Meet the Large Hadron Collider, the world's most powerful atom-smasher

The Large Hadron Collider is one of the most important scientific instruments in the world — and also one of the biggest humans have ever built.
John Loeffler
Views on the open CMS detector to be closed up after the Long Shutdown 2 (LS2) and to get ready for the new physics run in 2022


The Large Hadron Collider is the world's most powerful particle accelerator, situated along the border between Switzerland and France, just outside the Swiss city of Geneva. Still, that description doesn't quite do it justice.

It is also one of the largest scientific instruments ever built; the result of a decade of collaboration between over 100 countries, hundreds of universities and scientific institutes, and more than 10,000 scientists and researchers.

Operated by the European Organization for Nuclear Research (CERN), the atom-smashing accelerator is capable of producing energetic collisions of high-energy particles like protons, breaking them apart into their constituent subatomic components that can then be detected and studied.

In this manner, the Higgs boson — the subatomic particle that demonstrated the existence of the Higgs field, which is responsible for giving mass to matter — was detected in 2012, and subsequent runs of the collider have revealed more about the nature of the subatomic world than any other scientific instrument has done before or since.

Given the somewhat opaque nature of the research conducted by CERN (it is highly advanced particle physics, after all), it's not surprising that many have expressed skepticism and even fear about the work being conducted at the Large Hadron Collider.

It is dangerous work at times, but the Large Hadron Collider (LHC) doesn't threaten humanity. Instead, it allows humanity to study some of the most vexing problems in physics in an unprecedented and relatively safe way.

How big is the Large Hadron Collider?

Meet the Large Hadron Collider, the world's most powerful atom-smasher
The Large Hadron Collider, seen as the white rings at the bottom left, is the world's largest particle collider, for now.


The Large Hadron Collider, a multibillion-Euro project, was built between 1998 and 2008 and stretches for 17 miles (27 kilometers) and runs as deep as 574 feet (175 meters) below the surface.

Compared to other particle accelerators, there is nothing on the scale of the LHC. The second-largest particle collider in the world, the Tevatron, operated by Fermi National Accelerator Laboratory in Batavia, Illinois, had a circumference of 3.9 miles (6.28 kilometers), or just under a fourth of the size of the LHC, and was shut down in 2011.

The LHC might not remain the largest collider in the world for too much longer, though. CERN is already planning for the next generation of colliders - the Future Circular Collider, which would be an astonishing 62 miles (100 km) in circumference, or wide enough to encircle the city of Geneva and much of its surrounding countryside.

What exactly does the Large Hadron Collider do?

Meet the Large Hadron Collider, the world's most powerful atom-smasher
The tunnel for the LHC stretches for 17 miles.

The Large Hadron Collider works by lining miles-long and pipe-like "tracks" with superconducting magnets, which can bend, direct, and accelerate a beam of high-energy particles to nearly the speed of light.

The beams travel in opposite directions in separate beam pipes – two tubes kept at ultrahigh vacuum. The electromagnets are made from coils of electric cable that operate in a superconducting state, allowing them to conduct electricity without resistance or loss of energy. In order to achieve this, the magnets must be cooled to ‑271.3°C using liquid helium.

Once a pair of beams along these tracks reach sufficient speeds and thus possess an incredibly high level of energy, the magnets redirect the beams onto a collision course with each other, colliding at locations around the accelerator ring corresponding to the positions of particle detectors.

The particles in the beam smash into each other with enough force to overpower the strong force holding the quarks and subatomic particles bound together in the smashed particle. As particles crash into each other near the speed of light, some of their combined kinetic energy is converted into mass, creating new particles such as the Higgs.

Nearby detectors monitor them and observe the result of the collision, looking for the presence of hypothesized bosons, muons, and anything else a proton might be composed of.

There are nine detectors in total, located around four different crossing points where the accelerator's beams collide, each looking for different phenomena from the collisions.

The LHC can produce many different results for researchers in a single experiment to increase the chances of particle collisions, and many particles make up the individual beams. When the two beams intersect, there is still a slight chance that any two particles in either beam will come into contact with each other.

But just as a torrential downpour is really just a bunch of tiny droplets of water that nonetheless soaks you through and through, the quantity of individual particles in the beam is great enough that collisions still occur.

Whether those collisions produce the individual subatomic particles you are looking for is another matter, but the more particles you have in the beam, the better your chances of collisions producing what you need.

And since a great many particles do pass through unscathed, the LHC has four points along the paths of the two beams where the beams intersect, allowing different teams of researchers to look for several different subatomic particles and their various properties during a single operation.

Can the Large Hadron Collider destroy the world?

Meet the Large Hadron Collider, the world's most powerful atom-smasher
The open CMS detector at the Large Hadron Collider.

No, but we get why you're asking. The amount of energy the Large Hadron Collider uses is significant since keeping the thousands of superconducting magnets powered and cooled enough to produce the beam-controlling magnetic fields is no small feat.

