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B What particle(s) pass through Earth?

  1. Dec 23, 2017 #1
    What particles(s) can pass through hundreds of miles of the Earth? Is it only neutrinos, or is there some other particle(s)?
     
  2. jcsd
  3. Dec 24, 2017 #2

    mfb

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    Only neutrinos (unless they have very high energies), and gravitons if they exist.

    Muons can fly many kilometers through the Earth if their energy is high enough.
     
  4. Dec 24, 2017 #3

    Orodruin

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    And most likely dark matter if it has a particle nature.
     
  5. Dec 24, 2017 #4
    Thanks mfb and Orodruin. Now, since the question above asks do I "have something to add", I'm going to continue onward. The Gravitons sound really interesting as well as the Dark Matter, if Dark Matter is composed of particles; both being theoretical.

    If Gravitons or Dark Matter particles exist, could they be reflected by a mirror after flying through miles of Earth? Or, would they just pass through a mirror without any interaction?
     
  6. Dec 24, 2017 #5

    Orodruin

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    A mirror would have no relevant effect whatsoever on gravitons or dark matter particles. It is constructed to reflect light in the visible spectrum.
     
  7. Dec 24, 2017 #6
    Thanks Orodruin, you have a good point there. Hmmm....

    Theoretically, could gravitons or dark matter be emitted by a nuclear power plant?
     
  8. Dec 24, 2017 #7

    mfb

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    These particles pass through the Earth because an interaction with any kind of matter is extremely unlikely. That includes mirrors, every type of detector and everything else on Earth. That is the reason neutrino detectors have to be extremely large or need a huge neutrino flux (e.g. being close to a reactor or having a dedicated neutrino beam produced for them). Same for dark matter detectors, they are large as well. And we don’t even bother to try to measure individual gravitons - that would need a detector larger than Earth around a black hole or similar things.

    Nuclear reactors don’t produce dark matter. Technically nearly everything with accelerating masses produces gravitons but the intensity is completely negligible. It is also not specific to nuclear reactors - every car produces them as well.
     
  9. Dec 24, 2017 #8
    Thanks mfb!

    If you look up "neutrino detector fire extinguisher" you will find articles about a new handheld neutrino detector the size of a fire extinguisher than can be adapted to search for nuclear weapons. Here's one article: https://futurism.com/this-handheld-detector-spotted-a-never-before-seen-physics-phenomenon/

    People at Oak Ridge National Laboratory and the University of Chicago came up with a different neutrino detector that detects by bouncing neutrinos off of a nucleus. There must be some kind of interaction if they are bouncing neutrinos off of a nucleus. I wouldn't think that would be possible, but....

    I especially liked it when you stated that gravitons are not specific to nuclear reactors and every car produces them when moving. That was an unexpected answer that I really like!

    Here's a question... Do nuclear power plants produce gravitons or dark energy particles?
     
  10. Dec 24, 2017 #9

    mfb

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    • futurism.com is a bad source, they have a long history of misrepresenting stories to make them sound more spectacular. Here is the original publication
    • The researchers put this "fire extinguisher-sized" detector (14.6 kg active material is quite a lot for that size) in one of the most intense neutrino beams we have on Earth and measured for 15 months. That was just sufficient to see that the detector can measure anything.
    Yes of course, but it is rare. So rare that they needed such an extremely powerful neutrino source and 15 months of measurement time. They found 134±22 events, or about two per week.
    See above for gravitons.
    Dark energy is not expected to be associated to any particles, but even if it is, nuclear reactors wouldn't produce them.
     
  11. Dec 24, 2017 #10
    Thanks mfb. So much for the futurism article, thanks for pointing out the facts for me. Too bad you don't live in the Wichita, Kansas area, or we would have some very serious discussions. Very serious.
     
  12. Dec 25, 2017 #11

    Orodruin

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    In addition to what mfb said, note that dark energy and dark matter are two very different things. It is therefore important not to confuse them with each other.

    Unlike dark energy, many physicists do expect dark matter to consist of particles. Regardless, they would not be produced by nuclear reactors.
     
  13. Dec 25, 2017 #12
    The reactions in nuclear reactors are reasonably well known because they can be and have been investigated outside the reactors as well.
    Formation of dark matter particles (or gravitons) would be accompanied by disappearance of energy.
    Disappearance of energy is indeed observed, in beta decay, but all of it seems to be reasonably well modelled as neutrinos.
     
  14. Dec 25, 2017 #13
    Thanks Orodruin and snorkack. Gravitons seem to pick up my interest. So I started another thread on Gravitons, hope to see all of you there.
     
  15. Dec 27, 2017 #14
    There is most probably no graviton particle existing. Gravity field is a depression in spacetime fabric... and gravitational wave is a ripple in spacetime fabric.
     
  16. Dec 27, 2017 #15

    Nugatory

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    @mfb did qualify his reply in #2 with "... if they exist" but it's an overstatement to say that they probably don't exist. We just don't know yet.
    Although this metaphor of "fabric" and depressions and ripples is common in non-technical descriptions of general relativity, it is still just a metaphor and should not be taken too seriously.
     
  17. Dec 27, 2017 #16

    mfb

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    I don’t have a proper statistical analysis, but from my impression most physicists expect them to exist. Quantum field theory is extremely successful, and while we have some issues with the calculations, it is expected that gravity can be formulated as QFT as well.
     
  18. Dec 27, 2017 #17

    Orodruin

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    To add to what has already been said by Nugatory and mfb: What makes you think that GR would invalidate the existence of the graviton in any way? That is like saying that Maxwell's equations would invalidate the existence of the photon. On the contrary, quantum gravity is essentially required to have GR as a classical limit.
     
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