Ray Cummings 
The Gravity Professor 

Tubby said, “Why did we roll that ball?”

The professor’s face clouded again with anxiety. “To save the world, ” he said. His voice trembled with emotion. “In seven million nine hundred thousand and two years, one month, six days, four hours, thirteen minutes, eight and one-quarter seconds, the world would have been destroyed if we had not moved that ball just where we did.”