Category: Toward a Theory of Everything

The testing of hypotheses and theoretical predictions is such an integral part of science that we really have to question any theory that cannot be tested. If a scientific theory cannot be tested, is it really a scientific theory at all? Is it good enough that experimental tests may be possible in the distant future?…

Loop quantum gravity (LQG) is a theoretical framework that tries to quantize space and time directly. This seems to make a lot of sense, given that general relativity relates gravity to the shape of spacetime itself. If the ultimate goal is a quantum theory that applies to gravity, it stands to reason that space and…

String theory is actually a name for a class of theories which may eventually give us a theory of everything. The basic principle of string theory is that all of the elementary particles of the standard model are just different modes of vibration of a more fundamental object: a tiny, one-dimensional “string.” These are not…

The first extension of the standard model that attempts to address some of its shortcomings and incorporate gravity is called supersymmetry, or SUSY for short. SUSY proposes that every fermion has a boson partner that is a totally new particle (not one of the known exchange bosons). Not only that, but all the known bosons…

In the next few sections, we’ll briefly describe some of the ways that theorists are taking on the huge challenge of bringing gravity into the standard model.

As we have seen, the standard model does a pretty good job with three of the four fundamental interactions of nature. Fitting gravity in remains a huge challenge. Another shortcoming related to this is that there are still a fairly large number of free parameters in the model. A free parameter refers to a quantity that is…

It seems that physicists are never satisfied. Their goal is no less than a complete understanding of the universe—past, present, and future. Quantum physics has produced great progress toward this goal, and the standard model summarizes that progress and our current state of knowledge very well. But it certainly does not give us a complete…