If our simulated universe’s framerate drops because of the extra compute required for the nested simulations we’re running, would we even notice? It stands to reason that everything would slow down, including our perception of the universe.

For all we know, the smallest unit of time we can measure in our simulated existence could take an hour or more to render outside the simulation. To us, it’s nearly instantaneous.

But if the real world sets up a simulated world which more or less perfectly simulates itself

This is the crux of the logical error you made. It’s a common error, but it’s important to recognize here.

If we’re in a simulation, we have no idea the available resources in the simulation “above” us. Suppose energy density up there is 100x as high as ours?Suppose the subjective experience of the passage of time up there is 100x faster than ours?

Another thing is that we have no idea how long it takes to render each frame of our simulation. Could take a million years. As long as it keeps running though, and as long as the simulation above us is patient, we keep ticking. This is also where the subjective experience of time matters. If it takes a million years, but their subjective “day” is a trillion years long, it becomes feasible to run us for a while.

And, finally, there’s no reason to assume we’re a complete simulation of anything. Perhaps the simulation was instantiated beginning with this morning–but including all memories and documentation of our “historical” past. All that past, all that experience is also fake, but we’d never know that because it’s real to us. In this scenario, the simulation above us only has to simulate one day. Or maybe even just the experiences of one PERSON for one day. Or one minute. Who knows?

The main point is we don’t know what’s happening in the simulation above ours, if it exists, but there’s no reason to assume it’s similar to ours in any way.

As others have said, our reference of time comes from our own universe’s rules.
Ergo if rendering 1 second of our time took 10 years of their time, we wouldn’t measure 10 years, we’d measure 1 second, so we’d have no way of knowing.

It’s worth remembering that simulation theory is, at least for now, unfalsifiable. By it’s nature there’s always a counterargument to any evidence againat it, therefore it always remains a non-zero possibility, just like how most religions operate.

You’re thinking in terms of how we do simulations within our universe. If the universe is a simulation then the machine that is simulating it is necessarily outside of the known universe. We can’t know for sure that it has to play by the same rules of physics or even of logic and reasoning as a machine within our universe. Maybe in the upper echelon universe computers don’t need power, or they have infinite time for calculations for reasons beyond our understanding.

I think there are a few tricks that still make it possible. First, nothing says that you have to, or really that you can simulate a universe 1:1. When you think of it we already simulate millions of universes in video games, but they are dramatically simpler than our reality. So, our parent reality could be much more complex than our own.

Consequently, physics could be vastly different from one layer to another. Maybe in the real reality, entropy isn’t that significant and quasi-perpetual motion is possible, making energy super cheap. Maybe the limits in our universe like the speed of light and Planck constants are just hardware caps to prevent us from using too much compute.

You are correct, but missed one important point, or actually made an important wrong assumption. You don’t simulate a 1:1 version of your universe.

It’s impossible to simulate a universe the size of your own universe, but you can simulate smaller universes, or to be more accurately, simpler universes. Think on videogames, you don’t need to simulate everything, you just simulate some things, while the rest is just a static image until you get close. The cool thing about this hypothetical scenario is that you can think of how a simulated universe might be different from a real one, i.e. what shortcuts could we take to make our computers be able to simulate a complex universe (even if smaller than ours).

For starters you don’t simulate everything, instead of every particle being a particle, which would be prohibitively expensive, particles smaller than a certain size don’t really exist, and instead you have a function that tells you where they are when you need them. For example simulating every electron would be a lot of work, but if instead of simulating them you can run a function that tells you where they are at a given frame of the simulation you can act accordingly without having to actually simulate them. This would cause weird behaviors inside the simulation, such as electrons popping in and out of existence and teleporting over gaps smaller than the radius of your spawn_electron function, which in turn would impose a limit to the size of transistors inside that universe. It would also cause it so that when you fire electrons through a double slit they would interact with one another, because they’re just a function until they hit anything, but if you try to measure which slit they go through then they’re forced to collapse before that and so they don’t interact with one another. But that’s all okay, because you care about macro stuff (otherwise you wouldn’t be simulating an entire universe).

Another interesting thing is that you probably have several computers working on it, and you don’t really want loading screens or anything like that, so instead you impose a maximum speed inside the simulation, that way whenever something goes from one area of the simulation to the next it will take enough time for everything to be “ready”. It helps if you simulate a universe where gravity is not strong enough to cause a crunch (or your computers will all freeze trying to process it). So your simulated universe might have large empty spaces that don’t need that much computational power, and because traveling through them takes long enough it’s easy to synch the transition from one server to the next. If on the other hand maximum speed was infinite you could have objects teleporting from one server to the next causing a freeze on those two which would leave them out of synch with the rest.

And that’s the cool thing about thinking how a simulated universe would work, our universe is weird as fuck, and a lot of those weirdness looks like the type of weirdness that would be introduced by someone trying to run their simulation cheaper.

