“.... attempts to combine these two forces with the strong nuclear force into what is called a grand unified theory (GUT). This title is rather an exaggeration: the resultant theories are not all that grand, nor are they fully unified, as they do not include gravity. Nor are they really complete theories, because they contain a number of parameters whose values cannot be predicted from a theory but have to be chosen to fit in with experiment. Nevertheless, they may be a step toward a complete, fully unified theory.” PhysicsScience HumorGrand Unified Theory Book:A Briefer History of Time Source: A Briefer History of Time