How do you know this universe is not just a simulation?

If I were to give you 100% definitive proof that we lived in a simulation universe. What would change about you / your life / your thoughts / your world?

A holographic universe doesn't have anything to do with a simulated universe. People who watch too much sci-fi keep getting that wrong. A holographic universe is a theory about how complex dimensions in space-time are projected off of simpler dimensions. It has nothing to do with the virtual reality of a universe which as been constructed by outside forces.

Well, from an ontological standpoint, there is in fact a true nature of the universe. However, the universe itself has no understanding of what "true" or "nature" means. These are indeed entirely subjective human definitions which were invented long after we first became intelligent beings.

A simulation in realism is when something is just representative of a truth, not the truth itself. So unless our perceptions were not intended to represent actual "objects" such as a truthful statement, then they can't be considered a simulation under realism. This gets obscured when dealing with falsehoods. Are falsehoods simulations or are they just real lies?

There is another opinion that says something like the secret beyond matters. I hate to say it, but it is a simulation. Everything what you deem as "real" is just a projection by your sensors, a transformation of signals from outside into signals into your brain. These signals are not "reality," but just a cut-out piece of reality, highly arbitrarily chosen by the incidents of evolution. What's more ... it is a simulation in a very specific type of mind. Think it this way: We are apes of a special kind. We are not a swarm intelligence, nor any other type of comprehending entity. Even small deviations--like being color-blind or autistic--already create a very different perception and handling of the world. So you may say, it is all a strange projection in a weird cinema. That the world largely consists of "atoms" and "photons" and "neutrinos" changes nothing, as you don't actually ever observe them--you observe them by instruments, not directly. The fabric of the world truly escapes our immediate perception, and we are forced to simulate it in our minds in manners that are working for our inner composition.

Simulation or no simulation, the information that comprises our reality (energy, matter, force) is real. Not illusion or projection. What is not entirely real is our brain's interpretation of that information. You may not be really seeing a blue sky, but you are really experiencing the physical information that gave rise to a blue sky in your consciousness. You didn't create that. What you can't see is external reality for what it truly is. You are watching a puppet show, completely unaware of the hands that move the strings. In this case, the hands belonging to Nature, Causality, Physics. But I would not stop there, I will add God to the equations.

I don't know. I'm confuse too.