🚀 go-pugleaf

Matt Carey <matt.carey@ieee.org> writes:

> "Joseph.D.Warner" wrote:
>> 
>> Matt Carey wrote:
>>> <snip>
>>> 2) What is the "Room Temperature" of the universe?  The bright
>>> boys at Bell Labs measured the background radiation of the universe
>>> at about 3K (2.77K?) as I recall.  About 0.01 what we consider
>>> room temperature.  kbT is about 1/40 eV at RT, so the background
>>> "temperature" of the universe would be about 1/4000 eV.  Hardly
>>> enough to make a neutrino relativistic.
>> 
>> No one, as I understand,  has said that neutrinos are in thermal
>> equalibrium with rest of the universe
> 
> I just found the concept of a "room temperature" neutrino humorous.
> 
> "Every neutrino would be relativistic (kinetic energy exceeds rest mass) 
> near room temp"
> 
> This would imply that neutrinos are somehow in equilibrium with 
> someone's room.

This is known as a ``hypothetical'' question, i.e., a ``what if?''
*IF* it where possible for neutrinos to be at equilibrium at what 
humans consider ``room temperature,'' what would their mean speed be?
(Note that the question is not entirely silly --- somewhere between
the neutrino decoupling time (T_\nu ~= 1e10 Kelvin) and the current
epoch (T_\nu ~= 2 Kelvin), they must have passed through T_\nu ~= 300 K...


> Not only is it a silly notion, they would be barely relativistic at
> room temperature. (kinetic~0.5*rest mass)

Well, ``room temperature'' corresponds to about 0.03 eV, and we currently
only have upper bounds on the neutrino masses; it's not at all inconceivable
that the lightest neutrino is lighter than that...


-- Gordon D. Pusch   

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