X-Message-Number: 13675
From: "John Clark" <>
Subject: Minds, Machines, and the Multiverse
Date: Wed, 3 May 2000 12:28:35 -0400

I found an interesting quotation from a new book on quantum computers called
"Minds, Machines, and the Multiverse" By Julian Brown, if comes from a chapter
on the work of Ed Fredkin, one of the leaders of the "physics is computation"

  " [Fredkin] estimated the total amount of computation going on in the 

    producing, ironically, a figure that seems puzzlingly low. He calls this the

    of the missing workload. Essentially what he has done is calculate how large

    cellular automation would need to be to simulate the entire universe in all 
    its details.

    The answer, he argues, is that the CA that operated at the tiniest quantum 

     known as the Plank length and Plank time would only need to be not much 

     than a bigish star to faithfully simulate the entire macroscopic evolution 
     of our

     universe from the Big Bang to the present in about 4 hours. The difference 

     space time volume between the universe and such a system is a factor of 

     This figure is Fredkin's "missing workload", which he contrasts with two 
     other great

     mysteries of the cosmos: the missing neutrinos from the sun (a factor of 
     around 3)

     and the missing mass of the heavens (perhaps a factor of 50). So what 

     does he have for the missing workload? "Either something else is going on 
     in the

     universe that we don't know about" he says, "or God was incompetent on a 
     that boggles the mind"."

        John K Clark      

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