On 29/09/2014 15:41, Matt Mahoney via AGI wrote:
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.
Nope. Again, think of a reversble cellular automaton capable of supporting
self-reproducing systems
(of which there are plenty in the literature - e.g. see: "Logical universality
and self-reproduction in
reversible cellular automata" by Kenichi Morita and Katsunobu Imai).
Copying information requires storing the copied information somewhere - but
this *doesn't* require
overwriting the information that was stored there before. Maybe there was no
information there
before - or maybe that information has moved to somewhere else.
Copying decreases the entropy of your memory. It has to increase somewhere
else.
This doesn't seem like a very general argument. Copying is not confined to my
memory.
In the example of reversible copying I gave, it was in another type of system.
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.
I wasn't making a case for "infinite". Just that we do not know where the
limits are
(because we don't know how big the universe will eventually turn out to be).
There's a limit associated with the rate of change at any given location - due
to how
much information can be directed in with lazers before the region turns into a
black hole.
However, this is a far cry from the one-bit-per-generation figure that is
sometimes
bandied around. What I'm saying is that that figure - and its supporting
arguments -
are bunk. Evolution is not necessarily slow. The theories that claim otherwise
are wrong.
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