deletions | additions       diff --git a/Equation.tex b/Equation.tex  index cc3e8ab..6d5a2bb 100644  --- a/Equation.tex  +++ b/Equation.tex 
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Finally $L$ is the longevity of a communicative civilization (in years). Humankind has been "communicative" only for a few decades. Interestingly a detection (or even complete silence) would put strong constraints on $L$, in a sense telling something about the usual course of civilizations. In other words about the future of humankind.   $\stackrel{\leftrightarrow}{x}$  $\tensor{x}$