The Poincaré recurrence time of certain systems is the time for them to revert to a state almost identical to their current state. Don Page, physicist at the University of Alberta, Canada, has estimated the Poincaré recurrence time for the quantum state of a hypothetical box containing a black hole with the mass \(M\) equal to mass of observable universe using the equation \(t_{poincare}=e^{e^{4 \pi imes M^2}} \approx 10^{10^{10^{10^{2.08}}}}\) where time and mass \(M\) are expressed in planck units. This number is so large that the estimate remains the same whether measuring time in Planck times, years, millennia, or any other time units of the same exponential order.