• Question: Neutrinos… so they are a subatomic particle, but they aren’t one of the particles that make up atoms, is that right? How would you explain to a child, who has a basic understanding of protons, neutrons and electrons, what neutrinos are?

    Asked by Katie S to Susan, Scott, Savannah, Philippe on 7 Nov 2019.
    • Photo: Susan Cartwright

      Susan Cartwright answered on 7 Nov 2019:

      They don’t make up atoms, correct, though they are emitted in radioactive beta decay.
      I would say that neutrinos are like electrons, but with the electric charge taken away. Because the charge has been taken away, neutrinos find it very hard to interact with other particles, as most of the interactions that we see around us are related to electric charge. Therefore, a typical neutrino will go through almost anything without even noticing: 65 billion neutrinos from the Sun go through your thumbnail every second, but you will never notice! They also have even less mass than an electron: an electron weights only 1/1800 as much as a proton, but the neutrino probably weighs only a millionth as much as an electron!
      However, even though they are so small and so hard to detect, neutrinos are very important, because the nuclear reactions that allow the Sun to shine would not be able to happen without neutrinos.

Comments

  • Photo: Harrison

    Harrison commented on :

    Neutrinos are wonderful things as Susan explained. The most wonderful thing about them is how weakly they interact with matter. The 65 billion neutrinos per second that go through every square centimeter of your body were created a mere 500 second ago in the Sun’s core. Consequently, unlike light, neutrinos allow us to “see” the Sun’s core directly. The light that powers the Earth’s ecosystem is also created in the Sun’s core, but, because the light is constantly colliding with charged particles as it makes its way to the Sun’s photosphere and then on into space, it takes the light about a million years to reach the photosphere by which time, of course, it has lost almost all the information it once contained about the core. But the neutrinos from the Sun maintain the information they have about the Sun’s core. Moreover, the mere fact that the Sun emits neutrinos is a satisfying confirmation of the nuclear theory that describes the nuclear fusion reactions in the Sun’s core. These reactions convert four protons into one nucleus of helium and in the process produces light (photons) and neutrinos. But, alas, the very thing that makes neutrinos a wonderful solar messenger is the thing that makes neutrinos fiendishly difficult to detect.