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{{ :coursework:2014f:langtonsmall2.png?nolink&200|}}====== Christopher Langton ======

Chris Langton is a Computer Scientist and one of the founders of the Artificial Life field. He coined the term "artificial life" in the late 1980s. He was born in Cambridge in 1948 and received his PhD from the University of Michigan in 1991. Two of his most famous simple artificial life simulations are the Langton Ant and the Langton Loop.


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===== Langton's Ant =====
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Langton's Ant is a 2-D Turing Machine with very simple rules. You have an "ant" that runs on a grid of black and white cells. If the ant is on a white square, it colors it black, turns 90 degrees right, then moves forward one unit. If the ant is on a black square, it colors it white, turns 90 degrees left, then moves forward one unit. This .gif shows the first 200 steps of Langton's Ant. In 2000, [[http://www.dim.uchile.cl/~anmoreir/oficial/langton_dam.pdf|A. Gajardo, A. Moreira, and E. Goles]] showed that you could construct any boolean circuit using the trajectory of a single instance of Langton's Ant. This means that it would be possible to simulate a Turing Machine using the ant's trajectory for computation and therefore that the ant is capable of universal computation.

Multiple Ant's can exist on the same plane. [[http://youtu.be/w6XQQhCgq5c?t=1m40s|This video]] shows some interesting behavior that arises when you have multiple ants.


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===== Langton's Loops =====
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Langton's Loops are a cellular automata that consist of a loop of cells that contain genetic information which flows continuously around the loop and out along an "arm" of the loop. That outflowing information will become a daughter loop. It is one of the simplest known structures capable of reproducing itself. After a loop is surrounded by other loops and unable to reproduce into unoccupied space, it will "die". After a while, a colony will have formed with the living, reproducing loops in a ring around the outside and the dead loops forming the inside core of the colony. They will continue to expand indefinitely if they are in unbounded space. [[https://www.youtube.com/watch?v=2iDc4C6vbcc|This video]] shows the loops at work and explains how they work.