MArc Thomson, professor of experimental particle physics at the University of Cambridge, has landed one of the most coveted jobs in world science. But it's hard not to wonder, when you look at it from certain angles, whether he brought him on the team.
On January 1, Thomson takes over as director general of CERN, the Nobel Prize-winning nuclear physics laboratory located on the outskirts of Geneva. It is here, deep underground, that Large Hadron Collider (LHC), the largest scientific instrument ever built, recreates conditions that existed microseconds after the Big Bang.
The car took its place in history thanks to the discovery of a mysterious Higgs bosonthe accompanying field of which turns space into a kind of cosmic glue. But the first thing Thomson will do is turn off the machine for engineering work. It will not resume until it expires.
In an office on the ground floor of the Cavendish Laboratory, past a model of the DNA double helix discovered in Cambridge by James Watson and Francis Crick more than 70 years ago, Thomson is far from inconsolable about the lab's closure. If anything, he's enjoying what the next five years have in store for him.
“The machine works great and we record huge amounts of data,” he says. “We have a lot to analyze during this period. Physics results will continue to come in.”
Thomson's education was far from academic: he attended a comprehensive school in Worthing, West Sussex, and his taste for physics only developed after reading a popular book about science in CERN in early adolescence. “It kind of set my direction,” he says. “I wanted to understand how the universe works.” He became the first in his family to go to university, studying physics at Oxford.
The LHC accelerates protons, the nuclei of hydrogen atoms, to near the speed of light inside a 27 km (16 mile) ring beneath the French and Swiss countryside. At four points on the ring, protons flying in one direction are directed toward others rushing toward them. The energy from the impact creates a stream of new particles, which are recorded by the LHC detectors. According to Einstein's fundamental equation E = mc2more energy comes from more massive particles.
Starting in June, the stop will make room for High Luminosity LHCa major upgrade that includes the installation of powerful new superconducting magnets that compress the collider's proton beams and make them brighter. This will increase the number of collisions in the car tenfold. The detectors are also being strengthened, allowing them to better pick up subtle signs of new physical collisions. “This is an incredibly exciting project,” says Thomson. “It’s more interesting than just sitting here with the machine running.”
If the upgrade works, the LHC will be able to make more precise measurements of particles and their interactions, which could find cracks in today's theories that will form the basis of tomorrow's. Another mystery surrounds the Higgs boson. Elementary particles get their mass from the Higgs boson, but why the masses change so much is anyone's guess. It's not even clear how the Higgs bosons interact with each other. “We could see something completely unexpected,” says Thomson.
Getting the High Luminosity LHC up and running will dominate Thomson's five-year term. But a much larger and controversial project also requires his attention. The LHC will reach the end of its life around 2041, and CERN member states must decide what happens next. The leader is a colossal machine called Future circular collider or FCC.
According to CERN feasibility studyThe FCC will be more than three times the size of the LHC, requiring the construction of a new 91 km long circular tunnel up to 400 meters underground. The car will be built in two stages. The first, starting in the late 2040s, will collide electrons with positrons, their antimatter partners. At some point in the 2070s, the machine will be dismantled to make way for a new collider that will smash protons with seven times the energy of the LHC. The cost of the first phase is estimated at 15 billion Swiss francs or 14 billion pounds sterling.
The development itself is ambitious, but the FCC faces broader challenges. CERN member states, which will vote on the project in 2028, will not be able to foot the entire bill, so other participants are needed. Meanwhile, debate continues about whether this is the best machine for making new discoveries. There is no guarantee that it will answer any important questions in physics: what is the dark matter that clumps around galaxies; what is the dark energy that is pushing the Universe apart; why gravity is so weak; and why did matter defeat antimatter in the formation of the Universe? Without a clear goal to work towards, Thomson's job will be more difficult.
But CERN has always been about more than science. Because of the laboratory Europe is a world leader in particle physics, attracting tens of thousands of researchers and driving the need for new technologies. But other countries, especially the US and China, have their own plans for advanced colliders. Whether CERN maintains its dominance depends on the successor to the LHC.
“We haven't gotten to the point where we stop making discoveries, and FCC is a natural progression. Our goal is to understand the Universe at its most fundamental level,” Thomson says. “And now is absolutely not the time to give up.”
