Light cones inside the Schwarzschild radius, Ronald Gautreau, Am. J. Phys. 63(5), May 1995
Novikov has developed a reference system built around radially moving geodesic clocks that allows particle and light signal trajectories to be followed across the Schwarzschild radius RS, there exists a naturally occurring limiting timelike geodesic that divides the light cone into two parts. The limiting geodesic corresponds to a "last" particle that falls from, or rises to, RS. It is seen in all coordinate systems that allow trajectories to be followed inside RS.We show how the limiting geodesic appears in Kruskal-Szekeres coordinates in a geodesic clock analog to Eddington-Finkelstein coordinates. Limitation on the range of validity of the Novikov reference system are also described.