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The article discusses the U.S. National Aeronautics and Space Administration (NASA) Gravity Probe B and its mission that validated theoretical physicist Albert Einstein's theory of general relativity and its predictions regarding a spacetime continuum. The frame-dragging effect of the Earth's rotation and the history of the mission and its problems are discussed. INSET: Back Story.

The article discusses how the Earth's tug on space-time, known as frame dragging, takes place almost exactly as specified by relativity theory, according to Ignazio Ciufolini of the University of Lecce in Italy and Erricos C. Pavlis of the University of Maryland in Baltimore. The theory predicts that the two satellites LAGEOS and LAGEOS2 should be dragged about 2 meters in the direction of Earth's rotation as they orbit. Using 11 years' measurements from laser beams bounced off the satellites, Ciufolini and Pavlis found 99 percent of the expected orbital shift. "This is the first accurate measurement" of frame dragging, claims Ciufolini. Until recently, measurements of gravity variations around the world had lacked accuracy, fueling distrust of frame-dragging results based on those numbers.

Discusses research being done on the evidence of physicist Alfred Einstein regarding his theory of relativity. Reference to a study by Bruno Bertotti et al published in the September 1, 2003 issue of "Environmental Health Perspectives" journal; Overview of the concept that gravity is equivalent to the curvature of space-time.