Can a computer simulation simulate another computer running another simulation

[hendorog]

No, I don't think so - and I hope not.
Not due to the complexity, instead for the simple reason that would mean that the brain cannot make its own independent decisions.
A 386 is deterministic - it doesn't have true randomness, and so therefore given any starting state, any future state can be predicted.

Well, why isn't the human brain deterministic like the 386? Aren't both made out of matter?

Well no-one really knows if it is or not. However the 386 definitely is, and just because both are made of matter doesn't prove the brain is the same.

A CPU deliberately avoids random effects for obvious reasons. Conversely some randomness is an advantage in a brain.

In addition, capturing the 'state' of all of the particles in the brain is not possible according to the UP.

[apelly]

I haven't been smoking any funny stuff

Are you sure?

[elgonzo]

From the outside of the universe you can observe without interacting, so it won't apply.

Why do you think that observing from outside the universe would not be an interaction? Without interaction, no observation. It doesn't matter whether the observation is made from outside or inside the universe. To be able to observe something inside the universe from outside the universe, the universe and the "outside" have to interact in some way -- how else could information cross the boundary between the universe and the outside?

[TheAmmoniacal]

Just ask yourself the question, given the state of this universe as it is now according to the scientific consensus, how likely is this to happen?

Now consider the universe as a computer simulation, that implies a layer on top and intelligent beings who also have to live in a universe. The latter is massively more complex and at a minimum twice as unlikely (as it requires two universes), and it requires very specific things to happen in the future.

If you have no evidence for the latter, and it's a lot less likely, only a fool would believe it.

Personally I'm of the belief that computing power of that magnitude will never be attainable (practically or theoretically).

[elgonzo]

No, I don't think so - and I hope not.
Not due to the complexity, instead for the simple reason that would mean that the brain cannot make its own independent decisions.
A 386 is deterministic - it doesn't have true randomness, and so therefore given any starting state, any future state can be predicted.

So if the 386 truely emulated a brain it would mean that our path is also deterministic. Life would be pre-ordained and could not be changed. This is 'destiny'.
[...]

I would not worry about that. I would be concerned about much other things.
Before humankind would ever have a full and complete understanding of the brain, consciousness, et al, it would probably have developed a brain model which, while still incomplete, will be sufficient enough to understand how many of the conscious and subconscious aspects of people's mind are formed and work in the majority of cases. If this has been achieved, the knowledge learned from this model will be (ab)used to manipulate people on a scale and with an efficiency as never before. Todays methods of marketing, indoctrination and propaganda (which at best are using psychological models based on statistics and empirical studies) will look like tools from the stone age compared to that. The only thing i personally am truly uncertain of is how far away or how close we are to this...

[Artlav]

Unless there is some sort of randomness involved, perhaps from the probabilistic nature of quantum mechanics.

Noise from quantum mechanics are a bunch of orders of magnitude too small to affect the brain. Just think what thermal noise would have done to it, have this not been the case.

A regular CPU have a clearly defined set of inputs, a well understood internal state storage, and so on. You can easily set it up to be in some exact state. Any noise introduced would result in it either not working properly or not being large enough.

A brain, on the other hand, have trillions of inputs, and it's state is spread evenly across it.
It's properties can change from the tiniest chemical changes in the liquids going through, from how much the neurons fired recently, and so on.
Some actions would change it's configuration - the neurons forming new links and breaking the old ones.
The magnitude of the problem of getting it to some exact starting state is enormous.
Thus comes the appearance of it's unrepeatability.

But if you were to overcome all that difficulty, then it should repeat itself precisely.

In addition, capturing the 'state' of all of the particles in the brain is not possible according to the UP.

Why would you need the state of all the particles?
You don't need the state of all the particles in a transistor to know it's state, and neurons are quite a bit larger.

Why do you think that observing from outside the universe would not be an interaction?

Because if it was an interaction then the observer would, by definition, be part of the universe.

Think of this as asking an emulator about the content of a memory cell vs having the simulated CPU execute a read instruction to get the data from the same cell.
The first does not disturb the simulation in any way, the second can not be done without detectable disturbing.

[elgonzo]

Why do you think that observing from outside the universe would not be an interaction?

Because if it was an interaction then the observer would, by definition, be part of the universe.

Think of this as asking an emulator about the content of a memory cell vs having the simulated CPU execute a read instruction to get the data from the same cell.
The first does not disturb the simulation in any way, the second can not be done without detectable disturbing.

Ah, okay, if the universe is just a simulation (i completely forgot parts of the discussion here... doh...) then poking around in the simulator does not necessarily affect the simulation.

[Kilrah]

The only thing i personally am truly uncertain of is how far away or how close we are to this...

To me we're even further than what we could think of, just most are unaware of it just like of the fact they are in a simulation.

[strangersound]

Personally I'm of the belief that computing power of that magnitude will never be attainable (practically or theoretically).

But it already is, it's just biological. Think of the computation that involved getting all matter to just this point in the present. Just the DNA of living organisms is an amount of math that I'd have top call Numberphile to put an estimate on and describe. Mankind has only just started trying to mechanically compute. Nature, on the other hand, already has the power to compute on scales beyond human comprehension. An infinitely complex hyper threaded reality, likely spreading across multiple dimensions. Math going on that we struggle to define. But, just looking around at reality itself says anything's possible.