[extropy-chat] The Inevitability of Universal Immortality

[Gennady Ra]

At 08:56 PM 12/5/04 -0800, you Hara Ra wrote:

>2. Now uploading (or inloading, replacing the brain with computronium) is a 
>whole other matter. In NanoSystems, Drexler using a mechanocomputing model 
>estimates that less than 1ml is needed to create a human equivalent 
>computer. More fun with numbers: 200 billion neurons, average 2K synapses 
>per neuron is 10^11 x 10^3 x 4 = 4 x 10^14 synapses. If we allow a nanobuilt 
>"synapse" to use a cube of .1 micron on a side (and that is generous, even 
>allowing for the connections), now, .001 cubic micron per synaptic 
>equivalent, the volume comes to 4 x 10^14 x 10^-3 x 10^-18 = 4 x 10^-7 M^3 
>or 0.4 milliliters.

Each synapse is an enormously complex system: hundreds of vesicles 
containing a multitude of different neurotransmitters at presynaptic side 
and thousands of different receptors and innumerable subtypes of receptors 
at postsynaptic side with thousands of various possible substates for every 
connection. Not to mention dizzy cell machinery and chemo apparatus of 
environment. Even if a final result of interaction is just a definite 
postsynaptic potential you cannot emulate a synapse in a naive 
"wire-to-wire" setup unless you introduce external controlling unit that 
simulates (currently) unfathomable innards and functional repertoire for 
each synapse.

Best!

Gennady
Simferopol Crimea Ukraine