All matter is made of just three particles: two types of quarks (‘up’ and ‘down’) and electrons. Three interactions provide the ‘glue’ for building protons, neutrons, and then nuclei and atoms. The strong interaction binds three quarks to form protons or neutrons, and it holds protons and neutrons together in nuclei. Atoms consist of a nucleus surrounded by electrons, which are bound by the electromagnetic interaction. The weak interaction transforms up- into down-quarks (and vice versa), or electrons into (electron-) neutrinos. This process is crucial for fusion of nuclei in stars: it produces energy and creates heavy elements.

In collisions of particles moving with almost the speed of light, new and very short-lived particles are produced, and physicists have found that the basic quartet of particles (up-, down-quark; electron, electron-neutrino) is replicated two more times with similar quartets (or ‘families’) of more massive particles. These (three) sets of 4 particles, plus the “messenger particles” of the strong (gluons), electromagnetic (photons) and weak interaction (vector bosons) are the ingredients of the “Standard Model” of particle physics. Here is a short video explaining the essentials: CERN: The Standard Model Of Particle Physics.

Already in the 1960s, physicists noted that the standard model only makes sense if there was an explanation why particles have a rest mass. The proposed solution was that the entire Universe is uniformly filled by the so-called ‘Brout-Englert-Higgs’ field, and that particles obtain their mass through the interaction with this field. Peter Higgs noted that this field should have an associated particle, which was named after him: the Higgs boson. Watch these two lessons The Higgs Field, explained - Don Lincoln and The basics of the Higgs boson - Dave Barney and Steve Goldfarb.

Physicists have figured out how to produce new particles already in the 1940s: by accelerating particles (e.g. protons and electrons) and then colliding them with other particles. In these collisions, the energy of movement (E) is partially transformed into the mass (m) of new particles, according to the famous equation E= mc2 (energy = mass x speed of light squared). The biggest accelerator in the world today is the Large Hadron Collider at CERN, in Geneva (Switzerland), with a collision energy equivalent to the mass of about 14,000 protons. It is so powerful that new particles with a very large mass can be produced - and in this way, the Higgs boson was found there in 2012. This article by Rolf Landua explains the 12 steps necessary for the discovery of a new particle.

It is amazing to imagine that the particle collisions in the LHC gives us insight into the earliest moments of the Universe, when it was still extremely small, extremely hot and extremely dense. This animation: The beginning of the Universe, gives a good introduction to all these questions.

While particle physics has made incredible progress over the last 100 years, we still face many big questions related to the origin and the composition of the Universe: What happened to antimatter , CERN scientist Rolf Landua, returns to the seconds after the Big Bang to explain the disparity that allows humans to exist today.

What is dark matter and dark energy, that make up 95% of the mass-energy content of the Universe? Click here to find out.

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