```

Table:  Cosmic Parameters

Quantity               Value                    Short explanation

Hubble constant H_0    [70 (km/s)/Mpc]*h_70     present day relative expansion rate:  h_70 = H_0/[70 (km/s)/Mpc]
where H_0_fiducial = 70 (km/s)/Mpc
Hubble time 1/H        (13.968 Gyr)/h_70        characteristic time scale of observable
Hubble length c/H      (4.2827 Gpc)/h_70        characteristic length scale of observable universe

Hubble constant H_0    67.37(54) (km/s)/Mpc     present day expansion rate (Planck 2018, p. 14)
Hubble constant H_0    73.24(170) (km/s)/Mpc    present day expansion rate (Riess et al., 2018 p. 10)

Age of universe        13.797(23)               time since the Big Bang (Planck 2018 p. 14)
Radius of observable   14.4 Gpc                 current distance to the point from which
universe (AKA                                   light starting at cosmic time zero can have reached by now
the particle horizon)                           (Wikipedia:  Particle horizon)

Recombination era      377,700(2300) years      time when the protons and electron recombined to make
neutral hydrogen (Wikipedia:  Λ-CDM model:  Parameters)

critical density       (1.35989*10**11)*h_70**2 M_☉/Mpc**3 ≅ medium-sized galaxy per cubic megaparsec
in natural units.

Omega                  1                        by definition for Lambda-CDM model
(AKA density          1.0005(40)               ??? for extension Lambda-CDM Model (Planck 2018 p. 68)
parameter)                                       which is agrees within uncertainty  with being exactly 1
Omega = (mean universal density)/(critical density)

Omega_Lambda           0.6853(74)               Assuming Omega = 1 (Planck 2018 p. 14)
Omega_matter           0.3147(74)               Assuming Omega = 1 (Planck 2018 p. 14)
Omega_baryons          0.02233(15)/(h_100**2)   Assuming Omega = 1 (Planck 2018 p. 14)
≅ 0.045 = 4.5 %
Omega_stellar          0.004 = 0.4 %            Includes stars and ISM (cosmos_energy_pie_chart ...) ```

Note: Cosmological parameters always vary a bit between references since each reference does their analysis a bit differently. The above values are representative of year 2018 and will need updating before or circa 2025.
References:
Local file: local link: cosmic_parameters.html.
File: Cosmology file: cosmic_parameters.html.