deletions | additions       diff --git a/past light cones.tex b/past light cones.tex  index faeaa83..dd62115 100644  --- a/past light cones.tex  +++ b/past light cones.tex 
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eddington finkelstein  t = v - r r-2 M \log \mid \frac{r}{2M} -1 \mid  incoming light rays are at 45 degrees regardless of potion