10. A computer system, comprising: a first computer simulator configured to run a first simulation of a system based on a model of said system, said model having a plurality of state variables; a first user interface for receiving input data representative of user interaction with said first computer simulation to change values of one or more of said state variables in a manner consistent with an interaction with the simulated system; a first data output device delivering output from said first computer simulator; a second computer simulator configured to run, contemporaneously with said first computer simulation, a second computer simulation of said system based on the same model as said first simulation, said second simulation being accelerated relative to said first simulation so as to be running at further progression than said first simulation at a current time under the assumption of no further user interaction than those represented by the input data received from the first user input interface, said second computer simulation being used to generate information representing expected future events in said first simulation; a second user input interface for outputting said information representing expected future events, and for receiving input data while said first simulation is run and said information representing expected future events is outputted, said input data received by the second user input interface being used to adjust the extent to which a condition is present in said first simulation; a second data output device delivering as output from said second computer simulator the information representing expected future events in said first simulation; and a module configured to, while said first simulation is running, translate said input from said second user input interface to values for one or more state variables in said first computer simulation consistent with a description of said condition in terms of rules embodied in the model.
10. A computer system, comprising: a first computer simulator configured to run a first simulation of a system based on a model of said system, said model having a plurality of state variables; a first user interface for receiving input data representative of user interaction with said first computer simulation to change values of one or more of said state variables in a manner consistent with an interaction with the simulated system; a first data output device delivering output from said first computer simulator; a second computer simulator configured to run, contemporaneously with said first computer simulation, a second computer simulation of said system based on the same model as said first simulation, said second simulation being accelerated relative to said first simulation so as to be running at further progression than said first simulation at a current time under the assumption of no further user interaction than those represented by the input data received from the first user input interface, said second computer simulation being used to generate information representing expected future events in said first simulation; a second user input interface for outputting said information representing expected future events, and for receiving input data while said first simulation is run and said information representing expected future events is outputted, said input data received by the second user input interface being used to adjust the extent to which a condition is present in said first simulation; a second data output device delivering as output from said second computer simulator the information representing expected future events in said first simulation; and a module configured to, while said first simulation is running, translate said input from said second user input interface to values for one or more state variables in said first computer simulation consistent with a description of said condition in terms of rules embodied in the model. 19. The computer system of claim 10 , wherein said model is a flight simulator, and said condition is a malfunction of a plane or a severe weather condition.