Talk:Lense–Thirring precession

Expert attention needed[edit]

Following this question on the Wikipedia:Reference desk/Science I have added a request for expert attention. The German reference is interesting but does not include these exact formulae. These symbols need definitions (my wild guesses in parentheses).

{\boldsymbol {B}}={\frac {3}{5}}R^{2}q{\Big (}{\boldsymbol {\omega }}\cdot {\boldsymbol {r}}{\frac {\boldsymbol {r}}{r^{5}}}-{\frac {1}{3}}{\frac {\boldsymbol {\omega }}{r^{3}}}{\Big )}

normal R (radius of the large rotating mass?)
bold B (gravitomagnetic field?)
q
bold omega (angular velocity of small particle?)
bold r
normal r (distance between centres of large and small masses?)

{\boldsymbol {\omega }}=-4\int {\frac {\rho {\boldsymbol {u}}dV}{r}}

all the terms in the numerator of the above integral

{\boldsymbol {B}}=-{\frac {4}{5}}{\frac {\boldsymbol {\omega mR^{2}}}{r^{3}}}\cos \theta )

bold m (mass of ?)
bold R
${\boldsymbol {\Omega }}_{LIF}$ (angular velocity due to the local intertial field?)

-84user (talk) 14:04, 18 February 2010 (UTC)[reply]

Article now completely re-written. All questions should now be clear.67.198.37.16 (talk) 04:28, 3 May 2016 (UTC)[reply]

Experimental confirmation[edit]

Apparently Gravity-probe-B results this was confirmed (+/- 20%) in 2011 by Gravity Probe B, but (according to Greg's post there) had earlier been confirmed (+/- 0.1%) in 2008 using lunar range data (his refs [arXiv:0710.0890] and [doi:10.1038/nature06071] ), and even earlier in 2004 to +/- 10% by the Lageos I and II satellite experiment. If there are reliable sources can we add these confirmations to the article ? - Rod57 (talk) 10:26, 5 May 2011 (UTC)[reply]
LAGEOUS results are mentioned (with sources) in Gravity Probe B. - Rod57 (talk) 10:31, 5 May 2011 (UTC)[reply]
See also experimental results in Frame-dragging. - Rod57 (talk) 11:33, 8 May 2011 (UTC)[reply]

Elementary errors[edit]

The Derivation section contains a number of formulae. As described above (under Expert attention needed), there are explanations for the terms used in none of these equations. This makes the section incomprehensible.

Substituting the second equation in the first does not produce the third, which gives a value for B exactly 4 times that in the first! This elementary error makes the section nonsense.

The introduction says the LT effect occurs "near a large rotating mass such as the Earth". Yet the Derivation section proceeds to talk about "the gravitomagnetic field in the equatorial plane of a rotating star" without further ado. The same section casually introduces the Foucault pendulum without any obvious justification. Apparently for this (but we're not told why) "we only have to take the perpendicular-component to the Earth's surface. This means the first part of the equation cancels, where the radius r equals R and θ is the latitude". I'm hazarding a guess the author means the ${\boldsymbol {\omega }}\cdot {\boldsymbol {r}}$ term is zero because ${\boldsymbol {\omega }}$ is transverse: perpendicular to ${\boldsymbol {r}}$ . (Which gives us a clue that ${\boldsymbol {r}}$ and ${\boldsymbol {R}}$ are the distances between object centres and the radius of the more massive, probably in that order, since they would be equal only at the surface of the more massive.) However, the result would not be the fourth equation:

{\boldsymbol {B}}=-\left({\frac {1}{3}}{\frac {\boldsymbol {\omega }}{r^{3}}}\cos \theta \right).

but:

{\boldsymbol {B}}=-{\frac {4}{5}}R^{2}q{\Big (}{\frac {\boldsymbol {\omega }}{r^{3}}}{\Big )}.

The quality of this whole section is so poor that it's embarassing! It's simply wrong, not just once but as I've shown, at least twice.

Wouldn't it be better to pull - that is, delete - this section until we can get it something nearly right?

yoyo (talk) 17:00, 13 September 2011 (UTC)[reply]

The article has now been completely re-written, and I believe all these issues have been taken care of.67.198.37.16 (talk) 04:31, 3 May 2016 (UTC)[reply]

Lots of incorrect information[edit]

This page badly needs someone to fix things, there are a number of sentences which are factually incorrect, but I expect that there are sentences which are hoaxes, spoofs, placed in the extant article in the expectations that garbage sounds plausible enough to not be fixed. Someone who understands the physics needs to fix this article. Damotclese (talk) 17:55, 16 October 2015 (UTC)[reply]

The article has been completely re-written, I believe that its now correct. 67.198.37.16 (talk) 04:32, 3 May 2016 (UTC)[reply]

(1+rs/r)[edit]

do you really prefer this aproximated form $\left(1+{\frac {2GM}{rc^{2}}}\right)$ to the correct expression ${\frac {1}{\left(1-{\frac {2GM}{rc^{2}}}\right)}}$ ? Ra-raisch (talk) 12:38, 3 January 2017 (UTC)[reply]

Dunno. The form to use should be the one in the original Lense-Thirring papers, and/or the form that appears in most popular textbooks, neither of which I have at my fingertips. Maybe mention that the more general Kerr solution uses the latter. 67.198.37.16 (talk) 20:03, 5 March 2018 (UTC)[reply]