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The title statement is almost meaningless. It would be better just to say "simulating reality takes a LONG time". My research is in molecular dynamics. I sim

The title statement is almost meaningless. It would be better just to say "simulating reality takes a LONG time". My research is in molecular dynamics. I simulate systems up to 1 billion atoms on Kraken & Titan. HUGE approximations are made in simulating these systems, but depending on what exactly it is you're studying, these simulations still provide useful results. That is the key to all these studies: how well does your approximation reproduce whatever it is that you're attempting to model? In some cases, very well. For instance, I'm not going to get exact energy levels of a large system, but the system will qualitatively evolve in the same fashion that the experimental system does (which then guides the experimental counterpart to the research). I don't know the details of this brain simulation, but there is certainly some aspect of it that is not being reproduced anywhere close to real-life, and hopefully this isn't what they're interested in (and I'm sure they know that, but I don't think the article author does). The very best simulations of reality that we can perform handle at most just a few H/He/C atoms. And an issue called the fermion-sign problem means that the computational power necessary to simulate larger systems scales exponentially with the number of particles. Unfortunately what that means is -- short of developing quantum computers (which are polynomial order for the sign problem) -- we aren't ever going to simulate more than a few atoms with near-perfect accuracy, and certainly nothing like a human brain. EDIT: Didn't mean for my comment to sound so negative. Obviously, the researchers know exactly what they're doing. I was just trying to dispel the impression that we're close to simulating the human brain.

marcosdumay 13y ago
If we have a reliable model for how synapses fire, we can simulate the brain. Whatever problems quantum mechanics impose on molecular simulation is not relevant, the same way that you don't need to simulate the nucleons on your molecules even if you need precise energy measurements.
dekhn 13y ago
Generally, the people doing brain simulations like to claim that they can use a massively reduced representation (little more than a graph model that pushes signals around with some constants) and yet, somehow, the simulation is inherently capable of reproducing something complex about thought. I'm not sure how they get to this conclusion, but it's a massive reductionism. It would be nice if it were true- it would mean that for a reasonable expenditure, we could build a machine that, basically, "thought" and had a "mind" and we could convince ourselves that it was "living" much like we think of other humans. To date nobody has come up with a really compelling disproof that they are more or less correct- thought and mind seem to be best explained as "emergent behavior of a complex system". Now, whether can we bootstrap a thinking mind by running complex simulations on computers remains to be seen. I'd like to believe there is some interesting physics going on in brains we can't simulate with straightforward physical models, but there really isn't any good evidence for that.
- smosher 13y ago
  > something complex about thought Can you elaborate on this class of 'something'? There are intelligent behaviours that can be reproduced this way, so without more specifics I feel like you're making the same mistake you're condemning.
  - jonmrodriguez 13y ago
    For example, the glial cells are now believed to be vital to the brain's processing, but most "brain simulations" are still modeling neurons only, not glia. http://shahamlab.rockefeller.edu/pdf/CTDB_69_C_69003.pdf http://shahamlab.rockefeller.edu/pdf/CTDB_69_C_69003.pdf
    - smosher 13y ago
      Not helpful. My question demands an answer from the person making the claim, unless you happen to know what they're thinking. Besides, this sounds nothing like what they're talking about. Worse, I don't think you're prepared to prove that a mostly pure-neuron simulation is incapable of giving rise to that certain complex quality apparently far removed from the level of the simulation.
      - coldtea 13y ago
        >Not helpful. My question demands an answer from the person making the claim, unless you happen to know what they're thinking. No, questions can be answered by anyone, if they provide a relevant answer. What the person making the claim thought is irrelavent. The parent gave you a valid reply.
        smosher 13y ago
        I was literally asking someone what they were talking about. Instead I got an answer from someone else about something else. It's just some asshole who has one little nugget of information they want to spout at someone.
shardling 13y ago
>The very best simulations of reality that we can perform handle at most just a few H/He/C atoms. On a deeper level, we still have trouble simulating even a single proton. http://en.wikipedia.org/wiki/Lattice_gauge_theory http://en.wikipedia.org/wiki/Lattice_gauge_theory
- Xcelerate 13y ago
  That's true. However, unless I'm mistaken (my field is more chemistry-simulation than physics-simulation), the internal nature of the proton is not necessary for achieving chemical accuracy level results from something like FCIQMC, namely because the chemical properties of interest are the result of only the charge interactions of the protons/electrons as potential terms in the Schrodinger equation. I believe applying QMC to solve that equation for all charge-charge interactions (including electron correlation) is enough to reach essentially exact energy levels (in the limit of simulation time -> infinity) ... am I incorrect? I mean, there's probably some difference in the eleventh decimal place due to the lack of relativistic and radiative corrections. Hmm. I need to research this some more.
  - shardling 13y ago
    Sure, just wanted to point out how complicated truly "simulating reality" is. :) I mean, my doctorate involved calculating tiny, tiny corrections (8 or 9 decimal places) to hydrogen-like energy levels, but even there I could still treat the proton as point like!
    - Xcelerate 13y ago
      Wow, really? That kind of research fascinates me. I would be interested in seeing your thesis if it is available online!
slacka 13y ago
For all the reasons you listed, if we’re going to crack the problem of strong AI in the next century, we’re not going to be doing it by simulating the brain at the atomic or molecular level. However the lower level simulations are important because we still don’t have deep understanding of how neurons work. An overwhelming amount of neuroscience research data points to the neocortex reusing the same functional unit composed of 100's-1000's of neurons called a cortical column. For example one patient was able to regain her balance by rerouting the signal from her vestibular system to her tongue. So the cortical column is the layer of abstraction we should be shooting for. Hopefully we'll move away from the 1950’s style perceptron, whose mathematical simplicity has attracted researchers but has been a major distraction to AI as they share almost nothing in common with their biological counterparts. If we don’t want to see a 3rd AI winter, we need to move to more biologically inspired approaches.

