[ExI] Double-Earth (Was: kepler study says 8.8e9 earthlike planets)

[Anders Sandberg]

As practical jokes go, having a planet with oceans that go critical is 
pretty impressive.

On 26/11/2013 16:31, spike wrote:
>
>
> Here's something cool: the Pu alpha decays to 240Np, which is denser, 
> so it sinks toward the center, but really doesn't have time to go far 
> with that hour half-life to 240Pu, but then the concentration of 240Pu 
> goes up and heats up, so I suppose it would boil, but under enormous 
> pressure perhaps not, so it isn't clear if a critical mass eventually 
> results.
>

It is worth considering the neutron reflectivity properties of the 
original Pu too: it might act as a neutron mirror, in which case the 
critical mass goes down. Hmm, those alpha particles might also mess 
things up a bit. Not sure they have an effect, I need to check my 
literature. Wikipedia mentions that alphas can incite fission in Pu240, 
I have not yet checked out http://prola.aps.org/abstract/PR/v144/i3/p1046_1

Hmm, if the Pu gets close to critical I assume there would be 
mini-explosions or flare-ups that would be like mega-boiling: high 
concentration zones have chain reactions, heat up a lot, turn to big 
nuclear vapour bubbles and mix the ocean. You would only get a big 
detonation if it all quietly congregated together and then something 
eating the neutrons suddenly disappeared.

So maybe there would not be a big boom, just regular geysers of molten 
metal and nuclear plasma. Still awesome.

> Hey I wonder if the feds are getting nervous watching me google around 
> on plutonium and uranium?
>

It is when you start downloading neutron diffusion codes they get really 
nervous...



-- 
Anders Sandberg,
Future of Humanity Institute
Oxford Martin School
Faculty of Philosophy
Oxford University

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