Guided trace · 1 of 3
One ray approaches the edge.
It begins only six thousandths above the critical impact. It will not fall, but it cannot leave quickly.
Light at the critical edge
Black Glass
Aim a bundle past the dark centre. The glass at the observer is not a camera effect: every visible mark is assigned by the fate and exit direction of an integrated null geodesic.
Observer's black glassthe lensed sky assembles here
escapedorbit-delayedcaptured
Tracing…What is integrated?
Geometric units G = c = M = 1. Horizon r = 2M; photon sphere r = 3M; critical impact b = 3√3 M. Fixed RK4 evolves the Schwarzschild null Hamiltonian with smaller steps near the horizon. This is an ideal, non-rotating vacuum black hole.
Keyboard on the field: ←/→ aim, ↑/↓ move the observer, Q/E orbit. Hold Shift for fine aim. Pointer drag aims across the critical edge.