10 Things About the Large Hadron Collider You Wanted to Know But Were Afraid to Ask


Photo: Maximilien Brice, CERN

1. Why is it called the Large Hadron Collider?

The first one is easy: Large because it is really big. The LHC is a large circular tunnel with a circumference of 27 kilometers (17 miles), buried in the ground under an average of 100 m (328 ft) of dirt and rock.

In particle physics, hadron is a family of subatomic particles made of quarks and held together by the strong force*. Examples of hadrons are protons and neutrons. As you can guess from the name, the LHC uses mostly protons (with some ions) for its experiments.

Lastly, collider because the LHC accelerates protons into two beams travelling in opposite directions and then collides them to see what particles come out.

*There are four fundamental interactions: the strong force, the weak force, the electromagnetic force and gravity. Despite initial observations of the elusive metachlorian by Jinn, QG, et al (1999) Star Wars: Episode I - The Phantom Menace, the existence of "The Force" remains a controversial hypothesis unaccepted by most modern scientists.

2. Why is it underground?

Well, that's because finding 27 kilometers worth of real estate above ground is really, really expensive. Actually, the LHC uses a tunnel originally dug for a previous collider (the LEP or the Large Electron Positron collider), which was decomissioned in 2000.

All that dirt and rock also provide great shielding to reduce the amount of natural radiation that reaches the LHC's detectors.

3. Why is the LHC like a Werewolf?

Both are affected by the Moon! Like tides in the ocean, the ground is also subject to lunar attraction. When the Moon is full, the Earth's crust actually rises about 25 cm (9.8 in). This movement causes the circumference of the LHC to vary by (a whopping) 1 mm (out of 27 km, a factor of 0.000004%) ) but that's enough so that physicists need to take it into account. (Source: CERN FAQ: LHC, the Guide [PDF])

4. Why is the LHC like a Refrigerator?

The Large Hadron Collider is not only a cool particle physics gizmo, it's also a very, very cold one. Indeed, it is the largest cryogenic system in the world and is one of the coldest places on Earth.

To keep them at superconducting temperature, scientists have to cool the LHC's magnets down to 1.9 K (-271.3°C), which is lower than the temperature of outer space (-270.5°C). First, the magnets are cooled to -193.2°C using 10,000 tons of liquid nitrogen. Then 90 tons of liquid helium is used to lower the temperature down to -271.3°C. The whole cooling process takes a few weeks.

5. Who the heck is CERN anyway?

In 1952, eleven European countries came together to form the European Council for Nuclear Research (Conseil Européen pour la Recherche Nucléaire in French, which gave it the acronym CERN).

Two years later in 1954 it was renamed the European Organization for Nuclear Research, which would've given it the French name of Organisation Européenne pour la Recherche Nucléaire or the acronym OERN). Nobody liked "OERN", so the acronym CERN stuck.

If CERN sounds familiar to you even before this whole LHC business got started, that's because the World Wide Web was started by CERN employees Sir Tim Berners-Lee and Robert Cailliau (See: 10 Things You Should Know About the Internet)

6. How much does it cost, and who's paying for it?

The Large Hadron Collider is nearly 30 years in the making - and costs the member countries of CERN and other participating countries an estimated €4.6 billion (about US$ 6.4 billion). Like those late night infomercials, however, we can say "but that's not all!" Extra things like detectors, computing capacity, and extra warranty (just kidding!) cost an extra €1.43 billion.

The United Kingdom, for example, contributes £34 million per year, less than the cost of a pint of beer per adult in the country per year (Source).

The United States contributed approximately $531 million to the development and construction of components for the LHC (with the US Department of Energy shelling out $450 million and the National Science Foundation kicking in the remaining $81 million).

7. How much electricity is used to run the LHC?

It takes 120 MW to run the LCH - approximately the power consumption of all the Canton State of Geneva. Need a better comparison? 120 megawatt is equivalent to the energy used by 1,2 million 100 watt incadescent light bulb or 120,000 average California home.

