Crossing the Equator
Sally is traveling by ship from south of the equator to the north. She has a nice little cabin with a bathroom but no window. Sally has no compass nor other instruments. Just the general luggage one brings on board a long cruise. Yet without leaving her room or talking with anyone Sally will be able to tell when the ship has crossed the equator. How?
Six glasses are in a row. The first three are filled with milk and the last three are empty. By moving only one glass can you arrange them so that the full and the empty glasses alternate?