Show old experiment measures weight of the earth the measuring ot of the tha mass or weight of the earth is a familiar astronomical problem other bodies are weighed by measuring the attraction ot of the earth upon them the same end Is accomplished in the case of the earth by comparing the attraction which this globe exerts upon some body on its surface with the attraction exerted upon the same body by a known mass at a known distance there have been several methods tried to accomplish this the simplest of which Is that of observing the deviation from the vertical of a plumb line near an Isolated mountain the volume of the mountain must first be found of course by accurate survey and its density calculated from the geological structure and density of its component compon mt rocks but this plan though simple Is not nearly lyas as accurate in result as that of computation by means of the torsion balance this method Is known to astronomers as the cavendish experiment from the scientist who first applied it in 1789 methods consists of measuring very accurately the attraction exerted by two large spheres ot 61 metal on two much smaller metal balls two globe of lead are attached i to the te extremities ex of a large horizontal bar movable horizontally upon a center above this center a light horizontal rod having on its ends two very small balls of lead Is supported by a fine wire when the rod bearing the small balls la is in equilibrium the bell ball having the globes of lead is moved until these globes are brought nearly in contact with the small balls the force of their attraction then tends to draw the small rod from its position of equilibrium and the amount of torsion thus produced is measured carefully this experiment Is repeated several p times and the average of its results taken so as to be as nearly accurate a possible it is plain that the attraction of the large globes on the small ball la 13 to the attraction of the earth upon the small balls 1 e their weight weigh tas as the mass of the large balls is to the mass of the earth the result of these experiments has given the weight of the earth approximately P as s tons |