GR prediction for precession of perihelion of Mercury is not quite right
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From: Koobee Wublee on 26 Jun 2010 00:23 On Jun 25, 8:58 pm, Tom Roberts wrote: > Surfer wrote: > > See: > >http://en.wikipedia.org/wiki/Tests_of_general_relativity#Perihelion_p... > > > Amount: arcsec/Julian century > > 5603.24 Total predicted > > 5599.7 Observed > > -3.54 Discrepancy > > > The discrepancy is larger than the observational error > > Before one knows whether or not this is significant, one must compare the > discrepancy to the errorbars. The above-referenced article does not do that, and > does not include the errorbars. > > So you must look up the errorbars in the literature before you can determine > whether this is important or not. Not the errorbars again. What is the errorbar of the one due to other solar bodies? They seem to be very big, no? <shrug>
From: PD on 26 Jun 2010 11:19 On Jun 25, 11:23 pm, Koobee Wublee <koobee.wub...(a)gmail.com> wrote: > On Jun 25, 8:58 pm, Tom Roberts wrote: > > > > > > > Surfer wrote: > > > See: > > >http://en.wikipedia.org/wiki/Tests_of_general_relativity#Perihelion_p.... > > > > Amount: arcsec/Julian century > > > 5603.24 Total predicted > > > 5599.7 Observed > > > -3.54 Discrepancy > > > > The discrepancy is larger than the observational error > > > Before one knows whether or not this is significant, one must compare the > > discrepancy to the errorbars. The above-referenced article does not do that, and > > does not include the errorbars. > > > So you must look up the errorbars in the literature before you can determine > > whether this is important or not. > > Not the errorbars again. What is the errorbar of the one due to other > solar bodies? They seem to be very big, no? <shrug> No.
From: Tom Roberts on 26 Jun 2010 12:25 Koobee Wublee wrote: > On Jun 25, 8:58 pm, Tom Roberts wrote: >> Before one knows whether or not this is significant, one must compare the >> discrepancy to the errorbars. The above-referenced article does not do that, and >> does not include the errorbars. >> >> So you must look up the errorbars in the literature before you can determine >> whether this is important or not. > > Not the errorbars again. Yes, OF COURSE "the errorbars again [sic]". Comparison between theory and experiment (measurement) ALWAYS requires errorbars. > What is the errorbar of the one due to other > solar bodies? They seem to be very big, no? I do not know, and neither does the author of the post to which I responded, or the author of the referenced article. THAT IS THE PROBLEM. Yes, I suspect there are contributions to the errorbars on the measurement that are comparable to the discrepancy. If, for instance, the errorbar turns out to be 3 arcsec/century, then the claim "the discrepancy is larger than the observational error" is correct, yet the discrepancy is not SIGNIFICANT, and thus is not important. For those of you who don't understand errorbars, let me explain. When making a measurement, there is ALWAYS some experimental error [#]. So we model the measurement process as yielding a distribution of values, with the actual value as the mean of the distribution, and the sigma of the distribution being the errorbar. It is observed that most measurement processes yield values that are approximately Gaussian distributed, so this is usually a good model. The best way to determine the errorbar is to measure it by taking multiple measurements and determining mean and sigma from the different measurements. With that in mind, only ~68% of the measurements will yield a value within one errorbar (sigma) of the actual value, and ~5% of the time the value will exceed twice the errorbar from the actual value. Assuming one has confidence in the value of the errorbar, physicists generally consider a discrepancy of 2 sigma or less to be not significant, a discrepancy between 3 and 4 sigma as inconclusive but provocative, and a discrepancy of 5 sigma or more as pretty definitive. [#] Error in the sense of discrepancy from the actual value, not in the sense of "mistake". This is standard usage. That said, I would not consider this discrepancy of 3.54 arcsec/century to be a problem unless the errorbar on the measurement is smaller than about 0.7 arcsec/century. If it's less than about 1.2 arcsec/century then it's probably worth revisiting. [Astronomers know this, and the fact that they are not revisiting this makes me infer that it is not a problem. But new techniques can often reduce the errorbar, and that can make it worth re-doing.] Tom Roberts
From: oriel36 on 26 Jun 2010 15:44 On Jun 26, 5:25 pm, Tom Roberts <tjroberts...(a)sbcglobal.net> wrote: > That said, I would not consider this discrepancy of 3.54 arcsec/century to be a > problem unless the errorbar on the measurement is smaller than about 0.7 > arcsec/century. If it's less than about 1.2 arcsec/century then it's probably > worth revisiting. > > [Astronomers know this, and the fact that they are not revisiting > this makes me infer that it is not a problem. But new techniques > can often reduce the errorbar, and that can make it worth re-doing.] > > Tom Roberts Astronomers indeed !,in all the years on the newsgroups I have yet to meet one ! What would you like to know about orbital dynamics including the Earth's own motion ?,oh,that's right,you specialize in wordplays with others who know no better or inclined to this dull and dishonorable mathematical and non-geometric nonsense. I bet there is not one among you who can explain the seasons let alone figure out an Ra/Dec observation of the planet Mercury.
From: BURT on 26 Jun 2010 15:54
On Jun 26, 12:44 pm, oriel36 <kelleher.ger...(a)gmail.com> wrote: > On Jun 26, 5:25 pm, Tom Roberts <tjroberts...(a)sbcglobal.net> wrote: > > > That said, I would not consider this discrepancy of 3.54 arcsec/century to be a > > problem unless the errorbar on the measurement is smaller than about 0.7 > > arcsec/century. If it's less than about 1.2 arcsec/century then it's probably > > worth revisiting. > > > [Astronomers know this, and the fact that they are not revisiting > > this makes me infer that it is not a problem. But new techniques > > can often reduce the errorbar, and that can make it worth re-doing.] > > > Tom Roberts > > Astronomers indeed !,in all the years on the newsgroups I have yet to > meet one ! > > What would you like to know about orbital dynamics including the > Earth's own motion ?,oh,that's right,you specialize in wordplays with > others who know no better or inclined to this dull and dishonorable > mathematical and non-geometric nonsense. > > I bet there is not one among you who can explain the seasons let alone > figure out an Ra/Dec observation of the planet Mercury. Time slow effects elliptical orbit falling back by slowing the metric. Mitch Raemsch |