Particle Smasher Is Fired Up (Again)

After being down for more than a year for repairs, the Large Hadron Collider at CERN is running again. Physicist Drew Baden explains what went wrong with the Collider, how it was fixed, and what scientists are hoping to find by smashing beams of particles into each other.

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JOE PALCA, host:

This is SCIENCE FRIDAY from NPR News. I'm Joe Palca, sitting in for Ira Flatow.

Well, it's an exciting time for particle physicists these days. That's because they fired up the Large Hadron Collider again. The LHC is the world's most powerful particle collider. Last week, it achieved the first collisions between the two beams of protons, and this week, they set the record for the most energetic proton beams, passing Fermi Labs' previous record. And they've actually had some collisions. That's good.

Joining me now to talk more about what's next for the collider is my gust, Drew Baden. He's a professor and chairman of the physics department at the University of Maryland in College Park. Welcome to SCIENCE FRIDAY.

Mr. DREW BADEN (Chairman, Professor, Physics Department, University of Maryland in College Park): Thank you.

PALCA: And if you want to give us a call while we're talking about the LHC, our number is 800-989-8255. That's 800-989-TALK. If you're on Twitter, you can tweet us with your questions by writing to the @ sign, followed by scifri, and if you want more information about what we'll be talking about this hour, go to our Web site at www.sciencefriday.com, where you'll find links to our topic.

So Drew Baden, for those of us, or those of our listeners who have sort of forgotten about the LHC, give us a little primer on what it's all about.

Mr. BADEN: Well, it's all about basic science and doing experiments that try to figure out what the universe was like about a trillionth of a second or so right after the Big Bang, and it's been going on since people split the atom.

PALCA: You mean this idea of banging things into each other.

Mr. BADEN: Yeah, and trying to figure out what are the fundamental particles, what are their interactions, why the world is the way it is.

PALCA: And remind us where LHC is and how big it is and what keeps the protons spinning around in a circle.

Mr. BADEN: So the LHC is built at - it's a large, European physics lab called CERN. That's the European acronym, Center for European Research Nuclear. And it's right in the corner of Switzerland, straddling the border between Switzerland and France, right outside Geneva. And it's - so it's at the base of the Jura Mountains, which are a little north and west of the city. And the lab there has been - was built in the '50s, and it's a fairly decent-sized lab with decent-sized accelerators that have gotten bigger and bigger over time.

PALCA: Right, and it's got this big ring that goes across the border, 17 miles in diameter, I understand.

Mr. BADEN: Actually, it's 17 miles in circumference.

PALCA: Circumference.

Mr. BADEN: Yeah, and that's right. It's too big to be on site at the lab. So it's deep underground and straddles the border, and it's between the mountains and the lake on the plains there. And it's - the whole thing sits in a plain. It's perfectly - the ring defines a plane as perfectly flat, and it's underground about 100 meters here, 100 meters there, maybe a little bit.

PALCA: Right.

Mr. BADEN: But so it's deep underground.

PALCA: Right, and so the idea is to take these two beams going in opposite directions around this ring, and in about eight different spots around the ring, you can bring them together so they head-on collision into one another. And then there are these detectors that look at the collisions and decide what they're seeing.

Mr. BADEN: That's right, that's right.

PALCA: And it was supposed to start last year. What happened?

Mr. BADEN: Well, what happened, you know, is Murphy's Law�

(Soundbite of laughter)

Mr. BADEN: �a little bit - maybe a little bit worse than Murphy's Law. But they were commissioning for - they were doing the very first stages of commissioning, where you put a beam through - it's like threading a thread through a million needles, you know, to get the beam to go all the way around. And they were threading it, and then they needed to stop. A power supply needed to be replaced or something like that, and they said, well, while we're waiting for the power supply, why don't we check out some of our magnets at high fields, which is what you need to do to accelerate at high energies, at very high energies. And oops, all of a sudden they found a problem. It blew up one of the magnet - the connections to the magnets blew up when they were testing it.

PALCA: By blew up, you mean it didn't actually explode, but it sort of stopped working.

Mr. BADEN: Right. It didn't explode, but what happened was that, you know, you put a lot of current through something, it heats up, they're superconducting. There's super-cooled helium. The helium gets hot, and it turns into a gas, and that sort of explodes.

PALCA: Yeah, all right.

Mr. BADEN: It caused a lot of collateral damage, a lot of dirt in the beam pipes, a lot of magnets had to be replaced and a lot of hang-wringing and soul-searching for, you know, is this a problem? Is this going to be a problem later on? And that's what took a year, is to go back and take a look at all of the, you know, phenomenally complex device - if you can call it a device - and you know, to - you don't want this to happen again.

PALCA: Right.

Mr. BADEN: And so they took a long, hard look. They found a few other problems. They took their time - better safe than sorry.

PALCA: Yeah, now you're a part of this experiment. I mean, so I said physicists are excited. Are you excited? Is this an exciting time?

Mr. BADEN: Oh, absolutely.

PALCA: Are you heading over there?

Mr. BADEN: Yeah, in fact when I hang up, I'm going to catch a cab to Dulles Airport, and I'll be there tomorrow morning - well, for me tomorrow morning. For you, it'll be - I guess I arrive around 2 a.m.

PALCA: Yeah, yeah, yeah. And�

Mr. BADEN: And I go right to work.