It's estimated that the yearly energy cost of running the LHC is €19 million.

8. How much data is expected from the LHC?

The LHC experiments represents about 150 million sensors delivering data 40 million times a second. The data flow is about 700 MB/s, or about 15,000,000 GB (15 petabyte) per year. If you put all that in CDs, it'll stack 20 km tall each year! Perhaps it's better to put them in DVDs. That'll just be 100,000 DVDs every year ...

To prepare for the deluge of data, CERN built the Worldwide LHC Computing Grid - sort of a super-fast, private Internet connecting some 80,000 computers to analyze the data (Source).

9. Okay, will the LHC spawn a black hole that'll eat my planet?

Every time physicists come up with particle accelerators, party poopers come up with doomsday scenarios on how they will destroy Earth: black holes, killer strangelets, magnetic monopoles, and vacuum bubbles.

Let's talk about them one by one:

Micro black hole: Basically it's a region in space where gravity is so powerful that nothing, not even light, can escape. Planet-eating black holes are created when massive stars collapse on itself (and by massive, we mean massive - even our Sun isn't big enough to create a black hole if it collapsed. You'd need 10 times the mass of the Sun.)

There is a remote possibility that micro black holes can be created in the collisions at the LHC. These black holes are small: about 10-35 m across (the so-called Planck Length) and puny in mass (less than a speck of dust). These black holes would evaporate in 10-42 seconds in a blast of Hawking radiation. Even black holes with the mass of Mt. Everest would have a radius of about 10-15 m across. It would have trouble "eating" a proton, much less the entire planet. (Source: Pickover, C. (1997) Black Holes: A Traveler's Guide)

Strangelets: These are strange matters that, like the Ice-nine in Vonnegut's novel Cat's Cradle, would turn all matters it touched into strange matters and eventually all of the planet will be transmuted into strangelets.

The problem with strangelet doomsday scenario, besides being very bizarre, is that no one has ever seen a strangelet. It remains a hypothetical particle. Previous particle accelerators that operated at lower energy than the LHC were actually better candidates to producing strangelets, and so far, we're still here.

Magnetic monopoles: These are hypothetical particles with a single magnetic charge (hence the name) - either a north pole or a south pole, but not both. Magnetic monopoles "eat proton."

Actually, physicists have been looking for magnetic monopoles for a long time - and so far they've never found it. By calculations, magnetic monopoles are actually too heavy to be produced at the LHC.

Vacuum bubble: It is actually a very interesting idea in quantum field theory. It states that life, the universe and everything aren't the most stable configuration possible. Perturbations caused by the LHC could tip it into the more stable state (called the vacuum bubble) and all of us "pop" out of existence.

In all of these cases - if micro black hole, strangelets, magnetic monopoles, and vacuum bubbles were a problem to begin with, they would've been created by cosmic rays already. The continued existence of Earth and the rest of the universe tend to discount the validity of these doomsday scenarios.

But if you were itching to celebrate our continued survival, here's a "I Survived the Large Hadron Collider" T-shirt from Neatorama's Online Store for you: http://shop.neatorama.com/product-info.php?i-survived-the-large-hadron-collider-t-shirt-pid104.html - $9.95

10. How can I help?

Well, although over 7,000 physicists are tackling the hard sciencey stuff, your computer can help! The LHC@home project lets you contribute idle time on your computer to help calculate simulations of the real thing.


What is the source of your information? I've never heard of the earth's crust rising or falling with the pull of the moon and haven't been able to find any corroborating info online.
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I feel I learned more with this article than my high school pysics class...although our teacher did fall asleep in class often. Very interesting, talks of the LHC have been popping up all over the web.
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How long are they gonna keep colliding particles? Would a year's worth of hadron collisions be enough? Are we expecting a different result in every collision?