First, this is not really science so much as it is science-themed philosophy or maybe “religion”. That being said, to make it work:

• We don’t have anyway of knowing the true scale and “resolution” of a hypothetical higher order universe. We think the universe is big, we think the speed of light is supremely fast, and we think the subatomic particles we measure are impossibly fine grained. However if we had a hypothetical simulation that is self-aware but not aware of our universe, they might conclude some slower limitation in the physics engine is supremely fast, that triangles are the fundamental atoms of the universe, and pixels of textures represent their equivalent of subatomic particles. They might try to imagine making a simulation engine out of in-simulation assets and conclude it’s obviously impossible, without ever being able to even conceive of volumetric reality with atoms and subatomic particles and computation devices way beyond anything that could be constructed out of in-engine assets. Think about people who make ‘computers’ out of in-game mechanics and how absurdly ‘large’ and underpowered they are compared to what we would be used to. Our universe could be “minecraft” level as far as a hypothetical simulator is concerned, we have no possible frame of reference to gauge some absolute complexity of our perceived reality.

• We don’t know how much we “think” is modeled is actually real. Imagine you are in the Half Life game as a miraculously self-aware NPC. You’d think about the terribly impossibly complex physics of the experiment gone wrong. Those of us outside of that know it’s just a superficial model consisting of props to serve the narrative, but every piece of gadget that the NPC would see “in-universe” is in service of saying “yes, this thing is a real deep phenomenon, not merely some superficial flashes”. For all you know, nothing is modeled behind you at anything but the most vague way, every microscope view just a texture, every piece of knowledge about the particle colliders is just “lore”. All those experiments showing impossibly complex phenomenon could just be props in service of a narrative, if the point of the simulation has nothing to do with “physics” but just needs some placeholder physics to be plausible. The simulation could be five seconds old with all your memories prior to that just baked “backstory”.

• We have no way of perceiving “true” time, it may take a day of “outside” time to execute a second of our time. We don’t even have “true” time within our observable universe, thanks to relativity being all weird.

• Speaking of weird, this theory has appeal because of all the “weird” stuff in physics. Relativitiy and quantum physics are so weird. When you get to subatomic resolution, things start kind of getting “glitchy”, we have this hard coded limit to relative velocity and time and length get messed up as you approach that limit. These sound like the sort of thing we’d end up if we tried simulating, so it is tempting to imagine a higher order universe with less “weirdness”.

It’s simple - you cheat. In computer games we only draw the things you are looking at, and we only give the appearance of simulating the whole thing but the ‘world’ or universe is actually very limited and you can’t visit most places. Sound familiar?

I’ve always thought the sysadmin of our simulation must be really pissed that we keep inventing better and better telescopes.

The JWST probably cost him a weekend adding more nodes to the cluster.

My issue it is similar: each “layer” of simulation would necessarily be far simpler than than the layer in which the simulation is built, and so complexity would drop down exponentially such that even an incredibly complex universe would not be able to support conscious beings in simulations within only a few layers. You could imagine that maybe the initial universe is so much more complex than our own that it could support millions of layers, but at that point you’re just guessing, as we have no reason to believe there is even a single layer above our own, and the whole notion that “we’re more likely to be an a simulation than not” just ceases to be true. You can’t actually put a number on it, or even a vague description like “more likely.” it’s ultimately a guess.

https://xkcd.com/505/

Time doesn’t have to be 1:1 between a host and a simulation. The host can take as long as it wants to render the next step in a simulation, and any observers within the simulated universes would not be able to discern the choppiness of their flow of time.

Who says there’s resource requirements in the physics of the upper levels?

What am I not getting about this?

The assumption is that the simulation runs constantly and at least as fast as real time.

Neither needs to be true. A simulation might be to see what would have happened if we made different choices, it might be a video game, it might be a way to gen TV shows based on “the historical past” that we consider present time.

We might just be an experiment to see if free will exists. Start 10,000 identical simulations to run a century, and at the end compare the results, see what’s changed, and if those changes snowballed or evened out.

And just like how video games only “draw” what’s in field of view, a simulation could run the same way, drastically cutting down resource needs.

And “impossible levels of energy” isn’t really right. At a certain point a species can get a Dyson sphere. And once they get the first, every subsequent one is a cake walk. It’s as close as possible to “infinite energy” there’s no real reason to even go past one.

Hell, it doesn’t need to be “everything” everything. Generate a solar system and as long as no one leaves, you don’t need to generate anything past it other than some lights.

If someone has the resources to simulate a universe, they probably have the resources to stimulate an arbitrarily large number of universes. This also assumes that any civilisation within the stimulated universe reaches the level of technological advancement required to make a universe level simulation. We’re talking, probably, whole networks of Matrioska Brains, that sort of thing.