deletions | additions       diff --git a/Equation.tex b/Equation.tex  index a0d2e7b..c52b36f 100644  --- a/Equation.tex  +++ b/Equation.tex 
...
As I mentioned in a \href{https://www.authorea.com/10997/}{previous post}, we now know that there is on average one planet orbiting every star in the Universe \citep{2013ApJ...764..105S, 2012Natur.481..167C}. Just in our Galaxy this means we have 100 billions planets. Since we have about 100 billion galaxies in the Universe, there are about 10,000,000,000,000,000,000,000 = $10^{22}$ planets out there. But how many of these planets are hosting life? And in particular, particular,\textbf{  how many planets  host intelligent life we might be able to communicate with? with}?  In order to estimate the number of technological civilizations that might exist among the stars, in 1961 Frank Drake proposed the following simple equation