Re: Relic neutrinos

On Dec 3, 5:59 pm, "Dirk Van de moortel" <dirkvandemoor...@ThankS-NO-
SperM.hotmail.com> wrote:
"Eric Gisse" <jowr...@xxxxxxxxx> wrote in messagenews:844abd89-505a-414c-974b-665663144b21@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On Dec 3, 4:41 am, mluttg...@xxxxxxxxxx wrote:
Relic neutrinos

Fromhttp://kicp.uchicago.edu/~odom/compton_files/compton_lecture_02_hando...

"Big bang physics tells us that the heaviest neutrino is
lighter than some value: 0.14 eV
Experiments on mundane neutrinos (solar, reactor,
atmospheric) tell us that the mass of the heaviest
neutrino is greater than 0.05 eV.
Since neutrinos are so light, they usually move
at near the speed of light.

Relic neutrinos (from the big bang) have much lower
energies than solar neutrinos."

Lay person questions:

- Why do they have such a low energy?
(I presume that the expansion is responsible).

Very good, Marcel.

- Which formula allows to calculate the
present energy of relic neutrinos, assuming
an initial velocity v0?

You would have to use general relativity. Take the FRW metric and see
what happens to a particle with a given four momentum as time marches
on.

No no no...
He wants *you* to take the FRW metric and show him what happens
to a particle with a given four momentum as time marches on.
The idea is that you waste *your* time on *him* ;-)

Dirk Vdm

I don't think that responding to the

Lay person questions:


- Why do they have such a low energy?
(I presume that the expansion is responsible).
- Which formula allows to calculate the
present energy of relic neutrinos, assuming
an initial velocity v0?

is a waste of time.

Interested lay persons would probably prefer a straight answer
to the theoretical general GR solution proposed by Eric Gisse.

In particular, what could be the initial velocity (Iow,
the initial energy) of the BB neutrinos?
What is their fate after their emission?
How long will they survive as energetic particles?

Of course, such problems don't interest people like Vdm.

Marcel Luttgens








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