This is regardless of the cell's current state. If Life's rules said that any cell with a live neighbour qualifies for a birth and no cell ever dies, then any initial pattern would grow like a crystal endlessly. In the real world, matter-energy cannot be created or destroyed. If a colony of bacteria grow to cover a Petri dish, it is only by consuming nutrient. The Petri dish as a whole weighs the same before and after.
Simple rules can have complex consequences.
This simple rule has such a wealth of implications that it is worth examining in detail. It is the far from self-evident guiding principle of reductionism and of most modern investigations into cosmic complexity. Reductionism will not be truly successful until physicists and cosmologists demonstrate that the large-scale phenomena of the world arise from fundamental physics alone. Life is forward-deterministic . Endless Growth Conway wondered about the possibility of patterns that grow without limit.