“The Holy Ghost Particle” in the discovery of the neutrino and what is left to learn

Holy Spirit
Alan Chodos and James Riordan
MIT Press, $32.95

We live in a sea of ​​neutrinos. Second, trillions of them pass through our bodies. They come from the sun, nuclear reactors, cosmic ray collisions hitting the Earth’s atmosphere, even the Big Bang. Among the fundamental particles only photons are more numerous. But because neutrinos hardly interact with matter, they are notoriously difficult to detect.

The existence of neutrinos was first proposed in the 1930s and then verified in the 1950s.SN: 2/13/54). Decades later, much about neutrinos — so named in part because they have no electric charge — remains a mystery, including how many types of neutrinos exist, how much mass they have, where that mass comes from, and whether they have any magnetic properties.

These mysteries are in the heart Holy Spirit by Alan Chodos scientist and science journalist James Riordon. The book is an informative, easy-to-follow introduction to a complex subject. Chodos and Riordon guide readers through how the neutrino was discovered, what we know — and don’t know — about it, and the ongoing and future experiments that (fingers crossed) will provide answers.

It’s not just neutrino physicists waiting for those answers. Neutrinos, Riordon says, are “incredibly important to both understanding the universe and our existence in it.” Retrieving neutrinos could be the key to unlocking the nature of dark matter, for example. Or it could clear up the matter puzzle of the universe: the Big Bang must have produced pairs of matter and antimatter, opposite parts of electrons, protons, and so on. When matter and antimatter come into contact, they annihilate each other. So in theory, the world is free today – but it is not.SN: 9/22/22). It is full of matter, with very little antimatter for some reason.

Science News spoke with Riordon, a frequent user of the magazine, about these concerns and how neutrinos can act as a tool for observing the cosmos or even peering into our own planet. The following interview has been edited for length and clarity.

SN: In the first chapter about neutrinos, you list eight unanswerable questions. What is the most urgent to answer?

Riordan: Whether antiparticles are proper is probably among the largest. The proposition that neutrinos are proper antiparticles is an elegant solution to all kinds of questions about the existence of this residual matter. Figuring out how neutrinos fit into the standard model is another matter. [of particle physics]. It is one of the most successful theories, but it cannot explain why neutrinos have mass.

SN: Why is now a good time to write a book about neutrinos?

Riordan: All these questions about neutrinos seem to be coming to a head now – the implications that neutrinos can be antiparticles themselves, the questions about neutrinos not fitting well into the standard model, whether neutrinos are sterile. [a hypothetical neutrino that is a candidate for dark matter]. In the next few years, a decade or so, there will be many experiments [help answer these questions,] and resolution will excite both ways.

SN: Neutrinos have also been used to help scientists observe a range of phenomena. What are some of the most interesting questions neutrinos could help with?

Riordan: Some observations that simply have to do with neutrinos, there are no other technological conditions for them. There is a problem with using a telescope to look back in history. We have this really amazing James Webb Space Telescope that can really see far back in history. But at some point, when you go far back, the whole light is generally very dim; you cannot see in it. Once we were able to narrow down how to detect and how to measure the cosmic neutrino background [neutrinos that formed less than a second after the Big Bang]it will be a way to return to the beginning. Apart from gravitational waves, you can’t see much else. Thus the telescope will bring us back to the beginning of the world.

The other thing is, when a supernova happens, all kinds of really cool stuff happens inside, and you can see it with neutrinos, because the neutrinos come out immediately in a burst. We call it the “cosmic neutrino bomb”; but you can track the supernova along the way. With the light it takes time to come out [of the stellar explosion]. We are indebted to * [nearby] supernova Not one since 1987. The last supernova was visible in the sky and was a boon to research. Now that we have neutrino detectors around the world, the next one will be better [for research]He is also flattered.

And if we can develop better instruments, we can use neutrinos to understand what is going on at the center of the Earth. There is no other way to prove the center of the Earth. We use seismic waves, but the resolution is really low. So we could solve many questions about what a planet is made of neutrinos.

SN: Do you have a favorite “character” in the story of neutrinos?

Riordan: I am certainly very fond of my grandfather Clyde Cowan [he and Frederick Reines were the first physicists to detect neutrinos]. But Reines is a vain genius. He was a poet. He was a singer. This was truly a creative force. I said [in the book] they put the “SNEWS” code on their detector for “early supernova system”, which sounded like ballistic missile warning systems at the time. [during the Cold War]. It is so ripe.

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