Why CERN wants to build a giant particle collider

CERN's 70th anniversary celebrations in 2024 may be its biggest achievement since scientists there detected the "elusive" Higgs boson particle in 2012.

Over a decade later, CERN scientists are still smashing subatomic particles at the Large Hadron Collider (LHC) but have not reported any comparable discoveries since the Higgs boson.

But they do hope to make new, major discoveries with a much larger particle collider, which, if built, will be three-times the size of the LHC. 

The proposed Future Circular Collider (FCC) would be more than 90 km long. 

It would aim to serve as a so-called Higgs factory, producing Higgs boson particles for research. The Higgs boson is thought to be a building block of the universe. 

But at an estimated cost of CHF 15 billion (~€15.7 bn; ~$17.5 bn), and in a world of limited resources, is the FCC worth it? 

Criticism of CERN's expansion plans

CERN does "fundamental" research. It is so fundamental — exploratory — that the scientists can never be sure whether their research will produce any results. Certainly no results will immediately be of benefit to people's everyday lives. 

Some people argue that the proposed cost of FCC ($17 billion) would be better spent on more practical and urgent scientific questions of our time.

The world spent about $4.1 billion on malaria research in 2022. That same year, the World Health Organization says there were an estimated 249 million malaria cases and 608,000 malaria deaths in 85 countries.

Would the $17 bn be better spent on researching malaria or other real-time threats, such as climate change and emerging viruses?

Theoretical physicist Sabine Hossenfelder thinks so: Hossenfelder has been an outspoken critic of CERN's plans to expand.

"It's a high-risk, low-payoff project," said Hossenfelder in a video post. Hossenfelder noted that the FCC project would realistically cost much more once operations began.

CERN also came under public scrutiny regarding its energy expenditure during the shortage around the Russia-Ukraine war.

Despite this, dissenting voices against CERN, especially among other scientists, have been few. Many scientists believe that building a bigger particle collider can answer many fundamental questions, same as the Higgs boson.

Why is the Higgs boson such a big deal?

To put it unscientifically, the Higgs boson has been described as a "God particle" — it "glues" fundamental elements of the universe.  

It may seem like the universe came from nothing, but the Higgs boson explains how the Big Bang happened 13.7 billion years ago — it reveals why particles have mass.

When particles have no mass, they race about the universe at the speed of light like photons.

But having mass gives particles gravitational properties, ultimately slowing them down. And with gravitation, they are able to come together and form other elements.

In 1964, Peter Higgs, François Englert, and others proposed that particles gain mass by interacting with — what they called — a Higgs field. CERN's Large Hadron Collider experimentally proved this theory in 2012. And  Higgs and Englert won the 2013 Nobel Prize in Physics for their work.

What questions can Higgs boson still answer?

CERN is (at time of writing) the only lab equipped to study the Higgs boson. 

"It uses the biggest machines to study the smallest particles," said Judith Pirscher, the German State Secretary at the Federal Ministry of Education and Research (BMBF), at an event in Berlin.

But it's been 12 years since the breakthrough discovery. Why are scientists still smashing particles? And why should CERN continue, sinking billions in the process?

"With the Higgs Boson, we've found a key, but we still don't know everything it can unlock," said Klaus Desch, Germany's CERN delegate, who is based at the University of Bonn. 

Desch said that studying the Higgs further could reveal more about the universe's origins and dark matter — about which we know very little.

Beate Heinemann, director of particle physics at the German Electron Synchrotron, added that CERN's future research may explain why we observe more matter than anti-matter, suggesting "something is missing."

There is also global interest in this fundamental research, and international competition. 

In 2018, China proposed building a 100 km collider to produce a million Higgs bosons over seven years.

Meanwhile, the American Particle Physics Project Prioritization Panel (P5) chose to support upgrades at CERN over building a separate Higgs factory. There are also plans to build an International Linear Collider (ILC) in Japan.

After LHC: the Future Circular Collider

The LHC will complete and shut its operations in 2041. If the FCC goes ahead, the new tunnel will be at an average depth of 200 meters underground and include eight surface sites that will serve four experiments.

About a third of that $17 billion cost will be buried with this tunnel alone. The construction would result in about 16.4 million tons of excavated materials over a period of five years.

CERN is expected to file a feasibility report by 2025. It will investigate the technical, financial, geological, and the environmental impact of the project. 

"We are constantly looking for ways of reusing the waste energy from our scientific installation, for example, to power nearby villages," Director General Fabiola Gianotti told DW. "We are already doing so in some cases. Sustainability is a major priority at CERN."

At a 70th anniversary event for CERN in Berlin, speakers reminded the audience that the World Wide Web was born at CERN — you could say the WWW was another fundamental idea, which, like the Higgs boson, glues our lives together. 

CERN has also nurtured growth in research areas like big data analytics, quantum computing, super conducting magnets and carbon dioxide cooling of computers.

Pirsche said simply: "Basic research needs support." 

Edited by: Zulfikar Abbany