Starting with an ordinary cup of water, you add exactly one ice cube. Now, after you add the ice cube, you notice that the level of the water in the cup rises (I believe that everyone would agree with this scenario). After about an hour, you return to your cup of water and notice that the ice cube has melted entirely. Ignoring the evaporation of the water over time, has the water level risen, fallen, or has it remained the same? Explain.