To solve mysteries, scientists look to muons

I don’t usually sit at my desk thinking, “Hmm, a muon just flew through my thumbnail.” But now I know that these subatomic particles from the upper atmosphere do just that.

And thanks to this issue’s cover story, I also know that muons are so good at tunneling through objects that scientists are using them to make discoveries on Earth.

Muons aren’t a big deal in everyday life. These “awkward cousins of electrons,” as physics senior writer Emily Conover describes them, don’t play a key role in making atoms. But by tracking muons as they barge ahead, researchers can detect what’s inside otherwise impenetrable objects. The process, known as muography, is a bit like taking an X-ray or a CT scan, but with naturally occurring subatomic particles. Conover explains how tracking muons’ paths has revealed a secret chamber in the Great Pyramid of Giza and the plumbing of some volcanoes. Researchers hope these new pictures of volcanoes will help them more accurately predict eruptions.

As journalists, we tend to pay more attention to big scientific discoveries, so I was curious as to how Conover decided that it was time Science News paid attention to these arcane particles. Like all our reporters, she spends a lot of time digging through research journals to learn what’s new and sniff out trends. “If you see one paper in a journal you say, ‘Huh, there’s something cool happening in muography.’ Then you see another one and think, maybe this is the right time to write about it.”

Physicists are increasingly interested in studying muons, but what really grabbed Conover’s attention is how researchers are using muons as tools in other fields of science, including geology and archaeology. Muons are even being tested to see if they can help customs officials detect smuggled goods. “It’s so fun and interesting to learn about,” Conover says.

She is no stranger to subatomic particles, having studied neutrinos for her Ph.D. in particle physics. “For a lot of physics experiments, muons are kind of a pesky nuisance,” Conover says. “If you’re looking for something that’s rare or difficult to spot, muons can get in the way.” Her research involved building a muon detector to filter out the pesky particles. And many physics experiments are built deep underground, where the ground above muffles muons.

Rather than shunning muons as annoying uninvited guests, scientists are beginning to appreciate their humble virtues. Conover is one of them. “I’m personally familiar with muons being a nuisance, but it didn’t make me dislike them,” she says. “It made me respect them. They’re everywhere. And you can learn something from all the different particles, whatever they may be.”

This issue also marks a major scientific milestone: the first complete scan of a human genome. You may be wondering, wasn’t this announced back in 2003, when the Human Genome Project wrapped up? Yes, kinda. That epic project had to skip some key bits of DNA due to technological limitations. Better technology now means 3,604 more genes to explore, some of which play key roles in assembling the human brain and may help reveal how we evolved differently than other apes.

Nancy Shute is editor in chief of Science News Media Group. Previously, she was an editor at NPR and US News & World Report, and a contributor to National Geographic and Scientific American. She is a past president of the National Association of Science Writers.