marcosdumay 13y ago

If we have a reliable model for how synapses fire, we can simulate the brain. Whatever problems quantum mechanics impose on molecular simulation is not relevant, the same way that you don't need to simulate the nucleons on your molecules even if you need precise energy measurements.

dekhn 13y ago

Generally, the people doing brain simulations like to claim that they can use a massively reduced representation (little more than a graph model that pushes signals around with some constants) and yet, somehow, the simulation is inherently capable of reproducing something complex about thought. I'm not sure how they get to this conclusion, but it's a massive reductionism. It would be nice if it were true- it would mean that for a reasonable expenditure, we could build a machine that, basically, "thought" and had a "mind" and we could convince ourselves that it was "living" much like we think of other humans. To date nobody has come up with a really compelling disproof that they are more or less correct- thought and mind seem to be best explained as "emergent behavior of a complex system". Now, whether can we bootstrap a thinking mind by running complex simulations on computers remains to be seen. I'd like to believe there is some interesting physics going on in brains we can't simulate with straightforward physical models, but there really isn't any good evidence for that.

smosher 13y ago
> something complex about thought Can you elaborate on this class of 'something'? There are intelligent behaviours that can be reproduced this way, so without more specifics I feel like you're making the same mistake you're condemning.
- jonmrodriguez 13y ago
  For example, the glial cells are now believed to be vital to the brain's processing, but most "brain simulations" are still modeling neurons only, not glia. http://shahamlab.rockefeller.edu/pdf/CTDB_69_C_69003.pdf http://shahamlab.rockefeller.edu/pdf/CTDB_69_C_69003.pdf
  - smosher 13y ago
    Not helpful. My question demands an answer from the person making the claim, unless you happen to know what they're thinking. Besides, this sounds nothing like what they're talking about. Worse, I don't think you're prepared to prove that a mostly pure-neuron simulation is incapable of giving rise to that certain complex quality apparently far removed from the level of the simulation.
    - coldtea 13y ago
      >Not helpful. My question demands an answer from the person making the claim, unless you happen to know what they're thinking. No, questions can be answered by anyone, if they provide a relevant answer. What the person making the claim thought is irrelavent. The parent gave you a valid reply.
      - smosher 13y ago
        I was literally asking someone what they were talking about. Instead I got an answer from someone else about something else. It's just some asshole who has one little nugget of information they want to spout at someone.

shardling 13y ago

>The very best simulations of reality that we can perform handle at most just a few H/He/C atoms. On a deeper level, we still have trouble simulating even a single proton. http://en.wikipedia.org/wiki/Lattice_gauge_theory http://en.wikipedia.org/wiki/Lattice_gauge_theory

Xcelerate 13y ago
That's true. However, unless I'm mistaken (my field is more chemistry-simulation than physics-simulation), the internal nature of the proton is not necessary for achieving chemical accuracy level results from something like FCIQMC, namely because the chemical properties of interest are the result of only the charge interactions of the protons/electrons as potential terms in the Schrodinger equation. I believe applying QMC to solve that equation for all charge-charge interactions (including electron correlation) is enough to reach essentially exact energy levels (in the limit of simulation time -> infinity) ... am I incorrect? I mean, there's probably some difference in the eleventh decimal place due to the lack of relativistic and radiative corrections. Hmm. I need to research this some more.
- shardling 13y ago
  Sure, just wanted to point out how complicated truly "simulating reality" is. :) I mean, my doctorate involved calculating tiny, tiny corrections (8 or 9 decimal places) to hydrogen-like energy levels, but even there I could still treat the proton as point like!
  - Xcelerate 13y ago
    Wow, really? That kind of research fascinates me. I would be interested in seeing your thesis if it is available online!

slacka 13y ago

For all the reasons you listed, if we’re going to crack the problem of strong AI in the next century, we’re not going to be doing it by simulating the brain at the atomic or molecular level. However the lower level simulations are important because we still don’t have deep understanding of how neurons work. An overwhelming amount of neuroscience research data points to the neocortex reusing the same functional unit composed of 100's-1000's of neurons called a cortical column. For example one patient was able to regain her balance by rerouting the signal from her vestibular system to her tongue. So the cortical column is the layer of abstraction we should be shooting for. Hopefully we'll move away from the 1950’s style perceptron, whose mathematical simplicity has attracted researchers but has been a major distraction to AI as they share almost nothing in common with their biological counterparts. If we don’t want to see a 3rd AI winter, we need to move to more biologically inspired approaches.