I always wonder what the plans are after they finish colliding the particles. There's some $8 billion of highly specific equipments there, are they gonna convert the site to an amusement park?
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@Anaslex :: A particle accelerator usually sufferers from diminishing returns, the most discoveries will be straight after switch-on and the number of new discoveries will decrease with time from that point onwards. There are a number of limiting factors like the luminosity and energy of the colliding beams. As the energy of the beams in the LCH is much greater than anything anybody has done before CERN is expecting a lot of great data in the next few months. In approximately ten years time there are plans to upgrade the LCH to the Super LCH to improve these factors and collect more useful data.
They should still build an amusement park on top and make use of some of those amazing superconducting magnets.
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OK, I can buy that the land tide exists, but why would it have anything to do with the full moon? Shouldn't the tides fluctuate twice daily, like the ocean tides? Unless you are saying that the maximum high tide would be at full moon.
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My only question is this: The articles I read on-line repeatedly state that "Cosmic rays more powerful strike the earth all of the time (at least 100,000 times in its history)." And yet, I also constantly read articles that claim, "energies not seen since the big bang." Further, I ask myself, "well, the cosmic rays may be traveling at near the speed of light, but the particles they strike in the earth are not anywhere near the speed of light." This accelerator takes beams moving near the speed of light in both directions to double the energy upon collision.

So, where does the truth lie? Will the LHC create energies not seen since the Big Bang, or will it create energies that have been created 100,000s of times on the earth?

I hate to say it, but in this layman's mind, that's an important question... It seems to me one contradicts the other and we're going into powerful unknown territory if one of those statements is true.
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While I really am in awe of all this and am very interested in what the collider will find, I have a very difficult time getting past the costs. Those billions of dollars funded from governments around the world could feed, clothe, & shelter millions of people in need in all continents.
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I have just one question, which no-one seems to answer; How is the CMS at 21 m long, 15 m in diameter and weighing 12 500 tonnes, considered 'compact'?
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sparge: you're correct - tides pulled by the moon happen twice a day, and are stronger during full (and new) moons than at other times. This is exactly the same process that causes tides in the sea, but the effects on solids are obviously smaller than those on liquids.

george: individual cosmic rays can have energies higher than those of individual protons in the LHC. Strictly, the energy _density_ in the LHC is higher, but this isn't related to the nature of the collisions, only how often they happen.
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carye1: It is almost impossible to predict the long-term benefits of doing fundamental science research like on done LHC, as we explore the unknown, but time and again it proved to bring unforeseen technological benefits that were created during these explorations and pushed the humanity forward. Think of almost all electronics, Internet, etc, without science the world would still be stuck in the dark ages. Your argument of diverting the money to humanitarian causes is valid, but I would suggest on concentrating on diverting the money from the non-humanitarian causes first! Just put them side by side, the cost of the war in Iraq is nearing 600 billion, where this experiment is only 6. It is interesting that the government does not promote the science and its importance for the future prosperity of the humanity, creating negative public opinion about science and discouraging scientists...
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Andrew, your answer didn't entirely make sense to me (probably because of my limited understanding of the matter)...

Do I understand you to say that: although individual gamma rays may have more energy than "individual" photons in the LHC, that the LHC has a SUM energy of all of the photons circulating in it greater than any gamma ray to have struck earth?

Further, are you saying that: although the SUM energy in the LHC might be very great, that when there is a collision, it involves only 2 photons and is therefore not as powerful as, say, all of the photons in the LHC simultaneously colliding, or even one gamma ray striking somewhere in the earth?
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It's ridiculous what a fuss the press made about the end of the world!

I love this 'I survived' but my boyfriend preferred the one at http://www.madscistuff.com so we got one of each *grin*
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v.dog:
"I have just one question, which no-one seems to answer; How is the CMS at 21 m long, 15 m in diameter and weighing 12 500 tonnes, considered ‘compact’?"

CMS is compact when compared to ATLAS, which is light but takes a lot more volume: 46 metres long, 25 metres high and 25 metres wide; ATLAS weighs 7000 tonnes.

As you can find easily, the CMS volume is roughly 3700 m^3, while the ATLAS volume is roughly 22600 m^3.

