 Neutrinos are all around us. These tiny elementary particles travel through space at nearly the speed of light and have no positive or negative charge. Once thought to be massless, their mass is now believed to be incredibly tiny; it's estimated to be less than a billionth of the mass of a hydrogen atom. A neutrino is a particle, one of the so-called 'fundamental' particles like electrons, which means it isn’t made of any smaller pieces. They are the lightest of all the subatomic particles that have mass. They’re also extremely common; they’re the most abundant particle in the universe. Neutrinos come from all kinds of different sources. There are three kinds: electron, muon and tau neutrinos. Neutrinos first originated some 14 billion years ago, a few seconds after the 'Big Bang'. Scientists are trying to detect neutrinos that still survive from this primordial explosion by using powerful telescopes like the James Web Space Telescope to peer into the past. Neutrinos’ weak interaction with matter makes them almost impossible to detect, but also very interesting. Unlike most other particles, neutrinos are able to escape from dense regions such as the core of the sun or the Milky Way, and can they travel long distances from far-away galaxies without being absorbed, carrying information about these areas. Neutrino astronomy is becoming increasingly important. So far, only two sources of extraterrestrial neutrinos have been observed: the sun and supernovae. Like all stars, the sun emits electron neutrinos during the fusion process where lighter nuclei fuse into heavier ones. More than a thousand solar neutrinos hit every square centimetre of Earth every second. Unlike photons, which take about 100,000 years to travel from the core of the very dense Sun to its outer edge, and then travel to Earth in a mere 8 and a third minutes, neutrinos released in the same fusion process do the entire trip in just over 8 minutes. Solar neutrinos carry information about the current fusion processes inside the Sun, such as the chemical composition of its core. Neutrino detection is a good indication of an impending supernova, for example, because neutrinos emitted by the exploding star will arrive before the light does (because of how long it took light to get out of the star, where neutrinos escaped in minutes). Neutrinos are difficult to study. The only ways they interact are through gravity and the weak force. This weak force is important only at very short distances, which means tiny neutrinos can pass through the atoms of massive objects without interacting. Most neutrinos will pass through Earth without interacting at all. For example, in the time that you take to read this article, about 10,000,000,000,000,000 neutrinos will have passed through you without you noticing. To increase the odds of seeing them, scientists build huge detectors and create intense sources of neutrinos. Scientists never actually see the neutrino itself; instead, they see the other particles that are made when a neutrino interacts in a detector. Neutrinos are very useful for studying astronomical phenomena, and neutrino detectors are being built worldwide, deep underground to filter out the ‘noise’ of other particles. The recently finished IceCubew11 is the largest detector yet: a cubic kilometre of ice at the South Pole, acting as a telescope to search for neutrinos. Other detectors use different materials and strategies.  Inside the Super-Kamiokande Neutrino Detector in Japan Neutrinos are also detected in geophysics. The natural radioactive decay of uranium, thorium and potassium in Earth’s crust and mantle is what sustains the flow of molten material in convective currents, which drive continental drift, seafloor spreading, volcano eruptions and earthquakes. Some information from this page was obtained from the excellent site Science in School |