[extropy-chat] Singularity heat waste

[Robert Bradbury]

I largely agree with the much that Eugen said using relatively few words (if
one  is familiar with the topic he said a lot).  We might differ on a few
points but those are for long relaxed conversations rather than mailing
lists.

Now, with respect to the recent questions...

On 7/15/06, Martin Striz <mstriz at gmail.com> wrote:

>
> Is the heat generated due to internal resistance or information loss? :)


Currently both.  The heat from the transistors in most uP now is due to
moving electrons around (and thus resistance).  The heat from the DRAM chips
now (which are starting to require heat sinks) is coming primarily from
electron, i.e. information, loss.  When you reset a DRAM cell, which is
really a capacitor, you don't put the electrons back into the battery, you
throw them away (information converted into heat).  In reversible computing
you would put all the electrons back into the battery except those required
to communicate the final result and those which would absolutely be lost.
Of course using LN2 cooling, or superconductors, one can reduce the losses
due to moving the electrons around significantly.  Ideally, one would like
to convert the 0's & 1's the electrons would indicate into single photons
which would require even less energy to convey a single bit.  While we have
shown that doing things like switching single electrons and emitting or
detecting single photons *is* feasible from an engineering standpoint we are
still quite a ways from being able to manage millions or billions of such
devices on a small chip and structuring them such that they have near 100%
energy conversion efficiencies.

The larger point is that energy is well conserved in most chemical
> transformations.  It just gets shuffled around from chemical bonds in
> the reagents to chemical bonds in the products, hot potato style.


Agreed.  But I believe that only ATP synthesis is "really" efficient.  I'd
guess some large fraction of the reactions taking place in cells have a fair
amount of loss (10-50%???) involved.

phosphate gets removed from ATP and the energy released is
> used to cause a conformational change in a pump which tosses Na+ and
> K+ across the plasma membrane, etc.  Energy is conserved.


I would like to know the actual efficiency of this reaction compared with
the theoretical limit.  I presume that as the concentration gradients inside
and outside the cell membrane change more work is required to do the ion
exchange.  So just after a neuron discharge, much of the energy in ATP may
be thrown away while as the neuron becomes fully charged it uses an
increasing fraction of the energy ATP makes available.

Or is the full energy of each ATP required for each 3Na+/2K+ exchange and
the pumps simply slow down due to the decreased concentration of ions?

A semiconductor gets hot because it has a particular internal
> resistance, so the energy associated with electrons passing through it
> that can't go very fast gets dissipated as heat.


Less so in LN2, not at all in superconductors.  We *do* have superconducting
logic circuits developed by Likharev and perhaps others before him -- the
problem is that you need a really big freezer to keep them cool enough to
operate.  Cooling things to have zero resistance is a problem here on
Earth.  It becomes significantly less so if one is hanging out in the Oort
cloud.

I hypothesize that the reason we operate 5-10C above that
> (which introduces an energy cost through the homeostatic mechanism) is
> because pathogens have also evolved for ambient temperatures and we
> can fight them off by denaturing their proteins when we maintain
> slightly elevated temperatures.  Unfortunately, many human (or
> mammalian) pathogens have evolved optimal metabolic rates also at
> 35-40C in response.


Its an interesting hypothesis.  As Eugen points out one has to strike a
balance between higher operating temperatures and energy resources.  Maybe
as we unravel the genomes of various organisms and the protein structures
further we will gain some insights into what temperature dependent aspects
are incorporated into the various machines.

Robert
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.extropy.org/pipermail/extropy-chat/attachments/20060716/f05978f4/attachment.html>