TRANSCRIPT
Looking UP into the sky, what's behind the clouds is the boundless, mysterious universe that we, as humans, still have many questions about.
And in order to figure out how the universe evolved, this group of Chinese scientists decide to look DOWN and go underground.
They have built a massive detector 700 metres underground in southern China, just to look for neutrinos, a TINY particle that can help answer questions of the BIG universe.
Cao Jun is the director of Institute of HIgh Energy Physics and deputy project manager of the Jiangmen Underground Neutrino Observatory, or JUNO.
He explains what on earth is a neutrino.
“So neutrinos is one of fundamental particles that consist our matter world. Because it barely interacts with other matters, so up to now it’s the least understood particle in our world. That’s why we need to study it. We highly suspect neutrino may associate with several long-existing puzzles in our universe.”
The existence of neutrinos was discovered almost a century ago, but currently, research about the particle is still its early stage.
So far, it's been found that neutrinos date back to 13.8 billion years ago, when the universe expanded from a single, tiny point with extremely high temperature and density.
Scientists have speculated that many particles were present during this period, which is better known as the 'Big Bang'.
But unlike other particles, neutrinos rarely interact with other particles, making them very difficult to detect, or measure.
And that's why scientists are now turning to this giant, underground detector in Kaiping, China for help.
Wang Yifang is the former director of the Institute of High Energy Physics, chief scientist and project manager of JUNO.
He explains how the detector will work.
“So we try to measure neutrino mass differences by using this detector to know which neutrino is heavier, which one is lighter. That’s neutrino mass hierarchy. Of course, we also hope that during the lifetime of this experiment, we can see a supernova explosion nearby and we can see many neutrinos coming from there and that we can have a much better understanding of neutrino properties and also the supernova explosion mechanism."
And this detector is very big - it took over nine years to build. It has to be underground to block cosmic rays and radiation from disrupting the neutrinos.
The orb-shaped detector is filled with a liquid designed to produce light when neutrinos pass through.
The machine will then study the opposite of neutrinos, the antineutrinos.
They are produced from the collisions inside the two nuclear power plants nearby.
When these antineutrinos come into contact with particles inside the detector, they will produce light.
André de Gouvêa, theoretical physicist at the Northwestern University, says then the detector will capture the light and analyse it.
“So it's a big sphere with some liquid scintillator inside, and the instrument, the surface of the sphere with these photon detectors. And what makes JUNO special is that there are a lot of these photon detectors. They cover the entire sphere in a way that we have not done before in any kind of experiment.”
The detector is expensive - it costs $300 million to build it.
Across the world, the United States and Japan are also building their neutrino detectors, expected to go online around 2027 and 2031.
They will cross-check the results and data from the Chinese detector, by using different approaches.
For scientists like Dr Cao, not only do they hope the detector can address the existing questions about neutrinos, but also lead them to new discovery.
“Neutrino mass ordering is our primary goal. But actually, for any scientist, the most exciting thing is (what) we don't know. We actually expect something we have not planned, something we have never imagined from the data. That’s a really exciting thing, (that is) we don't know where it comes from, but we expect that in the future we will have some unexpected discoveries.”
