Symbol rho_m

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…decay, and impacts) for solid-like material to behave as a slow-moving fluid over geological time. The basic settling physics is captured by a Stokes-law sinking velocity for a dense blob of radius r and density $\rho_m$ moving through a less dense, viscous mantle of density $\rho_s$ and viscosity $\eta$ : $v = \frac{2 g r^2 (\rho_m - \rho_s)}{9\eta}$. This is a first-order model, not a complete theory of core formation — real planetary interiors involve diapirism, iron rain, and turbulent entrainment rather than single isolated blobs —…

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