CERN turned off the Large Hadron Collider on June 29, 2026, at the start of Long Shutdown 3 for major upgrades. It’s expected to come back in a new high- luminosity phase around 2030.

Quick Scoop

The shutdown was planned, not an emergency. CERN said the machine had finished its final physics run and was switched off to prepare the next upgrade cycle.

What changed

  • The LHC entered a multi-year maintenance and upgrade period called Long Shutdown 3.
  • The goal is to prepare the High-Luminosity LHC, which should begin operations in 2030.
  • News coverage on June 29, 2026, also reported that it was switched off that Monday.

In plain English

They didn’t “turn CERN off” entirely; they turned off the Large Hadron Collider, CERN’s main particle accelerator, for a planned overhaul.

TL;DR

June 29, 2026.