Neutrino
Definition and meaning of Neutrino in chemistry.
A neutrino is a tiny fundamental particle with almost no mass and no electric charge. It is made during certain nuclear reactions, especially a type of radioactive decay called beta decay. Trillions of neutrinos pass through your body every second without you noticing.
In more detail
Neutrinos come out of nuclear reactions where a neutron turns into a proton, or the reverse. There are three known types, or flavors, of neutrinos: electron, muon, and tau neutrinos. Neutrinos interact with matter only through the weak nuclear force, one of the four fundamental forces, and this force is extremely feeble at everyday energies.
Because of this, a neutrino can pass straight through the entire Earth without hitting a single atom. Despite being so hard to detect, neutrinos are essential for balancing energy and momentum during nuclear reactions. Without them, the math of many nuclear decays simply would not add up.
Major sources of neutrinos include nuclear fusion inside the Sun, radioactive decay of unstable atoms, cosmic rays striking Earth's upper atmosphere, and nuclear power reactors. Scientists detect neutrinos using huge, carefully shielded tanks buried deep underground, since the rare moments when a neutrino does interact are easiest to spot away from other radiation.
For decades, physicists assumed neutrinos had exactly zero mass. Experiments in the late 1990s proved otherwise, showing that neutrinos change from one flavor to another as they travel, a behavior called oscillation that is only possible if they carry a small amount of mass. This discovery, honored with a Nobel Prize in 2015, was one of the first clear cracks found in an otherwise very successful model of particle physics.
Key facts
| Field | General Chemistry |
|---|---|
| Particle symbol | nu (v) |
| Mass | Extremely small, best experimental upper limit is about 0.8 eV/c squared |
| Interaction mechanism | Weak nuclear force only |
| Flavors | Electron, muon, and tau neutrino |
| Major sources | The Sun, radioactive decay, cosmic rays, nuclear reactors |
When carbon-14 undergoes beta decay, one of its neutrons turns into a proton. This releases an electron and an electron antineutrino, and the atom becomes nitrogen-14 in the process.
Frequently asked questions
Why don't neutrinos interact with ordinary matter?
Neutrinos interact only through the weak nuclear force, which is extremely feeble at everyday energies. Trillions of neutrinos pass through normal matter for every one that actually interacts.
What are the main sources of neutrinos?
Neutrinos come from radioactive decay, nuclear fusion in the Sun, cosmic rays hitting Earth's atmosphere, and nuclear reactors.
How do scientists detect something that barely interacts with matter?
Scientists build huge, heavily shielded detector tanks deep underground. The extra shielding blocks other radiation, making the very rare moments when a neutrino does interact easier to spot.