A way to describe chaos is that it is deterministic, yet unpredictable. Deterministic means that with every cause there is a sane and logical effect. Consequently, in a chaos manifestation, you can get random results from logical equations, and a sequence can be found in what appears to be random data. .
How can something be deterministic and unpredictable at the same time? Consider the butterfly effect, a popular demonstration of chaos. The scenario is you have a deterministic computer program that predicts the weather from several factors: temperature, wind speed, humidity, etc. The program uses these factors to predict what the weather will be today, and uses the current day's forecast to predict what the weather will be tomorrow. Theoretically, assuming you entered absolutely perfect information, it would work.
But is it possible to enter absolutely perfect information? According to the chaos theory, no. Let's say you input almost perfect information into your program, except you overlook the effect of one butterfly flapping its wings, and let the program run. On the first day, the predictions would be accurate, because the butterfly, being so small, has trivial effect on the predictions. But eventually, the predictions will be wrong because the real weather takes into account the effects of the butterfly flapping its wings and the program doesn't. Over time, the predictions will become gradually more inaccurate and appear more random until they are completely useless. Therefore, chaos is in the weather because when you attempted to model it, even though you input almost perfect information into your program, you still get random results.
The Discovery of Chaos.
The first person to discover the idea of chaos was Edward Lorenz, a meteorologist at MIT in 1963. Lorenz had a computer program that modeled the weather from twelve equations. Its purpose was not to predict the actual weather, but more so to impress his colleagues.
