🚀 go-pugleaf

>[This is probably a good place to reiterate that cryonics is based
> on the concept that enough information will be saved by freezing
> brain tissues to recreate the brain with a mature nanotechnology--
> *not* that the brain could be restored to order simply by thawing 
> it out.  This is sort of the same difference as that between the
> murderer hanging around at the scene of the crime to await the
> cops, or having left enough clues that Sherlock Holmes can figure
> out who he was.

I'm sorry if my posting gave that impression. I too expect that a
great deal of nanotech reconstruction would normally have to be done.
I just don't think there is any guarantee that trail of clues you
refer to will exist, or if it does exist, point *uniquely* to only 
one possible starting condition.

> Given that it is common practice to freeze human embryos and 
> thaw them *in a viable state*, right now, it is hard to believe
> that the freezing process destroys so much information that 
> an atom-by-atom analysis could not figure out what had been there.

Why is this so hard to believe? The number of cells in an embryo, just
after fertilization, is on the order of tens or hundreds.  This is very 
much smaller than the number of cells in a human brain.

> The highest-level whole-animal experiment I know of involved a dog,
> which I understand is still alive.  Can someone fill in more details?
>
> --JoSH]

I dimly recall such an experiment involving a dog. I think it also
involved an experimental blood fluid substitute, as well.

Has it occurred to anyone to investigate the other possibilities for
preserving dead tissue, other than freezing? If irradiation were used,
for instance, you'd avoid the destruction caused by crystal growth
entirely. Also maintaining irradiation over even thousands of years
is a snap, since it doesn't require an external power source, unlike
freezing. Reconstruction, of course, would then mean complete body 
replacement with non-radioactive materials. (Although to a future
nanotechnological society, a tendency to leak radiation might be
considered no more than a minor faux pas, like body odor. :-)

Ed

[Sorry, Ed, I didn't intend that comment for you particularly, I just
 wanted to make sure that a big discussion didn't start up with 
 people not realizing what the real assumptions behind cryonics are.

 Re irradiation, I'm virtually certain that it would cause a lot
 more damage than freezing--irradiated foods appear less changed because
 the damage is at the molecular level and the gross structure is 
 unchanged.  (That does not mean, of course, that irradiated foods are 
 dangerous to eat--neither radiation or freezing is in the same league
 as cooking when it comes to rearranging molecules...)  In fact, my
 semi-educated guess is that future nanotech could restore frozen
 organisms but could not restore irradiated ones.
 --JoSH]