https://electroncafe.files.wordpress.com/2011/05/sciencerage.png

http://phdcomics.com/comics/archive.php?comicid=761

Oops — sorry for any miscopying; the above is what appears before the display; I managed to submit before finishing. The discussion after the display is:

“The confidence intervals around the estimates in Display 2.13 reflect uncertainty due to measurement errors. (The actual confidence levels are not given and are not important for this illustration.) After the first relatively crude attempts to measure gamma, little improvement was made until the late 1960’s and the discovery of quasars. Measurements of light from quasar groups passing near the sun led to dramatic improvement in accuracy, as evident in the narrower intervals with later years.

“

Then there is a heading “A Note About the Cumulation of Evidence”, followed by

“This example shows that theories must withstand continual challenges from skeptical scientists. The essence of scientific theory is the ability to predict future outcomes. Experimental results are typically uncertain. So the fact that some intervals fail to include the value, gamma = 1, is not taken to disprove general relativity, but neither would it prove general relativity right if all the intervals did include gamma = 1. When a theory’s predictions are consistently denied by a series of experiments — such as the Newtonian prediction of gamma = 0 in this example — scientists agree that the theory is not adequate.

]]>I easily found Ramsey and Schafer on my bookshelf, but didn’t find the figure until I tired “Einstein” in the index. The figure is on p. 48 (2002 edition). The accompanying text is:

“The parameter gamma, which is predicted by Einstein’s general theory of relativity to be 1 and by Newonian physics to be 0, was estimated in 1919 by British astronomers during a toal exlipes. Since then, measurements have been repeated many times, under various measurement conditions. The efforts are summarized in Display 2.13 (Date from C.M.Will, “General Relativeity at 75: How Right Was Einstin?” Science 250 (November 9, 1990): 770 -75.

]]>I got the graph from Statistical Sleuth, by Ramsey and Schafer from when I was in grad. school. I’d have to dig it out to see the accompanying text.

Justin

]]>But if there were no curvature, wouldn’t there then be no gravity since that is supposedly due to the curvature? I’m going to have to assume that wikipedia page is BS and there is something more going on.

]]>I believe so, “Management Directives” always have an effect – exactly opposite of that intended.

Not sure how to show that on a graph.

]]>You would seem to be correct. Gamma isnt “the deflection of light around the sun”, its a parameter in an approximation thats apparently zero for the Newtonian model and one in GR…

In the limit, when the fundamental speed of gravity becomes infinite, the post-Newtonian expansion reduces to Newton’s law of gravity.

gamma = How much space curvature g_i_j is produced by unit rest mass?

https://en.wikipedia.org/wiki/Parameterized_post-Newtonian_formalism

And a new thing to me is the amount of curvature caused by mass is supposed to depend on the speed of gravity? Ie if gravity was instantaneous there would be no curvature, according to this.

]]>Are you sure the plot is wrong? A quick google seems to indicate that gamma is a parameter that enters into the deflection equation as 0.5*(gamma + 1)…

E.g., eq. 1 here:

http://iopscience.iop.org/article/10.1088/0264-9381/32/12/124001/ampdf

Maybe the plot title is a bit misleading without the accompanying text.

]]>I think the joke is on you since that plot is wrong. The Newtonian value is exactly half the GR value.

]]>Henry Cavendish in 1784 (in an unpublished manuscript) and Johann Georg von Soldner in 1801 (published in 1804) had pointed out that Newtonian gravity predicts that starlight will bend around a massive object.[15][16] The same value as Soldner’s was calculated by Einstein in 1911 based on the equivalence principle alone. However, Einstein noted in 1915 in the process of completing general relativity, that his (and thus Soldner’s) 1911 result is only half of the correct value. Einstein became the first to calculate the correct value for light bending.[17]

Justin, this is great! I have The Course of Science on my office door, as a daily reminder when I start work. I will add this plot too. I now understand why Sabine Hossenfelder wrote in Lost in Math that physicists like the number 1 and they don’t like numbers smaller or larger than 1.

]]>http://www.statisticool.com/cis.jpg

Justin

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