Nucleosynthesis in the early universe. Graph showing how the proportions of the chemical elements formed in the early period of a Big Bang universe vary with the initial conditions. Their fraction by mass is the axis at left (mostly hydrogen and helium). Present-day solar system abundances are at right. 14 elements and isotopes are modelled: hydrogen (H, red), deuterium (D, black), helium (He, orange), oxygen (O, pink), carbon (C, light green), nitrogen (N, red), lithium (Li, blue), boron (B, grey), beryllium (Be) and magnesium and heavier elements (Mg, dark green). The initial conditions of the universes (top and bottom) include photon temperature (theta symbol), the deceleration parameter (q0), baryon density (p0), and the cosmological parameter h (related to the Hubble constant).