Blow of mouth
Since many years I work on relativistic cosmology and
I say that the usual interpretation of the energy-momentum tensor is
a problem, and that within the framework of the relativity of
Einstein, the use of
this energy-momentum tensor requires an interpretation in terms of
COdensity and of COpressure
in a COmoving reference frame.
Indeed, it is only in a locally inertial system that one can
interpret this tensor in terms of density and pressure.
However for the study of the models of universe, it is very practical
to work with a comoving reference frame; but a COmoving frame
is not locally inertial.
It is now well-known that, for the isotropic models of universe
(with " big-bang") it arises a great number of problems within the framework
of the model says " standard ":
1- The universe is 8 to 14 billion years old following the value
of the Hubble constant (varying Ho from 50 to 100 km/s/Mpc), and thus
younger than of local objects (globular clusters for example).
2- There is a problem of horizon! That implies that the 3K radiation,
which appears isotropic, is not easily explained.
3- The fluctuations of this isotropic radiation are explained even
with difficulty.
4- The cosmological constant remains in a cloud of mysteries.
5- The angular distance is not always increasing according to redshift.
6- The problem of the missing mass on any level (cosmological, cluster,
galaxies) arise in a so disconcerting way which it sets up
an extraordinary bestiary of super-theories or (and) of exotic beings
to try to cure it.
etc...
22- It is disconcerting to see a recourse to the " black holes " for stopping
vacuums.
etc...
421- There is an instability with the initial conditions.
etc...
1024- I pay a champagne bottle to which will explain me the law
known as law of black body, within the framework of general relativity
(without the recourse to the equivalence of this one with the
postnewtonian theory of the gravitation).
etc... 
Notes: 22 means that I am surprised of the role of cop played by
" groups of experts in relativity " who pontify without worrying
about the difference between radial distance and " radius of curvature"
or who don't see the difference between " comoving frame of reference "
and "locally inertial frame of reference".
421- means that the models of universe translate the results
of a lottery. Obviously this disadvantage does not constitute
a logical objection.
1024- this power has equal only epistemological blindness
to mix two theories of which of anyone affirms that one denies the other.
The observational facts are obstinate and
the astronomers respect them, thanks.
The second member of the equations of Einstein
is a beautiful marquetry