deletions | additions       diff --git a/With_an_estimated_diameter_of__.tex b/With_an_estimated_diameter_of__.tex  index 7db0694..5482405 100644  --- a/With_an_estimated_diameter_of__.tex  +++ b/With_an_estimated_diameter_of__.tex 
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With an estimated diameter of 93 billions light years and an age of 13.7 billions years, our Universe is an astonishingly big place and it's been around for a very long time. When you look up the sky you only get a short glimpse at a tiny fraction of the hundred billions of stars that populate our Galaxy (which in turns is one of the hundred billions in the cosmos), but that's enough to make us wonder: "Are we alone?"   In the \href{https://www.authorea.com/users/2/articles/24715/_show_article}{previous post} we discussed the likelihood of the emergence of (intelligent) extraterrestrial life. Starting from the famous Drake Equation (Fig.~\ref{drake})  and using the most recent findings in astrophysics and some astrobiology arguments, we obtained a simple way to estimate $N$, the number of communicative civilizations in our Galaxy. This reduces to the product of the chance of emergence of intelligent life $f_i$ and the average lifetime $L$ (in years) of a civilization's communicative phase: \begin{equation}\label{eq:Drake_simplified}  N \approx \, \frac{1}{4}\, f_i \, L \,.