Superluminous

A speed is said to be superluminous if it exceeds the speed of light, c. Just as in real life, information cannot be transmitted faster than the speed of light in Conway's Game of Life and similar CAs; there are, however, patterns that give the illusion of this happening, with the Fast Forward Force Field (shown below) and the star gate built on it being prominent examples.

x = 17, y = 7, rule = B3/S23 7bo6bo$8bo6b2o$2b2o2b3o5b2o$2ob2o$4o9bo$b2o9b2o$12bobo! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C [[ HEIGHT 360 WIDTH 600 AUTOSTART GPS 2 THUMBSIZE 2 ZOOM 28 T 0 PAUSE 2 T 6 PAUSE 2 LOOP 7 ]]

The Fast Forward Force Field (click above to open LifeViewer) RLE: here Plaintext: here

In more general classes of cellular automata, greater care must be taken when discussing the speed of light. If c is defined as the maximum speed at which any effect can propagate, then superluminosity is impossible by definition. If, on the other hand, c is defined as a speed of one cell per tick, then effects can propagate at superluminous speed, and information transmitted faster than the speed of light. Larger than Life rules are an example of a class of CAs where this distinction is important.

x = 11, y = 14, rule = R5,C0,M1,S34..53,B31..42,NM 5bo$3b5o$3b6o$2b7o$b5o2b2o$5o5bo$3o7bo$3o7bo$5o5bo$b5o2b2o$2b7o$3b6o$3b5o$5bo! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C [[ HEIGHT 360 WIDTH 600 GPS 2 THUMBSIZE 2 ZOOM 26 ]]

An example spaceship where this distinction is important. If c is defined as one cell per tick, this spaceship is 5c/4, a superluminous speed. However, if it is defined as the maximum speed any effect can propagate, it is c/4. (click above to open LifeViewer)