The GR Seeing program The GR Seeing program simulates the path of light around a black hole using the Schwarzschild metric. It also shows a plot of the proper time and angle the light is observed by a shell observer in order to demonstrate what a shell observer would see when looking at light sources near a black-hole. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the gr_seeing.jar file will run the program if Java is installed.
Quelle: Open Source Physics