Can not say enough to this great-short story. One of my favorites ever.
I have read this story countless of time and it continues being fascinating.
A barely functional robot (Multivac) is being asked the fundamental question of how can we decrease the amount of entropy of the universe in order to "save" it.
This question span eons into the future (is asked every couple of decades) while versions of the robot are more and more intelligent. We would guess that as the robot gathers vast amount of data with the passing of the centuries, it will be able to give a proper answer to the question.
A flawless story with a superb ending.