Geometry specific (eq. ( )) Homogeneous (eq. ( )) Homogeneous, small R (eq. ( )) estimate should be taken cautiously as it does not consider collective effects specific to the molecular structure. For instance, Tegmark also used a similar approach to estimate the decoherence in microtubules in 10 -13 s. However, a recent study by Babcock et al. detected superradiance effects in microtubules due to the collective interactions protecting the network against decoherence for more extended periods. As another example, let us gauge how long it takes for the wave function of a large chunk of matter to collapse, according to the Diósi-Penrose model. Consider a piece of iron crystal in its lowest-energy bcc structure (-Fe) with vacancies, as illustrated in Figure . In principle, these two iron structures can exist in a quantum superposition of the type 12 left right cc  =+ . We will not mind the geometric details of the structures and suppose that the atom involved in the defect is displaced by 2.8 Å between the two states, and all the remaining atoms remain fixed. Given a vacancy concentration of 10 14 mol -1 and a crystal volume much bigger than the superposition displacement, we can use (9) for the homogeneous medium to estimate the Diósi-Penrose collapse time as a function of the number of atoms (and, equivalently, the total mass).