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Author Topic: How many neutrinos are orbiting the Earth?  (Read 1655 times)

Offline chiralSPO

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How many neutrinos are orbiting the Earth?
« on: 12/09/2015 04:35:39 »
We know that neutrinos are constantly passing through our bodies at a very high flux. What percentage of them happen to be going at precisely the right speed (<11.2 m/s, depending on altitude...) at the right point for them to be captured and fall into orbit around the Earth?

Presumably most neutrinos are traveling at an extremely high velocity because they are so light, and are produced in high energy environments like stars and supernovae. But how many are traveling at the correct velocity relative to the Earth?

Furthermore, given how rarely neutrinos interact with matter, presumably there could be neutrinos orbiting the Earth at or below sea level...

Would the interconversion between neutrino types (electron neutrino, muon neutrino, tau neutrino) destabilize the orbits?


 

Offline evan_au

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Re: How many neutrinos are orbiting the Earth?
« Reply #1 on: 12/09/2015 12:35:01 »
Quote from: chiralSPO
Presumably most neutrinos are traveling at an extremely high velocity
The final results of the OPERA experiment showed that neutrinos are traveling so close to the speed of light that you cannot distinguish the two.

However, neutrinos will lose velocity due to the general expansion of the universe. The speed of these cosmic neutrinos follows a thermal distribution. It is thought that they will have an effective temperature of around 2K (slightly cooler than the 2.7K CMBR).

One paper suggests that there may be some neutrinos with velocities as low as 800km/s, which is slow enough to be captured by galaxy clusters. But this is still well above the escape velocity of the Earth.

Presumably there are a few with even lower velocities, that could be captured by the Earth's gravitational field...
 

Offline jeffreyH

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Re: How many neutrinos are orbiting the Earth?
« Reply #2 on: 12/09/2015 13:18:16 »
We know that neutrinos are constantly passing through our bodies at a very high flux. What percentage of them happen to be going at precisely the right speed (<11.2 m/s, depending on altitude...) at the right point for them to be captured and fall into orbit around the Earth?

Presumably most neutrinos are traveling at an extremely high velocity because they are so light, and are produced in high energy environments like stars and supernovae. But how many are traveling at the correct velocity relative to the Earth?

Furthermore, given how rarely neutrinos interact with matter, presumably there could be neutrinos orbiting the Earth at or below sea level...

Would the interconversion between neutrino types (electron neutrino, muon neutrino, tau neutrino) destabilize the orbits?

That is a very interesting idea in general. I would like to see where this is going.
 

Offline chiralSPO

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Re: How many neutrinos are orbiting the Earth?
« Reply #3 on: 13/03/2016 21:24:26 »
Neutron stars are expected to have escape velocities in the range of 11.5x108 m/s near their surfaces. Perhaps this would be the right location to look for "slow" neutrinos captured into stable orbit. Presumably all of the neutrinos produced in the supernova that created the neutron star would be far, far away, but perhaps a neutron star could capture neutrinos from other stellar events (or just radioactive decay of dust left over from a supernova...)

Perhaps one could imagine a neutron star even having an "atmosphere" of neutrinos!

(NOTE: sorry if anywhere I said neutron when I meant neutrino, or vice versa--I hope my intended meaning was not lost...)
 

Offline jeffreyH

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Re: How many neutrinos are orbiting the Earth?
« Reply #4 on: 13/03/2016 22:15:51 »
There could be an equatorial orbital band, for want of a better description. This would have to be a rare orbital path as the approach would have to be on a very precise trajectory. I am unsure of what such an orbit would tell us since no interactions would necessarily be detectable. However, it may in some way affect the profile of accretion disks.

Other orbits at an angle to the equatorial plane should be more common. These geodesics could maybe have some influence on the generation of relativistic jets. That is however speculative and not founded in observation.
 
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Offline chiralSPO

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Re: How many neutrinos are orbiting the Earth?
« Reply #5 on: 13/03/2016 22:55:51 »
Thanks Jeff, I think this topic is best suited for speculation--given the difficulty of detecting neutrinos, even when they are here, I imagine it will be quite a while yet before we can discuss observations of such particles in systems thousands of lightyears away...
 

Offline JoeBrown

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Re: How many neutrinos are orbiting the Earth?
« Reply #6 on: 14/03/2016 00:57:09 »
The final results of the OPERA experiment showed that neutrinos are traveling so close to the speed of light that you cannot distinguish the two.
Man made neutrinos may have nothing in common with the naturally occurring phenomena.

Quote
However, neutrinos will lose velocity due to the general expansion of the universe. The speed of these cosmic neutrinos follows a thermal distribution. It is thought that they will have an effective temperature of around 2K (slightly cooler than the 2.7K CMBR).

There is very no verifiable evidence to support the conclusion that the Universe is expanding.  Less evidence to supporting such phenomena would have an effect on neutrinos.

Neutrinos, by definition, are nearly impossible to detect, let alone observe.  There is evidence that they are produced at supernova episodes.  They were detected near the time of SN1987A.  But the data are limited.


WIMPs - Weakly Interactive Massive Particles aka Neutrinos are believed to be passing through us, the planet the solar system, the galaxy and more or less everywhere.

Counting or even estimating the amount in orbit is impossible, with present technology.

Most would likely be found near the super massive blackholes in the centers of galaxies.  I suspect the odds would suggest there are some orbiting Earth.  More orbiting Jupiter and more still, orbiting the Sol.

Oddly enough, some of their orbits may pass through the bodies they orbit, because they rarely interact with baryonic matter.
 

Offline evan_au

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Re: How many neutrinos are orbiting the Earth?
« Reply #7 on: 14/03/2016 10:11:35 »
Quote
Neutrinos, by definition, are nearly impossible to detect, let alone observe.
That is true - neutrinos are very hard to spot. But there are now a variety of neutrino telescopes that can spot neutrinos from a number of sources:
  • nuclear reactors (in fact compact neutrino detectors are proposed for monitoring of the nuclear non-proliferation treaty)
  • Particle accelerators
  • The Sun
  • Natural decay of radioactive minerals in the Earth
  • Cosmic rays striking the atmosphere
  • Supernovas (as mentioned)

Neutrinos with low enough energy to orbit the Earth (or even the Milky Way) have too low an energy to trigger our current detectors.
The same goes for neutrinos from the Big Bang.

Quote
Man made neutrinos may have nothing in common with the naturally occurring phenomena.
Neutrinos have very few quantum characteristics, which limits how different natural and man-made neutrinos can be.
  • There are 3 known flavors of neutrino: electron, muon and tau
  • There are 2 suspected types of neutrinos: a neutrino and an anti-neutrino (although it is still possible that these are identical)
  • Rest-Mass: Small (around 0.2eV), but not known accurately
  • Spin: 1/2
  • ..and a few more which have fixed values

Detectable neutrinos have a relativistic velocity, which increases their rest mass up to the energy levels found in nuclear reactions (millions of eV). This requires them to be traveling very close to the speed of light.

Neutrinos from a nuclear fission reactor start life as electron neutrinos from the Beta decay of the radioactive fission products (they then oscillate between the three flavors). This is exactly the same as natural radioactivity from the decay of uranium.

Particle accelerators are able to produce Muons and Tau particles, which can create neutrinos which start life as these other flavor of neutrino. These have more energy than the electron neutrinos from radioactive decay or solar neutrinos. It is thought that a supernova would produce a mix of all types of neutrino.
 

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Re: How many neutrinos are orbiting the Earth?
« Reply #7 on: 14/03/2016 10:11:35 »

 

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