Creep is also a materials science phenomenon. Materials subject to persistent stress even well below their yield strength can experience creep, whereby the atoms slowly "flow" in response to the stress and the material deforms accordingly. This is especially prevalent at elevated temperatures, when atomic mobility is increased. It is the dominant engineering concern with jet turbine blades, which experience high temperatures and tremendous centrifugal forces from spinning at tens of thousands of RPM.
Note: Vatican City and Switzerland have square flags. So, rectilinear, but not rectangular.
Creep is also a materials science phenomenon. Materials subject to persistent stress even well below their yield strength can experience creep, whereby the atoms slowly "flow" in response to the stress and the material deforms accordingly. This is especially prevalent at elevated temperatures, when atomic mobility is increased. It is the dominant engineering concern with jet turbine blades, which experience high temperatures and tremendous centrifugal forces from spinning at tens of thousands of RPM.