In Conway's Game of Life (and related cellular automata), the speed of light is a propagation rate across the grid of exactly one step (either horizontally, vertically or diagonally) per generation.
Similarly, the "lightweight spaceship" is said to have a speed of c/2, as it takes four generations for a given state to be translated by two cells.
(This is not true, though, for cellular automata in general; for instance, many light-speed spaceships exist in Seeds.)
[3] Certain patterns can appear to move at a speed greater than one cell per generation, but like faster than light phenomena in physics this is illusory.
If a lightweight spaceship (LWSS) hits the colliding gliders, it will appear to move forwards by 11 cells in only 6 generations, and thus travel faster than light.