[ExI] Why space tech isn't cutting edge
anders at aleph.se
Mon Nov 19 23:12:56 UTC 2012
On 19/11/2012 21:30, Adrian Tymes wrote:
> Neurons are not as tiny as modern CPU interconnect
> wires, therefore single-atom events aren't nearly so
> disruptive. Being highly parallel helps too.
> On Mon, Nov 19, 2012 at 1:01 PM, Giovanni Santostasi
> <gsantostasi at gmail.com> wrote:
>> How the brain does it?
>> How do we reboot from such high energy events? Is the brain affected by such
>> high energy events?
>> Is the brain more stable because of its high parallel architecture?
Parallelism certainly helps. But the brain is likely full of
error-correction too, since there is so much neuronal noise: action
potentials do get lost along the axon, synapses fire a random number of
vesicles as a response to a signal, ion channels open and close
randomly, the number of ions and molecules involved in a cellular
compartment can be down to a few hundred or worse. A cosmic ray ionizing
something so a cell fires randomly will not be too different from the
An action potential is around 10^-20 J, and we get around 2 nucleons
with more than 1.6*10^-10 J energy per square centimeter steradian per
second ( http://www.int.washington.edu/PHYS554/2011/chapter9_11.pdf )
Not certain about absorbption coefficients for such particles in the
brain, but at least in space there will likely be a few misfirings per
second due to local bumps.
BTW, I recently came across something *awesome*: Hinton et al.'s
"Improving neural networks by preventing
co-adaptation of feature detectors" http://arxiv.org/pdf/1207.0580.pdf
They reduce neural network overfitting *a lot* by randomly omitting
neurons during training, making a far more robust network. Maybe this is
a good reason for the brain to occasionally lose signals.
Future of Humanity Institute
Philosophy Faculty of Oxford University
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