  In cellular automata models a glider gun is an oscillating pattern of
non-quiescent states that periodically emits traveling localizations (gliders).
The glider streams can be combined to construct functionally complete systems
of logical gates and thus realize universal computation. The glider gun is the
only means of ensuring the negation operation without additional external input
and therefore is an essential component of a collision-based computing circuit.
We demonstrate the existence of glider gun like structures in both experimental
and numerical studies of an excitable chemical system -- the light-sensitive
Belousov-Zhabotinsky reaction. These discoveries could provide the basis for
future designs of collision-based reaction-diffusion computers.
