[ExI] Neutrino interaction web

Anders Sandberg anders at aleph.se
Sat Mar 5 12:00:19 UTC 2011

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
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 

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