Measurement of Earth's mass - with neutrinos

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Discussion Overview

The discussion centers on the measurement of Earth's mass using neutrino absorption, exploring the potential of neutrino tomography to provide insights into Earth's interior structure and density. The conversation touches on experimental methods, uncertainties in measurements, and the implications of findings related to dark matter.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that high-energy neutrinos absorbed by Earth could provide a method to measure its mass, noting that experiments detect more neutrinos from above than below, with the difference being mass-dependent.
  • Another participant mentions the large uncertainty in measurements, stating that while results are close to gravitational measurements, they carry a 25% uncertainty, which could be reduced with larger datasets and advancements like KM3NeT.
  • There is a proposal that Earth may contain dark matter, which could affect gravitational measurements but not necessarily neutrino absorption data.
  • One participant confirms that the density measurements of Earth's interior, particularly the core, align with previous seismic findings, indicating a higher density in the core.
  • A participant expresses curiosity about the classification of neutrinos in relation to photon energy, questioning whether neutrinos could be seen as a higher energy form of gamma radiation.
  • Another participant clarifies that neutrinos are fundamentally different from photons, despite both having varying energy levels, and discusses different energy ranges for neutrinos from various sources.

Areas of Agreement / Disagreement

Participants express interest in the study and its implications, but there is no consensus on the classification of neutrinos or the broader implications of the findings regarding dark matter. The discussion remains open with multiple viewpoints presented.

Contextual Notes

The discussion highlights uncertainties in measurement techniques and the potential for future improvements, particularly with upcoming experiments like KM3NeT. There are also unresolved questions regarding the relationship between neutrinos and other forms of radiation.

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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.
 
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How fun. :smile:
 
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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).
 
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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?
 
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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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