That is a factor 6 less in volume, more than the difference from a break to a compact car.
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Why would it matter if the moon was full or not? The mass (and therefore gravitational pull) of the moon is constant. The phase of the moon depends on the angle it is hit by the sun, not by changes in mass. I'd buy that the land rises slightly when it is closer to the moon, but the phase of the moon shouldn't affect the magnitude of the distortion.
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@My Pet Tiger: The phase of the moon does affect the magnitude of the distortion simply because the sun itself provokes a tidal effect. So, when both effects "pull" in the same direction, the distortion is bigger, when they "pull" in opposite directions, the moon's distortion is diminished by the sun's!
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The famous physicist Max Bohr could cause an experiment to fail simply by being present - was it his ghost that caused the failure of the LHC so soon after it turned on? - not to be r-started until spring?
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So yur wit ur honey, n ur makin out wen the phone rigns. U anser it n the voice is "wut u doing wit my daughter?" U hang up n tell ur girl. She say "my dad is ded."

THEN WHO WAS PHONE?
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Why why why!!!? After all that u're telling me that the world's NOT gonna end!! Take it back or i'm telling...

Hey Bin Laden, they say they can't do it so u better get back to work again. U too Bush...don't worry about Obama, he's trying to get the young generation educated so it's just a matter of time before the Indians & Chinese kills him...hey Obama's threating their job security.
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Large Hadron Collider ang A Reached Lord Rolling
Cost yeh right good one.You keep beliving them statistics what they tell u
400 yrs ago they said The world was flat
{Well for once chaps you might be right}
Iam i the only one that can see whats going on?
Like the girl said,about back to the Dark Ages
1/2 the population suvived that though
i dont think we will be as lucky this time
Not TO WORRY THOUGH
HONEST HATS OFF TO THE ONE WHO THOUGHT OF THE LOCATION NOW THAT IS VERY VERY CLEVER
geuine emails rams8785@rock.com
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Very interesting information and nicely articulated! The patience and forebearance of the originator was also very civilized. Thanks! I think it's clear that the trend towards politicizing science is misplaced, as suggested by Dr. Michael Crichton (Jurassicc Park) in some of his lectures on the topic.'Better to allow the domains of knowledge their own space to function without adulteration IMO. For more on this line of thought, R. Buckminster Fuller's exquisite life-work summary/bio "Critical Path" is recomended to all. He was ahead of his time in 1987 and still seems to be!
Money is the enemy. Real Waelth is knowledge and good works. BTW liberating 23 million Iraqis from a psychotic dicatatorial regime that was in many ways worse than the Soviet Union seems to me to qualify as a humanitarian effort, but then I am old fashioned. I insist on making sense comprehensively when I express myself on global issues.
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There's only one side of the moon that faces the earth. It turns around the earth so that the same side of the moon always faces the earth. Consequently, this visible side of the moon is closest to the earth at all times. The portion of the earth that is closest to the moon is the portion that is facing the moon. Everything on earth including land, water, etc will be pulled towards the moon by the moon's gravitational attraction. As a result, it's always the portion of the earth closest to the moon which is facing the moon that feels the moons gravitational pull. The phases of the moon correspond to the angle of the suns rays shining on the moon as observed from earth. If the earth was exactly between the sun and moon, the moon would be totally dark and the tides and land on earth wouldn't be pulled as much toward the moon because the sun is pulling it in the opposite direction. Likewise when the moon is full that corresponds to a gravitational attraction towards the moon with the least amount of counter-pull by the sun. This results in the highest tides and land occuring on full moons.
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"The problem with strangelet doomsday scenario, besides being very bizarre, is that no one has ever seen a strangelet. It remains a hypothetical particle. Previous particle accelerators that operated at lower energy than the LHC were actually better candidates to producing strangelets, and so far, we're still here."
"It is actually a very interesting idea in quantum field theory. It states that life, the universe and everything aren't the most stable configuration possible. Perturbations caused by the LHC could tip it into the more stable state (called the vacuum bubble) and all of us "pop" out of existence."

SOMEHOW, these answers don't give much comfort.
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