China Stopped Production On The World's Largest Particle Accelerator - Here's Why

Planned to be the largest particle accelerator in the world, China's Circular Electron Positron Collider (CEPC) was meant to be about 100 kilometers or 62 miles long. That's much bigger than CERN's Large Hadron Collider (LHC) with an approximately 27 kilometer circumference – or nearly 17 miles. These systems, especially the LHC, play a huge role in studying how the universe began during the Big Bang.

Development for CEPC started in 2012, around the time CERN discovered the Higgs boson particle; however, it appears the multibillion-dollar project is now paused. It was not included in the country's next five-year plan, spanning 2026 to 2030, which means it's considered a lower priority by the state — it will see less funding and resources. Wang Yifang from the Institute of High Energy Physics confirmed the change, but although the recent proposal to be included in China's five-year plan was denied, the team plans to resubmit the CEPC proposal in 2030.

While it hasn't been directly confirmed, the CEPC would cost an estimated $5.1 billion, money that the country might want to divert elsewhere. In that case, Wang says if the European Future Circular Collider (FCC) – the next-generation collider that would effectively be LHC's successor with a much larger 90.7-kilometer (or 56-mile) circumference – is approved before the 2030 proposals, they'll likely join forces with the related teams instead.

To summarize, China's CEPC is out, likely due to cost and resource requirements, but the European's FCC still has potential, and the Chinese physicist team may join up if the proposal is approved before the next round of China's plans.

Discoveries from the systems we have operating now, like the Higgs boson discovery at LHC, occur because of how particle accelerators actually work. They fire particles into a big tunnel, or underground rings, which circle around at incredibly fast speeds before colliding. By observing these collisions, scientists get a glimpse into what the early universe looked like, as well as other foundational elements like quarks, the building blocks of visible matter in the universe. Scientists also used the system to create quark soup, a substance that hadn't been seen for billions of years before that. Generally speaking, when two particles collide, for the infinitesimally small span of time afterwards, scientists can see traces or patterns that are otherwise invisible — that's exactly how they discovered the Higgs boson.

The larger colliders, like CEPC or FCC, would not only introduce larger tunnel systems but more advanced and unique equipment, to uncover heavier or different particles, many of which the LHC simply cannot create. Imagine what kind of alchemy could be achieved with the larger, more capable collider systems.

As the current system, the LHC is expected to be phased out by the 2040s; meanwhile, the FCC, if approved, will begin development in the 2030s. That said, construction can't start quite that easily: Before anything happens, the CERN Member States and international partners have to give the upgrade project a greenlight.