[ExI] Neutrino interaction web

[Anders Sandberg]

One of the classic simple models of atomic nuclei is the "droplet model" 
by Gamow, Bohr and Wheeler, which just treats them as liquid droplets of 
incompressible fluid with a heck of a surface tension. Insofar this 
model works, it suggests that nuclear matter in its normal state is a 
pretty lousy building material unless you like lumps of stuff.

However, Adrian, I am curious of why you thought a sheet of neutrons 
would stop neutrinos?

Personally I doubt it would work: any interaction would be by the weak 
force, and it is pretty wimpy. Lacking some lepton with the right charge 
the neutrino could not be absorbed by a reaction like n0 + v + e+ -> p+, 
so there might not even be any allowed reaction. But weird things happen 
when you spread out matter in low dimensional structures (think of 
graphenes), so intuitions might be misleading.

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