[ExI] Neutrino interaction web

[Anders Sandberg]

Adrian Tymes wrote:
>> Worse, if two particles have no interactions allowed
>>     
>
> Neutrons and neutrinos do interact gravitationally and through the strong
> nuclear force, to my understanding.  Just not electromagnetically.
>   

As far as I know leptons do not feel the strong nuclear force. So you 
would have to use the weak or gravitational.

Check out
http://cupp.oulu.fi/neutrino/nd-cross.html
It has the cross sections for various neutrino reactions. The typical 
cross section for your neutron-rich sheet is 9.3×10^-48 m^2 per MeV of 
neutrino energy. So if you need about 10^47 neutrons per square meter to 
have a solid chance of catching the neutrino. That sheet would weigh 
1.8×10^20 kg, a biggish asteroid mass. You can scale it down if you want 
to only catch the high energy neutrinos, of course. Trying to get the 
cosmic background neutrinos with energy 1.7×10−4 eV on the other hand, 
would require an insanely dense sheet, probably running afoul of the 
Schwarzschild limit.

-- 
Anders Sandberg,
Future of Humanity Institute 
James Martin 21st Century School 
Philosophy Faculty 
Oxford University