Neutrinos are an aloof member of the sub-atomic particle family: it's electrically neutral, super lightweight (its mass was considered to be zero for a long time), and very reluctant to interact with ordinary matter.
They are produced from a variety of sources, such as beta radiation decay, stellar nuclear reactions, artificial atomic devices, and explosive celestial events such as a supernova.
Most neutrinos can travel through matter like light ray passing through transparent objects. However, a particular type of these ghostly particles, known as the ultra-high-energy neutrinos, is more ready to interact with other particles, which make them relatively easier to be stopped and detected.
Since 2016, the scientists who operate the Antarctic Impulsive Transient Antenna (ANITA), a cosmic neutrino detecting device hung from a balloon far above Antarctica, have been getting some unexplainable signals. Particles that bear the signature of ultra-high-energy neutrinos were seen flying into the detector from straight underneath the balloon, indicating they must had traveled upward through the frigid continent and possibly Earth, too.
Physicists were baffled and excited at the same time, by this mysterious observation. Besides the possibility of false detections from ANITA, these neutrino-like events could have been caused by something unknown to the standard model of physics.
Source: Seeker via Youtube