deletions | additions       diff --git a/Box.tex b/Box.tex  index 8b5f862..b441fea 100644  --- a/Box.tex  +++ b/Box.tex 
...
$N =\overbrace{R}^{\sim10} \times \overbrace{f_p}^{\sim 1} \times \overbrace{n_e}^{\sim 0.2} \times \underbrace{f_l \times f_i \times f_c \times L}_{?}$  So the product of the first 3 terms is now well established and is, using a conservtive conservative  approximation, of order 1. So we can simplify the Drake equation and re-write it as: $N \approx f_l \times f_i \times f_c \times L$