A rotating cylindrical space habitat is modeled as a thin shell of mass $M$ and radius $R$, rotating freely about its symmetry axis to produce an artificial gravity $g_0 = \omega_0^2 R$ at its inner wall. An internal mechanism then slowly expands the shell radially to twice its original radius, preserving the thin cylindrical-shell mass distribution. No external torques act on the habitat. What is the artificial gravity at the new inner wall?