Very good article by Paul Rincon at the BBC, via Mark Trodden of Cosmic Variance:
In the 1970s, the theory known as the Standard Model was considered a triumph of theoretical physics, incorporating all that was then known about the interactions of sub-atomic particles.
Today it is regarded as incomplete, a mere stepping stone to something else.
The Standard Model cannot explain the best known of the so-called four fundamental forces: gravity; and it describes only ordinary matter, which makes up but a small part of the total Universe.
The $2.3bn Large Hadron Collider (LHC) at Cern (The European Centre for Nuclear Research), which is paid for by contributions from Cern’s European member countries (including the UK), should reinvigorate physics’ biggest endeavour: a grand theory to describe all physical phenomena in nature.
About 100m below us, in a tunnel that runs in a ring for 27km (17 miles), the LHC is being assembled from its constituent parts like a vast, impossibly complex Meccano set.
When it is switched on for a pilot run in summer 2007, this huge physics experiment will collide two beams of particles head-on at super-fast speeds, recreating the conditions in the Universe moments after the Big Bang.
The beam collisions should create showers of new particles, revealing new physics beyond the Standard Model. In order for that to happen, the LHC needs to reach much higher energies than previous colliders.
More here.