Anti-de Sitter space bell. It might be described as being the "opposite" of the surface of a sphere, which has a positive curvature. General relativity is a theory of the nature of time, space and gravity in which gravity is a curvature of space and time that results from the presence of matter or energy. Energy and mass are equivalent (as expressed in the equation "E" = "mc"), and space and time can be translated into equivalent units based on the speed of light ("c" in the "E" = "mc" equation). A common analogy involves the way that a dip in a flat
Williams–Landel–Ferry equation to temperatures at or above T only; the constants are positive and represent Arrhenius behavior. Extrapolation to temperatures below T is erroneous. When the constants are obtained with data at temperatures below T, negative values of C, C are obtained, which are not applicable above T and do not represent Arrhenius behavior. Therefore, the constants obtained above T are not useful for predicting the response of the polymer for structural applications, which necessarily must operate at temperatures below T. The WLF equation is a consequence of time–temperature superposition (TTSP), which mathematically is an application of Boltzmann's superposition principle. It is