Another example of this extensivity problem may occur in the photoisomerization of retinal chromophores in proteins. Despite the significant conformational changes that the chromophore experiences when moving from the cis to trans conformations, the geometric distortions in the protein and water environments are limited. That is so to the point that in advanced atomistic simulations, only the sidechain atoms of the residues forming the cavity around the retinal and a few water molecules are geometrically relaxed. Most and all remaining protein is unchanged. It could be that this initial photoisomerization process, with limited geometric displacements, does not reflect later, more extensive geometric distortions that could enhance the gravitational self-energy. However, it could equally be that these later distortions are still restricted to the immediate environment, implying a long collapse time.