[aikendrum]

> I think most physicists think that if you started with a description of the positions and velocities etc of all the particles in a human, and put them into a supercomputer the size of the moon, and had the computer run a simulation using the standard model, then the simulated human would act identically to a real human.

Just created a throwaway to reply to this. As a trained therapist (currently working in another field), with a degree in psychology, this seems... Seriously ill informed. Do physicists really think this?

Imagine you create your perfect simulated human, that responds according to the exact phenotype of the person you're simulating. Lets remember you'll have to either duplicate an existing person, or simulate both the genotype and the in-vitro environment (especially the mix of uterine hormones) present for the developing foetus. Now you have to simulate the bio, psycho, social environment of the developing person. Or again, replicate an existing person at a specific moment of their development - which depending on which model of brain function is correct may require star trek transporter level of functional neuroimaging and real time imagining of the body, endrocrhine system etc.

So lets assume you can't magically scan an existing person, you have to create a believable facsimile of embodiment - all the afferent and efferent signals entering the network of neurons that run through the body (since cognition doesn't terminate in the cortex). You have to simulate the physical environment your digital moon child will experience. Now comes the hard part. You have to simulate their social environment too - unless you want to create the equivalent of a non-verbal, intellectually disabled feral child. And you have to continually keep up this simulated social and physical environment in perpetuity, unless you want your simulated human to experience solitary psychosis.

This isn't any kind of argument against AGI, or AGI sentience by the way. It's just a clarification that simulating a human being explicitly and unavoidably requires simulating their biological, physical and social environment too. Or allowing them to interface with such an environment - for example in some kind of biological robotic avatar that would simulate ordinary development, in a normative social / physical space.

[andrewchambers]

The post said they simulated the universe (or you could assume just the parts close to earth), it would be simulating everything a human would interact with. I don't see the point this reply was trying to make.

[tremon]

The post said they simulated the universe

It doesn't? It only mentioned "a supercomputer the size of the moon" to simulate that one person. It says nothing about simulating the extra-person part of the universe.

[zinclozenge]

> Do physicists really think this?

Prior to quantum mechanics, they did indeed. But that's because classical mechanics was 100% deterministic. With quantum mechanics, only the probability distribution is deterministic. I don't think any physicist today believes it's possible, but merely "theoretically" possible if there was a separate universe with more energy available (hence outlandish conjectures like the universe is actually a simulation).

[orbifold]

You are right this is practically and theoretically impossible: The no-cloning theorem tells you that it is impossible to “copy” a quantum system. So it will never be possible to create an atomistic copy of a human. Technologically we are of course also miles away from even recovering a complete connectome and I don’t think anyone knows how much other state would be needed to do a “good enough” simulation.