AUDIE CORNISH, host:

From NPR News, this is ALL THINGS CONSIDERED. I'm Audie Cornish.

ROBERT SIEGEL, host:

And I'm Robert Siegel.

This year, the world's largest physics machine roared to life. The Large Hadron Collider is a 17-mile-long underground ring that tunnels back and forth across the French-Swiss border. It accelerates subatomic particles to near the speed of light and smashes them together.

Geoff Brumfiel traveled to Switzerland to find out how physicists are hoping to use these collisions to solve the mysteries of the Big Bang.

GEOFF BRUMFIEL: It's hard to explain how much the Large Hadron Collider means to physicists, but you get a sense of it when you speak to Srini Rajagopalan. He works on a giant, underground detector that records what's produced in the collisions. It's called ATLAS.

Dr. SRINI RAJAGOPALAN (High-Energy Physicist, ATLAS Trigger System): I've been working on ATLAS since 1996. I was down in that pit when it was completely empty and it was wonderful. It was huge. I have watched the detector being built. I was involved in the research and development, and the production and the testing, putting the whole thing together.

BRUMFIEL: Thousands of researchers like him have devoted the best years of their lives to getting the LHC and its detectors up and running. They switched on with great fanfare in 2008. Collisions were just days away when a faulty connection triggered an explosion in the machine's liquid helium coolant.

It was a devastating accident, though Steven Goldfarb, another researcher on ATLAS, puts the best face on it he can.

Dr. STEVEN GOLDFARB (Physicist, ATLAS Trigger System): As a lesson to the world, we arranged for the LHC to have a small explosion so that they could learn about...

(Soundbite of laughter)

Dr. GOLDFARB: ...what happens when liquid helium expands.

BRUMFIEL: That sounds like spin to me.

Dr. GOLDFARB: Yeah, it's spin. I agree.

(Soundbite of laughter)

Dr. GOLDFARB: We didn't really want this to happen, and it set us back for a good year or so.

BRUMFIEL: This year, the LHC finally got going, and that means researchers can finally start looking for new particles. At the top of their list is one called The Higgs. Researchers think The Higgs explains the masses of all the other particles. Its discovery would be a major find, and everyone is excited.

Goldfarb's even got a song.

Dr. GOLDFARB: (Singing) We got the LHC running, now ATLAS you're my home. The LHC is running, now ATLAS you're my home. I've been working all night out at point one, looking for The Higgs, that son of gun. The LHC is running, now ATLAS you're my home.

I'm not going to keep going. I could go forever.

BRUMFIEL: Think of the LHC as an underground racetrack. Instead of cars, the machine uses protons, the positive particles at the center of atoms. Two streams of protons travel in opposite directions around the 17-mile ring and collide inside of four detectors the size of buildings.

David Francis is another researcher working on ATLAS.

Dr. DAVID FRANCIS (Physicist, ATLAS Trigger System): It's a bit harsh, this comparison. But in two cars crashing and each car's got passengers in it, and they crash into each other and bits fly everywhere, right? And then your job is to identify what the cars were beforehand and how many passengers were in each car.

BRUMFIEL: Except it's more than just the contents of the cars. Smashing protons together actually makes new particles. Steven Goldfarb says turning on the collider is a bit like turning on the Hubble Space telescope.

Dr. GOLDFARB: When the Hubble turned on and looked out into space, they had some ideas what they were going to see. But they also didn't know, and that's probably the coolest part of what we do. Instead of looking out, we're looking in and we're looking for new things.

BRUMFIEL: The LHC produces hundreds of millions of collisions each second. Sorting through all those collisions to find something like The Higgs requires a lot of computers.

David Francis takes me inside the two-story building above the ATLAS detector.

(Soundbite of machinery)

Dr. FRANCIS: So if you're looking just down the aisle here, you see 19 racks -19 cabinets of computers with 31 computers in a rack.

BRUMFIEL: The interesting collisions get recorded to disk. Even throwing away most of them, researchers still end up with a lot of data.

Dr. FRANCIS: So I think if you do the numbers, you end up with a pile of DVDs per year which is higher than the Eiffel Tower in Paris, something like that.

BRUMFIEL: Once researchers have those data, they can start to look for The Higgs. But that's not the only thing they're looking for.

Joe Incandela is hoping they'll find a mysterious kind of matter called dark matter. He works at the CMS detector, which is five miles away from ATLAS on the opposite side of the ring.

JOE INCANDELA (Deputy Spokesperson, CMS): In fact, our galaxy is loaded with this dark matter, but we have no idea what it is. It's very likely to be heavy stuff that we could produce at the LHC. All the theories indicate there's a good chance we produce it.

BRUMFIEL: That's just the start of a list that gets progressively more sci-fi. The machine will study antimatter. It will probe milliseconds after the Big Bang. It could also turn up extra dimensions of space, microscopic black holes, or something nobody's even thought of yet.

So far, researchers haven't seen too much new, but with an Eiffel Tower's worth of data each year, they're optimistic.

After 15 years of waiting, Srini Rajagopalan says everyone is getting down to business.

Dr. RAJAGOPALAN: There are a lot of teams of people looking for signs of new physics. Ah, finally we have data. This is what we've been looking for, waiting for, for such a long time.

Dr. GOLDFARB: (Singing) We got the LHC running. Now ATLAS you're my home. The LHC is running...

BRUMFIEL: The LHC is starting to hum. Researchers may be singing the blues but they feel good.

For NPR News, I'm Geoff Brumfiel.

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