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We live on a billions-year old spaceship, shielded from natural radiation by a nuclear-powered[1] force field, and living by the emissions of a partially shielded fusion reactor. We fill birthday balloons with nuclear waste. We're mutants descended from generations of mutants. We eat greens, hoping their natural pesticides will keep us healthy, and give genitals as a sign of affection. We mostly eat the offspring of the most vulnerable organisms around us.

(Can you think of more to provocatively phrase?)

[1] Originally I had 'fission', but I'm reminded the heat comes more from spontaneous radioactive decay, not fission.

See the comment count unavailable DW comments at http://mindstalk.dreamwidth.org/335587.html#comments


( 10 comments — Leave a comment )
Sep. 28th, 2012 02:51 pm (UTC)
Oh, I like this! :-)

OK spaceship-> spaceship, that has already suffered one major, shattering collision and many minor ones ?

genitals refers to flowers?

something about our growing until we ruin our supporting ecology enough to start killing us?

Sep. 29th, 2012 09:05 pm (UTC)
Dude, nuclear decay is subcritical fission.

EDIT: sorry, wrong reply button.

Edited at 2012-09-29 09:06 pm (UTC)
Sep. 29th, 2012 09:33 pm (UTC)
I don't think alpha particle emission has anything to do with fission. Uranium does both, but I think decay dominates.
Sep. 29th, 2012 09:55 pm (UTC)
What makes some decays fissiony and alpha decay not?
Sep. 29th, 2012 11:45 pm (UTC)
Sorry, have to agree with mindstalk - fission occurs when a heavy nucleus spontaneously splits into two other nuclei, each of the order of half the original mass, but with random variations. As it turns out, that frequently also produces some small debris, including neutrons. If there are other fairly stable heavy nuclei around, one might absorb one of the neutrons (charge debris would be repelled) and that absorption might transform the heavy nucleus into one that would spontaneously fission pretty quickly, as opposed to hundreds of thousands of years. Get enough of the other heavy nuclei around and you might get a sustaining reaction - that's "critical". Not enough concentration of other heavy nuclei is "sub-critical". Some of that does, in fact, occur in naturally occurring isotopes. The critical concentrations of those burned out years ago. So, yes, there is some sub-critical fission still going on. Also a certain amount of minor decay, such as mindstalk mentions, that normally isn't considered fission - that is decay from heavy nuclei that are much more likely to emit an alpha particle than to split roughly into two. This is thought to majorly contribute to core temperature - but I don't see anything in the original post that referred to core temperature. But perhaps it should . . .
Sep. 29th, 2012 11:51 pm (UTC)
Core temperature presumably drives the dynamo which provides the magnetic field, i.e. force field.

One could conside splitting into a helium nucleus and a thorium nucleus to be a form of fission, but that's not how 'fission' is used in nuclear chemistry AIUI, also there's a distinct lack of neutrons. It's not subcritical fission; that's when U-235 or Pu-239 really are fissioning but not concentrated enough (or with slow enough neutrons) to keep a high rate going.
Sep. 30th, 2012 12:51 am (UTC)
I think it's more broadly understood that heat- driven convection in the fluid interior produces the earth's magnetic field, which provides the shielding against charged particles from space, and that radioactive decay provides that heat.

I'm still not sure why it's not "a clefting" between thorium and helium nuclei but between krypton and barium it is.
Sep. 30th, 2012 01:09 am (UTC)
I think that's a reasonable point, and I suspect it is due to the fact that in many cases, a helium nucleus is an overwhelmingly probable decay particle, and thus worth its own category. It has been several decades for me, but I don't recall any alpha decay that also produced neutrons, so it would be hard to argue for it being "sub-critical fission". :-) But it definitely produces energy, which takes a while to work its way out from the core.
Sep. 30th, 2012 01:19 am (UTC)
I figured it's a split producing two valid nuclei and there being no neutrons to contribute to crticality would make it unquestionably subcritical. I guess it's just one of those things passed on by immersion in other nuclear scientists' company.

I stand bazinga'd!
Sep. 30th, 2012 02:04 am (UTC)
I think it's partly the big mass difference and neutrons, and partly that alpha decay got discovered and named first.

Though the size also means that one of the alpha products can emit its own alpha particles, while fission is Over for the products. And their more equal size is more like the fission of an amoeba or other single cell.

Edited at 2012-09-30 02:05 am (UTC)
( 10 comments — Leave a comment )


Damien Sullivan

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