Tiny bits fly through everything.
They come from the sun. They move very fast. They can pass through you. You do not feel them. They are very small. Can you find them?
Tiny bits fly through everything.
They are called neutrinos. These bits are very small. They have almost no weight. They do not have an electric charge. This helps them move easily. They can pass through you. They can pass through the Earth. You do not feel them at all. Most of them come from the Sun. They are made by big fires in space.
These tiny bits are everywhere in our world.
A neutrino is a tiny particle. It is so small that people once thought it had no mass. Mass is how much something weighs. Neutrinos have a very tiny mass. They also have no electric charge. This means they do not feel electricity.
Because they are so small, they can pass through almost anything. They fly through walls and even through the Earth. Most neutrinos come from the Sun. They are made by nuclear reactions in the Sun's core.
There are three types of neutrinos. Scientists call these types flavors. The flavors are electron, muon, and tau. Neutrinos can change from one flavor to another. This is called oscillation. It is like a shape-shifter.
Scientists first thought of the neutrino in 1930. Wolfgang Pauli said it must exist to explain energy. Later, Clyde Cowan and Frederick Reines proved it. They used a nuclear reactor to find them. They even found neutrinos in a gold mine in South Africa. Now, we study them to learn about space.
A neutrino is a tiny, elementary particle. It is so small that people once thought it had no mass at all. The name comes from its tiny mass and its lack of electric charge. These particles only interact through gravity and the weak interaction. Because of this, they usually pass through normal matter without hitting anything. They can fly through walls or even the entire Earth.
Most neutrinos detected on Earth come from the Sun. About 65 billion solar neutrinos pass through every square centimeter every second.
There are three different types of neutrinos. Scientists call these types "flavors." The three flavors are electron, muon, and tau neutrinos. These flavors are linked to other particles called leptons. Neutrinos can actually change from one flavor to another while they travel. This strange process is called oscillation.
A neutrino might start as an electron flavor. Then, it might appear in a detector as a muon or tau flavor. This happens because neutrinos are a mixture of three different mass states.
Scientists first thought of the neutrino in 1930. Wolfgang Pauli suggested it must exist to explain how energy is saved during beta decay. He originally called it a "neutron," but that name was already used for a much heavier particle. In 1932, Enrico Fermi helped bring the name "neutrino" into science. The name means "little neutral one" in Italian. It was a joke used to tell it apart from the heavy neutron.
For a long time, no one could actually see a neutrino. In 1956, Clyde Cowan and Frederick Reines finally detected them. They used a nuclear reactor to create antineutrinos for their experiment. They looked for a specific signal of light and neutrons. In 1965, scientists found the first neutrinos from nature in a gold mine. This mine was located in South Africa at a depth of 3 km.
Neutrinos help us understand the history of our universe. They are created by stars and even by massive explosions called supernovas.
Some neutrinos were even made during the Big Bang. This creates a background of neutrinos throughout all of space. Scientists can even use them to look inside the Earth. This method is called tomography. By studying these tiny particles, we learn how the biggest things in space work.
A neutrino is an elementary particle that exists at the most fundamental level of our universe. These particles are electrically neutral, meaning they carry no electric charge. They also have an incredibly tiny rest mass. For a long time, scientists believed their mass was exactly zero. Because they lack charge and have such little mass, they interact with the world in very specific ways. They only interact via gravity and the weak interaction. The weak interaction is a force that has a very short range. Because they do not participate in electromagnetic or strong interactions, neutrinos usually pass through normal matter without hitting anything.
To understand how neutrinos behave, we must look at their three distinct flavors. These flavors are the electron neutrino, the muon neutrino, and the tau neutrino. Each flavor is associated with a corresponding charged lepton. For example, the electron neutrino is linked to the electron. One of the most surprising things about neutrinos is a process called oscillation. This is when a neutrino changes its flavor while it is in flight. A neutrino created as an electron neutrino during beta decay might interact in a distant detector as a muon or tau neutrino. This happens because a neutrino with a specific flavor is actually a quantum superposition. It is a mixture of three different mass states.
The history of the neutrino began with a mystery in nuclear physics. In 1930, Wolfgang Pauli proposed the particle to explain beta decay. During beta decay, particles are emitted from an atomic nucleus. Pauli wanted to show how energy, momentum, and angular momentum, also called spin, were conserved. He originally called his idea a "neutron." However, James Chadwick discovered a much heavier neutral particle and named it a neutron in 1932. To avoid confusion, the name "neutrino" was used. This name was jokingly coined by Edoardo Amaldi. In Italian, neutrino means "little neutral one." Enrico Fermi later used this name during scientific conferences in 1932 and 1933.
For many years, neutrinos remained theoretical because they were so hard to detect. In 1956, Clyde Cowan and Frederick Reines finally confirmed their existence. They conducted the Cowan–Reines experiment using a nuclear reactor. They used antineutrinos, which are the antiparticles of neutrinos. These antineutrinos reacted with protons to produce neutrons and positrons. The positron quickly finds an electron and they annihilate each other. This annihilation produces two detectable gamma rays. The coincidence of these gamma rays and the neutron capture provided a unique signature. This massive achievement earned them the Nobel Prize in 1995.
Neutrinos are produced by many different natural and artificial processes. They are created during the beta decay of atomic nuclei or hadrons. They are also produced in natural nuclear reactions inside the core of a star. Artificial reactions in nuclear reactors, nuclear bombs, or particle accelerators also create them. Massive cosmic events like a supernova also release them. A supernova is the explosion of a star.
Even the spin-down of a neutron star can produce neutrinos. The majority of neutrinos detected on Earth come from the Sun. At the surface of the Earth, the flux is about 65 billion solar neutrinos per second per square centimeter.
One of the greatest mysteries in science was the solar neutrino problem. In the 1960s, the Homestake experiment measured electron neutrinos from the Sun. It found only one third to one half of the predicted number. This discrepancy lasted for thirty years. Scientists eventually realized that the neutrinos were not missing. Instead, they were oscillating into different flavors that the experiments could not detect. This discovery was confirmed by experiments at Super-Kamiokande and the Sudbury Neutrino Observatory. This work helped explain how neutrinos change flavors as they travel through matter. This is known as the Mikheyev–Smirnov–Wolfenstein or MSW effect.
Today, neutrinos connect many different fields of study. They can be used for tomography of the interior of the Earth. This means scientists can use them to map what is inside our planet. They also provide clues about the history of the entire universe. A general background of neutrinos pervades all of space. Some of these came from the Big Bang about one second after it began. This is called the cosmic neutrino background. Others come from a diffuse background created by supernovas. By studying these tiny particles, we learn about the largest structures in existence.
Where will your curiosity go next?
🖼️ Images & Media (6)
More to explore
✨ What else?
Related topics you might enjoy
🔬 Go deeper
More advanced topics to explore
🪜 Step back
Simpler topics to build understanding
What is Nepedia?
A free, ad-free encyclopedia for children. Every article is written at five reading levels, so the same page works for a five-year-old and a fifteen-year-old — use the level switcher above to see this one change. No account needed to read.