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Cosmological anthropocentrism

I just looked at Weinberg's paper again. Kinda interesting.

The way I've been thinking about it is this: There's no obvious connection between dark energy existing, and life existing. Never mind dark energy happening to become dynamically significant right when we happened to be around to see it. So how to make use of an anthropic principle? (Of course if this guy I just wrote about is right, then there's a correlation without any necessary connection/causation, which is nice..)

Anyway, as I understand it, when Weinberg (http://www.arxiv.org/astro-ph/0005265 ) and others use the anthropic principle they dont mean something so imprecise. What they look for are models wherein the SuperDuperVerse is much, much bigger than the universe which we see (some sort of New Inflation scenario), and certain initial fields have quantum fluctuations which range over values that yield the "desired" universes in suitable abundance - one of which is presumably our "visible" universe. In these models, they try and rig it so if you take any of the universe sized bubble regions of the SuperDuperverse, you'll find, with high likelihood, conditions much like the ones we see. Thus they say "we see the universe the way it is because no matter which universe you take you'll see something like the one we see".
 
Like Wrath (I think), I don't understand what all the fuss is about. What is everyone saying other than "What a coincidence that intelligent life arose during the period of the universe that was conducive to intelligent life"? What am I missing?

~~ Paul
 
Paul C. Anagnostopoulos said:
Like Wrath (I think), I don't understand what all the fuss is about. What is everyone saying other than "What a coincidence that intelligent life arose during the period of the universe that was conducive to intelligent life"? What am I missing?

~~ Paul
Click to expand...

Paul the question becomes, what has dark energy got to do with the conduciveness or otherwise of the universe to intelligent life? If there was an obvious connection (e.g. dark energy was necessary in order to help matter and radiation decouple, or dark energy is necessary for galaxy formation or ...) then of course one could invoke some sort of anthropic principle (though such principles are ususally avoided as long as possible, since they are only marginally more useful than "intelligent design" as a way of seeing where to go next with the physics!).

In fact, what you need is stronger - you need for the dark energy dominated phase of the dynamics of the universe to somehow be correlated with the conditions that we (somewhat biased and naively) think are necessary for intelligent life. In effect, by saying there is no dark energy, (i.e the observations are explained by the process of structures being formed out of matter,) Rassanen's model gives such a correlation naturally. Part of what makes it appealing.
 
Ah, it was the fascination with the correlation with dark energy that I was missing.

I figured if I waited a few years for this whole dark energy thing to evaporate, I'd save myself a lot of cogitation. :D

~~ Paul
 
Wow, great stuuf!

I would hazard a guess that the question the unestimable SW is rasing is bsed upon the idea of isotropy. If the universe id going through this change, why is it that we are here to see it? In other words it is just a whacky coincidence.

My guess is that there was the observable life before the transition and there will be life after.

And from what the previous poster said about the logrithmic scale, it would be more suprising if we weren't at the transition. It sounds as though the transition equates to most of the know time of the universe.
 
Dancing David said:
Wow, great stuuf!

I would hazard a guess that the question the unestimable SW is rasing is bsed upon the idea of isotropy. If the universe id going through this change, why is it that we are here to see it? In other words it is just a whacky coincidence.

My guess is that there was the observable life before the transition and there will be life after.

And from what the previous poster said about the logrithmic scale, it would be more suprising if we weren't at the transition. It sounds as though the transition equates to most of the know time of the universe.
Click to expand...

After I made the initial postings here, I began to understand a little better why (to cosmologists) the timing is strange.

Basically, these guys talk in "z" - redshift factors. So a given "z" is imply a look back in time. Now the z's they talk about are things like "recent history" -- which means z up to a few thousand. (You can see this in the paper I linked to). So they observe that matter started dominating radiation at z=3500, radiation and matter decoupled at z=1088, and structure started forming at z about 10 (very, very recently). Meanwhile the transition from matter domination to dark energy domination is at z ~ 5. So, when phrased like this (and I have no real idea why this is really a better way of evaluating "coincidence" or otherwise on cosmic time scales) it does seem that we live at a special time with respect to the role of dark energy. Anthropically speaking, one can argue that structure is important - but why the dark energy transition to dominance?
 
It might simply be a coincidence.

If life is cosmically common, and if it is possible for life to exist at any cosmically important moment, then it's likely that someone will be alive at any particular important moment.

What are the chances that I would be alive at the right place and the right time to read your post?
 
Perhaps the biggest problem people have with the anthropic principle is that is self-referential. That seems rather fishy to many minds , but if you examine the theory in context of a universe that could have life evolve and it did so only coincidentally , It makes perfect sense. Very simp[ly that life may or may not arise and that if it does it will be a reflection of the environment around it. All one has to do is look at the super heated sulpher dioxide chimneys on the sea floor that harbors simple organisms under enormous pressure or the core of antarctic rock with bacteria in stasis of thousands of years that can be revived to see that this is possible.

The more subtle point is , can we ultimately know the intimate processes of a universe that we a part of. Thats like the scene in matrix where Cypher explains to Neo that "You can't observe the program directly because it's part of the construct". I'm don't believe thats the case as we have gone from spontaneous generation of rats in piles of straw to genetic medicine in a few hundreds of years , I think ultimately we will be able to quantify the universe around us.


