Dark energy, an illusion?

In 1998 the study of the explosion of 'Ia type' supernovae allowed scientists to state that the universe is in expansion. This statement was based on the cosmology standard model which implies for ease of calculation that the universe should be considered as homogeneous at large scale. So, in order to explain universe expansion, we are obliged to admit the existence of dark energy that may represent 68% of universe content and however, has not yet been discovered. An ancient explanation made a comeback recently. It consists in taking into account the heterogeneities in the spatial distribution of matter in the universe. Matter rich regions tend to bend space-time more, so that universe expansion is there slower than in empty areas. Updated computations show that these heterogeneities could explained universe dynamics without requiring the existence of dark energy. (A.C.)