The Minimum Requirement for Life -- Conway's Life Game

Biological life has many attributes: reproduction, metabolism, intelligence, etc. Although it is very difficult to define exactly what is life, we can easily to tell what is not alive. Anything cannot process information cannot be alive. All life activities (physical, physiological or psychological) can be performed only if many informtion can be processed. So, the ability to process infomation is the minimum requirement for life. It is a necessary condition, not a sufficient condition. Thus, a super computer is not yet alive.

In 1936, Alan Turing invented a Turing machine which is an ideal computer. No super computer of today can reach its capability.

In 1970, John Horton Conway wanted to find a set the simplest rules that could explode into the infinite power of a universal Turing computer. He invented a mathematical game, LIFE.

In the game of LIFE, there are many patterns appear. Most of them are stable patterns unless perturbed externally. In the web site of Most Seen Objects in Game of LIFE , it lists 60 objects.

Since every computer must have a counter, a clock, and a memory, all stable patterns will have no use in building a computer. In order to prove that the rules of LIFE (game) do support a universe in which a universal Turing computer could be embedded, it is necessary to show that LIFE (game) can generate some patterns which have a means of locomotion.

Such a walking pattern was indeed found in LIFE (game), and it was called glider. Glider not only walks but can reproduce itself. However, Conway must find a glider generator which can shoot out a stream of gliders in order to prove that LIFE is indeed a universal computer. The glider shooter was discovered by R. William Gosper at MIT in December 1970. Using glider streams to represents bits, all logic gates (And-, Or-, Not-gates) can be produced. In the web site of John Conway's Game of Life by Edwin Martin, it shows how both glider and glider shooter work. In the web site of Conway's Game of Life by Alan Hensel, you can experience yourself how to seed a small universe, and some artificial life activities arise. I will bring you to those sites in the next page.

Conway's Life game

Life (game) occurs on a virtual Go (checker) board. The squares are called cells. They are in one of two states: alive or dead. Each cell has eight possible neighbors, the cells which touch its sides or its corners. There are only three rules.

  1. Birth rule: A dead cell will come alive in the next generation (step) if and only if exactly three of its eight neighbors are currently alive.
  2. Survive rule: A living cell will survive in the next generation (step) if there are either two or three neighbors also alive.
  3. Death rule: A living cell will die of over crowding if there are more than three live neighbors, and it will die of exposure if there are fewer than two.

With these three simple rules and a few randomly seeded live cells on the board, many patterns appeared. Most of them quickly settled into stable patterns. Figure 1 shows such a pattern. The generation 0 consists of 4 live cells. Obviously, the two cells at each end must die of exposure in the next generation, and 4 dead cells will be born. So, generation 1 consists of 6 living cells which form a rectangular shape. Then, two middle cells in generation 1 must die of over crowding, and two dead cells will come alive to form a shape roughly resembling a beehive in the next generation. Since each live cell in beehive has exactly two live neighbors, beehive is stable unless perturbed externally.

Figure 1

Figure 2 shows the life cycle of a glider. A glider consists of 5 live cells. From generation 0 to generation 1, it moves down one row. From generation 2 to 3, it moves to right one column. Then the most important of all, it recaptures its original form in the next generation. It is fun to work out the transformation of glider from one generation to the next by applying the rules of game of Life. Try yourself. In the next page, you can go and visit some sites to see gliders and glider shooter in action.

Figure 2

If glider is also a graphic representation of some basic building blocks of matter (such as: proton or neutron), then laws of physics can give rise to biological life.

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