  The similarity in atomic structure between liquids and glasses has stimulated
a long-standing hypothesis that the nature of glasses may be more fluid like,
rather than an apparent solid. In principle, the nature of glasses can be
characterized by measuring the dynamic response of rheology to shear strain
rate in the glass state. However, limited by the brittleness of glasses and
current experimental techniques, the dynamic behaviors of glasses were mainly
assessed in the supercooled liquid state or in the glass state within a narrow
rate range. Therefore, the nature of glasses has not been well elucidated
experimentally. Here we report the dynamic response of shear stress to shear
strain rate of metallic glasses over nine orders of magnitude in time scale,
equivalent to hundreds of years, by broadband stress relaxation experiments.
The full spectrum dynamic response of metallic glasses, together with other
glasses including silicate and polymer glasses, granular materials, soils,
emulsifiers and even fire ant aggregations, follows a universal scaling law
within the framework of fluid dynamics. Moreover, the universal scaling law
provides comprehensive validation of the conjecture on the jamming phase
diagram by which the dynamic behaviours of a wide variety of glass system can
be unified under one rubric parameterized by thermodynamic variables of
temperature, volume and stress in trajectory space.
