Like the subatomic particles they hope to smash into one another underneath the Swiss-French border, rival factions of European physicists are on a collision course over plans to build the largest and most complex machine ever conceived.
The Future Circular Collider (FCC) would be a £13 billion particle accelerator that scientists claim could shed light on some of the universe’s most tantalising mysteries.
First, though, the same scientists must answer a much more mundane question: can they justify the cost of digging an underground tunnel that would stretch for 56 miles and burrow beneath Lake Geneva?
Its backers say the new collider could unlock a deeper understanding of the laws of physics. If built, it would dwarf its predecessor, the nearby Large Hadron Collider (LHC), in both size and cost.
They note that physics, for all its triumphs, remains riddled with gaps. The standard model — our best explanation of how the universe works — cannot account for dark matter, which comprises the bulk of the universe’s mass. It also fails to show how gravity fits into the quantum world.
However, many take a different view. Sir David King, a former chief scientific adviser to the UK government, is among those who say the money would be better spent elsewhere. “I’m not in favour and I note that the particle physics community themselves are split on this issue,” he said.
He added that the £13 billion cost estimate would almost certainly be exceeded and believed technologies to combat climate change were more urgent. “We can keep building higher and higher energy systems, and we will find new particles — but this science wouldn’t be relevant to the most pressing challenges we face on Earth,” he said.
The FCC is being proposed by Cern, the European Organisation for Nuclear Research, of which the UK is a member nation. Since 2010 it has used the LHC to smash protons together and to observe the spray of particles that emanate from the collisions. In 2012 those experiments revealed the Higgs boson, which had never been seen before.
One task of the FCC would be to build a clearer picture of the so-called Higgs field, which gives mass to other fundamental particles such as electrons and quarks. It would be capable of colliding particles — electrons and positrons to start with, and then protons with other protons — with ten times more energy than the LHC.
Professor Jonathan Butterworth of University College London acknowledged that physicists were far from united behind the plans. “There’s a lot of discussion about the scientific merits of different options,” he said.
“Some of it is on value for money and the opportunity cost of building one big thing when you could perhaps build lots of little things. We’re not united on a particular project — but robust discussion is to be expected and it would be worrying if it weren’t happening.”
The LHC, housed in a 17-mile underground tunnel, cost roughly £6.2 billion and is slated for retirement in 2041. Its successor, if approved, would take decades to construct, with operations possibly beginning in the mid-2040s.
Professor Mark Thomson, the British scientist who leads Cern, has compared building a new collider to astronomers acquiring a vastly more powerful telescope. “We can see finer detail and have the opportunity to discover something new,” he told The Times last year. “We know there is a lot more out there beyond our current understanding.”
Halina Abramowicz, from Tel Aviv University, is among the particle physicists who are more sceptical of the plans. “The first time heard I heard of the FCC was in 2014 and I thought it was extremely exciting,” she said. “But it’s a proton-proton machine. These are notoriously difficult, to get data and do analysis.” She said that she would prefer the field looked to other types of technology and collider.
“There are all kinds of new technologies and they are developing very quickly. But if there is no funding and no motivation, the principles will be shown and there will be nothing coming out of it.”
She said that the Large Hadron Collider had been brilliant at producing and analysing Higgs bosons, but it has not found the new physics they hoped for — and it’s not clear a bigger version would either. “There are no ideas past the Higgs. We know that something must be happening. But we have no clue where and how.
“With the LHC we went for the Higgs, and that paid off. That was 2012. Now we are in 2025 and there is no sign of anything new. How do you keep people excited?
Cern’s proposal has been worked on by more than a thousand physicists and engineers. It will be scrutinised by independent experts before the organisation’s member states decide in 2028 whether to proceed.
Advocates point to potential collateral benefits. Advances in cryogenics, superconducting magnets and vacuum technologies — achieved in the pursuit of exotic physics — will trickle down to industry and medicine, they say.
Butterworth acknowledged that physicists had to be “sensitive” about calling for money at a time when foreign aid budgets are being slashed in Europe to boost defence spending and as the UK government battles to reduce welfare payments.
“This is one of the very few high-tech areas of research where Europe has an undeniable world lead,” he said. “And that has societal and economic benefits. Maybe we can’t afford to keep it … But we’re in competition with the Chinese. Now, do we really want to hand over that leadership?”
