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A.DIM
2012-Dec-03, 02:28 PM
I came across this paper (http://arxiv.org/pdf/1206.3467.pdf) at arXiv and find it pertinent to various discussions here...

Abstact: The search for extraterrestrial life and intelligence constitutes one of the major endeavors in science, but has yet been quantitatively modeled only rarely and in a cursory and superficial fashion. We argue that probabilistic cellular automata (PCA) represent the best quantitative framework for modeling the astrobiological history of the Milky Way and its Galactic Habitable Zone. The relevant astrobiological parameters are to be modeled as the elements of the input probability matrix for the PCA kernel. With the underlying simplicity of the cellular automata constructs, this approach enables a quick analysis of large and ambiguous space of the input parameters. We perform a simple clustering analysis of typical astrobiological histories with ”Copernican” choice of input parameters and discuss the relevant boundary conditions of practical importance for planning and guiding empirical astrobiological and SETI projects. In addition to showing how the present framework is adaptable to more complex situations and updated observational databases from current and near-future space missions, we demonstrate how numerical results could offer a cautious rationale for continuation of practical SETI searches.

Selfsim
2012-Dec-03, 07:45 PM
I came across this paper (http://arxiv.org/pdf/1206.3467.pdf) at arXiv and find it pertinent to various discussions here…Which discussions? (Certainly not any discussions I've been involved in recently).

ADIM: What exactly would you like to discuss in this thread? I think its only fair to clarify what this thread is about (before it goes off whatever rails you were intending).

Cheers

A.DIM
2012-Dec-05, 12:25 AM
Which discussions? (Certainly not any discussions I've been involved in recently).

ADIM: What exactly would you like to discuss in this thread? I think its only fair to clarify what this thread is about (before it goes off whatever rails you were intending).

Cheers

Hi Selfsim.

Primariy, I wanted to simply share the paper and see what gets discussed. I've no intended "rails," as it were. Did you read it? If so, what do you make of the use of PCA for quantitative modeling of the astrobiological history of the Milky Way and its habitable zone? Is there something else of interest to you in the paper? Of course, as stated by the authors, this is only an initial argument or framework to be built upon, but it seems this approach could help inform future SETI searches and Astrobiology in general. That's what I think.

Cheers

eburacum45
2012-Dec-06, 03:07 PM
Milan Ćirković has some very intriguing ideas, and I'm always interested to read his papers.

There are some quite entertaining models of galactic colonisation presented in that paper, although I can't quite see where he (and his co-author Vukotić) have factored in galactic rotation. If a pair of adjacent but separate galactic empires last for tens of millions of years, they will mingle together because of the proper motion of the individual stars. On the other hand, the generally flat rotation curve of our galaxy would tend to limit this mixing to a fairly low level, much less than might be expected if all the stars in the galaxy followed simple Keplerian orbits around the centre.

Selfsim
2012-Dec-06, 09:33 PM
Milan Ćirković has some very intriguing ideas, and I'm always interested to read his papers.

There are some quite entertaining models of galactic colonisation presented in that paper, although I can't quite see where he (and his co-author Vukotić) have factored in galactic rotation. If a pair of adjacent but separate galactic empires last for tens of millions of years, they will mingle together because of the proper motion of the individual stars. On the other hand, the generally flat rotation curve of our galaxy would tend to limit this mixing to a fairly low level, much less than might be expected if all the stars in the galaxy followed simple Keplerian orbits around the centre.Long-lived spiral arm patterns have never been shown to persist in any numerical simulation1. They appear to be transient features (at astronomical timescales), breaking up and reforming other patterns over a period of about 80 - 100 million years. Stars move both outwards and inwards along the arms, (while they exist), and the arms eventually break up, due to the shear forces.

Reading too much into this apparent phenomenon (deduced from 'galaxy rotation'), results in a lot of complexity ... none of which is by any means predictable, (or certain).

1"The dynamics of stars around spiral arms" (http://arxiv.org/pdf/1112.0019v2.pdf) and "Stellar dynamics around transient co-rotating spiral arms". (http://arxiv.org/pdf/1110.3824v1.pdf)

TooMany
2012-Dec-06, 09:51 PM
Hi Selfsim.

Primariy, I wanted to simply share the paper and see what gets discussed. I've no intended "rails," as it were. Did you read it? If so, what do you make of the use of PCA for quantitative modeling of the astrobiological history of the Milky Way and its habitable zone? Is there something else of interest to you in the paper? Of course, as stated by the authors, this is only an initial argument or framework to be built upon, but it seems this approach could help inform future SETI searches and Astrobiology in general. That's what I think.

Cheers

Back in the 80's I recall a very simple, deterministic, cellular automaton dubbed "Life" that would make interesting patterns on a computer screen. This is a little off topic, but I wonder if we could explore the origin of self-reproductive, evolving entities by inventing some more complex cellular automata. I.e. could we make some sort of artificial life this way? It might be easier than what biologist have to mess with.

I buzzed through that paper but I did not come away with a very clear idea of what they think they are modeling. One problem I can see is that when the technology of a civilization reaches the capability of interstellar travel, it becomes very difficult for us to predict what we should expect. We simply don't know what ET wants to do with his superior technology.

I'm somewhat skeptical of assumptions that ET will want to make an ever bigger population and that something like a Dyson sphere would be an expected outcome. Perhaps that's too anthropomorphically conjectured, that some biological imperative leads to ever larger civilizations.