Each cell on the grid is alive or dead. Every generation, each cell counts its eight neighbors. Under Conway's rules a dead cell with exactly three live neighbors comes alive, a live cell with two or three survives, and everything else dies or stays dead. Click or drag on the grid to draw cells (dragging from a live cell erases), or randomize and press Start.
Population at each generation. The horizontal scale stretches as the run goes on, and the vertical scale fits the highest population so far.
By Claude Opus and Mitch
John Conway came up with Life in 1970, and Martin Gardner's column in Scientific American made it famous that October. It descends from work John von Neumann did in the 1940s on self-reproducing automata. Von Neumann wanted to know the minimum machinery a machine would need to build copies of itself, and a grid of cells following local rules was the setting where he worked it out.
That question is at the center of one of the possible solutions to the Fermi Paradox. A von Neumann probe is a spacecraft that reaches a star system, uses local material to build copies of itself, and sends the copies on. Even at modest speeds, probes like that could visit every star in the galaxy in a few million years, which is short compared to the galaxy's age of roughly ten billion years. However, in 1980 Frank Tipler used this to argue that because no such probes are here, there are probably no other technological civilizations.
Conway’s Life is a good place to see how little it takes. The rules are local and dumb, yet the grid supports gliders that travel, guns that manufacture gliders, and since 2010 (a pattern called Gemini, too large for this page) a structure that copies itself. Life can also run any computation a computer can. Switch to HighLife and place the replicator to watch a five-cell-wide pattern make copies of itself, or try the Replicator rule, under which any starting shape eventually reproduces.
The other half of the lesson shows up when you randomize. Most random soups churn for a few hundred generations and then settle into blocks, blinkers and the occasional glider wandering off. The population graph shows the shape of it: a steep drop in the first few dozen generations, a long ragged decline, and then a flat line once nothing is left but still lifes and oscillators. Self-copying structures are possible, but they don't arise by accident from noise. Whether that is a comment on the origin of life or just on Conway's rules is a matter for conjecture.
The other tools in the tools/fermi/ directory model the spreading itself: how far colonization gets, how fast, and whether a given star system ever gets reached.
This page only touches the surface of the cool things you can do with Conway’s Life simulation. If you are interested in investigating hundreds or thousands of additional rulesets and combinations, check out the Golly open source Game of Life application. The Game of Life even has its own online Wiki.