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# Cosmic Neutrino Background

09/14/2013 9:31 PM

Hi Folks;

I have a rather unusual set of questions.

First, is the cosmic neutrino background radiation theoretically of black-body spectrum?

Second, if the answer to the first question is yes, would not a relativistic spacecraft experience an increase in temperature for the cosmic neutrino background radiation that scales with gamma?

Third, if the answer to the second question is yes, then would not the spacecraft experience a neutrino irradiation power that scales with the fourth power of gamma as such would be the case for the CMBR? By irradiation power, I am referring to the total neutrino flux density from all angles combined eventhough the interaction power willl be miniscule.

Fourth, would not the neutrino background radiation also experience relativistic abberation of the same formulaic type as say the CMBR?

Here, I am assuming that the almost all of the neutrino radiation is traveling near the speed of light. I am also assuming that the spacecraft is traveling through space as an inertial reference frame and thus am not considering exotic propulsion schemes such as the still speculative warp-drive and the like.

Thanks very much for your consideration

Jim

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#1

### Re: Cosmic Neutrino Background.

09/15/2013 8:16 AM

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.

Cosmic_neutrino_background

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#2

### Re: Cosmic Neutrino Background.

09/15/2013 8:42 AM

Best;

Jim

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#3

### Re: Cosmic Neutrino Background

09/15/2013 10:11 AM

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

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#4

### Re: Cosmic Neutrino Background

09/15/2013 11:16 AM

Hi Jorrie;

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

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#5

### Re: Cosmic Neutrino Background

09/15/2013 12:35 PM

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

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#6

### Re: Cosmic Neutrino Background

09/15/2013 9:43 PM

Hi Jorrie;

I would have sent my thanks earlier but I was out at Sky Line Drive in Shenandoah National Park. Stopped at a lot of the rest stops. had a picnic lunch with my mother who came along for the trip, and hiked for 129 minutes. Had a great day out there today.

Thanks;

Jim

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