Hopefully, if the universe is a simulation, it is a stable one. And if it crashes, whatever intelligent entity is out there can call his or her IT guy, spin it up again, fast forward to where it left off, and we won’t know the difference. If it is a simulation, do we really want to know? This article in Scientific American says that if we really want to know, one way to test whether it is a simulation is to try to crash it on purpose. So how would you do that? One way is to build our own simulated universes, then let them build their own simulated universes, and so on. At some point, the hardware of our universe should not be able to run all those universes. So to get to this point, we need to keep working on building way faster computers.