PALCA: And okay, so here's one of the problems with describing the results of what you're going to get from CERN because you said that we're going to be able to get some idea of the conditions a few milliseconds after the Big Bang, but it's really, really hard for the public, I think, to understand what that means and why you need this 17-mile-circumference ring to smash protons together.

Mr. BADEN: Right.

PALCA: So you know, give it one more shot.

Mr. BADEN: Well, I can give it a try.

PALCA: Okay.

Mr. BADEN: And so you have to start at the beginning, and at the beginning, the universe was very, very tiny volume, I don't know, the size of a pea, maybe the size of an atom. I mean, all - it's not like�

PALCA: Everything. Everything was - okay, okay.

Mr. BADEN: �all the mass of the universe was in a small volume. The whole universe and everything in it was compacted, and that's quantum mechanically unstable, and it started expanding. And it expanded at a pretty furious rate, but all the matter and the energy in the universe occupies that whatever volume is in the universe, and as it expands, like any gas that expands, it cools down. It's got a bigger volume to hang out in, and it cools down.

And as it cools down, like any collections of molecules, any gas, it goes through phase changes. And the name of the game is to figure out where are these phase changes and what's happening in between the phase changes. And if you really want to know - I mean, a lot of the phase changes happen in the first millisecond, but you know, we're sort of guessing because we can't look back further than we can probe.

So the idea with the LHC is you take these beams, and you collide them, and at the point of collision, you have a very high energy density, which is equivalent to the universe at a particular small time after the start of it all, after the Big Bang started. And the LHC is about - the energies of the LHC, when it's at full energy, is equivalent to the universe at around maybe a trillionth of a second, to the minus-12th to the minus-13th, 14th, something around there.

There's a lot of action that happens just around there, and we are pretty anxious about it because we think we're going to see a lot of new stuff that's going to be very important for us to figure out exactly what's going on with the universe.

PALCA: Well, I'd like to know what's going on with the universe.

Mr. BADEN: Well, and you do actually know what's going on because, you know, people do cosmology large-scale structure studies. They look up there, and they see galaxies, and the galaxies are distributed the way they are. And you kind of scratch your head and say how could the universe have started out as this big, as this very hot soup, very homogeneous soup, very smooth, end up in this very lumpy, cold universe we have now.

And that's, you know, one of the big - that's one of the big open questions in physics. And what's great about what's going on now is that the high-energy physicists doing these kind of experiments cannot make a measurement and not - they can't make a measurement and not consider what happens 13.7 billion years later. And the people who are doing the cosmology, they can't make a measurement and say, well, is this consistent with what happens in the early universe?

PALCA: Yeah.

Mr. BADEN: So it's all fitting together now.

PALCA: It's complimentary.

Mr. BADEN: And that's what makes it a really exciting time.

PALCA: Cool. Let's take a quick call now and go to Michael(ph) in Arkansas City. Michael, welcome to the program.

MICHAEL (Caller): Good afternoon, gentlemen.

PALCA: Yeah.

Mr. BADEN: Good afternoon.

MICHAEL: Happy holidays.

PALCA: Thanks.

Mr. BADEN: Thank you.

MICHAEL: I was just curious. You know, I've been listening to you talk about the collider for a couple shows, and I was just wondering if there was anything that could go seriously wrong with this experiment.

PALCA: You mean like we blink out of existence, that kind of thing?

MICHAEL: Yeah, like poof, we're gone.

(Soundbite of laughter)

PALCA: We won't know if that happens, of course, but Drew Baden, what do you think about that?

Mr. BADEN: Yeah, there was a lawsuit about that. Some people said well, we're not doing our environmental impact statements correctly. You know, here's the way I look at it: The energy in the beams from the LHC is about 300 megajoules, and so you might ask what's a megajoule? But 300 megajoules is about the amount of energy your refrigerator would use in maybe four days. Now, does it sound like that kind of energy is going to make us all blink out of existence?

I mean, I wouldn't - you know, I'm not so worried about that. If that was the case, if that small amount of energy - although concentrated into a very small volume - but if that small amount of energy could make you blink out of existence, we probably would have blinked a long time ago. So most people are not really worried at all about this. This is very far from something that is real and you need to worry about.

PALCA: Okay. One more quick call and Janelle(ph) from Eldersburg, Maryland. Go ahead, Janelle.

JANELLE (Caller): Yes, hi, thanks for taking my call. I was wondering why the circumference is 17 miles, if there's something special about that number. And also I've heard that when these particles can collide, they can create black holes, and that was a concern. I know the last caller mentioned something about poofing out of existence, but are these tiny black holes of any concern?

Mr. BADEN: Right, right. Well, it's 17 miles because you need to get the beams to high energy, and the way to do that is to put them in a circle and keep adding energy to them. It's like something going around in a circle, and every time it goes past you, you give it a kick. And so that's a good trick to get it up to high energy. And the reason why you want this thing to be a very - as large as possible in circumference, in diameter, is that whenever a charged particle makes a turn, whenever it accelerates, it radiates energy away. And the bigger the turn, or the tighter the turn, the more energy it radiates away. So it's an efficiency issue. So you want to make this thing as, you know, as straight as possible, but then again if you make it too big, it would be too costly.

PALCA: Well, we learned that lesson. Anyway, Drew Baden, I'm sorry, that's all the time we have. I thank you very much for that primer on LHC.

Mr. BADEN: My pleasure, thank you.

PALCA: Drew Baden is professor and chairman of the physics department at the University of Maryland in College Park. We're going to take a short break, and when we come back, we're heading off to Mars. So don't go away.

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