Monday, November 22, 2010

Trapping Anti-Matter - How Does that Work?

Last week scientists at the CERN laboratory in Switzerland somehow managed to trap atoms of anti-matter for the first time in history. All of you Star Trek fans probably know that the Starship Enterprise used something called a matter/anti-matter drive as an engine - or some such nonsense.

According to one of the articles, there was also something about a plot to blow up the Vatican with antimatter in one of the Dan Brown books/movies - I'm sure that was accurate .

Anyway, this all sounds pretty cool. Two versions of the story - one from Big Think, and one from NPR. First up, a piece from Big Think, by physicist Michio Kaku.

Scientists at CERN laboratory in Switzerland scored a major breakthough recently when they trapped atoms of anti-matter for the first time in history. Fans of Star Trek know the potential implications of this achievement, since the Starship Enterprise uses matter/anti-matter annihilation to drive its engines. Maybe one day, we might be able to use anti-matter engines to take us to the stars.

A detail of the trap used to combine positrons and antiprotons to create antimatter atoms. Photograph courtesy Niels Madsen, ALPHA/Swansea/CERN

(Sean Gallup/Getty Images) Rolf-Dieter Heuer, the director of CERN, the European Organization for Nuclear Research, poses in front of a giant photograph of the CMS detector of the Large Hadron Collider (LHC) at the 'Weltmaschine' ('World Machine') exhibition on October 14, 2008 in Berlin, Germany

The advantage of using anti-matter is that it is potentially 100 times more powerful than an ordinary H-bomb. Nuclear bombs are only 1% efficient in converting mass to energy (via Einstein's famous equation). But anti-matter, when in contact with matter, yields a 100% efficient conversion of mass to energy. In principle, it is the greatest energy source in the universe.

Anti-matter was first predicted by physicist Paul Dirac, who won the Nobel Prize for it in 1933. It resembles ordinary matter, except it has the opposite charge. So an anti-electron has positive charge, and an anti-proton has negative charge. (Anti-electrons can be produced via radioactive decay. In fact, when I was in high school, I built a detector which photographed tracks of anti-matter. Later, I designed an atom smasher, whose purpose was to produce a beam of anti-matter). Watch a clip from my Big Think Interview speaking about my atom smasher. Anti-hydrogen, produced at CERN, has an anti-electron revolving around an anti-proton.

Anti-atoms at CERN were first produced back in 1995, but they only lived briefly before they annihilated with ordinary atoms. This time, physicists at CERN were able to trap 38 anti-hydrogen atoms (in a combination of magnetic and electric fields) for about 1/10 of a second, a remarkable achievement. It will take many, many decades or longer to produce large quantities of stable anti-matter, however. (In the movie "Angels and Demons," Tom Hanks has to stop terrorists who stole anti-matter from CERN and want to use it blow up the Vatican. Only a gram would be enough to blow up most of Rome, but producing a gram of anti-matter is way beyond our capability. It would bankrupt the U.S. to do so.)

Symbologist Robert Langdon (Tom Hanks) attempting to difuse the anti-matter bomb in the movie Angels and Demons.

So although the recent achievement at CERN was a milestone, it may take many decades to centuries before we can harness the full power of anti-matter. (This time period may be shortened if we find an anti-matter meteorite in outer space.) But Star Trek takes place in the 23rd century—so we still have plenty of time.

This slightly more serious interview is from NPR's Science Friday:

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?


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.

Professor JEFFREY HANGST (Aarhus University): 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?

Prof. 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?

Prof. 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?

Prof. 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?

Prof. 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?

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

(Soundbite of laughter)

FLATOW: You'd have to shoot me then.

Prof. 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?

Prof. 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?

Prof. 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.

Prof. 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?

Prof. 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?

Prof. 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?

Prof. HANGST: Very slowly.

(Soundbite of laughter)

Prof. 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.

Prof. 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.

Prof. 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...

Prof. 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.

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

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

Prof. HANGST: Thanks very much.

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

Prof. HANGST: Hey, it's my pleasure.

FLATOW: And...

Prof. 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.

Prof. HANGST: Okay. Thank you very much.

FLATOW: Thank you.

Prof. 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.

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

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