It’s also a little silly for the same reasons discussions of theoretical compatibility often are: time and space requirements. In practice the Universe, even if computable, is so complex that simulating it would require far more compute than physical particles and far more time than remaining until heat death.

I'm no mathematician, but doesn't this come up against Gödel's incompleteness theorem? My brain has that roughly as "If you have a system and a model of that system, but the model is also part of the same system, something something, impossible"

Thanks for this great comment!

> He also uses Rice’s theorem (old) to show that there is no uniform measure over the set of "possible universes."

I assume a finite uniform measure? Presumably |set| is a uniform measure over the set of "possible universes".

Anyway if I understood that correctly, than this is not that surprising? There isn't a finite uniform measure over the real line. If you only consider the possible universes of two particles at any distance from eachother, this models the real line and therefore has no finite uniform measure.

Exactly, it's paradoxical; how would you define the universe as a simulation, without being on the same substrate! The title should have focused more on the computability of the universe, as we know it.

Which of him is simulating which?

I've always wondered how you'd be able to rigorously distinguish breaking out of the simulation from just discovering novel things about your current universe.

Is a black hole a bug or a feature? If you find a way to instantly observe or manipulate things at Alpha Centauri by patterning memory in a computer on Earth a special way, is that an exploit or is it just a new law of nature?

Science is a descriptive endeavor.

I guess that some extreme cases would be obvious - if a god-admin shows up and says "cut that out or we'll shut your universe down", that's a better indication of simulation than the examples I gave. But even so, it could be a power bluff, someone pretending to be a god. Or it could be comparable to aliens visiting Earth rather than gods revealing themselves - i.e. some entity of a larger system visiting another entity of the same system, not someone outside it poking inside.

Also that Universe could use entities similar to hard and soft links (quantum entanglement), memory deduplication and so on.

How many people did we met in the world with similar face appearances and even personalities, almost like you are finding copycats everywhere? Also, it happens as if some kind of face/shape would just have a single personality with minimal differences spread over thousands of lookalikes...

That's what a simulated universe running inside Docker would say.