Want to know the fate of the universe? Dig a hole. That’s what physicists hope to do with the Indian Neutrino Observatory (INO) — an underground laboratory for large neutrino experiments located at a depth of nearly 2,000 ft in Ooty.
Neutrinos are sub-atomic particles like protons, neutrons, and electrons that make up all matter. But unlike them, neutrinos have no electrical charge, and almost no mass. This makes them as close to nothing as anything can get! Physicist Enrico Fermi coined their name (Italian for ‘little neutral ones’) in 1934. Neutrinos seldom interact with ordinary matter, pouring right through Earth as if it wasn’t there. As you read this, six trillion neutrinos are passing through your body at nearly the speed of light every second!
Neutrinos are produced in nuclear fusion that powers the Sun and other stars, while their antimatter equivalent, or anti-neutrinos, are created in fission reactions (as in nuclear power plants). Most are leftovers from the Big Bang, while others have their high-energy origins near black holes, inside gamma-ray bursts and supernovas, and within the Sun’s core. But neutrino detectors have ‘spotted’ only one-third of these particles that theory predicts. This is because the elusive particles simply change into different types, or ‘flavours’, called electron neutrinos, muon neutrinos, and tau neutrinos, each with its matter and antimatter forms.
When you add up the mass of all the visible matter in the universe, the total is too small to explain how large structures like the galaxies formed. So astronomers reckon 90 per cent of the universe is made up of ‘dark matter’, which we can’t ‘see’ but which nevertheless exerts a gravitational pull because of its mass.
If detectors like the INO determine the amount of mass neutrinos possess, it could join the dots. For even if each neutrino’s mass is negligible, they are so numerous as to have enough mass to resolve an even bigger question: will the universe expand forever, or does it have sufficient mass to eventually stop expanding and collapse in a Big Crunch — just as it began in a Big Bang? In the ‘nothingness’ of neutrinos lies the answer.