  I review some theoretical ideas in cosmology different from the standard "Big
Bang": the quasi-steady state model, the plasma cosmology model,
non-cosmological redshifts, alternatives to non-baryonic dark matter and/or
dark energy, and others. Cosmologists do not usually work within the framework
of alternative cosmologies because they feel that these are not at present as
competitive as the standard model. Certainly, they are not so developed, and
they are not so developed because cosmologists do not work on them. It is a
vicious circle. The fact that most cosmologists do not pay them any attention
and only dedicate their research time to the standard model is to a great
extent due to a sociological phenomenon (the "snowball effect" or
"groupthink"). We might well wonder whether cosmology, our knowledge of the
Universe as a whole, is a science like other fields of physics or a predominant
ideology.
