Locking Up Antimatter

Scientists at CERN, the European nuclear research facility, say they have produced and trapped molecules of antihydrogen, a form of antimatter. Physicist Jeffrey Hangst explains how they were made and captured. Will trapping antimatter help scientists learn about the construction of the universe?

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IRA FLATOW, Host:

Up next, on the trail of the elusive antimatter.

(SOUNDBITE OF MOVIE, "ANGELS AND DEMONS")

Unidentified Man (Actor): (as character) We have a signal on the (unintelligible) monitors. We have events.

FLATOW: Remember that scene from "Angels and Demons"? It showed scientists at CERN running experiments with a Large Hadron Collider and capturing antimatter in a bottle? Well, this week scientists at CERN - real scientists and not the movie variety - announced the same thing almost. They say they have finally produced and captured antimatter - antihydrogen, exactly - long enough to study it, not a very long time, though, it's about a second, but it doesn't last long enough to be captured in a vial like in the movie, so they didn't get that part down yet.

Here to tell us how they did it and what the physicists hope to learn from this antihydrogen is my guest Jeffrey Hangst. He's professor in the Department of Astronomy and Physics at Aarhus, the university in Denmark. And he joins us from Switzerland. Welcome to SCIENCE FRIDAY.

JEFFREY HANGST: Thank you very much. Although, I think it's going to be hard to follow that oboe stuff.

(SOUNDBITE OF LAUGHTER)

FLATOW: You mean antimatter is not sexy enough to follow an oboe made out of a straw. I think it is. How were you able to capture antimatter?

HANGST: Okay. We have kind of a magnetic trap. Antihydrogen is neutral, so it has no net charge. So you can't trap it the way we normally trap charged particles. It has a little magnetic character, like a little compass needle that flies around with the atom. So it can be deflected by very strong magnetic fields. And what we did here was we created the antihydrogen atom in the magnetic trap. So that if it was cold enough or moving slowly enough, it didn't escape this magnetic bottle.

FLATOW: Hmm. And how many atoms were you able to capture?

HANGST: Well, in this article we reported 38 as a proof of principle. This was the first signal that we saw, so of course we report the signal as soon as it comes because we've been working a long time to see anything at all. So this is a proof of principle experiment, but we're making steady progress since then.

FLATOW: Now, what is the difference between antihydrogen and the real or the regular hydrogen we see around us?

HANGST: That's exactly the question that we'd like to answer. The laws of physics say that hydrogen and antihydrogen should behave in the same way. The problem is that nature chose to only give us matter. You know, people think at the Big Bang there were equal quantities of matter and antimatter, but for some reason the antimatter has disappeared. It's like nature took a left turn instead of a right turn and chose matter. So we don't know what happened to the antimatter. So we'd like to study and see if there's some fundamental difference between the two that the current laws of physics have overlooked.

FLATOW: Hmm. And you were able to capture it for one second. Is that - and you say this is a proof of concept. Does that mean that theoretically you can capture it for a longer amount of time?

HANGST: Not just theoretically. The antimatter didn't escape in this experiment. We threw it out. The way we show that we've trapped it, we have to first trap it and then release it intentionally. The thing about antimatter is that when it meets matter it annihilates it. It makes a little microscopic explosion that we're very good at detecting. So the way that you show that you've trapped antihydrogen is to intentionally let it go at a given time. So the time that we stored the antimatter for in that experiment was by choice, not by some limit. We've already succeeded in storing it for much, much longer times.

FLATOW: How much longer?

HANGST: I can't tell you because we...

(SOUNDBITE OF LAUGHTER)

FLATOW: You'd have to shoot me then.

HANGST: Yeah. It's not like that. It's just that we don't quote published numbers. But I usually say it's a number that you could measure with a watch. Okay?

FLATOW: Okay. And when you say - well, isn't it there - we always see in the movies and we hear, you know, what happens when antimatter annihilates with matter is there's huge explosion. Wasn't there a huge explosion or danger one?

HANGST: But - on the microscopic level, it's a huge explosion. But the amount of energy from a few atoms is completely negligible. In fact, the total amount of antimatter produced at CERN in all of its history would barely boil your coffee. And so the - for us, it's easy to detect but it's of absolutely no danger to anyone anywhere. I usually say it would take longer than the age of the universe to create just one gram of antimatter. So you don't need to worry about that.

FLATOW: Yeah. And now, what practical value comes out of this work?

HANGST: Absolutely none. This is basic research at the most fundamental level. We're asking about, what's the structure of space and time? Can we learn something about what we usually refer to as symmetry in nature? Is there a difference between left and right? What happens if time runs backwards? Is there a difference between matter and antimatter? You can actually get paid for trying to answer those questions.

FLATOW: And we think you should, actually.

HANGST: Yes.

