Powerful vacuumInside the LHC, two beams of particles will whizz round at incredibly high speed in opposite directions.
Scientists need to know which particles are colliding inside the ring. So they suck everything out of the tube, creating a vacuum, and then add only the particles they want. This means there are so few particles left inside the ring that it is the emptiest place in the universe.
Image: Jennie Hills/Science Museum