Radial null geodesic in FLRW spacetime
= Radial null geodesic in FLRW spacetime
In conformal coordinates a radial light ray obeys $d\chi/d\tau=\pm c$, so the cosmological light cone is at forty-five degrees after setting $c=1$.
= Radial null geodesic in FLRW spacetime
In conformal coordinates a radial light ray obeys $d\chi/d\tau=\pm c$, so the cosmological light cone is at forty-five degrees after setting $c=1$.