Cosmology is a field of physics in which the use of general relativity theory is indispensable. However, a cosmology based on newtonian theory for gravity is possible in certain circumstances. The applicability of newtonian theory can be substantially extended if it is modified in such way that pressure has a more active role as source of the gravitational field. This was done in the neo-newtonian cosmology. The limitation on the construction of a newtonian cosmology, and the need for a relativistic theory in cosmology are reviewed. The neo-newtonian proposal is presented, and its consequences for cosmology are discussed.
newtonian cosmology; relativity
