 Consider a rock under the sun, early in the morning. During any time interval, the rock’s temperature rises, going from T to T+1, to T+2, to T+3. Now consider a NOT gate that feeds its output back to itself. At first, suppose the NOT gate receives ‘0’ as an input; it then returns a ‘1’. After the ‘1’ is fed back to the NOT gate, the gate returns a ‘0’ again, and so on. The NOT gate goes back and forth between outputting a ‘0’ and outputting a ‘1’. Now map physical states T and T+2 onto ‘0’; then map T+1 and T+3 onto ‘1’.