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Comment by bsza | Hacker News Reader

If the laws and initial state of the universe can be expressed in few enough bits, then all you need to store is a title and a date. Run a simulation of the universe, fast forward to the date the movie was released, use an AI to find a theater playing it, and digitize the tape. It may take longer to run than the current age of the universe, but eventually you’ll get it.

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I've thought about this a lot over the years. What you're asking is, can we accurately emulate our own universe inside our own universe at greater than 100% speed? If so, it would allow us to build a type of space-time machine where we could visit any location at any time.

I don't think it is totally inconceivable. It is definitely possible that there are hacks such as compression that would allow a simulator to run at above 100% speed. It also might not need to be 100% accurate -- we might find that running below that threshold still produces an output that is practically indistinguishable from the real events, yet allows it to run.

> I don't think it is totally inconceivable

You could create a kind of "reverse" grandfather paradox by preventing future events predicted by the simulation from happening. Perhaps it could run fine up to the point that it has to simulate itself, then it would slow down to the point of becoming useless.

Basically the plot of the wonderful TV series "Devs". Well worth the time investment.

Thank you, I never knew this is what Devs was about. I'm now watching the third episode already!

Quantum mechanics makes this impossible. This would require to know the position and speed of each particle precisely and that is in violation of the Heisenberg principle.

You're figuring that the universe is non-deterministic. If so, yes, this would be a more difficult problem.

If the universe is based on some solid deterministic rules with a fixed seed value, then it would work.

Quantum events appear non-deterministic, but that might just be because we don't have all the answers right now.

JS made a copy system, which behaves metaphorically exactly like a seed.

Yeah, but perhaps we're living in a multiverse and you'd have to encode which universe the movie was released in, which may require more bits than the entire movie :)

However, interestingly, by scanning other universes you may find similar movies with slightly different plot turns.

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