A Gold universe is a cosmological model of the universe. In these models, the universe starts with a Big Bang and expands for some time, with increasing entropy and a thermodynamic arrow of time pointing in the direction of the expansion. After the universe reaches a low-density state, it recontracts, but entropy now decreases, pointing the thermodynamic arrow of time in the opposite direction, until the universe ends in a low-entropy, high-density Big Crunch. There are two models of the universe which support the possibility of a reversed direction of time. The first begins with a state of low entropy at the Big Bang which continually increases until the Big Crunch. The second, a Gold Universe, posits that entropy will increase only until a moment of contraction, then gradually decrease.