Why is the LHC underground?

The LHC uses the tunnel that was built to house CERN’s previous large accelerator, the LEP, which was dismantled in 2000. Digging an underground tunnel proved to be the best option for a 27-km machine, since it’s cheaper than acquiring land to build on at the surface and the impact on the landscape is minimised. In addition, the Earth’s crust provides good shielding against radiation.

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