Radioactive decay and long-term preservation

Jeff Davis (
Wed, 20 Oct 1999 14:58:51 -0700

Robert Bradbury wrote:
>However, very *long* term solid state preservation is probably impossible >due to the damage caused by the radioactive decay of the frozen atoms....

Then spike wrote:
> I propose we dig up coal, a form of carbon
> free of carbon 14,...

Then Robert replied:
>I believe you're approach would work. However I think that most
>of our internal radiation exposure comes from K40, not C14.
>Perhaps a little radioactive iodine,...
>the...largest dose ... from Radon...

Uh, I disagree. Let's start at the beginning.

What do you mean by preservation? If every atom has to be exactly as it was at time t=0, then yes, preservation is impossible. If, however you're talking about preservation for the purpose of reanimation from cryonic (or some other form of) biostasis, then you're dealing with a particular set of variables which will determine what *degree of preservation* will be *adequate*. The crucial factor is usually seen as preservation of the unique information which manifests the unique you (synaptic patterns being the top candidate). Another school holds that a level of structural integrity demonstrated by survivability is the proper standard.

At one extreme, where repair or reconstruction is carried out by fully mature, almost-unimaginably-capable nanotech assisted by equally over-the-top AI, the information is all you need. At the other extreme where no repair is possible, you need a suspension-unsuspension procedure which inflicts no more damage than the body itself can repair (with assistance from some sort of future, but nevertheless semi-conventional, medical capability). In the latter case the additional damage due to radioactive decay could, conceivably play a role.

But here's the problem.

The seriousness of damage is a function of how many radioactive atoms there are to decay, how much time--how long is the period of preservation--passes, which will determine what fraction of them decay (you know, half-lives), the various destructive potentials of the various modes of decay (alpha, beta, gamma, spontaneous fission w/neutron emission), and perhaps most important, what is damaged.

My impression is that these factors, separately and in combination, tend to reduce to insignificance the consequence of damage due to radioactive decay.

First and foremost the fraction of radioactive atoms is, I suspect, too small to matter.

Second, my guess for preservation time--the time for the development of reanimation capabilities--is 150 years, give or take a hundred. Most, but not all, of the half-lives are, I would wager, much longer.

Thirdly, beta decays are insignificant, and alpha and gamma emissions will only cause a narrow linear pattern of molecular ionization along the path of the emitted particle/photon.

And finally, in regards to what gets damaged, the scale of synaptic structures is so much larger than the scale of radiation damage that the crucial identity information remains unaffected (in fact you have additional information in the form of a radioactive decay event artifact). DNA information is too redundant to be degraded. Non-neural structure is generic, so, in terms of information loss, unaffected.

As to damage that effects survival-related functionality, look at the radiation doses necessary to kill a living human (my impression is muy mucho rads), and compare that to the total dose potential contained in the body. I don't have these numbers. How much potassium is in the body? What fraction is radioactive? What's the half-life compared to say 500 years? The other isotopes?

And while it doesn't answer the above questions, with or without nano-repair or improved cryosuspension techniques (or a nicely balanced combo of the two) the issue of radiation damage is moot. With it, radiation damage is repairable, and without it, freeze damage predominates.

Spike, the zen master, wrote (approximately): "I don't care if they laugh with me or if they laugh at me, so long as they laugh." Then he wrote, "...coal, a form of carbon free of carbon 14,..." Then I laughed. The monastery curriculum not to strong on the radiochemistry of coal, eh, spike?

Next you'll be telling me that carbon 14 dating means that your girlfriend is radiant.

Best, Jeff Davis

	   "Everything's hard till you know how to do it."
					Ray Charles