CERN, Switzerland 2017
On July 15th, 2017; I I spent the night in Geneva looking across Lake Geneva, (pictured below).
My main destination in Geneva, was to visit CERN.
CERN, the European Organization for Nuclear Research, is the largest particle physics laboratory in the world and operates six particle accelerators plus the new Large Hadron Collider. Visiting CERN took a half a day. Most of it is underground.
(Pictured below), is the Large Hadron Collider, where it recently discovered the historically significant Higgs-Boson.
It may not always seem that way, but physicists like to keep things simple. From the lightest particle to the heaviest are 13 orders of magnitude, that’s a difference of a factor of 1 followed by 13 zeros. How do these particles obtain such different masses? This question led several physicists in the 1960s to propose the existence of a new field—now known as the Brout-Engbert-Higgs, or BEH field—that pervades all space. It is through interactions with this field that particles gain their mass. It was the discovery of the Higgs Boson at CERN in 2012 that proved the existence of such a field.
(Pictured below), I’m standing in front of CERN’s auditorium, across the street from Microcosm, (CERN’s interactive science center).
The sun shines due to a combination of the strong of the strong and the weak nuclear force. This latter is transmitted through W and Z bosons. These bosons are the only known force particles with a rest mass and were discovered at CERN in 1983. A key process inside the sun is the transformation of the neutrons into protons by the emission of the W boson, which then decays into an electron and an (anti-)neutrino.
It is the most common matter particle in the universe, yet you will never find a quark alone. The strong force confines them –through the exchange of aptly-named “gluons”- in bound states of quark and antiquark, or of three quarks. The strong force is the most powerful of the four fundamental forces, yet its sphere of influence is limited to within the atomic nucleus. Without the glue, quarks would fly apart repulsed by electromagnetism. In fact, it is impossible to isolate quarks: so much energy is needed, that a second pair of quarks is produced when trying to separate two quarks from each other.
There are 3 families of quarks. The lightest family, comprised of the up-quark and the down-quark combine to make up the nuclei of all atoms. The other quarks exist today only as products of high energy particle collisions.
You may have first encountered the electron when learning about electricity. The movement of this negatively-charged, fundamental particle creates electrical current. Electrons are part of all atoms. However tiny, their movement en masse creates all kinds of visible effects, from lighting to the northern lights. In the same particle family as the electron are the muon and tau, its heavier cousins.
The tiny centre of an atom, the nucleus, makes up a mere hundred-thousandth of its diameter, yet contains almost all of its mass. It is made of protons and neutrons, each over 1800 times heavier that an electron. Protons and neutrons are themselves each made of 3 quarks, bound tightly together by continuously exchanging gluons, the carriers of the strong nuclear force. The number of protons in a nucleus determines its atomic number and the position of the atom in the Periodic Table.
So small that a million of them fit across the width of a hair, atoms were once thought to be fundamental. However, for over a hundred years now we know they are in fact made up of a positively charged nucleus made of protons and neutrons (which are in turn made from quarks) surrounded by negatively charged electrons. Atoms are essentially empty space. If the nucleus were the size of this full stop—the average distance of the first electrons would be about 100m away. This is because of a fundamental property of the electron that does not like to share its (quantum) space with other electrons.
Not a moon Lander, but a particle detector. The 26-ton Big European Bubble Chamber (BEBC), filled with 30 cubic meters of liquefied gas, recorded the interactions of elementary particles. The sensitivity of the liquid gas was controlled by a huge piston. Each time the piston expanded, a burst of particles was photographed. Operational from 1973 to 1984, BEBC produced 3000 kilometers of film.
A Mother of a giant. The 25-ton Gargamelle bubble chamber, built in France, was named after the mother of the gluttonous giant Gargantua in the classic book by Rabelais. In 1973 it made one of CERN’s major physics discoveries—the ‘neutral current’, a new kind of particle interaction. Filled with 18 tons of heavy liquid (Freon or propane), it recorded the rare interactions of elusive particles called neutrinos.
Nature’s escape artist neutrinos are the most elusive of all fundamental particles. Many billions of them are passing through just your hand every second of every day, with no effect whatsoever! This is because they are point-like, have hardly any mass and hardly ever interact. When they do interact, it is through the weak nuclear force (which is transmitted by the massive W and Z bosons) and this force is extremely short-ranged and therefore…well, weak.
The pulse of a particle accelerator. 128 of these radio frequency cavities were positioned around CERN’s 27 kilometer LEP ring from 1989-1995 to accelerate electrons and positrons. The acceleration was produced by microwave electric oscillations at 352 MHz. The electrons and positrons were grouped into bunches, like beads on a string, and the copper sphere at the top stored the microwave energy between the passage of individual bunches. This made for valuable energy savings as it reduced the heat generated in the cavity.
Applications beyond CERN. Since 1954, discoveries made at CERN have advanced our understanding of the universe. They have also had impact in fields as diverse as medicine, electronics, civil engineering and computing. Extraordinary researcher needs extraordinary machines. Their design stimulates technological advances that have applications far beyond the field of particle physics. The world-wide web was invented in CERN in 1989 to facilitate exchanges between physicists. The hyper-text language, made available freely to the world, has since revolutionized communication. In the 1970s, CERN scientists helped build a PET scanner for the Geneva Cantonal Hospital. Today, PET scanners are bought off-the-shelf and many of them rely on crystal detector technologies developed for experiments at CERN. Some are able to carry out MRI scans as well as PET inspired by ideas from the CMS experiment at the LHC.