We think that, one day, with enough computational power and knowledge, we will be able to create an accurate model of weather or the human brain or any real world object or situation, thus gaining useful insight into the past, present or future. But as Esther Inglis-Arkell explains on io9, that's impossible:
All models break down, eventually. Whether they are physical models, mathematical models, or long, wordy descriptions, no model can completely describe what an object actually is. And that, according to business professor Charles Bonini, is only half the problem. As you try to make a model more and more accurate, you run into another kind of trouble.
Fascinating stuff ahead.