FLATOW: But everything has to have a, you know, discernible - who knows, somewhere down the line, there might be - was it "Star Trek" where they have antimatter running in their engines there?

HANGST: Yeah, that's true. I don't know where they found that. But if you found some antimatter, okay, first you should keep it at a safe distance. But then you could consider it as an energy source. The problem is that if you try to make antimatter in the laboratory, it requires much, much more energy than you would ever get out of it. It's a complete loser as an energy source. So that's really science fiction.

FLATOW: Hmm. But it's also a kind of science fictiony(ph) but fact to think that if there was equal amounts of matter and antimatter at the Big Bang, where did it all go?

HANGST: Yeah. But I'm not sure that our experiment will ever address that question. We're interested more in: Do the laws of physics be applied in the same way to matter and antimatter?

There are other experiments at CERN that are trying to address that question more directly. Those are at the LHC. Our experiment doesn't use the LHC in any way, in contrary to what you've seen in Dan Brown's films and movies. We work at a low energy accelerator.

In fact, CERN has the only accelerator in the world that works in reverse. We actually slow the antiprotons down. We need to have them at very low energy, very cold, in order to make them and hold on to them.

FLATOW: And how did you actually make this antimatter?

HANGST: Very slowly.

(SOUNDBITE OF LAUGHTER)

HANGST: What you do is you take the components of the antihydrogen atom. Okay. We start with hydrogen, because that's the simplest atom. Everybody remembers from high school, hopefully, it has a proton and a nucleus with a positive charge, and an electron negatively charged orbiting around it. That's the normal atom cartoon that we all see.

FLATOW: Right.

HANGST: So antihydrogen is the identical but opposite. So the antiproton has a negative charge and is in the center of the atom. And the positron, or anti-electron, is the thing doing the orbiting. We're at CERN because they provide us with antiprotons. We have to make those in the accelerator. And this is where Mr. Einstein comes in, E=MC2. What CERN does is use E, energy, to make M, mass, right?

FLATOW: Right.

HANGST: So we use energy to produce mass. And here's the curious thing. When you do that, you always make equal amounts of matter and antimatter. In the laboratory, if you produce an antiproton, you produce a proton at the same time. That seems to be a fundamental law. And that's why we're confused about the beginning of the universe.

So we make this stuff within the big accelerator and then slow it down. We want it at really cold temperatures when we combine antiprotons and positrons to make antihydrogen atoms.

FLATOW: Quite fascinating. And so, then you sort of recycle it when you're done with it, right? Getting - and so you - this could have been done years ago, do you think? Or just people...

HANGST: No, no, no. We've been working on this steadily since the - well, the history of the field goes to the late '80s. And there's been no pause or let up in the attempt to get this far. The last big breakthrough was in 2002.

There's another experiment that we had called ATHENA, where we actually produced a lot of antihydrogen atoms for the first time. So we've been producing them for the last eight years. It's only now that we've learned how to hold on to them so they don't run off and annihilate.

FLATOW: So you caught lightning in a bottle.

HANGST: That's a good way to look at it, yes.

FLATOW: Yeah. Well, we want to wish you good luck.

HANGST: Thanks very much.

FLATOW: And thank you for taking time to be with us.

HANGST: Hey, it's my pleasure.

FLATOW: And...

HANGST: And thank you for your interest.

FLATOW: Yeah, because we're very interested in this topic. And we'll check in with you when the research continues.

HANGST: Okay. Thank you very much.

FLATOW: Thank you.

HANGST: Okay.

FLATOW: We were talking about antimatter being caught in a bottle at CERN with Jeffrey Hangst, at - professor in Department of Astronomy and Physics at Aarhus University in Denmark, but he was in Switzerland when we were talking about him.

(SOUNDBITE OF MUSIC)

FLATOW: A quick note to mark the passing of astronomer Dr. Brian Marsden, supervisor of astronomy at The Smithsonian Physical Observatory and director emeritus of the Minor Planet Center, frequent guest on the program. Dr. Marsden was known for his expertise in identifying comets.

(SOUNDBITE OF ARCHIVED AUDIO)

BRIAN MARSDEN: Comets are a dirty snowball or a snowy dirt ball, if you want to call it that. As the ice vaporizes and turns to gas, it releases this dust. Some of the dust sticks around with some of that gas around...

FLATOW: And he was on our program back in 1994, talking about comets. He was an expert on that. He also was warning us to keep our eyes watching out for asteroids that might collide with the Earth. He was also, well you might remember, one of the first to call for the demotion of Pluto out of the family of planets. But none of his scientific work, I don't think, would have received the widespread attention that it deserved if he had not been such a vocal and visible scientist, and someone who was always eager to come on SCIENCE FRIDAY and talk to the public whenever he could.

Brian Marsden, dead at the age of 73 after a long illness.

I'm Ira Flatow. This is SCIENCE FRIDAY from NPR.

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