisation of all time, in which everything in the universe emerges from a simple network of relationships, with no fundamental building blocks at all.

 

Up to now, loop quantum gravity has seemed like a poor relation of string theory, which for years has been the most popular route to a "theory of everything" in which all ..."

 

If you have the issue and find anything noteworthy from that editorial you want to quote from it, I would be interested.

[insane_alien]

i like the cyclic model. although it does beg the question "what happens to entropy" i think we might have to rewrite thermodynamics a bit to accomodate it if we find out that it is true.

[Bettina]

Bee' date=' do you have the New Scientist issue #2564 that has this editorial?

I only can get a sample of it on the web

 

"Editorial: [b']Loop quantum gravity increases its pull[/b]

12 August 2006

Magazine issue 2564

String theory's main rival has earned the right to be taken seriously - it could be the most profound scientific generalisation of all time

THE accepted idea of matter is that it is made up of minuscule particles guided by quantum force fields. This is already far removed from the common-sense view that matter is, well, just chunks of stuff. If that seems hard enough to take, then brace yourself for another step away from common sense.

 

Theoretical physicists working in the rarefied field of loop quantum gravity have developed a way to describe elementary particles as merely tangles in space (see "Out of the void"). If they are right, it could be the most profound scientific generalisation of all time, in which everything in the universe emerges from a simple network of relationships, with no fundamental building blocks at all.

 

Up to now, loop quantum gravity has seemed like a poor relation of string theory, which for years has been the most popular route to a "theory of everything" in which all ..."

 

If you have the issue and find anything noteworthy from that editorial you want to quote from it, I would be interested.

 

Hi Martin...Yep... thats the copy I just received but have only quickly scanned it. I will get back to you on the rest of that editorial.

 

It has another neat article on the "Adept" probe looking for Dark Energy and Lee Smolins "Out of the Void" article.

 

Check back tomorrow morning.

 

Bee

[Martin]

... Lee Smolins "Out of the Void" article.

 

Check back tomorrow morning.

 

Bee

 

 

great, I have to go too. wife and I are going to see a MOZART OPERA! tonight.

looking forward to seeing some quotes about Smolin and QG tomorrow if you find any good ones

cheers (and thanks for doing the lookup)

[bascule]

Are you talking about this:

 

http://en.wikipedia.org/wiki/Cyclic_model

 

This describes the "colliding branes" model, at least how I heard it described

[Bettina]

Are you talking about this:

 

http://en.wikipedia.org/wiki/Cyclic_model

 

This describes the "colliding branes" model' date=' at least how I heard it described[/quote']

 

Yes. only its said better in "Fabric of the Cosmos" where I read it. Some times I thing theoretical physicists are just too cool. even though they can't prove anything.

 

I'm waiting for "The elegant universe" from Amazon to get here...

 

Martin....

 

I have two files for you attached. Its easier for me to do it this way than quote and miss something. I'll get back when I read more.

 

Bee

[Martin]

...

Martin....

 

I have two files for you attached. ... I'll get back when I read more.

 

Bee

 

Thanks Bee, I appreciate.

We can keep this a "Cyclic Universe" thread if you like. Could always make a separate thread about the recent braided networks version of Loop gravity (mentioned in the sample txt) if anyone wants. I will wait and see what you, Bascule, and others in this thread want to discuss.

[mustang292]

With a picture like that Bettina, I'll agree to whatever you think! If that's really you, then you are absolutely scrumptious!

[CanadaAotS]

And if thats really you mustang292 then you must be Jim Carrey!!!

 

*snickers*

[Bettina]

I would still like an idea of the percentage of scientists that believe in the cyclic model... Anyone?

 

Bee

[Martin]

I would still like an idea of the percentage of scientists that believe in the cyclic model... Anyone?

 

Bee

 

Bee' date=' I will try to help. but first I should explain. You can get an idea of what percentage of cosmologists think it is interesting enough to investigate. essentially that means counting research papers and conference talks

 

It would be harder to arrive at a percentage for how many working cosmologists BELIEVE the cyclic model (maybe actually zero, in fact) because it is a highly speculative untested model and it is not the professional cosmologists [b']job[/b] to believe or disbelieve.

