A cosmological limit on the possible variation of G

The observed light-element abundances in the Universe of $$X(\text{He}^4)=25^{+ 7}_{-3}$$ per cent and $$X(\text D)\sim10^{-3}$$ per cent interpreted within the framework of the standard big-bang theory are used to limit possible temporal evolution in the Newton gravitational ‘constant’, G, to |G/G|₀ ≲ 1.5 ± 0.7 × 10⁻¹² yr⁻¹. This limit is nearly two orders of magnitude stronger than that obtained by Shapiro using direct-radar ranging techniques. This result may be used to rule out and severely constrain proposed theories of gravity in which G is allowed to evolve in time. Examples are given and it is indicated how a similar method could considerably improve the limits upon allowed variations in other fundamental ‘constants’.