Light cones near black hole
Light cones near a black hole resulting from a collapsing star, drawn by CMG Lee based on Roger Penrose's "Cycles of Time" at https://chped.net:443/http/image.slidesharecdn.com/thestrangephoton-131118040905-phpapp01/95/the-strange-properties-of-photons-21-638.jpg . The purple dashed line shows the path of a photon emitted from the surface of a collapsing star. The green dot-dash line shows the path of another photon shining at the singularity.
Space
Space
Time
Singularity
Event horizon
Collapsing star