[amasad]

Not only that you can't know for sure that you're not living in a simulation, you actually can't surely tell that you existed before this point in time. Imagine that you are instantiated in a simulation with pre-installed memories that give you the illusion that you existed prior to this point.

This line of thought is really old and goes back to Plato (see allegory of the cave) but formalized by Descartes (see evil genius https://en.m.wikipedia.org/wiki/Evil_demon)

[SubiculumCode]

Not a creationist, but a common argument against the earth being only several thousand years old is that star light must have taken much longer to get here given c. However, the simulation of those photons could have begun in transit, as you say.