Why is most of the information about the matter that went into forming the black hole lost ?
formula_37 Under the assumption of an otherwise empty universe , so that no matter or cosmic microwave background radiation falls into the black hole , it is possible to calculate how long it would take for the black hole to dissipate : formula_38 Given that the power of the Hawking radiation is the rate of evaporation energy loss of the black hole : formula_39 Since the total energy E of the black hole is related to its mass M by Einstein 's mass - energy formula : formula_40 formula_41 We can then equate this to our above expression for the power : formula_42 This differential equation is separable , and we can write : formula_43 The black hole 's mass is now a function " M " ( " t " ) of time " t " .