Grand Unified Theories (GUTs)
After the electroweak force which successfully combines and weak and electromagnetic forces, the next attempt is to combine the strong and electroweak forces. There are many theories that describe this unification. They are collectively called grand unified theories (GUTs). None has yet emerged as a correct one. This is because the predicted energy scale for the forces to unite is in the order of
1015 GeV. This is about 1011 times the energy produced by the largest particle accelerators to date! Construction of accelerators to achieve this energy scale is not possible at present time, even in the foreseeable future.
For this reason, we have to indirectly test GUTs based on experiments with obtainable energies. One prediction of GUTs is that proton is not strictly a stable entity but should decay on a time scale greater then 1031 years (the age of our universe is, give or take, only around 1010 years). One experiment setting to test this idea is the Super-Kamiokande detector. The setting consists of
a huge underground (to shield against cosmic ray) chamber contains 32 000 tons of water. Large volumes are required to probe the extremely rare decay event. The decays should produce flashes of light (Cerenkov light) which may capture by photomultiplier detector tubes lining the walls.
So far, no decay has been dectected and the quest continues...
Another prediction of GUTs are magnetic monopoles which carry magnetic but not electric charge. These have long been predicted but never detected.
Theory of Everything (TOE)
Particle physicists love theories and they take the quest of unifications even a step further. This final step is to include gravity into GUTs to create a theory of everything. It is also sometimes referred to as super unified theory. One assumption is that the known particles should each have a 'superpartner' of different spin. These superparticles are predicted to be very heavy, way beyond the
current achieveable energy scale. At the moment the development of TOE is difficult due to lack of a viable quantum theory of gravity. At present time the superstring theory is a popular theoretical approach that might provide a realistic TOE.
What do you get from TOE? Perhaps the knowledge of the mystery of creation/formation of our universe.