How can the earth be weighed?
On a summer night you can look up and see a starry constellation called libra, the scales. But this celestial balance cannot be used to it1easure the weight of the world. However, this weighty problem can be solved with equations of force, distance and matter. If you knew the right figures to use you might be able to perform a tricky experiment and solve this problem for yourself. The actual measuring job requires patience and unusual skills, but at least you could figure out how and why the experiment works. First, the job requires a thorough knowledge and understanding of the laws of gravitation. These laws immediately put us right on the difference between weight and mass. Mass is the amount of matter packed into the volume of an object. Weight is the force exerted upon the object by the attraction of gravity between it and its planet. A 100 pound earth boy would weigh 25 pounds on little mercury and 264 pounds on giant Jupiter; but his mass, the amount of material in his body, woul