 

It is their job to decide whether a new model is interesting, and if so, then to STUDY it, and then to test it. they will spend a long time checking for consistency and testing something empirically, while remaining skeptical.

 

Come to think of it, I could probably walk over to Campbell Hall where cosmologists hang out and find some grad students and postdocs and say "how many of you believe in Steinhardt's "cyclic model"-----aka the Ekpyrotic cosmological model----the colliding branes thing?" And they would probably say NOBODY. but one or more might still think it was interesting and worth studying-----ultimately that is what matters with a new theory.

 

even if you suspect a theory is wrong, it can be good professional experience, and you can learn something (!) if you try to prove it wrong.

 

Indeed I recently have come across papers like that----trying to show that the WMAP3 data disfavored Cyclic. You can actually publish, and advance your career, by doing that. It is fair game.

 

And it makes sense because professionals are supposed to test stuff and tell us if it passes or fails various checks. BELIEF is kind of like your private life. Intellectual commitments can be intense but that is not part of work---work is supposed to be objective.

 

Well maybe I wasted time saying what everybody already knows. But anyway I can try to help get an idea of what percentage cosmologists RESEARCH the colliding branes model.

 

A key to it would be to use the ARXIV.ORG search engine with the right keywords.

 

Firstoff here are the overall arxiv stats

http://arxiv.org/

 

http://arxiv.org/Stats/hcamonthly.html (note that red, astro-ph, has just overtaken and passed blue, hep, which is now declining)

 

we can try the search engine

http://arxiv.org/multi?group=physics&%2Ffind=Search

 

here I found 52 papers with "ekpyrotic" in the abstract summary or title

http://arxiv.org/find/astro-ph/1/abs:+ekpyrotic/0/1/0/all/0/1

 

here are 70 that had either "ekpyrotic" OR "cyclic universe"

http://arxiv.org/find/astro-ph/1/OR+abs:+AND+cyclic+universe+abs:+ekpyrotic/0/1/0/all/0/1

 

of these 4 were posted in 2005

http://arxiv.org/find/astro-ph/1/OR+abs:+AND+cyclic+universe+abs:+ekpyrotic/0/1/0/2005/0/1

 

we can look at a sequence and see if there is a trend

http://arxiv.org/find/astro-ph/1/OR+abs:+AND+cyclic+universe+abs:+ekpyrotic/0/1/0/2002/0/1

http://arxiv.org/find/astro-ph/1/OR+abs:+AND+cyclic+universe+abs:+ekpyrotic/0/1/0/2003/0/1

http://arxiv.org/find/astro-ph/1/OR+abs:+AND+cyclic+universe+abs:+ekpyrotic/0/1/0/2004/0/1

http://arxiv.org/find/astro-ph/1/OR+abs:+AND+cyclic+universe+abs:+ekpyrotic/0/1/0/2005/0/1

 

Hmmmm 16, 10, 12, 4 seems like a downwards trend of interest in "cyclic universe" models

 

I have just been searching astro-ph, which is where professional cosmologists usually post, but we could enlarge it to all physics and astrophysics

 

http://arxiv.org/find/grp_physics/1/OR+abs:+AND+cyclic+universe+abs:+ekpyrotic/0/1/0/2002/0/1

http://arxiv.org/find/grp_physics/1/OR+abs:+AND+cyclic+universe+abs:+ekpyrotic/0/1/0/2003/0/1

http://arxiv.org/find/grp_physics/1/OR+abs:+AND+cyclic+universe+abs:+ekpyrotic/0/1/0/2004/0/1

http://arxiv.org/find/grp_physics/1/OR+abs:+AND+cyclic+universe+abs:+ekpyrotic/0/1/0/2005/0/1

 

I get 28, 12, 16, 15

 

well none of this really proves anything, but it gives some idea----these are papers posted per year

and the whole field of cosmology would be quite a bit more than that, so basically one gets the idea that cosmologists are mostly working on other things, which is hardly surprising----lot of interesting ideas and data to work on in that field!

