AbstractWe studied the isotropic ball using data of Preliminary Reference Earth Model (PREM). It is shown that such a ball should be either destructed or gone into a more stable equilibrium state with uneven distributed deformation under thermobaric condition of the inner core. Body elastic waves with real velocities cannot propagate in it. This manuscript is devoted to study the situation from the standpoint of nonlinear geomechanics. A number of necessary principles of Mechanics of Deformable Solid Body (MDSB) is given at the beginning of the analysis. A brief review of the published latest experimental work is performed. It is established that proper attention to the role of the MDSB principles in micro‐scale (nano) experiments of the physical level has not been given. Deformation properties of solid bodies are emphasized in microscale and macroscale. Application of linear acoustoelasticity and extrapolation of Birch's linear law of the inner core and use of an idea on variability of elasticity moduli with the increase of pressure and temperature have contributed to obtained pseudo data for the geological medium of the Earth's core instead of linear data on the physicomechanical properties. It is proposed that parallel to elimination of the indicated disadvantages, collection, processing and interpretation should be performed using nonclassically linearized approach. This set of necessary actions is offered as the “key” of geomechanical analysis. The proper application will allow conducting similar analysis concerning other solid‐state structures of the Earth.