This may be the reason for sleep. Clean up the mess every day after a hard period of thinking. A new cleanup system is found:-http://www.washingtonpost.com/national/health-science/brains-flush-toxic-waste-in-sleep-including-alzheimers-linked-protein-study-of-mice-finds/2013/10/19/9af49e40-377a-11e3-8a0e-4e2cf80831fc_story.html?wpisrc=nl_headlines

That's pretty much the theory of the purpose of sleep 
that I've long found the most convincing, 
from my own experience. So it's nice to have 
some experimental corroboration.-I saw another article recently about IBM using 
an "artificial blood" system to cool a computer, 
by analogy with the way the brain operates. 
I think it said the human brain only works on 20 watts!

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GPJ

George: I saw another article recently about IBM using 
> an "artificial blood" system to cool a computer, 
> by analogy with the way the brain operates. 
> I think it said the human brain only works on 20 watts!-Energy conservation! But it is said the brain takes 1/4-1/5 of all our caloric output per day.