system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: what is chaos theory?
gpt
Chaos theory describes chaotic systems, which are systems where very small differences in the starting conditions lead to wildly different end states.

To put that a little more simply, imagine you’re dropping a ball off a building. If you know exactly where the ball is being dropped from, how big it is, how much it weighs, and how strong the wind is blowing in what direction, you can  accurately predict exactly where the ball is going to land. 

If your estimate for any of these things is off by a little bit, the predicted place that you expect the ball to land will be off by a little bit. If your estimated value for any or a bunch of them is off by a lot, your prediction with be off by a lot. As long as you have roughly accurate starting values, you can make a roughly accurate prediction.

Now imagine that you are dropping the ball down one of those boards with lots of pegs that causes the ball to bounce around a bunch before reaching the bottom.

Very small differences in the starting position of the ball, or the size of the ball, or the weight of the ball, etc, may cause it to bounce in different directions and take *very different* paths down the board. This means that if the values that you are using are off by even a little bit, instead of your prediction about where the ball lands being off by a little bit, it may be off by *a lot*.

Because of their sensitivity to initial conditions and propensity to yield wildly different results, chaotic systems are difficult to predict very far ahead unless you have absolutely perfect and complete information. This is why things like, for example, weather tend to be given as percentages and is only really accurate for a few days or even hours ahead of time, rather than being able to predict the weather months or years in advance.