A definitive answer does not appear forthcoming from the Planck data set. Wiki quotes a critical mass density of 8.62 ^10-27 kg/m3. Others quote an overall mass density of 9.9 ^10-27 kg/m3, which means the Universe is closed - which it clearly is not. The standard equation 3H^2/8pi G at 70 (km/s)/Mpc gives an answer of 9.22 ^10-27 kg/m3, so the current value of 67.4 (km/sec)/Mpc - is clearly even lower. Can some true expert come forward give a detailed answer and clarify this crucial question?
While it is possible to express the mass density in kg/cubic meter, it’s not useful, because the Universe is expanding-at a rate that, itself, is increasing. That’s why the most useful way of expressing the msss density is in terms of ratios. So what Planck has found is that the known particles contribute about 4% towards the total density, hitherto unknown particles contribute about 21% and the rest can be identified with the energy density that can’t be attributed to matter, i.e. any kind of particles, but can be understood in terms of the cosmological constant, that’s as much a property of gravity as Newton’s constant.
The Planck 2018 final results paper is here:
https://arxiv.org/pdf/1807.06209.pdf
It gives various matter densities.
Spatial curvature is discussed in section 7.3 starting on page 41 and is consistent with a flat universe. In fact it favours a slight negative curvature but at a level of less than 0.4 sigma which is meaningless.
The Planck project by ESA (see Planck Collaboration, 2020) derived parameter values of H0=67.36 km/s/Mpc (6.889e-11 a-1), Ωbaryon=0.05249, and Ωcdm=0.2628. The sum of those fractions of the critical density correspond to a density value of 2.688e-30 g/cm3. The volume unit is based on comoving distance. Other recent estimates are similar, +/- 10%.
Planck 2020 H0= 67.41, Planck 2021 reanalysis H0 = 67.66. Hubble TRGB = 69.8 (km/s) /mpc. Other values are much higher but less reliable. There is what is called scientific tension on this question, which does seem to be easily resolvable.
Please verify
1.Eqn. 34 of the following paperArticle Dark Energy Is a Phenomenal Effect of the Expanding Universe...
shows the calculation as
4.9 x10^-27kg/m3
2.Further regarding experiments on Expanding universe explained in the paper
doi:10.20944/preprints202009.0452.v1
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