The "butterfly effect" seeks to explain why scientific models don't necessarily produce expected results. It's the idea that a seemingly trivial thing like a butterfly flapping its wings can result in enormous consequences, like a tornado or hurricane in another part of the world.
Lorenz, a meteorologist, began experimenting with chaos theory after 1960, when he accidentally discovered that identical computer models for weather forecasts can produce dramatically different results when very minor variations are introduced in the data.
The underlying notion that a thing as a complex as our life or our world can be predicted with any certainty was replaced by the idea that conditions can never be sufficiently articulated to ensure long-range predictions. This is why weather forecasts are never reliable past four or five days. This is also why, for example, if I text a friend from the supermarket today, it could conceivably change the course of my entire week without me even knowing it.
Life, biology and physics is ordered and rule-oriented; and yet, despite those rules, it's also random and chaotic and filled with chance. That's cool.