Gravity Probe B


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Gravity Probe B

A US mission to test two predictions of Einstein's general theory of relativity, launched Apr. 2004. The mission, developed jointly by NASA and Stanford University, aims to verify these predictions: it will seek to assess (1) how the presence of the Earth warps space and time and (2) how the Earth's rotation drags space and time around with it. The effects of the Earth on space and time are minute and have hitherto gone undetected and therefore unmeasured. The Gravity Probe B is designed to measure them for the first time. It will seek to do so using four gyroscopes housed within an artificial satellite orbiting directly over the Earth's poles at an altitude of 640 km. Free from external disturbances and cooled to near absolute zero to eliminate disruptions caused by their own molecular structures, the gyroscopes are near perfect spheres spinning in a vacuum and designed to provide direction measurements that are 30 million times as accurate as any gyroscope ever built before. If Einstein's predictions are correct, the gyroscopes should help to detect that very small amounts of space and time are missing from each orbit. In order to measure each orbit accurately, the gyroscopes are lined up with a guide star by means of a tracking telescope, and a magnetic-field measuring instrument records any changes with respect to the guide star. The mission was scheduled to run for a total of 18 months, including 16 months of data collection. It is set to end in late 2005.
References in periodicals archive ?
The Gravity Probe B team is the most heroic bunch of scientists I've ever been affiliated with," says Peter Saulson, a physicist at Syracuse University who monitored the mission as part of a NASA-organized advisory committee.
After delays and false starts, Gravity Probe B was launched in 2004.
This effort, Gravity Probe B, would ultimately cost NASA at least $750 million.
Despite this setback, in 2007 the Gravity Probe B team confirmed one prediction of general relativity.
Gravity Probe B confirmed the so-called geodetic effect--in which the curvature of space shortens the length of the craft's orbit by 1.
Still, skepticism about the laser method lingers, especially from researchers associated with a space experiment known as Gravity Probe B (SN: 9/25/04, p.
27, the Gravity Probe B (GP-B) experiment, which was launched into Earth orbit on April 20, finally began what's now expected to be a 10-month run of gravity measurements.
Many relativity experts are enthusiastic about the prospects for Gravity Probe B (GP-B), as the spacecraft is known.
303), and fielding ultrasensitive space-time experiments, such those on the upcoming Gravity Probe B satellite (SN: 11/15/97, p.
Scheduled for launch in 1999, Gravity Probe B (GP-B) represents an ambitious, space-based attempt to test the general theory of relativity.
Scheduled for launch in 1999, Gravity Probe B represents an ambitious attempt to test the general theory of relativity.
The original design of Gravity Probe B called for the use of four gyroscopes, each an ultrasmooth quartz ball coated with niobium.