But over the years, physicists studying neutrinos produced by the sun, the upper atmosphere, and nuclear reactors and particle accelerators have often found fewer than expected. Neutrinos, which swarm unnoticeably through our bodies and the entire thickness of the planet, have often been assumed to have no mass.

Weighing only a small fraction of what an electron does, these particles may nevertheless have enough heft to shake up the Standard Model-the theory that describes the behavior of elementary particles. It also describes how these concepts apply to the work that the Department of Energy’s Office of Science conducts as it helps the United States excel in research across the scientific spectrum.TAKAYAMA, JAPAN-A team of Japanese and American physicists at the Neutrino '98 conference presented strong evidence today that neutrinos switch identity as they travel-something that is only possible if they have mass. DOE Explains offers straightforward explanations of key words and concepts in fundamental science.

the Deep Underground Neutrino Experiment.

DOE’s Direct Current Podcast – DUNE: The Neutrinos Must Flow.

Hunting for Neutrinos: When the Ordinary is Unexpected.

Neutrinos change between types as they travel, something scientists call neutrino oscillation.

Scientists named the three types of neutrinos they have discovered so far for the other matter particle they interact with: the electron neutrino, muon neutrino, and tau neutrino.

Still other neutrino experiments, including NOvA and the upcoming international Deep Underground Neutrino Experiment, study a phenomenon called “neutrino oscillation,” which looks at how mass differs between different types of neutrinos. Scientists are using the MAJORANA Demonstrator experiment deep under the Earth’s surface to determine whether neutrinos are their own antiparticle or not. Other experiments, including PROSPECT and the Fermilab Short-Baseline Neutrino program, use neutrinos from reactors and accelerators to search for unknown types of neutrinos beyond the three that scientists have discovered so far. For example, the KATRIN experiment aims to directly measure the neutrino mass. Today’s investments continue that legacy through experiments and U.S.-hosted international facilities. The Department of Energy’s support for neutrino science has led to many surprising-and Nobel Prize winning-discoveries. DOE Office of Science: Contributions to Neutrino Science Some scientists think neutrinos might be why all antimatter (the antiparticles of all matter) disappeared after the Big Bang, leaving us in a universe made of matter. Today, scientists are trying to determine the neutrino’s mass, how it interacts with matter, and whether the neutrino is its own antiparticle (a particle with the same mass but opposite electric or magnetic properties) or not. Theorists predicted the neutrino’s existence in 1930, but it took experimenters 26 years to discover the particle.

Tens of trillions of neutrinos from the sun stream through your body every second, but you can’t feel them. Once produced, these ghostly particles almost never interact with other matter.

Even a banana emits neutrinos-they come from the natural radioactivity of the potassium in the fruit. Every time atomic nuclei come together (like in the sun) or break apart (like in a nuclear reactor), they produce neutrinos. Neutrinos are the most abundant particles that have mass in the universe. The neutrino is perhaps the best-named particle in the Standard Model of Particle Physics: it is tiny, neutral, and weighs so little that no one has been able to measure its mass.