Frame-dragging

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According to Albert Einstein's theory of general relativity, space and time get pulled out of shape near a rotating body. This is known as the frame-dragging effect and was first derived from the theory of general relativity in 1918 by the Austrian physicists Joseph Lense and Hans Thirring. Other names for this effect are gravitomagnetism and the Lense-Thirring effect.

Frame-dragging is one of the last predictions of relativity remaining to be confirmed by experiment. More familiar and already proven effects include the conversion of mass into energy (as seen in atomic bombs and stars) and back, the Lorentz transformations that make objects near the speed of light grow shorter (Length contraction) and heavier and stretch time, and the warping of space by gravity (as seen when light is bent by a massive object).

Lense and Thirring also predicted that the rotation of an object would alter space and time, dragging a nearby object out of position compared to the predictions of Newtonian physics. This is the frame-dragging effect. The predicted effect is incredibly small, about one part in a few trillion, which means that you have to look at something very massive, or build an instrument that is incredibly sensitive and put it in orbit.

Table of contents

1 Attempts to test the existence of frame-dragging
2 References
3 External links

Attempts to test the existence of frame-dragging

Using recent observations by X-ray astronomy satellites, including NASA's Rossi X-ray Timing Explorer, a team of astronomers announced in 1997 that they had seen evidence of frame-dragging in disks of gas swirling around a black hole. The team included Dr. Wei Cui of the Massachusetts Institute of Technology, and his colleagues, Dr. Nan Zhang, working at NASA's Marshall Space Flight Center, and Dr. Wan Chen of the University of Maryland in College Park.

An analysis of the laser-ranging data obtained by the two LAGEOS satellites, published in 1997, claimed to have found evidence of the predicted frame-dragging effect with an accuracy of about 20 percent.

The Gravity Probe B experiment aims to detect any frame-dragging effects in its orbit around the Earth with high precision. It was successfully launched on April 20, 2004 for an 18 month experiment.

References

Thirring, H. ÃÂÃÂber die Wirkung rotierender ferner Massen in der Einsteinschen Gravitationstheorie. Physikalische Zeitschrift 19, 33 (1918). [On the Effect of Rotating Distant Masses in Einstein's Theory of Gravitation]
Thirring, H. Berichtigung zu meiner Arbeit: "ÃÂÃÂber die Wirkung rotierender Massen in der Einsteinschen Gravitationstheorie". Physikalische Zeitschrift 22, 29 (1921). [Correction to my paper "On the Effect of Rotating Distant Masses in Einstein's Theory of Gravitation"]
Lense, J. and Thirring, H. ÃÂÃÂber den Einfluss der Eigenrotation der ZentralkÃÂÃÂ¶rper auf die Bewegung der Planeten und Monde nach der Einsteinschen Gravitationstheorie. Physikalische Zeitschrift 19 156-63 (1918) [On the Influence of the Proper Rotation of Central Bodies on the Motions of Planets and Moons According to Einstein's Theory of Gravitation]

External links

An early version of this article was adapted from public domain material from http://science.msfc.nasa.gov/newhome/headlines/ast06nov97_1.htm