The Electric Universe (Plasma Cosmology) theory can explain the observed structure and behavior of the universe without recourse to theoretical dark matter/dark energy, which are by their very nature unobservable. In essence the existing theories do not account for the electromagnetic force in space, assuming a "gravitation only" environment. When the gravitation only model was observed there were serious anomalies. Instead of reexamining their underlying assumptions cosmologists "created" speculative dark matter/energy to explain the anomalous observations.

Here is a link with more detailed info:

http://www.electric-cosmos.org/introduction.htm