Using a light-sensitive reaction-diffusion system to visualize the black hole horizon effect*

We are using light-sensitive chemical reaction-diffusion waves to visualize a black hole event horizon. The event horizon of a black hole is the radius from its center of gravity at which not even light can escape its gravitational pull, but light is able to enter this region. In our table-top analog, we employ a light-sensitive chemical Belousov-Zhabotinsky (BZ) reaction to create visible fronts moving in a quasi-two-dimensional system. The black hole is created through a radially symmetrical light gradient with increasing intensity going outward until the black hole horizon, where the light intensity drops back to zero. BZ waves created outside our circular light gradient can pass the sharp intensity jump and enter the center regions. Outward moving BZ waves, created at the center, experience an uphill light intensity gradient and die before reaching the maximal radius. Our experiments are supported by Python simulations using a two-variable, light-sensitive reaction-diffusion model, replicating our experimental observations.