[ExI] Old Chemically Mature Galaxies and Fermi Paradox

[Anders Sandberg]

Jeff Davis wrote:
> On Sat, Nov 5, 2011 at 3:07 AM, Anders Sandberg <anders at aleph.se> wrote:
>   
>> One reset mechanism that was suggested by Milan Circovic (and then, with
>> some minor input from me, developed by him into a paper with Robert
>> Bradbury)
>>     
>
> Is there a link to that paper?
>   

Hmm, I thought it was http://arxiv.org/abs/astro-ph/0506110 but it is 
mentioned in http://arxiv.org/PS_cache/astro-ph/pdf/0306/0306186v1.pdf 
and refers back to Annis 1999 paper, http://arxiv.org/abs/astro-ph/9901322

It might be that the full analysis has not been published. I'll ask 
Milan when I meet with him, and if there is something resting in drawers 
we need to finish it.

> Regarding the intensity, and consequent destructiveness of a GRB:  I'd
> like to get some idea of the damage as a function of  distance.  How
> close for utter obliteration (ie planet flat out gone)?  how close to
> reduce the entire planet to scorched rock?  How close for scorched
> rock on one side?  How close for atmosphere stripping?  How close for
> surface searing without loss of atmosphere? And finally, how close for
> a severe, transient, non-lethal climate "excursion" with substantial
> survival on the planet's far side? 

The big killer of biospheres is apparently the formation of large 
amounts of nitrous oxide in the stratosphere and the destruction of the 
ozone layer. Doesn't matter that one side is not hit.

http://www.andrewkaram.com/andy/pdf/HPJ.pdf
http://arxiv.org/abs/astro-ph/0601711
http://arxiv.org/abs/0809.0899
http://arxiv.org/abs/astro-ph/9912564
http://arxiv.org/ftp/arxiv/papers/0903/0903.4710.pdf
http://arxiv.org/ftp/arxiv/papers/0804/0804.3604.pdf

This one might be cool for the hobbyists who want to model things:
http://arxiv.org/PS_cache/arxiv/pdf/0804/0804.3207v4.pdf

However, as some of the above papers show, the effects are likely rarely 
enough to destroy biospheres, just mess with them.

-- 
Anders Sandberg,
Future of Humanity Institute
Philosophy Faculty of Oxford University