Speculation...................
Brian Greene states that varying the underlying constants of our universe would produce a different reality, while that may exclude the development of "Human" type life it doesn't exclude a very different form of self-replicating organism. We do tend to be species centristic.


Off topic "a bit "

The idea that our 4 dimensional universe may embedded in an extra spatial macro dimension rather then compactified ( Kaluza-Klein model) ones seems more likely as our understanding of the forces that govern our see-able reality expands . The traditional argument is that Newtonian rules precluded an existence because e.g. the square of the distance rule would change into the cube of the distance.. The one thing we know is that the Newtonian ruleset collapses at both quantum and relativistic scales, therefor any violation would appear to be less inviolable then say c.

Brane theory offers some accommodation to macro scale dimensions. The HEP experiments at CERN look promising. The most noted and embraced extra definitional model is compacted dimensions in SST and a seeming acceptance of the HE Physicists at large.
Still learning the maths , I'm at a.3 the goal is somewhere around x.

Good paper here: http://ej.iop.org/links/q18/DZrhoGmwv+D62IfpjlCVUQ/jhep082001005.pdf
 
Greg Egan's Diaspora includes a fascinating exploration of life in a six-dimensional world. This seems to be related to the matters you brought up, TE.
 
The paper looks really interesting, though some of it is over my head.

From what I understand, "dark matter" is the non-luminous matter known to exist in galaxies by calculations of orbital speeds at various radii; "dark energy" is the intergalactic mass-energy propounded to explain the discrepancy between the matter known to exist in galaxies and clusters and the average energy density of the universe. As the universe expands, the matter density decreases so the dark energy component must increase to compensate and keep omega = 1.

Why is dark energy repulsive? I thought that dark energy was a way of explaining why we see the energy density as nearly equal to the critical density despite no indication as to where the missing energy is.
 
Wrath of the Swarm said:
It might simply be a coincidence.

If life is cosmically common, and if it is possible for life to exist at any cosmically important moment, then it's likely that someone will be alive at any particular important moment.

What are the chances that I would be alive at the right place and the right time to read your post?
Click to expand...

True, but this is far from the anthropic principle as originally conceived (see e.g.)

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

i.e. the principle is more about wondering why conditions are such that life can exist at all.

However I agree the "some intelligent critter will be around" principle is quite appealing in many circumstances. And if pushed a little further, it seems to me that one can say something along the lines of "you'll notice the interesting things far more than the uninteresting ones, and thus will always think you live in interesting times", which I think is perfectly valid.

However (i) it would be too easy to use this principle to carte blanche give up on looking for possible hidden correlata underlying interesting things, and (ii) once adopted you're not left with much further to go. Thus its not the sort of principle I'll resort to unless I havent the energy or ability to go further...
 
I think that even if we embrace the anthropic principle, that doesn't necessarily preclude the investigation of causality or the thread of evolution ( in cosmological terms).

In plain terms ( without sounding too Clintionesque) Things are the way they are , precisely because things are the way they are. The reality that exists at this time could not seed or propagate life other then the way we recognize it (generally).It can only arise in a universe that has the ~exact qualities that exist at this time. ( Give or take a few millions of years).
 
TillEulenspiegel said:


Speculation...................
Brian Greene states that varying the underlying constants of our universe would produce a different reality, while that may exclude the development of "Human" type life it doesn't exclude a very different form of self-replicating organism. We do tend to be species centristic.
Click to expand...
Although timing from big bang to heat death, or to big crunch, is the biggest problem iirc. Also the universal solvent water sure has interesting characteristics (phase change temperatures, ice floats, etc. ). What parameters could be changed even slightly & maintain that result?

Water, as it is, must occur in this universe with the constants we have.
 
Tilly

Did you understand the implication of time -- or do you think viruses appeared magically in the first few /milliseconds / years/ centuries / millenia / whatever/ length of time the universe forms, if it ever forms?
 
Yes , I understood the time considerations, but unless I'm completely ignorant, Your position was the reduced possibility of life without the existence of H2O,. That as I stated is not the case in even our current reality.

Matter first appears at ~1M yrs.@ 4000k ( the 4th epoch ) so any construct that requires atomic or molecular structures must have occurred after that time. The question You raise has no bearing in this discussion.
 
TillEulenspiegel said:

Matter first appears at ~1M yrs.@ 4000k ( the 4th epoch ) so any construct that requires atomic or molecular structures must have occurred after that time.
Click to expand...
Sounds raesonable, and for anything else to occur there must be a bit more time to "end-of-that-universe".


The question You raise has no bearing in this discussion.
Click to expand...
Nor do viruses, imnsho. At least not until we worry about those "constructs" you mention forming. And what are those constructs made of?

What seems to be highly precise physical/energetic characteristic tuning that also encompasses dark matter should have some bearing on the discussion of this topic.

Yes, I'm de-railing this discussion, and will now cease doing so. :)
 
I suggest you not continue that conversation, TE, unless you have access to a ready source of fire or acid. Prevents regeneration, you see.
 
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