 

wish could be more helpful, maybe something will occur to me later

 

BTW just for terminology, some wikipedia:

http://en.wikipedia.org/wiki/Ekpyrotic

http://en.wikipedia.org/wiki/Cyclic_Model

http://en.wikipedia.org/wiki/Cyclic_Universe

http://en.wikipedia.org/wiki/Brane_cosmology

[Bettina]

Bee, I will try to help.

 

You did. Thanks for those links. Lots of stuff over my head, but thanks.

 

Bee

[Martin]

You did. Thanks for those links. Lots of stuff over my head...

 

lot of stuff over anyone's head:-)

the links were just to get paper-counts, as a gauge of research activity.

it is not to expect to understand all the technical language!

 

my impression is (warning: just my impression)

that people keep finding stuff wrong with colliding brane scenarios

and research activity has tapered off since 2001 and 2002

 

but even if that is true, the slump could turn around, there could be some new ideas of how it works, a new burst of interest. that might happen, and might not.

 

dont be discouraged about all the links. I wanted to illustrate how you can do arxiv.org keyword searches and find out stuff. you could easily be doing an arxiv search sometime in pursuit of your own interests

[bascule]

lot of stuff over anyone's head

 

Bingo

[Martin]

Bingo

 

Hi Bascule, I should apologize for exposing everybody to such a mass of raw indigestible links. At the time I couldnt think of any way to get a handle on Bee's "what percentage of scientists" question.

[J.C.MacSwell]

Hi Bascule, I should apologize for exposing everybody to such a mass of raw indigestible links. At the time I couldnt think of any way to get a handle on Bee's "what percentage of scientists" question.

 

I didn't check the links but your approach is interesting. I am always amazed when anyone "believes" a theory of the universe at or near 100%, often based on "no more plausible explanation". I remember Martin Rees claiming he had moved from 90% towards 99%+ certainty in the Big Bang Model. (I think it was in his book "Just Six Numbers" published in 2001). Regardless of the level of consistency with what we have observed in the past few hundred years it seems to huge an extrapolation to have that degree of "faith" in it, though I suspect it is mostly based on the weakness of the alternatives.

 

The Cyclic Universe is an extended extrapolation of the Big Bang Model in some presumably Sinusoidal form (I think?)

 

Personally I "prefer" a steady state model from a philosophical point of view, though it would require a different set of assumptions from those that presently disfavour it, including further rewriting of the second law of thermodynamics than that needed for the Cyclic Universe (as Insane Alien pointed out).

 

Can't say I "believe" any theory in particular, but find it very interesting what "odds" others, scientists or armchair scientists such as myself, would give each theory. It would be interesting to see some well thought out polls on this.

[Martin]

...

 

The Cyclic Universe is an extended extrapolation of the Big Bang Model in some presumably Sinusoidal form (I think?)

 

...

 

that's just the trouble J.C., it is NOT.

Steinhardt and Hurok STOLE the natural name for a perfectly sensible idea and applied it to something fairly bizarre in higher dimensions.

 

BTW just for terminology, some wikipedia:

http://en.wikipedia.org/wiki/Ekpyrotic

http://en.wikipedia.org/wiki/Cyclic_Model

http://en.wikipedia.org/wiki/Cyclic_Universe

http://en.wikipedia.org/wiki/Brane_cosmology

 

In Loop QG gravity does naturally become repellent at high densities and the (unphysical) classical bigbang and bigcrunch singularities are replaced by a quantum BOUNCE.

So it is an obvious possibility to consider a universe that goes thru cycles, each crunch bouncing and re-expanding, to be followed after billions of years by another crunch.

Maybe that does not fit our universe, maybe it does, but at least it is very reasonable to consider and it is what one naively thinks of when one hears the phrase CYCLIC universe.

 

but Steinhardt and Hurok captured that terminology and applied it to something quite different involving quite a stretch of the imagination---their 'cyclic' requires CLASHING BRANES IN HIGHER DIMENSIONS.

