Another proposed danger is a thing called a strangelet. A strangelet is a hypothetical subatomic particle composed of roughly an equal number of up, down and strange quarks.

Mind you, there is zero evidence that strangelets are anything other than an idea born in the fertile imagination of a theoretical physicist. But, if they exist, the claim is that a strangelet is essentially a catalyst. If it impacts ordinary matter, it will make the matter it touches also turn into a strangelet. Following the idea to its logical conclusion, if a strangelet were made on Earth, it would result in the entire planet collapsing down into a ball of matter made of strangelets … kind of like turning the Earth into an exotic version of neutron star. Essentially a strangelet can be thought of as a subatomic zombie; one that turns everything it touches into a fellow strangelet zombie. Particles are smashed together with such enormous energies that the collisions create a cascade of new particles — most of them extremely short-lived. The important thing for scientists is to work out what all these particles are, and that's not an easy task. To give a sense of scale, the LHC collides particles together with a total energy of 13 trillion (or tera) electron volts of energy (TeV). The highest-energy cosmic ray ever recorded was an unfathomable 300,000,000 TeV of energy. Right now, we've got five years of justification of the study to do, then probably another five years or so of detailed engineering design. Then we would proceed at whatever pace we could, which was limited by the money,” said Newbold. “It’ll probably be a minimum of 20 years from now and maybe longer.” The purpose of MoEDAL is to look out for any monopoles that might be created in collisions inside the LHC. It could also potentially detect certain "stable massive particles" that are predicted by theories beyond the Standard Model. If it's successful in finding any of these particles, MoEDAL could help to resolve fundamental questions such as the existence of other dimensions or the nature of dark matter. Climate scienceThe Compact Muon Solenoid (CMS) pictured here can capture images of particles up to 40 million times per second. (Image credit: xenotar via Getty Images) All hadrons are made up of quarks, but LHCb is designed to detect particles that include a particularly rare type of quark known as 'beauty'. Studying CP violation in beauty-containing particles is one of the most promising ways to shed light on the emergence of matter-antimatter asymmetry in the early universe. Hunting exotic particles We are in a situation where the Standard Model cannot explain various phenomena,” said Gianotti. “There are many other theories, but we have no clue which one is the right one. And so, making a step forward in terms of energy scale … can help redirect our thoughts.” The bad

One of the leading theories beyond the Standard Model is known as supersymmetry. Seemingly abstract at first glance, the basic concept of supersymmetry is actually rather straightforward. Supersymmetry predicts that for each of the 17 fundamental particles in the Standard Model, there exist a hypothetical partner particle -- thus the “symmetry” -- and each of these hypothetical particles would be heavier than their corresponding, already discovered partner -- thus the “super.”

When Run 3 commences we can expect a whole new spate of discoveries, so it's a good time to take a closer look at what makes the LHC — and the rest of CERN — so unique. What is the Large Hadron Collider? Two of the four collision points around the circumference of the LHC are occupied by large general-purpose detectors. These include the Compact Muon Solenoid (CMS), which can be thought of as a giant 3D camera, snapping images of particles up to 40 million times per second. One of the key mysteries of the universe is the striking asymmetry between matter and antimatter — why it contains so much more of the former than the latter. According to the Big Bang theory, the universe must have started with equal amounts of both. Yet very early on, probably within the first second, virtually all the antimatter had disappeared, and only the normal matter we see today was left. This asymmetry has been given the technical name 'CP violation', and studying it is one of the main aims of the Large Hadron Collider's LHCb experiment. This is a beautiful time, you know, because the best time to be an experimentalist is when the theorists have run out of ideas. Because then anything we discover is new,” said David Newbold, who directs the particle physics program at Rutherford Appleton Laboratory in the U.K. and is currently leading an effort to upgrade one of the main detectors at the LHC.

And, occasionally, that inconvenient bit of matter is the Earth. We call these intergalactic bullets — mostly high-energy protons — "cosmic rays." Cosmic rays carry a range of energies, from the almost negligible, to energies that absolutely dwarf those of the LHC. Those are but two ideas for how a supercollider could pose a threat, and there are more. We could list all of the possible dangers, but there remains something more unsettling to keep in mind: Since we don't know what happens to matter when we start studying it at energies only possible with the LHC (that is, of course, the point of building the accelerator), maybe something will happen that was never predicted. And, given our ignorance, maybe that unexpected phenomenon might be dangerous. Thus, the barrage of cosmic rays from space have been doing the equivalent of LHC research since the Earth began — we just haven't had the luxury of being able to watch. Scientists are still trying to figure out why the universe contains more matter than antimatter. (Image credit: sakkmesterke via Getty Images)

The paths of the particles inside the detector are controlled by a gigantic electromagnet called a solenoid. Despite weighing 12,500 metric tons, it's quite compact, as the detector's name suggests. That middle word, muon, refers to an elusive particle similar to the electron but much more massive, which requires its array of subdetectors wrapped around the solenoid. Sharing the same underground cavern as LHCb is a smaller instrument called MoEDAL, which stands for "Monopole and Exotics Detector at the LHC". While most CERN experiments are designed to study known particles, this one is aimed at discovering hitherto unknown ones that lie outside the present Standard Model. A monopole, for example, would be a magnetized particle consisting only of a north pole without a south one, or vice versa. Such particles have long been hypothesized, but never observed.