|
 |
 advertisement
| |
|
|
|
|
|
Physicists Work Forces Earth to Drop Weight
By
Pasadena Bureau Chief
posted: 04:17 pm ET
01 May 2000
|
Physicists Work Forces Earth to Drop Weight Two physicists announced Monday that they have made the most precise calculation yet of Isaac Newtons gravitational constant -- a number that has allowed them to weigh in with a revised mass for our Earth. According to the new figures, the Earth weighs 5.972 sextillion -- thats 5,972 followed by 18 zeroes -- metric tons. Previous estimates put the globes mass at 5.98 sextillion metric tons. Jens Gundlach and Stephen Merkowitz, of the University of Washington, arrived at the new figure by refining the measurement of Newtons gravitational constant, or G, which tells us how much gravitational force acts between two masses separated by a known distance. English physicist Henry Cavendish first calculated a value for the constant in 1798, but as of 200 years later there is still a 0.15 percent uncertainty about the number. Gundlach, a research associate physics professor at the Seattle university, called that a "huge embarrassment for modern physics." "Gravity is the most important large-scale interaction in the universe, theres no doubt about it," Gundlach said in a statement. "It is largely responsible for the fate of the universe. Yet is relatively little understood." The pair made their measurement with an updated version of a device used by Cavendish called a torsion balance. The computer-controlled version recorded the tiny accelerations from the gravitational effects of four 17.9-pound (8.14-kilogram) stainless steel balls on a small gold-coated Pyrex plate just 0.06 inches (1.5 millimeters) thick. Analysis of the first measurements from the device gives an uncertainty of only about 0.0015 percent for G, which if verified represents a substantial improvement, the two report. Gundlach and Merkowitz, a postdoctoral researcher, presented their results Monday at the American Physical Societys spring meeting in Long Beach, Calif.
|
|
|
|
|
