actually naw. no reason to waste energy simulating every atom in the universe.. let alone simulating anything not percieved by participants of the simulation. for that matter.. the sim has to be only detailed enough to fool the simulated consciousness. you'd need orders of magnitude of orders of magnitude less energy, time, processing power to run a 'convincing enough" simulation than a full on every-atom sim. you should check out Isaac Arthur's youtube.. he goes super in depth into topics like this. check out his episode on a 'matrioshka brain' (sp?). like.. an advanced civ might build rotating habitats and solar statites all around their start to use its energy (more habital surface area around 1 star than if u terraformed every rocky planet in milky way.. by far).. but even MORE advanced.. theoretical.. digital beings might have cause to build a megastructure around a sun to utilize all of its power for computations. basically has layers like onion.. about 50% gets used for computations at each layer.. the next layer uses the suns energy+ waste heat from previous computations. idk. apparently u can build a pretty fucking beefy computer using all the energy one 1 star. ppl have done rough maths on how much processing power it would take to simulate every neuron in a body for a lifetime.. and supposedly 1 matrioshka brain could simulate every human being at every point in history billions of times over in 1 second. like.. billions of earths worth of conscious experience in 1 second lol anywayz if u do check out Isaac Arthur u gotta get used to his speech impediment lol. content is worth tho