The big idea is that the universe is spherical. As all the matter in the universe makes its way around the sphere, it'll all eventually come together to a point, then wildly explode again in the other direction, as a cycle. Since we don't have billions of years to wait around to prove if this is true or not, we can recreate the conditions somewhat by using this collider. Instead of "all the matter in the universe," they'll collide protons. Hopefully the explosions are small.