‘Ghost Particles’ Tell the Story of What’s Left to Discover and Learn from the Neutrino

ghost particle
Alan Chodos and James Riordan
MIT Press, $32.95

We live in a sea of ​​neutrinos. Every second, trillions of them pass through our bodies. They come from collisions with the Sun, nuclear reactors, cosmic rays hitting Earth’s atmosphere, even the Big Bang. Of the fundamental particles, only photons are in excess. Yet because neutrinos rarely interact with matter, they are extremely 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 the neutrino — so named partly because it has no electric charge — remains a mystery, including how many types of neutrino exist, how much mass they have, where that mass comes from and so on. Do they have any magnetic properties?

they lie at the heart of the mystery ghost particle By physicist Alan Chodos and science journalist James Riordan. The book is an informative, easy to follow introduction to the complex particle. Chodos and Riordan guide readers to how the neutrino was discovered, what we know — and don’t know — about it and the ongoing and future experiments that will (fingers crossed) provide answers.

It’s not just neutrino physicists who are waiting for those answers. Neutrinos, Riordan says, “are incredibly important to understanding the universe and our existence in it.” For example, unmasking neutrinos could be the key to unlocking the nature of dark matter. Or it could clear up the nitty-gritty of the matter of the universe: The Big Bang should have produced equal amounts of matter and oppositely charged counterparts of antimatter, electrons, protons, and so on. When matter and antimatter come in contact, they annihilate each other. So in theory, the universe must be empty today – it is not yet (Sn: 9/22/22, It’s full of matter and, for some reason, very little antimatter.

science news talked to Riordan, a frequent contributor to the journal, about these puzzles and how neutrinos could act as a tool to observe the universe or even look into our own planet. The following conversation has been edited for length and clarity.

Sn: In the first chapter, you list eight unanswered questions about neutrinos. Who is most under pressure to answer?

Riordan: Whether they are their own antimatter is probably one of the grandest. The proposal that neutrinos are their own antiparticles is an elegant solution to all kinds of problems, including the existence of remnants of the matter we live in. Another is figuring out how neutrinos fit into the Standard Model. [of particle physics], It is one of the most successful theories, but it cannot explain the fact that neutrinos have mass.

Sn: Why is this a good time to write a book about neutrinos?

Riordan: All these questions about neutrinos are kind of coming to a head right now – hints that neutrinos may be their own antiparticles, issues of neutrinos not quite fitting the Standard Model, whether there are sterile neutrinos [a hypothetical neutrino that is a candidate for dark matter], in the next few years, a decade or so, there will be a lot of experiments that will [help answer these questions,] And the resolution will be exciting either way.

Sn: Neutrinos can also be used to help scientists observe a wide variety of phenomena. Which of the most interesting questions can neutrinos help with?

Riordan: There are some observations that have to be made only with neutrinos, for which there are no other technical alternatives. There’s a problem with using light-based telescopes to look back in history. it’s really amazing we have james webb space telescope Which can actually be traced very far back in history. But at some point, when you go back far enough, the universe is basically opaque to light; You can’t see in it. Once we nail down how to detect and measure the cosmic neutrino background [neutrinos that formed less than a second after the Big Bang], This would be a way of looking back at the beginning. Apart from gravitational waves, you can’t see anything else that far back. So this would give us a kind of telescope to the beginning of the universe.

The other thing is that when a supernova happens, there’s all kinds of really cool stuff inside, and you can see it with neutrinos because neutrinos get ripped off immediately. We call this a “cosmic neutrino bomb”, but you can track the supernova as it’s going along. With the light, it just takes a while to get out [of the stellar explosion], we are due to a [nearby] Supernova. we haven’t had one since 1987, this was it last visible supernova in the sky And it was a boon for research. Now That We Have Neutrino Detectors Around The World, This Next One Is Going To Be Even Better [for research]even more exciting.

And if we develop better instruments, we can use neutrinos to understand what’s happening at the center of the Earth. There is no other way you can probe the center of the Earth. We use seismic waves, but the resolution is really low. So we can solve a lot of questions about what the planets are made of with neutrinos.

Sn: Do you have a favorite “character” in the Neutrino story?

Riordan: I definitely adore my grandfather Clyde Cowan [he and Frederick Reines were the first physicists to detect neutrinos], But Reines is an interesting character. He was poetic. He was a singer. He really was this creative force. I mentioned [in the book] That he put this “SNEWS” sign on his detector for the “Supernova Early Warning System”, which was like a ballistic missile early warning system at the time. [during the Cold War], That’s so ripe.

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