# The Limits of Inference

The ‘*Concordance Model*’
that encompasses an initial ‘*inflationary
model’* and the subsequent *‘Lambda
Cold Dark Matter (ΛCDM*)’
model still aligns to the basic idea of the `*Big
Bang*` model. This composite model has evolved in response to
an increasingly detailed study of the Cosmic Microwave Background (CMB)
radiation plus the large-scale structures of the cosmos, which appear
to exist within an accelerating expanding universe. As such, it is possibly
the most accepted model that is in general agreement with observed phenomena.
However, it is also a model based on normal matter only constituting
4% of the universe with the remaining 96% described in terms of 23%
cold dark matter and 73% dark energy; the exact nature of which are
essentially unknown and unverified.

It is stated from the outset that this discussion does not intend,
or aspire, to replicate the in-depth technical details supporting the
concordance model, which may be found within other websites. Instead,
the goal is to select certain key issues and see what, if any, physical
interpretation can be associated with this model. The discussion also
attempts to strike some balance in terms of arguments for and against
the model; for while this model is supported by many observations, there
are some key aspects that still remain conjecture. So, as in other areas
of science, we need to recognise where aspects of this model are based
on speculative assumptions, especially those that may have been extrapolated
well beyond the `*limits of inference’.
*This is not a criticism, just a statement of the processes involved
and one that the reader may wish to take into consideration.

However, to begin this final section of the overall discussion, we
shall assume that the concordance model is an accepted cosmological
model, which includes, and requires, the conceptual ideas of cold dark
matter and dark energy; although they are not really explained by the
*standard particle model*
of physics and, as such, may be said to be unverified. So, in essence,
the concordance model describes a universe that is 13.7 billion years
old and made up of 4% baryonic matter, 23% dark matter and 73% dark
energy. In addition, the Hubble constant [H] is said to reflect an expanding
universe with a measured value of 71 km/s/Mpc linked to an overall energy
density, which is very close to the critical energy-density value. As
far as can be ascertained at this time, this model appears to conform
to certain key observations, although this statement should not be interpreted
as a statement that the model has pass all reasonable criteria of empirical
verification.