The Largest Machine Ever Built Is Colder Than Space
To smash protons together, CERN's 27-kilometre collider chills its magnets to 1.9 kelvin — colder than the depths of the universe.
The Large Hadron Collider is the world’s largest and most powerful machine: a ring of superconducting magnets 27 kilometres around, buried 50 to 175 metres beneath the French–Swiss border outside Geneva.
To steer protons at almost the speed of light, the magnets must be superconducting, which means they have to be brutally cold. CERN chills them to 1.9 kelvin — about -271.3 C, just shy of absolute zero.
That makes long stretches of the collider colder than outer space, where the residual heat of the Big Bang keeps the void at around 2.7 kelvin. Cooling the ring uses the largest cryogenic system on Earth, flooding the magnets with superfluid helium.
Only at these temperatures does electrical resistance vanish entirely, letting the magnets carry the enormous currents needed to bend a proton beam around such a vast circle.
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