- astronomical_distances_larger.html.
- cosmos_energy_pie_chart.html.
- Keywords: Cosmology.
- Planck 2018 results. I. Overview and the cosmological legacy of Planck 2018: The last word from the Planck spacecraft (2009--2013). Note especially age of the observable universe = 13.797(23) Gyr (Planck 2018) (see Planck 2018: Age of the observable universe = 13.797(23) Gyr).
- Riess et al. 2018.
- Wikipedia: Λ-CDM model: Parameters.
- Wikipedia: Observable universe.
- Wikipedia: Particle horizon.

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.