Problem: To make a simulator of a real world, a lot of performance will be needed. One way to achieve this is to use a massively parallel computer. One problem with such a simulation would be that every event that happens anywhere would influence every other part of the simulation (through one of the forces in nature). This would be expensive, and has to be minimized.
Solution: Limit the speed with which events can influence other parts.
Our world: No information can travel faster than the speed of light.
Problem: Given time, events will eventually have effects on all other parts of the simulation, even if there is a speed limit.
Solution: Let the simulated world expand in such a way that there is a limit where changes can no longer catch up outside of a limited sphere.
Our world: The universe is expanding, and we will never be able to see beyond a certain point because that point is moving away too fast.
Problem: Computing exact results with infinite precision takes infinite time.
Solution: Impose a limitation on the precision of computations.
Our world: There is something called the Heisenberg Uncertainty principle. It states that precise inequalities that constrain certain pairs of physical properties, such as measuring the present position while determining future momentum; both cannot be simultaneously done to arbitrarily high precision.
Problem: There are many computations that may never be observed and may never have any effects outside a limited environment.
Solution: Make use of a lazy algorithm. Things are not computed until the result is actually needed somewhere.
Our world: In quantum physics, there is something called quantum entanglement, whereby the degrees of freedom that make up the system are linked in such a way that the quantum state of any of them cannot be adequately described independently even if the individual degrees of freedom belong to differentobjects and are spatially separated.
