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This Defense Intelligence Agency reference document, dated 11 March 2010, is one of the advanced technology reports produced in FY 2009 under the Advanced Aerospace Weapon System Applications (AAWSA) program. It introduces the Statistical Drake Equation, which replaces each factor of Frank Drake's 1961 equation with a uniform random variable to estimate how far away the nearest extraterrestrial civilization is. In the worked example, there is a 75% probability that the nearest civilization lies between 1,361 and 3,979 light years from Earth.
“Carl Sagan”3 pages
UNCLASSIFIED/ /f81il 8ffll1Als WliEii SUllslf ET _Distance between any two ncighbnring ET Randnm variable Civilizati(]ns in Galaxy assuming they arc lJNirORMLY di~tributed thrnughnut the wlmlc Galaxy vnlumc. Prnhahilit,, distributinn Unnamed (Paul Davies Sil" rested ·'Maccune di.~trihutinn") 1:lnl fiRi,,.,.',\h,,, ,_, 1-,r Prnhability density function ' I' ) 3 I --:>a- . ET_Di,t.rn«:(r = - •--- ,, ' 5a (Defining the positive numeric comtant C) C = v6 Rt"'"'' he"'"'' :::e 28845 light years " o· - Mean value (Er _Di.~lanee) =Ce 3 e 18 'Variance a~T .2 - '/I 9 9, ,-[,' l DLStana' -1 (T' a -6/: r,, -4c ,, - 3c ,, + 12 c ' 4a' " 2 (T- K, - - - Kurtosis --=c " + 2 C 3 +3c ' -6 (K,)' Expression of JI in terms of the lower (11,) and upper _L' ( \_L' h,[ta(h;)-1]-a;[h,(a,)-1] (b,) limits of the Drake uniform input random JI- Y,;- 1-l 1-l h; -a, variables D, Expression of a 2 in tcrms of the lowcr (a,J and upper ' ' a,h, [la (h, )- la (a, )]', L , CL'-(h,) limits of the Drake uniform input random a-= ar, (b, - a,)' variables D, ,_, i-1 Table 3. Summary of the properties of the prohahility diqrihution that applies to the random variable ET _Distance yielding the (average) distance between any two neighboring communicating civilizations in the Galaxy. 51 UNCLASSIFIED//Flilll. lilFFllilil\l! l!l!il! 8111!¥
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Report, from the dia collection. The PDF is mirrored here; the original link is above. 55 pages are in the text index: search them above, or from the library's search.