A neutrino is an electrically neutral, weakly interacting elementary subatomic particle with a disputed but small non-zero mass. It is able to pass through ordinary matter almost unaffected. The neutrino (meaning "small neutral one" in Italian) is denoted by the Greek letter ν (nu).
Neutrinos do not carry electric charge, which means that they are not affected by the electromagnetic forces that act on charged particles such as electrons and protons. Neutrinos are affected only by the weak sub-atomic force, of much shorter range than electromagnetism, and gravity, which is relatively weak on the subatomic scale.
Most neutrinos passing through the Earth emanate from the Sun. About 65 billion (6.5×1010) solar neutrinos per second pass through every square centimeter perpendicular to the direction of the Sun in the region of the Earth.
In September 2011, neutrinos apparently moving faster than light (aka FTL neutrinos) were detected. If this finding is confirmed, it would change generally-accepted understanding of the theory of relativity and could have significant impact on radioactive decay methods for the age of the earth and universe and arguments built around the speed of light.
- Neutrino article on Wikipedia [retrieved 2011.11.23]