This flash is far too faint for your eyes to see. That rare interaction may generate a tiny flash of light or leave some free electrical charge. But occasionally, very rarely, like once every ten-million trillion times, a neutrino will strike one of the atoms that make up a water molecule. Most of these mysterious particles move right through without making a sound or leaving a trace. If you place a glass of water on a table, a trillion neutrinos will pass through every second. Neutrinos rarely interact with ordinary matter, so they are very hard to detect. Neutrinos may even help us understand what was going on when our universe first formed nearly 14 billion years ago! How to Catch a Ghostlike Particle But because neutrinos carry information about what is happening inside the hearts of stars and galaxies, scientists want to know a lot more about them. In that way, they seem a bit like ghosts-there, and yet invisible. They stream from the sun and outer space and pass right through ordinary matter-even our own bodies and Earth itself-without us ever knowing. No matter what their source, neutrinos are completely harmless because they do not stick together or interact with much of anything. Credit: Tiffany Bowman, Brookhaven National Laboratory. Understanding the behavior of neutrinos may help reveal important secrets of the universe.Figure 1 - Decay of a radioactive atom, potassium-40-which is found in bananas and has 40 protons (p) and neutrons (n) in its nucleus-into calcium-40, plus an electron (e –) and a neutral “ghostlike” messenger particle called a neutrino (Greek letter: ν, pronounced “nu”).But far more neutrinos come from the nuclear reactions in the sun than from any other source. Minerals in rocks and even potassium in bananas decay to produce neutrinos (see Figure 1). Such radioactive decay happens all around us. They are emitted when unstable atomic nuclei decay. Neutrinos are very light particles with no electric charge. When scientists decode the messages, they learn about the connection between neutrinos and the makeup and history of the stars, galaxies, and the universe. These giant detectors are helping scientists to pick up the “messages” that these ghostlike particles carry. The matter that makes up Earth helps shield out signals from other particles, so that the signals of neutrinos’ rare interactions stand a chance of being detected. To “see” neutrinos, scientists build really big, sensitive detectors, often deep underground. But unlike the sunlight we see and feel on our faces, these ghostlike particles do not often interact with ordinary materials. Trillions of them pass through us every second without leaving a trace! They mostly come from the nuclear reactions that power our sun. Neutrinos are tiny, subatomic particles that seem almost like ghosts. In this article you will learn how these giant detectors can help decode the “messages” these ghostlike particles deliver about the makeup and history of the stars, galaxies, and the universe. Scientists do that by building neutrino detectors deep underground. To “see” them, we have to build really big detectors and block out signals from any other particles. But unlike the sunlight we can easily see, neutrinos are very hard to detect. Billions of them pass through us every second-mostly coming from our sun.
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