And the idea of smashing atoms together in a "nuclear" laboratory has "World-Ending Mushroom Cloud" written all over it. But nuclear, in this sense, isn't the atom bomb kind of nuclear, but the study of the atomic structure itself, principally what is contained inside the nucleus of an atom.

To find out, we need to crack open the nucleus (the proton of a hydrogen atom, in most cases, but sometimes heavier elements as well), which does take a lot of energy, relatively speaking.

But the amount of energy involved is far less than what we are naturally exposed to from cosmic radiation interacting with our atmosphere. All of the violent supernova and neutron star collisions and all that out in the universe are constantly shooting off high-energy protons like bullets, which fly through the universe with ferocious energy and speed until they hit something like the Earth. We call these high-energy particles cosmic radiation or cosmic rays, and it is constantly bombarding the Earth.

According to, the highest-energy cosmic ray ever recorded possessed 300,000,000 TeV of energy, or about 23 million times greater than the highest-energy collision ever produced by the LHC (13 TeV). The Earth is being bombarded by cosmic rays with the energy of a single beam in the LHC about 500 trillion times a second.

All of this is to say that the energy potential of the LHC is enormous, but it is nothing compared to what the Earth has weathered for 4.5 billion years, and we're all still here.

Ok, but what about accidentally forming a Black Hole?

Meet the Large Hadron Collider, the world's most powerful atom-smasher
Could the LHC produce a micro black hole that eventually consumers the Earth? No.

Before it was fired up, one of the biggest fears about the Large Hadron Collider was that it would accidentally create a "micro" black hole from a particle collision, which would then start consuming surrounding matter and grow large enough to swallow the entire planet.

The problem with this theory is that things on the subatomic scale do not work the same at the macro level. Namely, the force of gravity on a subatomic scale is much too weak to create a black hole out of a particle collision, micro or otherwise.

And if a micro black hole were even possible, it would vanish just as quickly as it was created. Black holes are affected by something called Hawking radiation, which is where the spontaneous creation and destruction of virtual particle and anti-particle pairs along the event horizon gets 'short-circuited' by one of those virtual particles slipping past the event horizon before it has a chance to eradicate with its partner.

That partner particle on this side of the event horizon shoots away from the black hole just as quickly. But, the law of the conservation of energy means that energy is neither created nor destroyed and that escaping particle (known as Hawking radiation) is a debit on the universe's energy balance sheet.

The energy was added to the total energy in the universe, so to maintain the conservation of energy, that energy needs to be subtracted from something else, in this case, from the black hole. And since energy and mass are interchangeable, the black hole gets the tiniest bit smaller due to Hawking radiation. In isolation, even the biggest supermassive black holes will evaporate into nothing given enough time, and the rate of this evaporation accelerates the smaller the black hole gets.

If you formed a micro black hole with the mass of a couple of protons, Hawking radiation would all-but-instantaneously blink it out of existence.

Dangers of the Large Hadron Collider

Meet the Large Hadron Collider, the world's most powerful atom-smasher
Make sure to unplug your particle accelerator before performing any maintenance.

None of this is to say that there aren't dangers with something as complex and energetic as the Large Hadron Collider, but its risks are much more industrial than existential.

The most significant danger would be to the collider itself or anyone working in the tunnels housing it. A malfunction known as a magnetic quench, where there is a failure in the superconductivity of a magnet along the miles-long array, could suddenly turn all of the stored energy in the failing magnet into heat energy, which could spread to other magnets, disrupting their superconductivity in a cascading chain reaction.

The resulting heat can rapidly boil the liquid helium coolant used to keep the magnets supercold, creating an explosive depressurization as the helium "steam" is vented. This gas would displace the oxygen in the immediate area, so such a failure can even be deadly if anyone is actually in the tunnels housing the LHC when this type of failure occurs, which is highly unlikely ever to happen. Still dangerous? Yes, but capable of destroying the world? No.

There are also safeguards to ensure that failures don't do irreparable damage to the collider itself, and the LHC is designed to accommodate such events from time to time. It may require replacing a few dozen magnets along the accelerator (once the area is safe to enter), but that is about it.

There are also the standard industrial hazards of working on machinery with a considerable amount of electricity coursing through it, along with the dangers of working with the coolants required to keep the superconductive magnets at their extremely low temperatures.

Anyone who has seen how quickly liquid nitrogen can flash-freeze objects can imagine what would happen if someone accidentally slipped on a wet floor and comically put their hand in a bucket of liquid helium to catch themselves, but that's why places like the LHC have safety procedures and equipment to minimize that sort of risk. And we highly doubt CERN keeps open buckets of liquid helium just sitting around like that, anyway.

Ultimately, the Large Hadron Collider is as safe as the people who operate it make it, but it does not pose a danger to the rest of us. On the plus side, we benefit from such an incredible facility digging deep into the mysterious quantum world to uncover the most fundamental building blocks of the universe itself.

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