Since the dawn of history, human activities have always been closely related to friction, the resistance to sliding. It is thanks to friction that one can stand and walk on the ground, one can wear clothes, one can make fire by rubbing two sticks together, or one can even start and stop a car. In these cases friction is very useful for human beings. In many other cases, however, human activities have been very much hampered by friction since ancient times. How to diminish friction is one of the most basic technological problems. For example, when a heavy.
