<html><head></head><body><span data-mailaddress="pharos@gmail.com" data-contactname="BillK" class="clickable"><span title="pharos@gmail.com">BillK</span><span class="detail"> <pharos@gmail.com></span></span> , 1/10/2014 12:01 PM:<br><blockquote class="mori" style="margin: 0px 0px 0px 0.8ex; border-left-width: 2px; border-left-color: blue; border-left-style: solid; padding-left: 1ex;"><<a href="http://arxiv.org/abs/1409.2506" target="_blank" title="http://arxiv.org/abs/1409.2506">http://arxiv.org/abs/1409.2506</a>> <br>Quote: <br>Using recent determinations of the rate of GRBs, their luminosity <br>function and properties of their host galaxies, we estimate the <br>probability that a life-threatening (lethal) GRB would take place. <br>We find that the probability of a lethal GRB is much larger in the <br>inner Milky Way (95% within a radius of 4 kpc from the galactic <br>center), making it inhospitable to life. Only at the outskirts of the <br>Milky Way, at more than 10 kpc from the galactic center, this <br>probability drops below 50%. <br>-------------- <br><br>One more factor pointing to life being rare and occurring far enough <br>apart that contact with other aliens will be unusual. </blockquote><div><br></div><div>I am sceptical of their conclusion. While a GRB no doubt can cause mass extinctions they do not remove biospheres: a few cm of water or rock protects against the radiation in their paper. </div><div><br></div><div>The GRB rate is also low enough that it cannot cause effective synchronization of advanced life a la the Annis/Cirkovic scenario. </div><br><blockquote class="mori" style="margin: 0px 0px 0px 0.8ex; border-left-width: 2px; border-left-color: blue; border-left-style: solid; padding-left: 1ex;"></blockquote><br>Anders Sandberg,
Future of Humanity Institute
Philosophy Faculty of Oxford University<br><div><blockquote class="mori" style="margin:0 0 0 .8ex;border-left:2px blue solid;padding-left:1ex;"><br></blockquote></div></body></html>