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Talk:Theory of relativity (view source)
Revision as of 20:32, September 4, 2018
, 20:32, September 4, 2018→Numbers for claims about Mercury's precession.: reply
ASchlafly compares the relativistic prediction for the precession of Mercury's orbit with observed values and states that "the conflict is greater than the margin of error." However, he does not show what these values are or provide a link to an external reference. Elsewhere on the same page some numbers for observed and predicted anomalous precession are provided, and they appear to be in agreement: the uncertainties overlap. For example, a predicted value of 42.98 ±0.04 arcseconds per century is provided, which does overlap with the provided observed value of 43.13 ± 0.14 arcseconds per century. Interestingly, there is no reference for the predicted value of 42.98 ±0.04. There are values in tables that do not match the values in the references that seem to be associated with the tables as well. Lastly, a formula for the approximation of precession under GR is provided in two places which is off by a factor of 2Π, in the reference frame of the orbiting body in question. Use of that formula as stated provides neither the correct predicted precession per orbit, nor the correct predicted precession per 100 Earth years (which is how the precession is normally presented). It's unclear when the incorrect formula was added to the page or for what purpose. <br />
ASchlafly compares the relativistic prediction for the precession of Mercury's orbit with observed values and states that "the conflict is greater than the margin of error." However, he does not show what these values are or provide a link to an external reference. Elsewhere on the same page some numbers for observed and predicted anomalous precession are provided, and they appear to be in agreement: the uncertainties overlap. For example, a predicted value of 42.98 ±0.04 arcseconds per century is provided, which does overlap with the provided observed value of 43.13 ± 0.14 arcseconds per century. Interestingly, there is no reference for the predicted value of 42.98 ±0.04. There are values in tables that do not match the values in the references that seem to be associated with the tables as well. Lastly, a formula for the approximation of precession under GR is provided in two places which is off by a factor of 2Π, in the reference frame of the orbiting body in question. Use of that formula as stated provides neither the correct predicted precession per orbit, nor the correct predicted precession per 100 Earth years (which is how the precession is normally presented). It's unclear when the incorrect formula was added to the page or for what purpose. <br />
If ASchlafly would cite or report the specific numbers that he is comparing, or point to his source for those numbers, his argument could be evaluated. Currently, his claim is in clear conflict with the numbers provided elsewhere on the page. The issue of the incomplete/incorrect formula and possible errors (or incorrect references) in the tables should probably be addressed by a more senior party than myself.--[[User:Brossa|Brossa]] ([[User talk:Brossa|talk]]) 14:14, 4 September 2018 (EDT)
If ASchlafly would cite or report the specific numbers that he is comparing, or point to his source for those numbers, his argument could be evaluated. Currently, his claim is in clear conflict with the numbers provided elsewhere on the page. The issue of the incomplete/incorrect formula and possible errors (or incorrect references) in the tables should probably be addressed by a more senior party than myself.--[[User:Brossa|Brossa]] ([[User talk:Brossa|talk]]) 14:14, 4 September 2018 (EDT)
:Ummm, yeah. I may have gotten the two "approximations" wrong. The one in footnote 46 or so was the approximation in Einstein's paper. The other one was just put together by me as an ''extreme'' back-of-the-envelope rough approximation designed to show how the precession depends on the planet's speed relative to the speed of light, without fussing over the orbital eccentricity. I'll go look at that again. It's made confusing by the need to choose really consistent units (what exactly is the Schwartzschild radius? Are we using c=1 units?). And the standard "theoretical" formulas are in Mercury years, whereas we traditionally describe this in Earth years.
:But keep in mind that the real test is whether the precession ''as observed through telescopes'' and the precession ''as precisely calculated from the Einstein field equations and the Schwartzschild metric'' agree. That's what the error bars are about. The two approximations are just that. You need to solve the equations, and (unlike for Newtonian/Keplerian gravity) that has to be done by computer.
:So I'll look at that and try to clean it up. And not have one of the approximations in the text while another is in a footnote. That's just dumb. Thanks for pointing out the problem. [[User:SamHB|SamHB]] ([[User talk:SamHB|talk]]) 16:32, 4 September 2018 (EDT)
== References ==
== References ==
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