Electromagnetism, nuclear strong, nuclear weak, and the weird notably weaker force of gravity. Now a force is something fundamental to reality, gravity described as the bending of spacetime causing objects with mass to change tregectery. While the 3 remaining forces use quantum fields, and apply change through elementary particles. The Standard Model is old fashioned, and sticks to four forces already mentioned. Then Einstein wasn't convinced gravity belonged with the other three, even suggesting gravity is a byproduct of the curvature of spacetime. Currently there is no quantum field theory for gravity.
The ultimate goal of studying the 4 forces is to combine them into to a grand unified theory. When energies are in excess of the mass energies of the W and Z particles for the weak interaction, or in the neighborhood of 100GeV, the weak and electromagnetic forces appear to be unified. However, the conditions required to also include the strong force is thought to occur at even higher temperatures 1014 GeV. If the ordinary concept of thermal energy applied, it would require a temperature of 1027 K for the average particle energy to be 1014 GeV. The likely final and hardest force to unify will be gravity. How would a 5th force effect unification? Would we be completely clueless in attempting to combine a 5th force to the electroweak combination?
When people attempt to describe or reveal a 5th force. Why? What would it mean for our current understanding of physics, and is there any information suggesting or implying how a 5th force could possibly behave? Could a temporal force exist, the way a temporal dimension can?
