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Featured I Measurement of Earth's mass - with neutrinos

  1. Nov 5, 2018 #1


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    At very high energies Earth absorbs a relevant fraction of neutrinos passing through it. Experiments receive more of these neutrinos from above than from below and the difference depends on the mass of Earth. So why not measure it?

    Neutrino tomography of Earth

    The uncertainty is very large, of course. While the result is very close to the number from gravitational measurements they have a 25% measurement uncertainty. Larger datasets and KM3NeT will help reducing the uncertainty. While unlikely, Earth might have accumulated something dark matter like - it would appear in gravitational measurements but not necessarily in neutrino absorption data.

    Apart from the overall mass they also measure the density in different regions of the interior of Earth and confirm that the core has a higher density than the surrounding material. Again no surprise (seismic measurements have measured this long ago) but a nice confirmation, and with a lot of potential for future improvements.
  2. jcsd
  3. Nov 5, 2018 #2


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    Staff: Mentor

    How fun. :smile:
  4. Nov 6, 2018 #3


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    So they did get it published in Nature. :smile:
    Andrea gave a talk at IFT in the beginning of the year where he could not show us certain things because they were waiting for the referee reports from Nature. His explanation was along the lines "I can probably show you in a few weeks when we are rejected by Nature". One of the better seminars I went to the last few years.

    I think it is a good and interesting study. I know all three authors (I have papers with two of them).
  5. Nov 10, 2018 #4
    Wow, that KM3NeT sounds magnificent! Very interesting stuff... I'm curious though so I have a "dumb" question. I saw mention of Cherenkov radiation and wonder if neutrinos should just be "classified" as the next step in photon energy above Gamma radiation?
    Last edited: Nov 10, 2018
  6. Nov 10, 2018 #5


    Staff: Mentor

    Neutrinos are completely different particles.
    Just like photons they can have different energies. The experiments discussed here look at TeV and higher energies, experiments with neutrinos from accelerators look in the GeV range, neutrinos from nuclear reactors are in the MeV range. PTOLEMY is a proposal to measure neutrinos with less than 1 eV energy.
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