Cosmic Neutrino Background

If you check Wikipedia (and trust it) you can get an answer to your first question and, with that, probably answer the rest of your questions yourself.

First, is the cosmic neutrino background radiation theoretically of black-body spectrum? Yes, but it's slightly cooler, at 1.95 K rather than at 2.725 K. The reason for this is given in the Wiki article.

...would not a relativistic spacecraft experience an increase in temperature for the cosmic neutrino background radiation that scales with gamma? That seems like a reasonable conclusion to me, in the direction of its motion; and correspondingly it would see a lower temperature in the opposite direction.

Here's the link:

Cosmic_neutrino_background

Thanks for the reply Usbport and also the link.

Best;

Jim

Hi Jim,

Yes, I think what you assumed are essentially all correct for mass-less neutrinos, AFAIK. However, if the neutrino has a small mass (as we think it has), it may be at a very much lower temperature at present, because there will be cosmic momentum (hence, velocity) decay over the time since it was released.

Take note that the cosmic neutrino background (CvB) is not observable with present technology - presently it has a very tiny energy density when compared to dark matter.

-J

Hi Jorrie;

Thanks for the above reply.

Another quick question, is it possible that the answers to all four of my questions is yes to a good approximation provided that the bulk of the cosmic neutrino background particles travel at nearly the speed of light? I would think that the closer the cosmic neutrino background is to the speed of lght, the more accurate the approximation.

Thanks;

Jim

Yes, with neutrino speed observations seemingly converging to within one in a millionth from the value of c, I guess the approximations are fairly good. It probably still means that we will not be able to detect the CvB neutrinos any time soon...

The only time when they could have had an observable influence on our universe may have been long before the CMB were released (from a few seconds to a few thousand years after the BB). This was through gravitational interaction, not directly through collisions or similar interaction.

-J