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Delta 2 Launches Gravity Probe B

A Delta 2 Launch
Vandenberg - Apr 20, 2004
After a 24-hour delay, Gravity Probe B (GP-B) was launched Tuesday, April 20 at 12:57 p.m. EDT on board a Boeing Delta II rocket from Vandenberg Air Force Base, on the central coast of California.

GP-B is among the most thoroughly researched programs ever undertaken by NASA. GP-B will measure two parts of Einstein's general theory of relativity by assessing how the presence of Earth warps space and time, and how Earth's rotation drags space and time.

"The geodetic effect" describes how the presence of Earth changes space and time. Visually, it is similar to holding a bedsheet by four corners and placing a basketball in the center. The bedsheet will slightly wrap around the ball, somewhat similar to the way Earth warps space and time.

GP-B will also measure the "frame dragging," the effect of Earth's rotation on space and time. Einstein predicted that very large objects in space distort time and space as they spin, like a tornado. Frame dragging has not been measured because the effect is so small that technology hasn't yet been able to record it.

The experiment uses three key components: a spinning sphere, a telescope and a star. Building GP-B required fundamental breakthroughs in a variety of technologies to ensure this experiment could be performed.

At the heart of the experiment are four gyroscopes, instruments for studying the Earth's rotation by means of a freely suspended flywheel. The gyroscopes for Gravity Probe B are not flywheels but electrically supported spheres, spinning in a vacuum.

The center of the gyroscope is a jewel-like sphere of fused quartz. These spheres, the size of Ping-Pong balls, are the roundest objects ever made by man. The tiny spheres are enclosed inside a housing chamber to prevent disruption from sound waves, and chilled to almost absolute zero to prevent their molecular structure from creating a disturbance. The accuracy of these gyroscopes is 30 million times greater than any gyroscope ever built.

If Einstein's predictions were right, the gyroscopes should detect that small amounts of time and space are missing from each orbit. To measure each orbit, the gyroscopes are aligned with a guide star using a tracking telescope. A magnetic-field measuring device records the changes in respect to the guide star.

Using cutting-edge technology, the GP-B mission will provide researchers with a better understanding of the underlying structure of the universe and a clearer picture of how our physical world relates to the theory of gravity.

The GP-B experiment will have two months of preparation before calculating data for 16 months.

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Arizonian Optical Engineers Play Key Role In Gravity Probe B
Tucson - Apr 15, 2004
University of Arizona optical scientists have played important roles in the Gravity Probe B experiment, which will test key ideas in Albert Einstein's theories of space and time. The Stanford University experiment, first proposed 40 years ago, will finally start Monday (April 19) when NASA launches the $700 million science mission.

Einstein's Theory To Get Field Tested
Cambridge MA - Apr 06, 2004
When NASA's Gravity Probe B (GP-B) satellite launches on April 17th, it will begin a rigorous test of Einstein's general theory of relativity. The result will either support or challenge one of the fundamental tenets of modern physics.

World's Most Precise Gyroscopes Ready To Test Einstein Theory
Vandenberg AFB - Apr 05, 2004
NASA's Gravity Probe B mission, also known as GP-B, will use four ultra-precise gyroscopes, orbiting the Earth in a unique satellite, to experimentally test two extraordinary predictions of Einstein's 1916 theory that space and time are distorted by the presence of massive objects.

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