Observational limits on the time evolution of extra spatial dimensions

Limits are imposed upon the possible rate of change of extra spatial dimensions in Kaluza-Klein and superstring theories by considering the consequences of such changes for primordial nucleosynthesis and the positioning of nuclear resonance levels in samarium, carbon, and oxygen. Previous limits from nucleosynthesis had not included strong-interaction effects. The strongest limits constrain the present rate of change of the mean radius of any additional spatial dimensions to be less than about ${10}^{\mathrm{-}19}$ ${\mathrm{yr}}^{\mathrm{-}1}$.