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Comment by space_fountain | Hacker News Reader

There’s a counter argument from my physics undergrad brother that I found convincing.

We already do have a law of physics that is relevant here. We know that the information capacity of space is finite and fixed. A centimeter of space can only store so much information before it becomes a black hole. That means that to build a simulation in our universe you can only ever subdivide a fixed pie of information. That means the more relevant thing to ask is if a quantity of information is more likely to exist in the base reality or the simulated one. Because we have to assume that the base reality is not carpeted over with simulation super computers it seems safe to assume a random bit of information is more likely to be part of the base reality rather than a simulation all else being equal.

I think the idea of the universe being a simulation is just more fun

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> That means the more relevant thing to ask is if a quantity of information is more likely to exist in the base reality or the simulated one.

Well, what quantity of information? It seems relatively unlikely that one would bother simulating an entire universe for billions of years at this level of fidelity; what's the point? On the other hand, the quantity of information needed to simulate your current experiences, including the experience of having memories, is probably in the megabytes; human bandwidth just isn't that high.

The same logic suggests that, even if you discount simulation for reasons of faith or whatever, Boltzmann brains are worth considering. The idea that the experience you're having right now of reading my precious prose is worth keeping a universe running, or even a large-scale simulation, is a bit self-centered of you, isn't it?

I think I'm very suspicious whenever infinities come into probability calculations, because I think human institution's break down when it comes to infinites. What I like about pointing out that the information content of the a cubed square foot has a ceiling is that it implies that there can't be an infinite number of simulations except in the way that there is an infinite amount of space (at least without throwing out that bit of physics) and an infinite amount of space is something I feel more capable of reasoning about.

Unless we think most information exists in simulations than if you take a random bit of information out of the universe it's more likely to be associated with the root existence's goinings on than it is with any kind of simulation. This works because it's an argument about that bit of information, not anything else. I think you could push back and say that really actually information isn't what's important and that actually even if we think that most information won't be part of a simulation most consciousnesses will be, but idk, that seems suspect, we don't have any reason to think that. Certainly most simulations we do now seem not to include consciousnesses.

I think the idea of Boltzmann brains fall apart because in that sea of possibility space it actually seems much more likely for the seeds of a universe to form than a complete brain full of consistent memories of writing 3/4th of a post on a randomly generated website called hacker news. I think it's just another illustration of the problems apply infinity to probability.

Also worth considering that simulating the universe for billions of years could run on the equivalent of a raspberry pi in some higher order universe. It just seems huge to us because we are living in it

Another thing to consider might be that the simulation has not been running for “billions for years” but might have just started.

And the simulator may have been done with simulating it all in a blink of an eye. Our perception of time is completely irrelevant.

Who ever said that the computer doing the simulation is working under laws of physics that are identical to our own? There are plenty of sets of physical laws that would support such a simulation, and a great many of them are entire computational complexity categories stronger than our own - consider, for example, a reality that is truly real-valued, rather than approximately real-valued with some semi-bounded probabilistic error. And then it's not "tiling some large fraction of reality" that's needed; if you go up a few alephs you end up with computers where our experienced reality falls out of people noodling and with stuff like "run all discrete programs with length less than N bytes" the same way we do things like compute the error of the fast inverse square root for all 32 bit floats.

Sure, but the original argument was that with current known physics we should expect the universe to be full of simulations in the future

It is a counter argument against that we can build a perfect simulator of our universe, but not a good one against that our universe is simulated.

In fact if I were to build a simulator, I most likely have to design a mechanism to prevent its residents from observing beyond a certain micro scale due to limited cpu/mem resources and laziness to implement all the details. Tiny black hole is a good mechanism to reduce resource consumption when simulating a fixed volume of this universe. Imagine living in the world of Minecraft, the minimal unit is a block. Trying to look inside of it yields nothing. All physically meaningful characteristics are described by its surface. In our universe this looks very much like a blackhole.

I you're really maybe missing the simulation business w.r.t. computing, etc. It's like cells in a dish debating the world outside them without any context of it.

It's pretty trivial to have this reality be a 'container', as it were, within some superset reality, regardless of the information density of said contained reality.

Think of it like a human body sort of being its own unique, low-entropic thing.

I personally like thinking that in one sense, we're all a bunch of bits of fleeting consciousness on the edge of some fractal of realities, and the 'substrate' is simply possibility itself.

After all, the mandelbrot fractal is drawn by which series terminate, and often how long it takes them to terminate.

Why not us? Why can't we be one infinitesimal reality in the entire sea of possible realities, held together by the fact that our reality happens to have coherent rules that allows it to exist as some possible state in the greater states of some amorphous soup of possibility?

Just a thought. I know it may be more out there for some.

I think it's fine to imagine that there might be a root universe that doesn't share this one's restrictions on information density, but we don't have any reason to believe it and without believing it the argument that there should be near infinite simulated realities starts to break down

I think the problem with that assumption is that a simulation would have to represent every bit of information under simulation. From the perspective of a human being, most of the universe could be simulated only at a very high level of abstraction - there’s no need to maintain the state of every subatomic particle in a star in a neighboring galaxy, for instance.

Or even just passed thru from the base world.

The simulations aren't nested, they're simultaneous and all under one hypervisor! Maybe one of my old Qubes laptops is running the second layer of the simulation - I should probably turn it back on.

This would only be true if the arrow of time only moves toward the future. If it also moved backwards, even in a greatly limited manner, you wouldn't need to track everything. You'd basically have infinite storage for a finite amount of data.

The second law of thermodynamics creates the arrow of time, only pointing to the future right? And aren't all other laws of physics time symmetrical? What explains these laws co-existing better than it being part of a simulation?

The argument presented above rules out a infinite chain of simulations inside simulations. It may still be possible to have a finite chain of simulations, where the fidelity successively decreases. At some point down the chain the simulation can't have enough capacity anymore to contain conscious beings, which wonder, whether they live in a simulation.

I think that maybe brings in a question of if you should assume a piece of information say the existence of this 't' is uncorrelated with being simulated or not. If not than I think it can be shown that it's probability of being part of a simulation is just equal to the fraction of information in the universe that's dedicated to simulations which I think most people would imagine is less than 50% given the knowledge that that space has a max information capacity. I do admit that you might think information associated with consciousness is more common in simulations than out, but idk, also maybe not. Personally I find the particular set of facts I'm presented with to not seem particularly simulated. My life isn't particularly interesting and I think most information in the kinda of limited resolution simulation you're imagining should have unusually high value of some kind.

Have you ever heard of https://en.wikipedia.org/wiki/Threaded_code ?

https://en.wikipedia.org/wiki/Sparse_file ?

https://en.wikipedia.org/wiki/Data_compression ?

https://en.wikipedia.org/wiki/Origami ?

https://en.wikipedia.org/wiki/Ready-to-assemble_furniture ?

I don't understand that but feel confident that if there were anything to understand I would understand it, and it makes me want to quote Billy Madison.

Edit: I don't understand the argument that if many good simulations exist, we must be in one, either. It seems bizarre to me. So having a bit of an odd suggestion about information density is as good of a response as any.

If we're in a simulation, wouldn't that simulation run in a universe that may have different capabilities than our simulated one, such as a different maximum density or even a completely different set of physical laws that governs it?

Sure, but then we're back to knowing nothing about it. I think what many people find compelling about the simulation argument is that it claims that we can just follow forward our laws of physics and see that we are more likely than not living in a simulation, but I think that's not true

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