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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> extropy-chat [mailto:extropy-chat-bounces@lists.extropy.org] <b>On Behalf Of </b>Anders Sandberg<br><b>Subject:</b> Re: [ExI] SETI for Post Singularity Civs<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal><span class=clickable>BillK</span><span class=detail> <<a href="mailto:pharos@gmail.com">pharos@gmail.com</a>></span> , 16/1/2015 12:41 PM:<o:p></o:p></p></div><blockquote style='border:none;border-left:solid blue 1.5pt;padding:0in 0in 0in 6.0pt;margin-left:4.8pt;margin-right:0in'><p class=MsoNormal>On 15 January 2015 at 23:43, Flexman, Connor wrote: <br>> A big strike against the strong version of that hypothesis is that we can <br>> map out DM in galaxies and see that it's relatively uniformly distributed <br>> throughout each galaxy and out to > 4 times the luminal galaxy radius. <br><snip> <br><br>Don't you just hate it when somebody makes sensible comments to spoil <br>a neat thought? :) <o:p></o:p></p></blockquote><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><p class=MsoNormal><span style='color:#1F497D'>>…</span>That happened to Robert Bradbury's original idea of dark matter being M-brains too. When he proposed it on this list back in the 90s we still did not know if DM was lumpy MACHOs or WIMPs, and it seemed just barely possible that it could all be quiet supercivilizations. Then we found out that it was both smooth and way heavier than previously expected, and the halo of Elder Civilizations evaporated :-)<span style='color:#1F497D'>…</span> Anders Sandberg<span style='color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Robert’s thermal model for M-brains as dark matter never agreed with observation either. We struggled mightily to explain how they could be sufficiently cool but I never could get the equations to go there. For a few heady weeks back in 2011, I thought I had the answer: they could appear sufficiently cool by reflecting a very large fraction of the light in one direction. Then it occurred to me there should be a few very bright objects, M-brains which pointed their energy our way. Again grasping at straws, I thought of Halton Arp’s work which suggested that quasars are associated with galaxies. Perhaps quasars were M-brains spraying light directly at us. Again the equations didn’t work, damn.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Robert was never fully convinced by my entropy equations in any case, so it is unclear he ever completely abandoned the notion. I need a good thermodynamic simulation to really prove it out. Reasoning: I think we as a species are near the technological capability level to start creating an M-brain.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>There was a silver lining to that cloud however: those same equations led me to realize that not only can an M-brain direct its energy, as far as I can tell, it must. Otherwise it eventually overheats. By the time I realized that however, Robert had already perished, which was late February 2011. I was not able to share that finding with him. I presented the finding to an aerospace engineering group in November 2011.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Is it not astonishing Robert has already been gone nearly four years? I miss him like he left us yesterday.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>spike</span><o:p></o:p></p></div></body></html>