> It also existed in a physical world where forces are constantly applied to everything it does. Opposed to a virtual world which is basically a vacuum.

I don't understand this at all. I have no idea what is meant by "a virtual world which is basically a vacuum". As for "a physical world where forces are constantly applied to everything it does", how does this contradict anything about computability? Turing machines can compute worlds "where forces are constantly applied to everything"...

Are you talking about the sort of naive, approximate, numerical simulations used by scientists to model things like protein folding or galaxy formation? If so, those aren't actually implementing the known laws of physics, they're just convenient, somewhat-efficient approximations. By analogy, just because display machinery used by humans in the early 21st century just-so-happens to be based on a grid of pixels for convenience and efficiency, that doesn't preclude the existence of computations involving other representations, like vectors with unbounded precision (or, if you prefer, busy-beaver-bounded precision).

> there is a ton of stuff going on we don't understand.

This sounds like an argument from ignorance, which would be a fallacy in itself, but in this case we do understand some of what's going on! This "ton of stuff" is 'merely' a consequence of the underlying physics. Whether those consequences are complicated or not doesn't matter at all, because computability has nothing to do with being complicated.

If I run `while true; do python < /dev/urandom; done` my laptop will do "a ton of stuff" that I don't understand, some of which may be quite complicated; but I can say for certain that it will never produce jelly beans out of the USB port, since there is no mechanism for such a thing to occur, regardless of how complicated the signals in the wires are. On the other hand, if there were such a mechanism, it would only take one simple command (`sudo eject /dev/jellybean`) to cause its dispensement; no need for any appeal to complication at all.

Likewise, regardless of how complicated the interactions were in the formation of the Earth, life, our brains, etc. we know that such things must be computable, since there are no mechanisms in the known laws of physics which can lead to incomputability.

You can string together as many computable calculations as you like, far more than the universe could ever have performed in its entire history, and the result will still be computable. That's just how computability works.

In order to have anything that's incomputable, you need something other than computable components (i.e. jellybean-dispensing hardware, rather than more software). It doesn't even need to be complicated at all! If even just something tiny, like the magnetic moment of an electron, were incomputable by a Turing machine, given the laws of physics and history of the universe as input, that would be enough to support your argument. You don't need "tons of stuff", it's makes no difference. Yet even that seemingly tiny quirk would require that we throw away the known laws of physics. It seems unlikely.

> The amount of variables are incalculable.

Do you mean this as a linguistic gesture, or in a technical sense? For the latter, I would say it's maybe impractical to calculate, but certainly finite. We could upper-bound it by, say, Graham's number.

> To think we can replicate all this with some nano scale transistors, and mathematical approximations, is just bizarre.

I never said that, and as far as I can tell neither did any others in this thread.

Firstly, I would think of such claims as hubris. That such engineering feats could be achieved by a planetsworth of apes after only a few million years would be very surprising, and I certainly wouldn't want to bet on it happening either way before we become extinct.

Secondly, I don't understand what you mean by "all of this"; are you claiming that the entire history of the Earth must be reproduced before a conscious being can be made? In that case, what do you think is happening inside testicles, ovaries and wombs that can manage "all of this" in nine months?

Regardless, the arguments I made, and that of user nnq, were discussing computability. Computability (AKA universal computation) is a mathematical phenomenon regarding what can and cannot be computed by particular mathematical systems. The reason it's called universal computation is that, if something can be computed by one universal computer (e.g. the universe, a brain, a laptop, etc.) then it can be computed by all universal computers (e.g. the universe, a brain, a laptop, etc.).

This applies to all computations, whether we know what they are or not. Nobody (yet? ever?) knows what computation is being performed by some particular brain which gives rise to the phenomenon we call "consciousness", but we don't need to in order to know that that exact same computation can also be carried out by any other computer (e.g. a laptop).

No need for approximation. No need for appeals to ignorance. No need for appeals to "emergence". No need to even know what it is that brains do (since it must be a subset of what the laws of physics do, and the known laws of physics are computable).

But, as I said earlier, this isn't a constructive argument: it doesn't give us an x86 binary we can run. Also, as nnq pointed out, even if we did have such a binary, there's no reason to think that it might be in any way practical; it may take many trillions of times the age of the universe before it finishes calculating a single neuron activation. Such things don't matter at all for computability, but they're inconvenient for us mere mortals.