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2 Scientists Win 2015 Nobel Prize In Physics


This is Nobel Prize season, and this morning comes the prize in physics. Joining me in the studio is NPR science correspondent Geoff Brumfiel. Geoff, good morning.


GREENE: All right, so who won?

BRUMFIEL: It was Takaaki Kajita of Japan and Arthur McDonald of Canada. And they won for experiments they led on tiny particles known as neutrinos. Specifically, they won for discovering that the neutrinos have mass.

GREENE: OK, before we get to neutrinos having mass, you've got to tell us first what are neutrinos exactly?

BRUMFIEL: Right, for those not in the know.

GREENE: For those not in the know, including myself.

BRUMFIEL: (Laughter) So neutrinos are these very small particles. They're all around us. In fact, billions are going through our bodies right now while we're talking.

GREENE: Did you say billions...

BRUMFIEL: Billions.

GREENE: ...Passing through our bodies as we speak here?

BRUMFIEL: Yes, there are a quite a few them...

GREENE: That is strange.

BRUMFIEL: Yes, it is strange. The reason you don't know about them is because they are very rarely interacting. In fact, most neutrinos pass through the entire Earth without even seeing them - seeing it. They come from nuclear reactions. So most of the ones we see around us come from the sun, which is this big nuclear fusion reactor, actually. And because they don't interact, people didn't even know about them until the mid-1950s, I think.

GREENE: Well, OK, if they're this tiny, I mean, can researchers actually see them and know that they're there, know where they are?

BRUMFIEL: Yeah, they can see them. It takes an awful lot of work. What they do is they build these giant detectors. They put them way underground, usually in abandoned mines because they don't want any other radiation to foil their detections, and then they just wait. And every now and then, neutrinos interact with these detectors and produce little flashes of light. They can see this light, and that's how they know they're there. Now, there are actually three types of neutrinos, and that's what led to today's prize. When they started looking at specific types, they saw fewer of certain types than they expected. There weren't as many. And that meant that the neutrinos were changing from one type to another, they realized. As a result of that, according to the laws of physics, neutrinos must have mass, like you and I.

GREENE: They must have mass. So these scientists have discovered that they definitely do have mass. Now that we've established what neutrinos are and that they're everywhere around us, why is it important to actually figure out that they do have mass?

BRUMFIEL: Right, exactly, like, so what?

GREENE: Right.

BRUMFIEL: (Laughter) Well, for that, you have to know about something called the Standard Model of particle physics...


BRUMFIEL: ...Which is this giant framework that physicists use to predict everything about the universe. It basically explains all particles out there. The Standard Model's pretty much an airtight theory. It's right about everything, and it sort of suggested that neutrinos wouldn't have mass. It suggested that they would be more like particles of light, which are massless. So this is an example of something that was completely unexpected and unpredicted. And there's a lot we still don't know about the universe. So now researchers are studying neutrinos more. They're hoping that by looking at them and trying to figure out how much mass they have, which they still don't know exactly, and why, they can really unpick some of the bigger mysteries out there.

GREENE: So lots of mysteries left. I mean, this is not the end of this here.

BRUMFIEL: No, this is the start. And I think that's why it won the prize.

GREENE: Which is the beauty of science, I guess.


GREENE: All right, we have been in physics class this morning with NPR science correspondent Geoff Brumfiel. Geoff, thanks a lot.

BRUMFIEL: Thank you. Transcript provided by NPR, Copyright NPR.

Geoff Brumfiel works as a senior editor and correspondent on NPR's science desk. His editing duties include science and space, while his reporting focuses on the intersection of science and national security.