arXiv:astro-ph/0503715 v2 31 Mar 2005 Late time failure of Friedmann equation Alessio Notari* Physics Department, McGill University, 3600 University Road, Montr´eal, QC, H3A 2T8, Canada (Dated: March 31, 2005) It is widely believed that the assumption of homogeneity is a good zeroth order approximation for the expansion of our Universe. We analyze the correction due to subhorizon inhomogeneous gravitational fields. While at early times this contribution (which may act as a negative pressure component) is perturbatively subdominant, we show that the perturbative series is likely to diverge at redshift of order 1, due to the growth of perturbations. In this case, the homogeneous Friedmann equation can not be trusted at late times. We suggest that the puzzling observations of a present acceleration of the Universe, may just be due to the unjustified use of the Friedmann equation. This would nicely solve the coincidence problem, without invoking a Dark Energy component.