Discovery: Big and Bigger

The smaller the thing one looks at, the bigger the microscope required. That's why the circular Large Hadron Collider at Cern, where they discovered the Higgs boson, is 27kms long and its detectors tens of metres across. But to dig deeper still into the secrets of the Universe, they're already talking about another machine four times bigger, to be built by the middle of the century. Roland Pease asks if it's worth it.