Just to add to Amos' list and to broaden the scope:

(1) Even long before the advent of the computer the military has used simulations, small scale in a bit of sand with reduced size figures, large scale simulations involving real humans and vehicles called manouevres.

(2) After the invention of the computer, simulations have entered all areas of human activity:
- Evil environmentalists have simulated the full scale earth with all its physical properties and possible human actions to warn about global warming.
- In Germany, animal leftists even demand (with a bit of physical threat) simulations in our university curricula to replace real experimentation on frogs etc. They only want to alienate us from the physical contact with nature.
- In Germany, evil authorities simulate the possible movements of real humans in simulated to full scale real towns in preparation for the next football world championship. I'm sure they only want to prevent a warm human face to face contact between mild-mannered fans eager to discuss the deciding penalty from the last minute.
- Evil Bolshevik Kasparov lets simulate his next opponents in computer programs in preparation for a chess tournament.
- Not to forget the plane constructing industry. By simulating flight properties of future planes they take most of the former fun out of real life testing.
- And I'm sure you all prefer in the next flight emergency you encounter as a passenger the pilot not to be routinely trained on a simulator. His actions this way will be much more spontaneous.

   Simulations are really everywhere now. They are suboptimal compared to reality for several reasons. One example for these reasons is you cannot simulate everything: The pilot in the flight simulator just does not experience real fear of death. But they are great for training (see Kasparov), they are close to perfect in areas with a borad knowledge and a restricted set of parameters (flight behaviour of not yet existing planes), and they are a very poor but better than nothing instrument in situations involving a system with many hardly known variables and more or less unknown feedback looks (simulating the future temparature of the earth).

Wolfgang