The world’s largest particle-physics laboratory is approaching a pivotal moment in its history

What CERN does next matters for science and for international cooperation

The world’s largest particle-physics laboratory is approaching a pivotal moment in its history

Fresh from their historic discovery of the Higgs boson in 2012, researchers using CERN’s Large Hadron Collider (LHC), the main particle accelerator at the European particle-physics laboratory near Geneva, Switzerland, set their sights on an even more momentous task. They aimed to explore what lies beyond the standard model of particle physics, the spectacularly successful — and frustratingly incomplete — description of fundamental particles and the forces that act on them. And yet, more than one decade later, the LHC has found no clues of any new physics. The nature of both the dark matter that strongly outweighs the amount of normal matter in the Universe and the Higgs boson itself remain elusive. And the clock is ticking. By the early 2040s, the LHC, which has a circumference of 27 kilometres, will reach the limits of its usefulness. The question is, what should follow?

The answer from CERN’s management is a still more massive accelerator, this time with a circumference of 90 kilometres: the Future Circular Collider (FCC), which will ultimately smash particles together at eight times the energy that the LHC does. If endorsed by the lab’s governing body, the CERN Council, this hugely consequential decision will set the course of high-energy physics for the rest of the century, with important implications for science, international collaboration and society. But the FCC plan is controversial and faces steep challenges to being funded (see Nature 639, 560–563; 2025).

Much of the technology needed to make it happen does not exist yet — including superconducting magnets strong enough to bend high-energy particle beams around the accelerator’s tunnel. For that reason, a first phase of the project would involve digging the tunnel and using existing technology to install a lower-energy machine designed to study known particles, including the Higgs boson, in finer detail. Particle collisions at the highest energies would come later, starting from around 2070.

Many physicists say that particle physics needs a long-term ambition such as this. But not everyone is convinced about how to go about it. The FCC lacks the clear rationale the LHC had of finding the Higgs boson — the last remaining particle predicted by the standard model to be found. Many physicists agree that there is a case for exploring the existence of new particles at higher energies, but what they do not agree on is at what cost.

Alternative plans do exist, including linear collider designs and options for reusing the existing LHC tunnel. A group of physicists appointed by the CERN Council is now conducting a ‘strategy update’, soliciting input from the physics community. Researchers around the world are submitting proposals to inform this process and they will discuss the ideas at a town-hall-style meeting in Venice, Italy, in June. The strategy group will then submit its recommendations to the council in December.

The debate is already vigorous. Some particle physicists fret that if the FCC gets the green light, it will take so long to build that even their students won’t be able to reap the benefits during their working lives. But projects that are passed down generations are precisely what makes the FCC worthwhile, say others. Others still are concerned about a perception among physicists who work on other types of experiment that CERN scientists have a ‘sense of entitlement’ — that they deserve more money than other fields just because they are probing the physics of the highest energies.

Overshooting costs are yet another worry. If CERN overextends itself to finance its next big project, it could end up unable to pursue other activities. Although the LHC gets the most headlines — and the next big collider will do so, too — CERN is much more than its flagship. The lab hosts world-leading experiments on antimatter and the physics of clouds and has built a cutting-edge cosmic-ray detector that has been flying on the International Space Station since 2011. Its facilities have been a testing ground to validate technologies for two of the world’s largest projects now under construction, Japan’s Hyper-Kamiokande experiment and Deep Underground Neutrino Experiment (DUNE) in the United States, both of which will study neutrinos. These new technologies are also important to CERN, which is why putting them at risk is not a smart thing to do.

It is unclear whether, or which, countries could step up to fill funding gaps. Germany — which already provides 20% of the lab’s budget — in particular, has already signalled that it won’t raise its contributions.

Since its inception more than 70 years ago as Europe emerged from the shadow of the Second World War, CERN has been a paragon of multilateral collaboration. European countries have found in CERN a source of common pride and a tool to extend the continent’s prestige and scientific ties around the globe. It now has 24 countries as full members, plus many others, including the United States, that contribute to its activities and community in crucial ways. Several other international organizations, including the European Molecular Biology Laboratory and the European Southern Observatory, have been modelled after CERN. Other scientific communities that lack such an authoritative point of reference — such as those that study cosmic rays or gravitational waves — have aspired to either emulate the lab’s governance model or receive its support.

The CERN Council will now face a difficult decision. Unless some nations step up with a major infusion of cash, the FCC faces an uncertain prospect of being funded. But waiting too long could mean that there will be a large gap between the new facility opening and the closure of the LHC, and precious expertise could end up being lost.

Although physicists might disagree on what CERN should do, they nearly unanimously care about the lab’s future. They and their leaders must now make the case for why European taxpayers, who fund most of the lab’s yearly budget should care, too. The stakes are beyond science, and even beyond Europe.

doi: https://doi.org/10.1038/d41586-025-00787-9

This story originally appeared on: Nature - Author:furtherReadingSection