Concept of radiometric dating
These seemingly metaphysical questions are today, in these ways, slowly being converted into hypotheses of the physical sciences.
The current consensus hinges upon the Boltzmann-Shannon identification of the logarithm of phase space volume with the negative of Shannon information, and hence to entropy.
The time reversal of a black hole would be a hypothetical object known as a white hole. While a black hole has a beginning and is inescapable, a white hole has an ending and cannot be entered.
The forward light-cones of a white hole are directed outward; and its backward light-cones are directed towards the center.
One can, however, equally well imagine a state of the universe in which the motions of all of the particles at one instant were the reverse (strictly, the CPT reverse).
However, quantum noninvasive measurements are predicted to violate time symmetry even in equilibrium, A toy called the teeter-totter illustrates, in cross-section, the two aspects of time reversal invariance.
The name comes from a thought experiment described by James Clerk Maxwell in which a microscopic demon guards a gate between two halves of a room.
It only lets slow molecules into one half, only fast ones into the other.
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co.
Although in restricted contexts one may find this symmetry, the observable universe itself does not show symmetry under time reversal, primarily due to the second law of thermodynamics.
Our daily experience shows that T-symmetry does not hold for the behavior of bulk materials.