pub const T_CMB_0: f64 = 2.726;Expand description
Default CMB temperature today, in K.
Value 2.726 K (Mather et al. 1999) chosen for compatibility with
CosmoTherm v1.0.3 reference data used in validation. Differs by 0.02%
from the Planck-era Fixsen (2009) value 2.7255 K; the
crate::cosmology::Cosmology::planck2018 preset overrides this.