deletions | additions       diff --git a/The Moon.tex b/The Moon.tex  index 46b01a0..f0b0994 100644  --- a/The Moon.tex  +++ b/The Moon.tex 
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\item {\it What is the Moon's radius?}  A nice rule of thumb is that the human thumb held at arm's length subtends about 1~degree. The moon is half as wide as my thumb, so we'll use $\theta_m \approx 0.5$~degrees. Using the skinny angle rule, $R_m = \theta_m a_m$. There are $2 \pi$ radians for every 360 degrees, so $0.5~{\rm degrees} = 8.3\times10^{-3}$~radians.  \begin{equation}   R_m = 3.2\times 10^8$~cm   \end{equation}     Did you catch that mistake of mine? The angular size of the Moon corresponds to its {\it diameter}, not it's radius. Thus     \begin{equation}   R_m = 1.6\times 10^8$~cm   \end{equation}     A more precise estimate is $1.7374\times10^8$~cm.  \item {\it What is the Moon's mass?}  \end{enumerate}