LAGEOS confirms frame dragging.

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Discussion Overview

The discussion centers on the confirmation of frame dragging as predicted by General Relativity (GR) through measurements from the LAGEOS satellites. Participants explore the accuracy of these measurements, the methodologies used, and the challenges involved in isolating the frame dragging effect from other gravitational influences.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes that LAGEOS 1 and LAGEOS 2 have confirmed frame dragging within 99% of the predicted value, with a margin of error of +/- 5%.
  • Another participant shares links to journal articles discussing the topic and expresses intent to contribute further findings to the discussion.
  • A reference to a 1997 paper is provided, which claimed a 25% accuracy that was later revised to 20%.
  • Concerns are raised by a participant regarding the challenges in isolating the Lense-Thirring effect due to larger tidal changes and other influences on the Earth's gravitational field.
  • A participant cites a Nature article that reports an updated analysis claiming a measurement of 99% ± 5% of the predicted frame-dragging effect, with a revised error term of ±10% for unaccounted errors.
  • Another participant emphasizes that the method used significantly affects satellite positioning, as the Earth's non-spherical shape introduces additional perturbations that complicate measurements.

Areas of Agreement / Disagreement

Participants express varying views on the accuracy and reliability of the measurements, with some highlighting the challenges and uncertainties involved. There is no consensus on the implications of the findings or the validity of the methodologies used.

Contextual Notes

Limitations include the dependence on precise knowledge of other gravitational influences and the unresolved nature of the error terms in the measurements.

ohwilleke
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I haven't seen it posted anywhere, but unsurprisingly LAGEOS 1 and LAGEOS 2 have confirmed the frame dragging predicted by GR in the solar system within 99% of the predicted value. The margin of error was +/- 5%.

http://www.spacetoday.net/Summary/2609
 
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I finally came across some links to journal articles about this
and posted something in relativity forum

your link points to this:
http://www.newscientist.com/news/news.jsp?id=ns99996552

and also to the Nature article (but unfortunately I don't have a subscription)

glad you called attention to this, Willecke, and my intention is, if I find any more on it, to add it to the thread in relativity forum
 
http://www.phy.duke.edu/~kolena/framedrag.html

A little more info on first quoted paper.

Dr. John Ries, an expert in satellite geodesy at the
University of Texas at Austin, cautions that it is very
challenging to remove the much larger effects of tidal changes and
small zonal influences in the Earth's gravitational field, so that
estimating the possible errors in the measurement of the Lense-
Thirring effect is itself uncertain.
 
Last edited:
A snip from Wikipidia,

The 20 October 2004 online edition of Nature reports an updated analysis by Ciufolini and Pavlis of the LAGEOS data, now enhanced by using NASA's GRACE gravity model. They claim to have measured an effect which is 99% ± 5% of the value for the Earth's frame-dragging effect predicted by relativity theory, which they have revised to a ±10% error term to allow for errors not taken account of in their analysis.
 
The thing with this is the method used has a huge effect on the sattelites' positions due just to the fact that the Earth isn't a sphere. They're looking for a very small deviation in the sattelites' orbits when they have already been perturbed greatly by other factors. The accuracy of their measurements hinges on knowing these other factors very precisely.
 

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