Protons begin circling as Large Hadron Collider switches on

The Large Hadron Collider was built to explain the mysteries of the universe ? what everything is made of and how the universe is held together. On its first day of operation, scientists circulated a beam of protons around the collider’s 27 km tunnel. Eventually, scientists will introduce another beam traveling in the opposite direction, both traveling close to the speed of light. What happens when the two beams collide? The Takeaway talks with BBC science correspondent Tom Feilden. Guest: Tom Feilden, BBC Science Correspondent