 

One good swipe with Occam's razor would get rid of the SteinhardtHurok "ekpyrotic" or "cyclic" model. We don't need higher dimensions to get rid of the classical singularities and model a bounce. And there is no evidence of higher dimensions. Occam's razor says don't add extra entities to the picture unnecessarily.

 

I think interest in these brane cosmology scenarios is declining, but can't be sure.

[J.C.MacSwell]

that's just the trouble J.C.' date=' it is NOT.

Steinhardt and Hurok STOLE the natural name for a perfectly sensible idea and applied it to something fairly bizarre in higher dimensions.

 

BTW just for terminology, some wikipedia:

http://en.wikipedia.org/wiki/Ekpyrotic

http://en.wikipedia.org/wiki/Cyclic_Model

http://en.wikipedia.org/wiki/Cyclic_Universe

http://en.wikipedia.org/wiki/Brane_cosmology

 

In Loop QG gravity does naturally become repellent at high densities and the (unphysical) classical bigbang and bigcrunch singularities are replaced by a quantum BOUNCE.

So it is an obvious possibility to consider a universe that goes thru cycles, each crunch bouncing and re-expanding, to be followed after billions of years by another crunch.

Maybe that does not fit our universe, maybe it does, but at least it is very reasonable to consider and it is what one naively thinks of when one hears the phrase CYCLIC universe.

 

but Steinhardt and Hurok captured that terminology and applied it to something quite different involving quite a stretch of the imagination---their 'cyclic' requires CLASHING BRANES IN HIGHER DIMENSIONS.

 

One good swipe with Occam's razor would get rid of the SteinhardtHurok "ekpyrotic" or "cyclic" model. We don't need higher dimensions to get rid of the classical singularities and model a bounce. And there is no evidence of higher dimensions. Occam's razor says don't add extra entities to the picture unnecessarily.

 

I think interest in these brane cosmology scenarios is declining, but can't be sure.[/quote']

 

Thanks Martin, I will check the Wiki's out. Though I do not agree with (read understand) string theory I do suspect there may be some kind of extra dimensions, mostly because there seems to be no logical explanation without them but for other reasons also inspite of my inability to "fit them in" in a consistent way (my best ideas on this are half baked noise).

 

I do like Occam's razor though if I shave with it quickly I usually lop an ear off.

[bascule]

In Loop QG gravity does naturally become repellent at high densities and the (unphysical) classical bigbang and bigcrunch singularities are replaced by a quantum BOUNCE.

 

So that's how a fecund universe would be born out of a black hole? Eventually the density becomes so great that gravity becomes repulsive?

[Martin]

So that's how a fecund universe would be born out of a black hole? Eventually the density becomes so great that gravity becomes repulsive?

 

that is right

numerical simulation studies are going on at penn state

there is a deterministic evolution of the wave function through the classical singularity

 

(deterministic in the quantum sense, yeah it sounds contradictory)

 

some papers on this have been published but there is a lot more to do.

 

they have not numerically modeled the case of black hole bounce AFAIK

(but have suggestive analytical results for BH bounce in special cases assuming symmetry)

 

so far only the case of a classical universe collapsing and evolving thru a quantum regime of very high (but not infinite) density and leading to a bigbang has been studied

 

the "fecund universe" idea is only a scenario or conjecture, not proven by any means (!) but beginning to seem more plausible

 

the "repellent gravity" thing was not put in by hand, but came out (orig. in 2001) from the equations during an attempt to quantize the simplified General Relativity model used in cosmology.

 

you like to fly by intuition, I think, so i will not bother you with links to papers about what I'm talking. Say if you ever want technical paper URLs. You seem to do OK flying by intuition.

[bascule]

you like to fly by intuition, I think, so i will not bother you with links to papers about what I'm talking. Say if you ever want technical paper URLs. You seem to do OK flying by intuition.

 

You've pointed me to some great papers, but unfortunately I have trouble getting anywhere much deeper than the abstracts. My favorite paper is still that one I found where they derive Lorentz transforms from a CA. That was damn cool!