On Mon, Sep 29, 2014 at 7:15 AM, Tim Tyler via AGI <[email protected]> wrote:
>>> There's no known speed limit on evolution. >> >> Yes there is. Copying one bit of information in any form including DNA >> requires at least kT ln 2 energy, or about 3 x 10^-21 J at room >> temperature. > > That's the cost of *deleting* a bit of information (from Landauer's > principle). Copying > is a reversible operation that doesn't require deleting anything. This has > been proven - > for example by building reversible self-reproducing cellular automata. Copying information requires storing it somewhere. That requires overwriting the information that was stored there before. Copying decreases the entropy of your memory. It has to increase somewhere else. >> The speed of evolution is limited by the 3.8 x 10^26 W of >> energy from the sun, of which only 10^-9 reaches the >> Earth, and only 1% of that is converted to chemical energy by >> photosynthesis. > > That's a proposed limit for evolution on the earth driven only by sunlight. > However there are other plants, other stars and other fuel sources besides > sunlight. This proposed "limit" doesn't seem very limiting to me. Yes, it could be 10^11 times faster by using all of the sun's energy at the limit of thermodynamic efficiency, then another 10^2 times faster by using a Dyson sphere at 10,000 AU which would be cooled to near the cosmic microwave background temperature of 3K, then 10^11 times faster by using all the stars in the galaxy, and 10^12 times faster by using all the galaxies in the universe, then 10^3 times faster by directly converting matter into energy by dumping it into black holes instead of using hydrogen fusion. Now you are at about 10^89 reversible operations, which is about the size of the largest possible memory estimated by Seth Lloyd (10^90 bits), instead of the 10^50 operations that evolution has used so far. According to Lloyd we could increase that to 10^120 using reversible computing (no copying), which requires energy h/2t to switch in time t, given the mass and age of the universe. That's a lot, but still finite. -- -- Matt Mahoney, [email protected] ------------------------------------------- AGI Archives: https://www.listbox.com/member/archive/303/=now RSS Feed: https://www.listbox.com/member/archive/rss/303/21088071-f452e424 Modify Your Subscription: https://www.listbox.com/member/?member_id=21088071&id_secret=21088071-58d57657 Powered by Listbox: http://www.listbox.com
