The Nobel winner searching for deep-space neutrinos in Antarctica

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Flora Lichtman (1:03)

Hey, it's Flora, and you're listening to Science Friday.

This week is Nobel Prize week, and this year's prize in physics went to researcher Francis Halzen, quote, for decisive contributions to the IceCube Neutrino Observatory and the discovery of high-energy neutrinos of astrophysical origin. But way before all that excitement, back in 2013, Ira traveled to Madison, Wisconsin, and talked with Dr. Halzen about his work. And I think you'll enjoy the conversation. Here's Ira.

Ira Flatow (1:35)

Astronomers and astrophysicists have traditionally, for centuries, looked upwards to the sky to learn more about the universe. We've launched telescopes into space. We have sent probes beyond our solar system to study dark matter, colliding galaxies, how the planets formed. But there is a group of scientists that is turning its eyes downward. And I mean way down. They have built a telescope a mile deep into the ice at the South Pole.

Wow. What if you have to fix that? The Frozen Observatory is appropriately named IceCube. And it's not looking for your typical star stuff, but the elusive neutrino. What are neutrinos? Why build a telescope a mile deep in the Antarctic ice? Well, here is a man with all the answers. Francis Halzen is the Hildale and Gregory Bright Professor in the Physics Department, University of Wisconsin–Madison. Welcome to Science Friday.

What are neutrinos and why are we so interested in them?

Francis Halzen (2:39)

Well, I think your introduction was to the point. I mean, when we know of another way to look at the sky and at the universe, you know, we have never been able to resist it. And this was probably the hardest way to do it, and that made it a challenge. And so neutrinos you can think of, of just another way, another form of light. And we discovered them in 1956, and as they have no electric charge, they make beams just like light beams. And so we knew we could look at the sky with them. The only problem is that we collect light with our eyes and with a mirror.

Neutrinos come as elementary particles, and we know how to detect elementary particles. The only problem is that to actually look at the sky in an effective way, you had to build a kilometer-cube detector.

And this had never been done before. And so we took us about, since the idea to now, it took just half a century.

Ira Flatow (3:49)

Just half a century?

Francis Halzen (3:50)

Just half a century.

Ira Flatow (3:52)

Why do you build it a mile down beneath the ice, where it's absolutely dark, right?

Francis Halzen (3:57)

Well, as I said, it's a particle detector.

If we build it on the surface, in fact, it's not impossible, but it would be much more complicated, because the surface of the Earth is bombarded by cosmic rays, incredible numbers.

And you would have to find these neutrinos in this rain of cosmic rays, and it would be very challenging. If you go a mile deep, then you have to only find one neutrino in a million events that impersonate a neutrino. So your background is much lower. Most of the radiation that can impersonate a neutrino is shielded. And of course, the best way to shield the radiation that impersonates neutrinos is to detect them through the Earth. So our favorite way to look at the universe at the South Pole is to look at the sky above Madison.

Ira Flatow (4:56)

Oh, it's focused at Madison? The other end of the telescope looks at Madison from the South Pole?

Francis Halzen (5:04)

That's our favorite direction.

Ira Flatow (5:07)

Well, you've come to the right place there. Neutrinos are really tiny, aren't they? They go through just about everything, don't they?

Francis Halzen (5:15)

They are just like light.