deletions | additions       diff --git a/cosmology.tex b/cosmology.tex  index 041a0f7..5998331 100644  --- a/cosmology.tex  +++ b/cosmology.tex 
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ds^2 = -dt^2 + a^2 (t) (dx^2 + dy^2 + dz^2)  \end{equation}  geodesics are of the form $x(t) = \sqrt{t_0 t}$ \rightarrow look like parabolas. Line cones are area in between. Everyone has a common history so we can be causally connected.