The vacuum inside the Large Hadron Collider is emptier than the space surrounding the Moon.

The Large Hadron Collider (LHC) at CERN requires an ultra-high vacuum to ensure that proton beams do not collide with gas molecules. If air were present, the high-energy particles would scatter, making the experiments impossible. To achieve this, engineers must evacuate a volume of 9,000 cubic meters, which is roughly equivalent to the interior of a large cathedral.The internal pressure of the LHC is maintained at about 10 to the power of minus 13 atmospheres. This is significantly lower than the pressure found on the surface of the Moon, which is roughly 10 to the power of minus 12 atmospheres. Achieving this state takes several weeks of pumping using a complex three-stage system of vacuum pumps and specialized materials.Temperature also plays a critical role in maintaining this void. The LHC's magnets are cooled to 1.9 Kelvin, or -271.3 degrees Celsius, using 120 tons of liquid helium. This temperature is actually colder than the average temperature of outer space, which sits at approximately 2.7 Kelvin.This extreme cold helps the vacuum by causing any remaining gas molecules to freeze onto the cold surfaces of the pipes. This process, known as cryopumping, ensures the beam pipes remain clear for the trillions of protons traveling at 99.99 percent the speed of light. Without these precise conditions, the LHC could not function as the world's most powerful particle accelerator.