The End of an Era — And a New Beginning

On June 29, 2026, the Large Hadron Collider (LHC) — the world's largest and most powerful particle accelerator — was switched off. It will not operate again until 2030.

This isn't a故障. It's Long Shutdown 3 (LS3), a planned four-year pause to transform the 27-kilometer (17-mile) ring beneath the French-Swiss border into the High-Luminosity Large Hadron Collider (HiLumi LHC) — a machine ten times more powerful than its original design.

What the Upgrade Means

The core mission: increase the collider's luminosity — the number of particle collisions per second — by a factor of 10. This will: - Triple the current collision rate - Produce an estimated 380 million Higgs bosons over its lifetime (vs. 55 million to date) - Increase the odds of observing rare, never-before-seen phenomena

"This is a very important moment," said HiLumi LHC project chief Markus Zerlauth. "From Monday, we will be entering a new phase."

To achieve this, 1.2 kilometers of magnets and components will be removed and replaced — a logistics and engineering challenge involving thousands of personnel.

The Scientific Stakes

The LHC was instrumental in discovering the Higgs boson in 2012, completing the Standard Model of particle physics. But the Standard Model only describes 5% of the universe. Dark matter, dark energy, and the nature of the early universe remain profound mysteries.

"It really is an opportunity to explore the universe in a way we haven't done before," said Mark Thomson, CERN's director general.

What Happens Next

- 2026–2030: Construction, magnet replacement, and systems testing - 2030: HiLumi LHC goes online - ~2040s: End of operational lifespan, with plans for a successor accelerator

During the shutdown, researchers will continue analyzing data already collected. And some CERN-developed technologies — from medical imaging to art restoration — will continue finding their way into everyday life.

For now, the LHC sleeps. When it wakes, it may redefine our understanding of the universe.

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