X-Message-Number: 9828
Date: Sun, 31 May 1998 21:47:35 -0400
From: Thomas Donaldson <>
Subject: more re Ralph Merkle's posting

Hi everyone!

In response to Bob's defense, I have gotten another copy of Ralph
Merkle's posting and reread it. I believe I should clarify my
objections, of which the main one still stands.

On rereading this posting, I note that the main advantage of 
"advanced technology" will be that it will allow us to locate every
atom and molecule in the damaged brain. My objection to this claim
is simple: the main structures which cause our memories do not 
exist at the level of atoms or molecules. They are very likely 
to be the connectivity of our neurons, which is not something that
the location of atoms and molecules in a damaged brain will tell us.
Please understand: this is not in itself an argument against 
nanotechnology of any kind. But no amount of information about 
where atoms and molecules may be will tell us about such higher
level structures. We need to look for them particularly, and in
doing so we must look for objects and structures much larger than
atoms or molecules.

After rereading Ralph's posting, I do feel happier about his arguments
that comparatively little movement will occur, and even against 
turbulence. I must add, however, that neither observation really
requires much knowledge of physics, and the simple argument that 
"brain tissue" will be viscous is not, logically, enough. The problem
is that "brain tissue" consists of many different structures, each
of which will respond differently to fluid motion. Some may well
encounter turbulence while many others do not. However the micrographs
I have seen strongly suggest that neither turbulence nor long-distance
motion (ie. motion enough that the original structure cannot be 
seen, IF we had that motion and no other changes) play much of a role,
if any. Other events happening during freezing, such as accumulation
of salts, can still do plenty of damage. And on both movement and
turbulence, I will point out that, again, knowledge of the location of
atoms and molecules will tell us nothing about either. We need to
look at structures on a larger scale, and that is exactly what Ralph
is doing when he discusses these issues.

And here is an example of just why I say that locations of atoms and
molecules will tell us very little, if anything: consider a sand 
castle of the kind people make on beaches. Every grain of sand that
makes it up, for the sake of argument, is identical to every other.
And if waves come and destroy that sand castle, we may well be able
to locate every grain that made it up in the flat expanse of sand 
that results --- but that location will tell us nothing about the
original structure of the sand castle, not even that it once existed.
But note something else, too: suppose we catch that sand castle while
the waves have eroded it but not destroyed it. We can then rebuild it,
since we will see how it was put together despite the erosion. And 
even more interesting, when we do that rebuilding we need not bother
at all to use the original sand grains, we only need more sand.

Those higher level structures do survive, though damaged. Every 
micrograph I've seen of brains after cryopreservation tell me that.
And it is those higher level structures that we should pay close 
attention to in any attempt at revival.

			Best and long long life to all,

				Thomas Donaldson

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