Uncertainty in Newton’s constant and precision predictions of the primordial helium abundance

The current uncertainty in Newton's constant GN is of the order of 0.15%. For values of the baryon to photon ratio consistent with both cosmic microwave background observations and the primordial deuterium abundance, this uncertainty in GN corresponds to an uncertainty in the primordial ⁴He mass fraction YP of ±1.3×10^-4. This uncertainty in YP is comparable to the effect from the current uncertainty in the neutron lifetime τₙ, which is often treated as the dominant uncertainty in calculations of YP. Recent measurements of GN seem to be converging within a smaller range; a reduction in the estimated error on GN by a factor of 10 would essentially eliminate it as a source of uncertainty in the calculation of the primordial ⁴He abundance.