Apparent horizons are one of the ways of locating black holes is Einstein's theory of general relativity. Locating the apparent horizon is much more straightforward than the event horizon, but still not easy.

This is a simplified apparent horizon finder and some associated scripts and notebooks, which show some examples of how the horizon varies with the locations and masses of the singularities.

For the basic scipt you will need the standard IPython distribution with matplotlib and scipy. For the full capabilities of the notebook you will need IPython 2.0 (development version) for the interactive features.