But why do we say Π is not random? Chaitin proposed a clear answer: a number is not random if it is computable—if a definable computer program will generate it. Thus computability is a measure of randomness. For Turing computability was a yes-or-no quality—a given number either is or is not. But we would like to say that some numbers are more random than others—they are less patterned, less orderly. Chaitin said the patterns and the order express computability. Algorithms generate patterns. So we can gauge computability by looking at the size of the algorithm. Given a number—represented as a
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