where ħ is the reduced Planck constant, a is the local acceleration, c is the speed of light, and kB is the Boltzmann constant. Thus, for example, a proper acceleration of 2.47×1020 m·s-2 corresponds approximately to a temperature of 1 K. Conversely, an acceleration of 1 m·s-2 corresponds to a temperature of 4.06×10−21 K.