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Gravitational and Relativistic Physics (GRP)

    PAST: Gravity Probe A Seperator Dot Viking Seperator Dot Lunar Laser Ranging Seperator Dot LAGEOS I & II
PRESENT: Ongoing Research
    FUTURE: Gravity Probe B Seperator Dot AMS Seperator Dot STEP Seperator Dot LISA Seperator Dot SUMO


Launch Date: 2002
Mission Duration: 1 year
Principle Investigator: Prof. Francis Everitt, Stanford University

 

Gravity Probe B

Gravity Probe B is a relativity experiment developed to test two parts of Albert Einstein's General Theory of Relativity. To make the experiment work, a wide range of technologies were created to help construct a satellite with instruments that explore the basic foundations of space-time.

To conduct the experiment, four gyroscopes will be placed in Earth orbit to study their behavior outside the pull of gravity. The gyroscopes will be precisely checked for tiny changes in their direction of spin caused by their interaction with the Earth. The gyroscopes will be contained in a satellite orbiting at 400-miles over the Earth's poles. The gyroscopes will be so free from interference that they will provide a nearly perfect system for measuring the Earth's effects on them.

The gyroscopes will check for two effects that have far-reaching implications for our understanding of the structure of the Universe.

  • Frame Dragging - A rotating massive body drags space and time around with it. A gyroscope orbiting Earth tends to tilt away from the plane of its orbit because the Earth is dragging it. GP-B will be the first experiment able to sense the frame-dragging effect and will measure it to 1% precision.
  • Geodetic Effect - According to Einstein's General Theory of Relativity, space and time in the vicinity of a massive body is distorted. For a gyroscope orbiting near the Earth, this distortion leads to a tilting of the gyroscope's spin axis in the plane of the orbit. This effect is predicted by general relativity theory to be 150 times larger than the frame dragging. GP-B will measure this effect to a part in 10,000.

Gravity Probe B, in measuring how space and time are warped by the presence of the Earth and how the Earth's rotation drags space-time around with it, will provide the most precise test of Einstein's theories ever attempted.

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