Some people have theorized that we might be living in a computer simulation left to run. There is nothing truly physical about our universe. Well, there's a problem. Let's say someone from the real physical universe wants to create a simulation. They would need to use physical material from their universe to run the computations. The material would have to configured in such a way as to have variations that represent data whether its gears in a mechanical computer or a on-off switch representing 0's and 1's in an electronic computer. Since the computer would have to be made from material from the real universe, the simulation can not have the same level of variability/complexity as the real universe that it occupies. If anything, it would be a simplified dumb down version of it. This is more of an issue if there are sapient programs in the simulated universe the programmer is trying to fool. The way around this is to give the illusion of a whole, complex universe.
An example is the night sky in a video game. The white dots in the black background are just that-white dots against a black background. The programmers did not program the video game to simulate convection currents of the plasma, which composes a star, as it interacts with gravity, magnetic fields, and fusion reactions. So each time someone looks through a telescope and sees something that is not visible to the naked eye, they offer evidence that we are not living in a simulation.
Okay, so the programmer is hiding the cheats deeper in the software. That he has a telescope.foolsims subroutine that gives a false image in every telescope. But then he would need another .foolsims program for microscopes and another one for Geiger counters and another one for X-ray machines and another one for space probe instruments and...you get the point.

(continue on next post)