Distance between two points on the Moon
Wolfram Language (Mathematica), 48 bytes

ArcCos[Sin@#*Sin@#3+Cos[#2-#4]Cos@#*Cos@#3]1737&amp;


Try it online!

Uses the formula d = r * acos( sin ϕ1 sin ϕ2 + cos ϕ1 cos ϕ2 cos(λ2 - λ1) ) where r = 1737