LONG BEACH, Calif. -- Using a new, more precise measurement of the force of gravity, physicists have recalculated the mass of the Earth and determined the planet is a bit lighter than previously thought.
The new estimate is that the third rock from the sun has a mass of 5.972 sextillion metric tons, or 5,972 followed by 18 zeros. Textbooks currently list the mass at 5.978 sextillion metric tons."We think we know the weight of the Earth better than anyone else before," Jens Gundlach, a physicist at the University of Washington, Seattle, said Saturday at a meeting of the American Physical Society.
The new measurement stems from a recalculation of the force of gravity, a constant represented by the letter "G." It is one of three fundamental numbers that physicists believe are consistent across the universe. But in recent years, different measurements of G have produced wildly different results, raising the level of uncertainty.
"That is a huge embarrassment for modern physics, where we think we know everything so well and other constants are defined to many, many digits," Gundlach said.
If the new value is accepted, it would reduce the uncertainty of G by a factor of 100.