https://www.pbs.org/wgbh/nova/video/particles-unknown/Watched a re-broadcast of the latest PBS NOVA, 'PARTICLES UNKNOWN.'
Particle physicists are looking very hard at the three-known 'flavors' of neutrinos, and considering the existence of a fourth, non-detectable,' sterile neutrino, which may affect the trio of oscillatory fundamental particles of which their existence is known.
They have no confidence that they can construct a detector capable of direct observation, but believe they may be able to experience a sterile neutrino by its
effects.
Since we're constantly bombarded and penetrated by neutrinos without any experience of the events, particle physicists interpret this as a way of thinking about a dark matter which has mass, travels at sub-relativistic velocity, and so far, is known only because of its gravitational effects on celestial bodies.
They mention a generic atom, with a 'diameter' of 1-nanometer, 'orbiting' a nucleus of 1 / 100,000 of a nanometer, with the rest basically 'space.'
Neutrinos just blow right though the space in the atoms, rarely colliding with anything at all.
When they manage to strike Chlorine or Deuterium, photo-detectors can pick up a visible light streaks, as collision energy falls back to rest state and photons are liberated.
Interesting show.
